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Design, syntheis and post-synthetic modifications of functional metal-organic materials

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Title:
Design, syntheis and post-synthetic modifications of functional metal-organic materials
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Book
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English
Creator:
Nouar, Farid
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University of South Florida
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Tampa, Fla
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Subjects / Keywords:
Rht
Hydrogen storage
Physisorption
Supermolecular building block
Zeolite-like metal-organic frameworks
Dissertations, Academic -- Chemistry -- Doctoral -- USF   ( lcsh )
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non-fiction   ( marcgt )

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Abstract:
ABSTRACT: Porous solids are a class of materials of high scientific and technological significance. Indeed, they have the ability to interact with atoms, ions or molecules not only at their surface but also throughout the bulk of the solid. This ability places these materials as a major class involved in many applications such as gas storage and separation, catalysis, drug delivery and sensor technology. Metal-Organic Materials (MOMs) or coordination polymers (CPs) are crystalline compounds constructed from metal ions or clusters and organic components that are linked via coordination bonds to form zero-, one-, two or three-periodic structures. Porous Metal-Organic Materials (MOMs) or Metal-Organic Frameworks (MOFs) are a relatively new class of nanoporous materials that typically possess regular micropores stable upon removal of guests. An extraordinary academic and industrial interests was witnessed over the past two decades and is evidenced by a fantastic grow of these new materials. Indeed, due to a self-assembly process and readily available metals and organic linkers, an almost infinite number of materials can, in principle, be synthesized. However, a rational design is very challenging but not impossible. In theory, MOMs could be designed and synthesized with tuned functionalities toward specific properties that will determine their potential applications. The present research involves the design and synthesis of functional porous Metal-Organic Materials that can be used as platforms for specific studies related to many applications such as for example gas storage and particularly hydrogen storage. In this manuscript, I will discuss the studies performed on existing major Metal-Organic Frameworks, namely Zeolite-like Metal-Organic Frameworks (ZMOFs) that were designed and synthesized in my research group. My research was also focused on the design and the synthesis of new highly porous isoreticular materials based on Metal-Organic Polyhedra (MOP) where desirable functionality and unique features can be introduced in the final material prior and/or after the assembly process. The use of hetero-functional ligands for a rational design toward binary or ternary net will also be discussed in this dissertation.
Thesis:
Dissertation (Ph.D.)--University of South Florida, 2010.
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Includes bibliographical references.
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by Farid Nouar.
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Title from PDF of title page.
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Document formatted into pages; contains X pages.
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Includes vita.

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ABSTRACT: Porous solids are a class of materials of high scientific and technological significance. Indeed, they have the ability to interact with atoms, ions or molecules not only at their surface but also throughout the bulk of the solid. This ability places these materials as a major class involved in many applications such as gas storage and separation, catalysis, drug delivery and sensor technology. Metal-Organic Materials (MOMs) or coordination polymers (CPs) are crystalline compounds constructed from metal ions or clusters and organic components that are linked via coordination bonds to form zero-, one-, two or three-periodic structures. Porous Metal-Organic Materials (MOMs) or Metal-Organic Frameworks (MOFs) are a relatively new class of nanoporous materials that typically possess regular micropores stable upon removal of guests. An extraordinary academic and industrial interests was witnessed over the past two decades and is evidenced by a fantastic grow of these new materials. Indeed, due to a self-assembly process and readily available metals and organic linkers, an almost infinite number of materials can, in principle, be synthesized. However, a rational design is very challenging but not impossible. In theory, MOMs could be designed and synthesized with tuned functionalities toward specific properties that will determine their potential applications. The present research involves the design and synthesis of functional porous Metal-Organic Materials that can be used as platforms for specific studies related to many applications such as for example gas storage and particularly hydrogen storage. In this manuscript, I will discuss the studies performed on existing major Metal-Organic Frameworks, namely Zeolite-like Metal-Organic Frameworks (ZMOFs) that were designed and synthesized in my research group. My research was also focused on the design and the synthesis of new highly porous isoreticular materials based on Metal-Organic Polyhedra (MOP) where desirable functionality and unique features can be introduced in the final material prior and/or after the assembly process. The use of hetero-functional ligands for a rational design toward binary or ternary net will also be discussed in this dissertation.
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Design, Synthesis a nd Post Synthetic Modifications o f Functional Metal Organic Materials by Farid Nouar A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemistry College of Arts and Sciences University of South Florida Major Professor: Mohamed Eddaoudi Ph.D. Mickael J. Zaworotko, Ph.D. Randy W. Larsen, Ph.D. Julie Harmon, Ph.D. Date of Approval: March 19 2010 Keywords: zeolite like metal organic frameworks, supermolecular building block, physisorption, hydrogen storage, rht Copyright 2010 Farid Nouar

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Dedication I would like to dedicate this dissertation to my father who died in 2008 from a cavum cancer at the age of 64. I also dedicate this work to all my family and especially my mother who always believed in me and of course my wife and my son who was born shortly after my father died and since then illuminated my life.

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Acknowledgment First and foremost, I would like to thank my advisor Dr. Mohamed Eddaoudi for allowing me to conduct a very exiting research in his group, I thank him for his guidance and his help. I would als o like to thank Dr. Coleman for his help and for putting me in contact with Dr. Eddaoudi. In addition, I would like to thank the members of my supervisory committee Dr. Larsen, Dr. Zaworotko and Dr. Harmon for their invaluable help. I would like to thank D r. Wojtas as well for his help i n crystallography. I also want to thank Dr. Forster for crystallography and Dr. Eckert for Inelastic Neutron Scattering assignments. Finally I would like to thank all the members, past and present, of my group.

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Note to Reader The original of this document contain color that is necessary for understanding the data. The original dissertation is on file with USF library in Tampa, Florida.

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i Table of Contents List of Tables v ii List of Figures viii List of Abbreviations x v i ii Abstract xx Chapter 1. Background on Metal Organic Materials 1 1.1. Introduction 1 1.2. Overview of History 2 1.3 Metal Or ganic Materials (MOMs) C onstructed from N itrogen D onor L igands 5 1.4 Metal Organic Materials (MOMs) Constructed form O xygen D onor L igands 7 1.5 Metal Organic Materials (MOMs) Constructed from Hetero F unctional L igands 12 1.6. Applications 15 1.7 References Cited 17 Chapter 2. Introduction to Physis orption and Hydrogen S torage in Porous Metal Organic Materials 24 2.1. Introduction to P hysisorption 24

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ii 2.1.1. Adsorption F orces 25 2.1.2. Adsorption Isotherms and Isotherm S hapes 26 2.1.3 Surface Area E valuation 29 2.1.3 .1. Evaluation by Sorption I sotherms 29 2.1.3 .2. Evaluation by Geometrical M eans 3 2 2.1.4 Pore Volume and Pore Size Characterization 33 2.1. 4.1. Pore Volume Evaluation 33 2.1.4.2. Pore Size Characterization 33 2.1.5 Mesoporous M aterials and Hysteresis L oops 34 2.1.6 Isosteric Heat of A dsorption 35 2.2. Hydrogen Storage by P hysisorpt ion in Metal Organic Frameworks (MOFs) 37 2.2.1. Introduction to Hydrogen S torage 37 2.2.2. Current T echnology 38 2.2.3. Physisorption v ersus C hemisorption 39 2.2.4. Factors Influencing Gas S torage in MOFs 41 2.2.4.1. Surface Area and Pore V olume 41 2.2.4.2. Accessible Metal S ites 43 2.2.4.3. P olariz able L igands 49 2.2.4.4. Pore S ize 49 2.2.4.5. Electrostatic F ield 52 2.2.5. Other Modifications 53

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iii 2.2.5.1. S pillover 53 2.2.5.2 Sample A ctivation 54 2.2.5.2.1. S olvent E xchange 54 2.2.5.2.2. Supercritical CO 2 A ctivation 55 2.2.6 Conclusion 56 2.3. References Cited 57 Chapter 3. Hetero functional Tetrazolate/Carboxylate Ligands for the Design and Synthesis of P orous Metal Organic Materials 63 3.1. From Molecular Building Blocks (MBBs) to Supermolec ular Building Blocks (SBBs) 64 3.2. Design and S ynthesis of (3,24) C onnected rht N et s 67 3 .3. Tetrazolylisophthalic Acid L igand (H 3 TZI) and rht 1 synthe s es 70 3.3.1 Tetrazolylisophthalic Acid S ynthesis (H 3 TZI) 70 3.3.2. rht 1 S ynthesis 70 3.4. Sorption S tudies on rht 1 75 3.5 I soreticular rht L ike S tructures 77 3.5 .1. Design of rht L ike Nets 77 3.5 .2. Synthesis of rht L ike S tructures 78 3.5 .3. Sorption S tudies of rht L ik e S tructures 80 3.5 .4. rht L ike Structures from other G roups 90 3.5 .5. Encapsu lation of Porphyrin D erivatives 93 3.6. Hetero Functional Ligands for the Construction of Multinodal Nets 94

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iv 3.6.1. Introduction 94 3.6.2. Structures Based on Tetrazolylisophthalate 94 3.6.2.1. sra Net 94 3.6.2.2. sqc Trinodal Net 95 3.6.3. Structures Ba sed on 4 Tetrazolylbenzoate 96 3.6.3.1. A New Binodal Net 97 3.6.3.2. lvt Net 98 3.7. Conclusion 99 3.8 Experimental S ection 100 3.8 .1. Organic S ynthese s 100 3.8 .2. M etal Organic Frameworks (MOFs) S yntheses 105 3.8 .3 Supercritical CO 2 Activation and Gas Sorption Experiments 114 3.8.4. Single Crystal Structur a l Analysis and Refinement 116 3.8.4.1. Crystal data and structure refinement for rht 1 116 3.8.4.2. Crystal data and structure refinement for rht 2 117 3.8.4.3. Crystal data and structure refinement for rht 3 118 3.8.4.4. Crystal data and structure refinement for Zn TZI (sra) 119 3.8.4.5. Crystal data and structure refinement for Y TZI (sqc ) 120

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v 3.8.4.6. Crystal data and structure refinement for Cu TZB (new topology ) 121 3.8.4.7. Crystal data and structure refinement for Cu TZB (lvt ) 122 3.9 References Cited 123 Chapter 4 Post S ynthetic M odification of Zeolite L ike Metal Organic Frameworks 127 4 .1. Introduction 12 7 4 .2. Zeolite L ike Metal Org anic Framework (ZMOFs): Design S trategy 12 8 4 .3. Zeolite L ike Metal Organic Framework (ZMOFs): Lithium and Magnesium I on E xchange and H 2 ( rho ZMOF) I nteraction S tudies 133 4 .3.1. Li and Mg Ion E xchange in rho ZMOF 13 3 4 .3.2. Mg rho ZMOF Single Crystal X R ay D iffraction 135 4 .3.3. Sorption D ata on DMA Mg and Li rho ZMOF 137 4 .3.4. Inelastic Neutron Scattering (IN S) D ata on DMA Mg and Li rho ZMOF 14 1 122 4 .3.5. Summary and C onclusion 14 7 4 .3.6. Experimental S ection 14 7 4 .4. Zeolite L ike Metal Organic Framework s (ZMOFs): Encapsulation and H 2 S torage Studies 151

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vi 4 .4.1. Introduction 151 4 .4.2. Encapsulation of F uller ene D erivatives 153 4 .4.3. Sorption Studies 155 4 .4.4. Summary and Conclusion 156 4.4.5. Experimental Section 157 4 .5. Zeolite like Metal Or ganic Framework (ZMOFs): Other Post S ynthetic M odifications 159 4 .5.1. Introduction 159 4 .5.2. rho ZMOF Protonation 160 4 .5.3. Summary and Conclusion 161 4.5.4. Experimental Section 16 1 5.7. References Cited 164 Chapter 5 Summary and Conclusion 168 5 .1. Summary 168 5 .2. Conclusion 17 2 About the A uthor End Page

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vii List of Tables Table 2.1. Sorption data in select MOFs with high surface area 43 Table 2.2. Sorption data in select MOFs containing potential open metal sites 46 Table 2.3. Sorption data in select MOFs with reduced pore size s 52 Table 2.4. Sorption data obtained from spillover experiments in MOFs compared to the data from typical experiments 54 Table 4 .1. Sorption data for DMA Mg and Li rho ZMOF 13 8 Table 4 .2. Assignment s for DMA Mg and Li rho ZMOF INS data 14 2

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viii List of Figures Figure 1.1. Example of a Werner complex with formula MX 2 L 4 where M represents Ni, X represents NCS and, L is 4 methylpyridine (form ref. 1e). Ni, N, C, S and H are represented in green, blue, grey, yellow and white respectively 2 Figure 1.2. A typical Hofmann clathrate structure (from ref. 3e). Hydrogen atoms were omitted for clarity. Cu, Ni, N and C are represented as green, yellow, blue and grey respectively 3 Figure 1.3. Picture of a Prussian Blue structure with formula Mn 3 (Co(CN) 6 ) 2 ( from ref. 4). Mn, Co, N and C are represented in green, yellow, blue and grey respectively. 4 Figure 1.4. A fragment of a diamond like structure obtained after tetracyanotetraphenylmethane (from ref. 5a). Hydrogen atoms were omitted for clarity. Cu, N and C are represented in green, blue and grey respectively 5 Figure 1.5. Examples of nitrogen based ligands: a) 1,4 bis(4 pyridyl)butadiyne (from ref. 12); b) 1,2 bis(4 pyridyl)ethane (from ref. 13); bipyridine; d) pyrazine; e) 1,4,5,8,9,12 hexaazatriphenylene (from ref. 14); f) 2,4,6 Tri(4 pyridyl) 1,3,5 triazine (from ref. 15); g) 1,3,5 tris(3,5 pyrimidyl)benzene; h) 5,10,15,20 tetra 4 pyridyl 21 H,23H porphine (from ref. 16) 6

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ix Figure 1.6. Examples of work done on azolate ligands: a) example of a trigonal building block obtained with 1,4 benzeneditetrazol 5 yl and Mn (from ref. 21); b) another example of a trigonal tetramethyl bipyrazole and Ag (from ref. 20); c) 1,3,5 tri p (tetrazol 5 yl)phenylbenzene (top left) and 1,3,5 Tris(2 H tetrazol 5 yl)benzene (down left) were used with Cu and Mn to form a cube like clusters; d) Schematic of the structure obtained after reaction of CuCl 2 or MnCl 2 and 1,3,5 Tris(2 H tetrazol 5 yl)benzene (from ref. 22 and 23). Hydrogen atoms were omitted for clarity. M, N,C, O, Cl are represented in green, blue, grey, red, light blue r espectively. 7 Figure 1.7. Examples of carboxylate based ligands: a) Benzene 1,4 dicarboxylic acid; b) Benzene 1,3 dicarboxylic acid; c) Benzene 1,3,5 tricarboxylic acid; d) Benzene 1,2,4,5 tetracarboxylic acid 8 Figure 1 8 Select metal carboxylate clusters commonly used as Molecular Building Blocks (MBBs): a) Basic zinc acetate used as octahedral building units (from ref. 24); b) Paddlewheel used as square building units; c) Basic chromium acetate used as trigonal prism units. Hydr ogen atoms are omitted for clarity, the metal is shown in green, C and O are shown in grey and red respectively 9 Figure 1 9 a) Pictures of some organic ligands used to construct isoreticular MOFs, named IRMOF n where n is 1 to 16; b) Two example s representing IRMOFs, left IRMOF 1 and right IRMOF 10. M, C, O, N and H are represented in green, grey, red, blue and white respectively 10 Figure 1.10. Examples of the use of padllewheel building blocks to generate a) Metal organic Polyhedra (rhom bicuboctahedron) also called nanoball form isophtalic acid; b) Cross linked nanoballs using 1,3 bis(5 methoxy 1,3 benzene dicarboxylic acid)benzene (from ref. 33b). Hydrogen atoms are omitted for clarity. M, C, O, N and H are represented in green, grey, re d, blue and white respectively 11

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x Figure 1.11. Examples of hetero functional ligands that have been used to construct MOMs. Top (from left to right): 2,3 pyrazinedicarboxylic acid; 4 pyridinecarboxylic acid; 3 pyridinecarboxylic acid; 2,5 pyridinedicarboxylic acid; 2,4 pyridinedicarboxylic acid; 4,5 Imidazoledicarboxylic acid. Bottom (from left to right): 4 pyrimidinecarboxylic acid; 2 pyrimidinecarboxylic acid; 4,6 pyrimidinedicarboxylic acid; 4 tetrazolylbenzoic acid; 5 tetrazolylisop hthalic acid 12 Figure 1.12. Schematics illustrating the strategies to build porous frameworks form hetero functional ligands a) Imidazole 4,5 dicarboxylic acid and Indium ions were used to generate a zeolitic material referred to as rho ZMOF; b) Tetrazolylisophthalic acid was used to generate a material with 3,24 connected rht topology (only a portion of the structure is shown). M, C, O, N and H are represented in green, grey, red, blue and white respectively 14 Figure 2.1. Types of sorption isotherms (IUPAC) 2 28 Figure 2. 2 Schematic of a typical BET plot where the intercept and the slope can be used for surface area evaluation. 31 Figure 2.3. Schematic depicting the accessible surface area (green), the connolly surface area (red), and the van der Waal s surface area (blue) (from figure 1 in ref.14). 32 Figure 2.4 T ypes of hysteresis loops (IUPAC ) 2 34 Figure 2.5 a) A plot of two isotherms at two different temperatures: If we consider two isotherms recorded at temperature T 1 and T 2 respectively, the isosteric heat of adsorption at a given coverage is: Qst = R((ln P 2 ln P 1 )/((1/T 2 ) (1/T 1 ))). b) A plot of Qst vs. the amount adsorbed. 36 Figure 2.6 Correlation between surface area (BET or Langmuir) and a) pore volume; b) density 41 Figure 2.7 Some MOFs gravimetric uptake data at high pressure versus surface area (black for BET surface area and red for Langmuir surface area) 42

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xi Figure 2.8 Pictures of selected building blocks that possess potential open binding sites. 1 : M 2 (O 2 CR) 4 ; 2 : M 3 O(O 2 CR) 6 ; 3 : M 3 O(N 4 CR) 3 ; 4 : M 4 Cl(N 4 CR) 8 ; 6 : M 3 (N 4 CR) 6 ; 5 and 7 : Chain like motifs Potential H 2 biding sites are represented as yellow spheres; green, blue, red, grey, light blue, purple and orange represent the metal, N, O, C, Cl, Na and S, respectively. 44 Figure 3.1. Schematics depicting some select SBBs that can be used as nodes for the construction of the framework: a) a tetrahedron SBB (ref. 15); b) a cube SBB (ref. 16); c) cuboctahedron SBB (ref. 17) and; d) rhombicuboctahedron SBB (ref. 18 20). 65 Figure 3.2 Linking squares at their vertices results in three types of faceted polyhedra: a) cubohemioctahedron, b) small rhombihexahedron, c) small rhombidodecahedron. 66 Figure 3.3. Schematic depicting a pcu like net that was formed by employing a ligand that contains the necessary features to cross link the nanoballs (shown in red and green). Each nanoball is linked to six nanoballs through four ligands (shown in yellow and green). 67 Figure 3.4 The 5 position of the isopthalate ligands in the truncated cuboctahedron (green) SBB sits directly on the vertices of the rhombicuboctahedron (yellow/orange frame), serving a s the TBU. 68 Figure 3.5 The (3,24) connected rht net and the two vertices and correspondin g vertex figures when augmented 69 Figure 3. 6 Schematic showing the corresponding strategy from MBBs to SBBs (generated all together in situ ) to the resulting framework: rht 1. the 5 position of the 1,3 BDC ligand is highlighted in orange; the yellow spheres indicate the cavity of truncated cuboctahedra; some spheres, all solvent molecules and all hydrogen atoms have been omitted for clarity (C = gray N = blue, O = red, Cu = green). 69 Figure 3.7 Schematic of the synthesis of H 3 TZI from 5 aminoisophthalic acid 70 Figure 3.8 T he (3,24) connected rht net 7 2

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xii Figure 3.9 The unprecedented ternary topology of the compound: a) schematic of the 3 MBBs and the corresponding 3 SBUs b) Picture of the augmented ternary net (Topological terms for each node: (a) 6.6.8.8.8(2).8(2), Coordination Sequence: 4, 8, 18, 29, 52, 61, 106, 120, 170, 187 TD 10 755(0.654); (b) 6.8(3).8(3), Coordina tion Sequence: 3, 8, 15, 29, 40, 69, 81, 131, 146, 206 TD 10 : 728(0.630); (c) 8(3).8(3).8(3), Coordination Sequence: 3, 6, 18, 24, 42, 63, 84, 93, 183, 175; TD 10 : 691(0.598).) 73 Figure 3.10 The present framework can also be interpreted as a) lta cage: blue; and d4R : red) and reo e (rhombicuboctahedron: yellow, green; cuboctahedron : blue ; and d4r: red) nets 7 4 Fig ure 3 .11 Schematic represent ing the arrangement of the different cage s in the structure. 7 5 Figure 3 .1 2 rht 1 sorption graphs a) Nitrogen and argon sorption isotherms at 78K and 87K, respectively. b) Hydrogen sorption isotherms at 77K and 87K. c) Graph of the isosteric heat of sorption 7 6 Figure 3 .1 3 rht 1 was used as a blueprint for the design of new rht nets where the length of H 3 TZI has been increased by additional benzene rings in the X direction to lead to rht 2 and rht 6 and in the Y direction to lead to rht 3 (using TBPDC, TBBD and TTPDC ligands respectively to construct rht 2, rht 6 and rht 3 respectively). 78 Figure 3 .1 4 rht 1 was used as a model for the design of new rht nets where the Cu oxo trimer was replaced by benzene and triazine derivatives 8 0 Figure 3 .1 5 Sorption data on rht 2 after supercritical CO 2 activation a) Argon isotherm; b) Low pressure hydrogen isotherm at 77K and 87K; c) Isosteric heat of sorption plot. 82 Figure 3 .1 6 Pore size distribution in rht 2 (calculated from the Ar isotherm) using DFT & Mon te Carlo method (spherical/cylindrical model). 83

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xiii Figure 3.17. Schematics of the three types of cages (from left to right: truncated octahedral, truncated tetrahedral and rhombicuboctahedra) present in rht 1, rht 2 and rht 3. Cavities dimensions are shown on top of each cages and windows (triangular or quadrangular) are shown on the side. 84 Figure 3.18. S orption data on rht 3 after supercritical CO 2 activation: Argon isotherm. 85 Figure 3.19. Pore size distribution in rht 3 (calculated from the Ar isotherm) using DFT & Monte Carlo method (spherical/cylindrical model). 86 Figure 3.20. Sorption data on rht 3 after supercritical CO 2 activation a) Low pressure hydrogen isotherm at 77K and 87K; b) Isosteric heat of sorpti on plot. 87 Figure 3.21. S orption data on rht 3 after supercritical CO 2 activation (second attempt): Argon isotherm. 88 Figure 3.22. Pore size distribution in rht 3 (calculated from the Ar isotherm) using DFT & Monte Carlo method (spherical/cylindrical model) after the second attempt. 88 Figure 3.23. S orption data on rht 3 after supercritical CO 2 activation (third attempt): Argon isotherm. 89 Figure 3.24. Pore size distribution in rht 3 (calculated from the Ar isotherm ) using DFT & Monte Carlo method (spherical/cylindrical model) after the third attempt 90 Figure 3.25. Schematics of the ligands that have been used to construct rht [1,3,5 benzenetriyltris (carbonylimino)]tris 1,3 benze nedicarboxylic acid (from ref. 43); b) 1,3,5 biphenyl] 4 benzene 1,3,5 triyltris(1 ethynyl 2 isophthalate) (from ref. 45 and ref. 46 ) and d) nitrilotris(benzene 4,1 diyl)t ris(ethyne 2,1 diyl))triisophthalate (from ref. 45 ). 92 Figure 3.26. Schematics of Zn TZI structure: sra net (zeolite ABW topology) depicting a) the ligand and b) the metal as tetrahedral nodes in the structure; c) views of the structure in the x, z and y directions (from left to right). Hydrogen atoms have been omitted for clarity. Zn, C, O and N are shown in violet, grey, red and blue respectively. 95

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xiv Figure 3.27. Schematic of the structure with sqc topology. a) a view in the z axis; b) left: four ligands assemble to form a ~ 10.2 cage (vdw) and right: a 6.6 window (vdw); c) a vue in the x axis; d) the tetrahedral arrangement around the metal with the tetrazolat e moieties (left) and the square arrangement around the metal cluster and the carboxylates. Hydrogen atoms have been omitted for clarity. Y, C, O and N are shown in turquoise, grey, red and blue respectively. 96 Figure 3.28. Schematic pictures dep icting the Cu TZB structure with a binodal topology. a) a view in the y, z and x direction (from left to right respectively); b) a partial view of a cage like arrangement and c) a top view of (b). Hydrogen atoms have been omitted for clarity. Cu, C, O and N are shown in orange, grey, red and blue respectively. 98 Figure 3.29. Schematic pictures illustrating the polar Cu TZB structure. a) a view in the x direction (left) describing the arrangement of the channels in the structure (yellow rods repres ent the void available space in the channels, dimensions and angles in the channels are given (right) b) a portion of the structure depicting the arrangement of the chain like arrangement of the ligands c) a view in the y direction (top) and a view in the z direction (down) showing windows of ~ 3.3 (vdw). Hydrogen atoms have been omitted for clarity. Cu, C, O and N are shown in orange, grey, red and blue respectively. 99 Figure 3.30 (1H tetrazol 5yl)biphenyl 3,5 dica rboxylic acid (TBPDC). 101 Figure 3.31 (1H tetrazol 5yl) terphenyl dicarboxylic acid (TTPDC). 103 Figure 3.32 (4 (1 H tetrazol 5 yl)benzamido)benzene 1,3 d ioic acid respectively (TBBD). 104 Figure 3.33 C alculated and experimental XRPDs for rht 1. 106 Figure 3.34 C alculated and experimental XRPDs for rht 2 107 Figure 3.35 Calculated and experimental XRPDs for SPP rht 2. 108

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xv Figure 3.36 UV vis spectra of the SPP (green), Cu metallated SPP (blue) compared with the spectrum of CuSPP rht 2 (red). Only the visible region is shown. When compared to the Q bands, too large intensities are associated with the Soret bands (at ~ 420 nm), this wa velength region is not shown in the graph. 109 Figure 3.37 Calculated and experimental XRPD for rht 3. 110 Figure 3.38 Calculated and experimental XRPD for rht 6. 111 Figure 3.39 Calculated and experimental XRPD for Zn TZI (sra). 112 Figure 3.40 Calculated and experimental XRPD for Y TZI (sqc5588). 113 Figure 3.41 Calculated and experimental XRPD for Cu and TZB (lvt net). 114 Figure 4 .1. Schematic representation showing the building blocks necessary for the assembly of ino rganic RHO zeolite (left) and rho ZMOF (right). rho zeolite formula is: | (Na + ,Cs + ) 12 | [ Al 12 Si 36 O 96 ] RHO where Silicon and Aluminum ions arrange as tetrahedra linked by oxygen atoms forming a ~140 angle. rho ZMOF, with a formula | (HPP 2+ ) 24 | [ In 48 (C 5 N 2 O 4 H 2 ) 96 ] rho ZMOF, consist in the assembly of Indium tetrahedra linked by 4,5 Imidazole dicarboxylates resulting in a framework with a volume up to 9 times higher than inorganic rho zeolite. O, C, N, H and In are shown in red, grey, blue, white and green re spectively. 13 0 Figure 4 .2. Representation of a zeolite with rho cages (green and blue) containing 8, 6 and 4 membered rings, are connected through double 8 membered rings (D8R) (red) cage in rho ZMOF. O, C, N, H and In are shown in red, grey, blue, white and green respectively (right). 13 1 Figure 4 .3. Experimental PXRD spectra of DMA rho ZMOF, Mg rho ZMOF, Li rho ZMOF compared to the original HPP rho ZMOF (experimental and simulated). 134

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xvi Figure 4 .4. Top: A fragment of the single crystal structure of Mg rho cages (green) and the cubohemioctahedral arrangement (shown as a yellow polyhedron) of the twelve [Mg(H 2 O) 6 ] 2+ per cage. All H atoms have been omitted for clarity. Bottom: hexa aqua magnesium complex is located near each of the twelve 4 cage, interacting with the framework through hydrogen bonds (shown as black dotted lines, Oxygen to oxygen distance is ~2.9 ) with four of the aqua ligands. Intra cubohem membered ring) is 6.532 . O, C, N, H, In and Mg are shown in red, grey, blue, white, green and yellow respectively 13 6 Figure 4 .5. a ) H 2 adsorption isotherms for DMA Mg and Li rho ZMOF at 78 K. b) Enlarged view of the low pressure range in (a). 137 Figure 4 .6. Isosteric heats of adsorption for DMA Mg and Li -rho ZMOF calculated from the corresponding isotherms at 78 and 8 7 K. 139 Figure 4 .7. INS spectra of DMA rho ZMOF at 0.5, 1, 1.5 and 3 H 2 per In 14 3 Figure 4 .8. INS spectra of Mg rho ZMOF at 0.25, 0.5, 1 H 2 per In 14 3 Figure 4 .9. INS spectra of Li rho ZMOF at 0.5, 1, 2 and 4 H 2 per In 14 4 Figure 4 .10. The INS spectra of Li rho ZMOF (red) and DMA rho ZMOF (black) at a loadings of 1 H 2 /In 14 5 Figure 4 .11. TGA spectra of a) Li rho ZMOF and b) Mg rho ZMOF showing (for both compounds) a loss of acetonitrile at temperatures below 100C; at temperatures above 250C, a loss of water and framework degradation are observed. 149 Figu re 4 .12. Schematic of the synthesis of Tetra(N methyl piperazine)C 60 epoxide from fullerene C 60 and 1 methylpiperazine in chlorobenzene under open air for 20 hours with a 60 W incandescent light at room temperature. 153

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xvii Figure 4 .13. Schematic representation of Tetra(N methyl piperazine)C 60 epoxide as it could exist inside the framework. Only a portion cage in rho ZMOF (18 ligands and 18 metals) is shown for clarity and to depict the available guest host space. The size of a regular C 60 molecule is ~10 ; the longest dimension for the present C 60 derivative is ~ 17 ; dimensions of ~ 4 to 5 separate the host from the guest on average (the shortest distance between the host and guest is ~ 1.5 from the methyl group to a H from the framework) and; the size of the cages in rho ZMOF is at least 18.5 . VDW are taken into account for all dimensions. In, C, N, O, H are shown in green, grey, blue, red and white respectively. 154 Figure 4 .14. H 2 sorption isotherm at 77K (left) and; isosteric heat of adsorption for C 60 rho ZMOF (right). 155 Figure 4.15. Experimental PXRD spectrum of TAC 60 rho ZMOF compared to the simulated PXRD spectrum of DMA rho ZMOF. 158 Figure 4 .1 6 Imidazole 4,5 dicarboxylic acid dianion present in rho ZMOF structure (the hydrogen bond is shown as a black dotted line). 159 Figure 4 .17. DMA rho ZMOF protonation graph: pH vs. number of millimoles of H + (blue) and blank (red). 16 2 Figure 4.18. Na rho ZMOF protonation graphs: pH vs. number of millimoles of H + ; the percentage losses of Na+ in the materials are shown for the 4 graphs. 163 Figure 4.19. Na rho ZMOF protonation graphs: pH vs. number of millimoles of H + ; the same sample was used to perform 5 consecutive protonation experiments. 164

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xviii List of Abbreviations Acronym Full name BDC Benzene 1,4 dicarboxilic acid CP Coordination Polymer DMF Dimethylformamide DMA Dimethylamonium EtOH Ethanol H 2 O Water H 3 TZI 5 Tetrazolylisophthalic acid H 2 TZB 4 Tetrazolylbenzoic acid HImDC 4,5 Imidazoledicarboxylic acid INS Inelastic Neutron Scattering MOM Metal Organic Material MOF Metal Organic Fr amework MBB Molecular Building Block MOP Metal Organic Polyhedron PTMOI [1,3,5 phenyltri(methoxy)] tri isophthalic acid SPP Meso t etra(4 sulfonatophenyl)porphine SBB Super molecular Building Block

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xix SBU Secondary Building Unit TBU Tertiary Building Unit TTIMI T riazine 2,4,6 triyl)triimino]triisophthalic acid TBPDC (1H tetrazol 5yl)biphenyl 3,5 dicarboxylic acid TGA Thermo gravimetric analysis TTPDC (1H tetrazol 5yl) terphenyl dicarboxylic acid TBBD (4 (1 H tetrazol 5 yl)benzamido)benzene 1,3 dioic acid UV Vis Ultraviolet v isible XRPD X Ray Powder Diffraction ZMOF Zeolite like Metal Organic Framework

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xx Design, Synthesis and Post S ynthetic Modification s of Fun ctional Metal Organic Materials Farid Nouar ABSTRACT Porous solid s are a class of materials of high scientific and technological significance. Indeed, they have the ability to interact with atoms, ions or molecules not only at their surface but also throughout the bulk of the solid. This ability places these materials as a major class involved in many applications such as gas stor age and separation, catalysis, drug delivery and sensor technology. Metal Organic Materials (MOMs) or coordination polymers (CPs) are crystalline compounds constructed from metal ions or clusters and organic components that ar e linked via coordination bonds to form zero one two or three periodic structures Porous Metal Organic Materials (MOMs) or Metal Organic Frameworks (MOFs) are a relatively new class of nanoporous materials that typically possess regular micropores sta ble upon removal of guests. An extraordinary academic and industrial interests was witnessed over the past two decades and is evidenced by a f antastic grow of these new materials Indeed, due to a self assembly process and readily available metals and organic linkers an almost infinite number of materials can in principle, be synthesized. However, a rational design is very challenging but not impossible. In theory, MOMs

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xxi could be designed and synthesized with tuned functionalities toward specific prope rties that will determine their potential applications The present research involves the design and synthesis of functional porous Metal Organic Materials that c an be used as platforms for specific studies related to many applications such as for example gas storage and particularly hydrogen storage. I n this manuscript, I will discuss the s tudies performed on existing major Metal Organic Frameworks namely Zeolite like Metal Organic Frameworks (ZMOFs) that were design ed and synthesized in my research group My research was also focused on the design and the synthesis of new highly poro us isoreticular materials based on Metal Organic Polyhedra (MOP) where desirable functionality and unique features can be in troduced in the final material prior and/or after the assembly process. T he use of hetero functional ligands for a rational design toward binary or ternary net will also be discussed in this dissertation

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1 Chap ter 1. Background on Metal Organic Materials 1.1. Introduction Metal Organic Materials (MOMs) or coordination polymers (CPs) are organic in organic hybrid compounds constructed from metal ions or clusters and organic components that are linked via coordination bonds to generate zero one two or three periodic structures. The pool of advantages that these materials can offer resulted in a constant industri al and academic growing interest First the hybrid organic inorganic nature of MOMs permits properties of both the organic and the inorganic components to be taken advantage of In addition, t he lability of the coordination bonds and the reversibility of the interaction s permit the formation of highly ordered structures by trial error processes that can be characterized by X ray crystallography. Structures with ordered regular pores and homogeneity throughout the whole material are indeed very important f or optimal properties of the compound s Moreover, t he coordination bond is strong enough to enable the formation of robust structures. Other important benefits include the possibility to somewhat predict the geometry of the coordination by judicious ly choosing the metal Also, the size, the shape and the functionality of the organic ligands can be tune d Finally, the synthesis is done under mild conditions. The following sections will give a brief overview of the coordination polymer history then

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2 mater ials constructed from nitrogen donor ligands, oxygen donor ligands and hetero functional ligands will be discussed L astly, some applications related to these materials will be highlighted. 1. 2 Overview of H istory The so called Werner type complexes, which involve nitrogen metal bonds, are e arly examples of coordination complexes. In fact, these complexes were named after Alfred Werner for his work in the octahedral coordination geometry at the end of the 19 th century. The typical formula of Werner complexes is MX 2 L 4 where M represents the metal in an octahedral geometry (Ni, Co, Fe, Mn, Zn, Cu) X is an anionic ligand (e.g. SCN, CNO, NO 2 ) and L represents a alkylarylamine (figure 1.1.) 1 Figure 1.1. Example of a Werner complex with formula MX 2 L 4 where M represents Ni, X represents NCS and, L is 4 methylpyridine (form ref. 1e). Ni, N, C, S and H are represented in green, blue, grey, yellow and w hite respectively

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3 Other studies include a family of Hofmann clathrates derived from the original compound with formula Ni(NH 3 ) 2 Ni(CN) 4 2C 6 H 6 that w as first discovered by Karl Andrea Hofmann in 1897 2 Afterward, compounds of Hofmann clathrate types were thoroughly investigated by Iwamoto and cow orkers (figure 1.2.) 3 Figure 1.2. A typical Hofmann clathrate structure ( from ref. 3e ) Hydrogen atoms were omitted for clarity. Cu, Ni, N and C are represented as green, yellow, blue and grey respectively. Other early compounds include a coordination compound known as Prussian blue that was first synthesized in the early 18 th century, and although many studies followed after, it was only in 1970 that a structure was determined by X ray diffraction techniques (figure 1.3.). 4

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4 Figure 1.3. Picture of a Prussian Blue structure with formula Mn 3 (Co(CN) 6 ) 2 ( from ref. 4 ). Mn, Co, N and C are represented in green, yellow, blue and grey respectively. It was probably not until 1989 1990 that the interest in coordination polymer really started to grow significantly with a communication and a subsequent full paper by Hoskins and Robson. 5 The authors discussed some design principles to build functional infinite structures, they proposed a way to afford new polymeric materials by linking tetrahedral o r octahedral nodes with rod like units. In these reports, it was emphasized that these materials might display attractive molecular sieves, ion exchange or catalysis properties (by functionalization of the organic linkers). Mechanical and electrical proper ties were also highlighted. A cationic diamond like infinite structure with large pore sizes was obtained (figure 1.4 ).

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5 Figure 1.4. A fragment of a diamond tetracyanotetraphenylmethane ( from ref. 5a ) Hydrogen atoms were omitted for clarity. Cu, N and C are represented in gr een, blue and grey respectively 1. 3 Metal Organic Materials (MOMs) Constructed from Nitrogen donor Ligands Many examples of MOMs built from nitrogen donor ligands were reported by different groups during the 1990 and examples of ligands employed are shown in figure 1.5. Particularly, t he use of bipyridine or pyrazine as linear linker s resulted in a large set of compounds such as bipyridine and Zn, 6,7 Cd with reported catalysis properties 8 Co 9,10 (a 2D structure was also reported with pyrazine and Co 10 ) and Cu (a honeycomb like structure was also obtained after reaction of pyrazine and Cu) 11 Other early examples listed in figure 1.5, include the use of several nitrogen based ligands. 12 16

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6 Figure 1.5. Examples of nitrogen based ligands: a) 1,4 bis(4 pyridyl)butadiyne (from ref. 12) ; b) 1, 2 bis(4 pyridyl)ethane (from ref. 13) ; c) bipyridine ; d) pyrazine ; e) 1,4,5,8,9,12 hexaazatriphenylene (from ref. 14) ; f) 2,4,6 Tri(4 pyridyl) 1,3,5 triazine (from ref. 15) ; g) 1,3,5 tris(3,5 pyrimidyl)benzene ; h) 5,10,15,20 tetra 4 pyridyl 21 H,23H porphine (from ref. 16) Other examples of nitrogen based heterocyclic ligands in which more control over the geometry of the metal involved in the coordination complex is possible, in clude non linear azolate, pyrimidine or imidazolate ligands 17 In fact, the construction of 3 dimensional frameworks with zeolitic topologies using imidazol ate ligands was reported only recently 18 ,19 Other structures were obtained using approaches that involve metal clusters as building blocks with azolate ligands such as pyrazole s or tetrazoles (figure 1. 6 ). 20 2 2 Particularly, remarkable isoreticular structures were obtained with 1,3,5 Tris(2 H tetrazol 5 yl)benzene or 1,3,5 tri p (tetrazol 5 yl)phenylbenzene (figure 1.6 c and d) 21,22 a) b ) c ) d ) e ) f ) g ) h )

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7 a) b ) c ) Figure 1.6. Examples of work done on azolate ligands: a) example of a trigonal building block obtained with 1,4 benzeneditetrazol 5 yl and Mn (from ref. 21) ; b) another example of a trigonal building block obtained with tetramethyl bipyrazole and Ag (from ref. 20) ; c) 1,3,5 tri p (tetrazol 5 yl)phenylbenzene (top left) and 1,3,5 Tris(2 H tetrazol 5 yl)benzene (down left) were used with Cu and Mn to form a cube like cluster s; d) Schematic of the structure obt ained after reaction of CuCl 2 or MnCl 2 and 1,3,5 Tris(2 H tetrazol 5 yl)benzene (from ref. 22 and 23) Hydrogen atoms were omitted for clarity. M, N,C, O, Cl are represented in green, blue, grey, red, light blue respectively 1. 4 Metal Organic Materials (MOMs) Constructed from Oxygen donor Ligands Another group of ligands frequently used to construct coordination polymers are the carboxylic acid family (figure 1.7). In fact, the carboxylic acid ligands can coordinate to metal ions in diverse fashions such as monodentate bis monodentate and bidentate T herefore various possible geometries around the metal ions can result and thus a significantly high diversity of structures can be formed d )

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8 a) b) c) d) Figure 1.7. Examples of carboxylate based ligands: a) Benzene 1,4 dicarboxylic acid ; b) Benzene 1,3 dicarboxylic acid; c) Benzene 1,3,5 tricarboxylic acid; d) Benzene 1,2,4,5 tetracarboxylic acid The coordination via a bis monodentate fashion is particularly intere sting since multinuclear clusters are involved, which enhances the rigidity and the stability of the resulting building block and thus the final network. I n contrast to for example, nitrogen donor ligands such as bi pyridine where bis monodentate types of coordination is not possible. Moreover, upon coordination, the resulting anionic carboxylate is able to counter balance the positive ly charge d metal ion that often precludes the need for counterions. However, systematically generating these buildi ng blocks in situ is quite challenging. Some select metal carboxylate clusters that can be used as building blocks to construct robust 3 dimentional structures are shown in figure 1.8. For example, the M 4 O(RCO 2 ) 6 cluster 24 (basic zinc acetate, figure 1.8a) can be employed as a 6 connected octahedral building unit, the M 2 (RCO 2 ) 4 cluster 25 (so called paddlewheel, figure 1.8b) could be used as a square building unit, and the M 3 O(RCO 2 ) 6 cluster 26 (basic chromium acetate, figure 1.8c) can be utilized as a trigonal prismatic building unit.

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9 Figure 1.8. Select m etal carboxylate cluster s commonly used as Molecular Building Blocks (MBBs): a) Basic zinc acetate used as octahedral building units (from ref 24) ; b) Paddlewheel used as square building units; c) Basic chromium acetate used as trigonal prism units. Hydrogen atoms are omitted for clarity, the metal is shown in green, C and O are shown in grey and red respectively like 27 i.e. a material that remains stable upon removal of solvent molecules present inside the pores, was proven to be possible for MOMs when a revolutionary material was synthesized by Omar M. Yaghi and coworkers. Indeed, the basic zinc acetat e building block was used to build a spectacular porous material with a primitive cubic (pcu) topology referred to as MOF 5 (Metal Organic Framework 5) 2 8 Later, a series of isoreticular materials, the so called IRMOFs were reported with the prototypical MOF 5 representing IRMOF 1 (figure 1.9) 29 T he spectacular exponential grow of reports that was witnessed during the last decade including the industrial interest (e.g. BASF) were most probably initiated by the large potential set of applications offered by these materials. a) b) c)

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10 Figure 1.9. a) Pictures of some organic ligands used to construct isoreticular MOFs named IRMOF n where n is 1 to 16; b) T wo examples representing IRMOFs, left IRMOF 1 and right IRMOF 10. M, C, O, N and H are represented in green, grey, red, blue and white respectively It should be noted that around the same time, Susumu Kitagawa and coworkers also reported a method for synthesizing stable porous networks. A pillaring strategy was proposed, a porous coordination polymer was constructed and the stability of the framework was assessed by methane adsorption isotherms. 30 Other examples of employing molecular building blocks involve the use of the M 2 (RCO 2 ) 4 cluster or paddlewheel. For instance, discrete compounds based on the self assembly of molecular polygons result ing in the formation of small rhombihexahedron polyhedr a that are referred to as nanoballs or Metal Organic Polyhedra (MOP) were synthesized in 2001 by Zaworotko et al. 31 and Yaghi et al. 32 (figure 1.10 a) a) b ) 1 2 3 4 5 6 7 8 1 0 1 2 1 4 1 6

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11 Figure 1.10. Examples of the use of padllewheel building blocks to generate a) Metal organic Polyhedra ( rhombicuboctahedron ) also called nanoball form isophtalic acid; b) C ross linked nanoballs using 1,3 bis(5 methoxy 1,3 benzene dicarboxylic acid)benzene (from ref. 33b) H ydrogen atoms are omitted for clarity. M C, O, N and H are represented in green grey, red, blue and white respectively Later, extensive work by the Zaworotko group resulted in the generation of infinite networks that contain nanoballs as nodes (figure 1.10 b). 33 The M 3 O(RCO 2 ) 6 cluster or trimer 34 was also employed and served as a trigonal prismatic building unit for the construction of porous 3 dimensional networks. For instance, Gerard Ferey and co workers synthesized a porous M etal Organic M aterial with giant pores from chromium and Benzene 1,3, 5 tricarboxylic acid referred to as MIL 100 (Materiaux Institut Lavoisier 100 ) 35 Later, a very porous MOF with the highest surface area at that time, named MIL 101, built from chromium and b enze ne 1,4 d icarboxylic acid was reported. 36 Other materials were reported thereafter with for example trimers based on aluminum or iron 37 38 a) b )

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12 1. 5 Metal Organic Materials Constructed from Hetero F unctional Ligands Hetero functional ligands are organic molecules that contain at least two types of atoms that can serve as donor s for coordination bonds (for example O donor and N donor ) Incorporating multiple donor s within a single ligand increases the variety of building blocks and thus permit s the construct ion of a high er diversity of materials and possibly more complex ones Also, if the donors are close enough, hetero chelation is possible and may enhance the rigidity of the building block by completing the coordination around the metal ion and precluding terminal liga nds. Examples of hetero fun c tional ligands that have been used to build MOMs are shown in figure 1.11. Figure 1.11. Examples of hetero functional ligands that have been used to construct MOMs. Top (from left to right): 2, 3 pyrazinedicarboxylic acid; 4 pyridinecarboxylic acid; 3 pyridinecarboxylic acid; 2,5 pyridine d icarboxylic acid; 2,4 pyridinedicarboxylic acid; 4,5 Imidazoledicarboxylic acid. Bottom (from left to right): 4 pyrimidinecarboxylic acid; 2 pyrimidinecarboxylic acid; 4,6 pyrimidinedicarbo xylic acid; 4 tetrazolylbenzoic acid; 5 tetrazolylisophthalic acid For example, 2,5 pyrazinedicarboxylic was used by Kitagawa and coworkers to construct a material based on hetero chelat ing Cu ligand building blocks, with magnetic

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13 properties. 39 Other early examples of hetero chelation using 2,5 pyrazinedicarboxylic include copper or cobalt chain like coordination polymers. 40 Design strategies based on hetero chelation were later developed by our group using the single metal ion building block approach where a relative control of the coordinati on sphere around the metal ions is possible by a judicious choice of metal ions and ligands. 41 ,42 In fact, directionality of the topology is given by the nitrogen groups and the rigidity of the building block is e nsured by the carboxylate groups that lock the geometry into its place through formation of 5 membered rings. This approach has led to the construction of a large diversity of materials. 43 ,44 Materials of particular interests are the so called Zeolite like Metal Organic Frameworks, in which indium metal ions were reacted with 4,5 Imidazoledicarboxylic acid and remarkable structures with sod and rho topology were obtained (figure 1.12 a). 45 Other structures of particular interest where obtained thereafter, for instance, a material with an unprecedented zeolitic topology, namely usf ZMOF 46 and other zeolite like frameworks using pyrimidine derivatives, 47 and new porous hydrogen bonded Metal Organic cubes. 48 Other hetero functional ligands have the nitrogen and the carboxylate sufficiently far apart so that hetero chelation is not possible. For example, materials built from pyridine derivative ligands, such as 4 pyridinecarboxylic acid, 3 pyridinecarboxylic acid and others, are discussed and their nonlinear o ptical NLO properties highlighted. 49 The use of tetrazolate carboxylic acid hetero functional ligands, such as 4 tetrazolylbenzoic acid, resulted in diverse materials. 50

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14 Figure 1.12 Schematics illustrat ing the strategies to build porous frameworks form hetero functional ligands a) Imidazole 4,5 dicarboxylic acid and Indium ion s were used to generate a zeolitic material refered to as rho ZMOF ; b) Tetrazolylisophthalic acid was used to generate a material with 3,24 connected rht top ology (only a portion of the structure is shown) M, C, O, N and H are represented in green, grey, red, blue and white respectively Another remarkable material was constructed with 5 tetrazolylisophthalic acid where two types of building blocks were produced and an unprecedented ternary net was formed that can also be interpreted as a MOF with rht topology (figure 1.12 b). 51 a) b)

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15 1.6. Appl ications MOMs and especially those that are porous offer many advantages that can be exploited in many applications. Like other porous solids, they possess a unique set of characteristic s, such as high surface area, various pore sizes and geometry, and diverse surface composition and properties Extensive investigations toward the potential industrial use of MOMs have been witnessed and especially a significant amount of work is related to their specific properties. 52 98 Catalysis for instance has attracted the attention of many researchers over the years. Indeed, catalysis in porous materials other than zeolites is possible if several conditions can be met. MOMs offer in fact several advantages and limitations over zeolit es. Higher surface area, pore volume and pore sizes can be achieved with MOMs as well as possible tunability of the organic link in which functionality can be introduce d. However, when compared to zeolites, MOM s are not as ther mally stable and many do not poss ess the so in react ions involving mild conditions 52 Early reports include cyanosilylation of aldehydes in a MOF by Fujita and coworkers in 1994. 8 Other work followed thereafter in which MOF based catalysis was described. 52 73 For example, aldol reactions 53 alkene oxidation 54 or reactions involving porphyrin derivatives as MOF functional struts or as MOF guests. 55 57 Acyl transfer reactions 55 or alkane hydroxylation 56 are examples of possible reactions when porphyrin derivatives are part of the framework skeleton. Examples of p orphyrin derivatives encapsulated in a MOF are very rare though 57 Rosseinsky and others constructed a MOF based on amino acid ligand s which possess a bronsted acid site 58

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16 Other examples include the work of Kitagawa and coworkers, 59 The Ferey group research involving Bronsted basic catalyst s 60 Other work focus ed on the synthesis of homo chiral MOFs 6 1 67 and some homochiral MOFs are capable of enantioselective catalysis 61,68 73 Gas storage and gas separation are also widely investigated in MOFs. Gas storage studies include mainly hydrogen, methane or carbon dioxide. Hydrogen storage will be thoroughly discuss ed in chapter 2. In 2002, Eddaoudi and coworkers reported methane storage application in a family of isoreticular MOFs. 29 Later, Zhou et al. reported the highest uptake in PCN 14. 74 Other examples have been reported 75 Carbon dioxide applications were also studies. For instance the work by Yaghi et al. 76,77 by Ferey and coworkers 78,79 80 Gas separation is another possible application for MOFs and reports of separation of, for example O 2 /N 2 H 2 /CO, H 2 /N 2 81 or H 2 /CO, Ar/N 2 82 or work on MAMs (Mesh Adjustable Molecular Sieves) 83 and work by Kitagawa and coworkers 59,84,85 Others reported CO 2 /CH 4 CO and N 2 separation or C 2 H 2 /CO 2 CH 4 /CO 2 76,86,87 Thomas et al. demonstrated H 2 /D 2 separation. 88 Moreover, MOFs have ideal candidate for a better control of drug release. 89 91 anticancer drug delivery. 92 Some other applications include sensor field 45a,93 or magnetism 94 Post synthetic modification s 95 coordination polymer particle s 96 polymerization reactions 97 or thin films 98 have also been investigated in MOMs. The next chapter will focus on physisorption and Metal Organic Frameworks (MOFs) as H 2 storage materials. In the following chapter s research on the design, synthesis and p ost synthetic modifications on two major platforms will be discussed.

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17 1.7. References Cited 1. a) Lipkowski, J. Comprehensive Supramolecular Chemistry 1996 6 691 714. b) Lipkowski, J. NATO ASI Series, Series C: Mathematical and Physical Sciences 1996 480 265 283. c) Lipkowski, J. Organic Crystal Chemistry 1991 4 27 35. d) Lipkowski, J. Inclusion Co mpo u nds 1984 1 59 103. e) Lipkowski, J ; Suwinska, K ; Andreetti, G D.; Stadnicka, K J. Mol. Struct. 1981 75 101 112 2. Hofmann, K. A. ; Kiispert, F. Z. Anorg. Chem. 1897 15 204 207. 3. a) Iwamoto, T.; Miyoshi, T.; Miyamoto, T. Bull. Chem. Soc. Jpn. 1967 40 1174 1178. b) Iwamoto, T.; Nakano, T.; Morita, M. Inorg. Chim. Acta 1968 2, 313 316. c) Iwamoto, T.; Nakano, T.; Morita, M.; Miyoshi, T.; Miyamoto, T.; Sasaki, Y. Inorg. Chim. Acta. 1968 2 313 316. d) T.Miyoshi, T. Iwamoto and Y. Sasaki, Inorg. Nucl. Chem. Lett., 1970 6 21 24 e) Miyoshi, T.; Iwamoto, T.; Sasaki, Y. Inorg. Chim. Acta. 1973 7 97 101. 4. Ludi, A.; Guedel, H. U.; Ruegg, M. Inorg. Chem. 1970 9 2224 2227. 5. a) Hoskins, B.F ; Robson, R. J. Am. Chem. Soc 1989 111 5962 5964. b) Hoskins, B.F. ; Robson, R. J. Am. Chem. Soc 1990 112 1546 1954. 6. Gable, R.W.; Hoskins, B.F.; Robson, R. J. Chem. Soc., Chem. Commun. 1990 23 1677 1678. 7. Subramanian, S.; Zaworotko, M.J. Angew. Chem 1995 34 2127 2129. 8. Fujita, M.; Kwon, Y.J.; Washizu, S.; Ogura, K. J. Am. Chem. Soc. 1994 116 1151 1152. 9. Losier, P.; Zaworotko, M.J. Angew. Chem. 1997 35 2779 2782. 10. Lu, J.; Paliwala, T.; Lim, S.C.; Yu, C.; Niu, T.; Jacobson, A.J. Inorg. Chem. 1997 36 923 929. 11. MacGillivray, L.R.; Subramanian, S.; Zaworotko, M.J. J. Chem. Soc., Chem. Commun. 1994 11 1325 1326. 12. Abrahams, B F.; Hardie, M J.; Hoskins, B F.; Robson, R. ; Sutherland, E E. J. Chem. Soc., Chem. Commun. 1994 9 1049 1050 13. Fujita, M ; Nagao, S ; Iida, M ; Ogata, K ; Ogura, K J. Am. Chem. Soc. 199 3 11 5 1574 1576

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19 30. a) Kondo, M.; Yoshitomi, T.; Seki, K.; Matsuzaka, H.; Kitagawa, S. Angew. Chem. 1997 36 1725 1727. b) Kondo, M.; Okubo, T.; Asami, A.; Noro, S. I.; Yoshitomi, T.; Kitagawa, S ; Ishii, T ; Matsuzaka, H ; Seki, K Angew. Chem. 1999 38 140 143. 31. Moulton, B.; Lu, J.; Mondal, A.; Zaworotko, M. Chem. Commun. 2001 9 863 864. 32. Eddaoudi, M.; Kim, Jaheon; Wachter, J. B .; Chae, H. K.; O'Keeffe, M.; Yaghi, O. M. J. Am. Chem. Soc. 2001 123 4368 4369. 33. a) McManus, G. J.; Wang, Z.; Zaworotko, M. J. Cryst. Growth Des. 2004 4 11 13. b) Perry, J J.; Kravtsov, V. Ch.; McManus, G. J.; Zaworotko, M. J. J. Am. Chem. Soc. 2007 129 10076 10077. 34. a) Serre, C.; Millange, F.; Surble, S.; Ferey, G Angew. Chem. 2004, 43, 6286 6289. b) Liu, Y.; Eubank, J. F.; Cairns, A. J.; Eckert, J.; Kravtsov, V. Ch.; Luebke, R.; Eddaoudi, M. Angew. Chem. 2007 46 3278 3283. 35 Ferey, G .; Serre, C.; Mellot Draznieks, C.; Millange, F. ; Surble, S.; Dutour, J.; Margiolak i, I Angew. Chem. 2004 43 6296 6301. 36. Ferey, G.; Mellot Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surble, S.; Margiolaki, I. Science 2005 309 2040 2042. 37. a) Loiseau, T.; Lecroq, L.; Volkringer, C.; Marrot, J.; Ferey, G.; Haouas, M.; Taulelle, F.; Bourrelly, S.; Llewellyn, P. L.; Latroche, M. J. Am. Chem. Soc. 2006 128 10223 10230. b) Horcajada, P ; Surble, S ; Serre, C ; Hong, D Y.; Seo, Y. K.; Chang, J. S.; Greneche, J. M.; Margiolaki, I.; Ferey, G. Chem. Commun. 2007 27 2820 2822. 38. Serre, C.; Mellot Draznieks, C.; Surble, S.; Audebrand, N.; Filinchuk, Y.; Ferey, G. Science 2007 315 1828 1831. 39 Okubo, T.; Kon do, M.; Kitagawa, S. Synth.Met. 1997 85 1661 1662 40. a) Richard, P.; Tran, Q. D.; Bertaut, E. F. Acta Crystallogr. Sect. B 1973 29 1111 1115. b) O'Connor, C. J.; Klein, C. L.; Majeste, R. J.; Trefonas, L. M. Inorg. Chem. 1982 21 64 67. 41. Brant, J.A. ; Liu, Y. ; Sava, D.F. ; Beauchamp, D.; Eddaoudi, M. J. Mol. Struct. 2006 796 160 164. 42. Eddaoudi, M.; Eubank, J.F. in Organic Nanostructures ; Atwood, J.L. and Steed, J.W. Eds.; WILEY VCH Verlag GmbH & Co. KGaA: Weinheim, 2008 251 276.

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20 43. Liu, Y.; Kravtsov, V.Ch.; Walsh, R.D.; Poddar, P.; Hariharan, S.; Eddaoudi, M. Chem. Commun. 2004 24 2828 2829. 44. Liu, Y.; Kravtsov, V.Ch.; Beauchamp, D.A.; Eubank, J.F.; Eddaoudi, M. J. Am. Chem. Soc. 2005 127 7266 7267. 45. a) Liu, Y.; Kravtsov, V.Ch.; Larsen, R.; Eddaoudi, M. Chem. Commun. 2006 1488 1490. b) Eddaoudi, M ; Eubank, J F.; Liu, Y ; Kravtsov, V Ch.; Larsen, R. W.; Brant, J. A. Studies in Surface Science and Catalysis 2007 170B (From Zeolites to Porous MOF Materi als), 2021 2029. 46. Liu, Y ; Kravtsov, V Ch.; Eddaoudi, M Angew. Chem. 2008 47 8446 8449. 47. Sava, D F.; Kravtsov, V Ch.; Nouar, F.; Wojtas, L.; Eubank, J. F.; Eddaoudi, M J. Am. Chem. Soc. 2008 130 3768 3770. 48. Sava, D F.; Kravtsov V. Ch.; Eckert, J.; Eubank, J. F.; Nouar, F.; Eddaoudi, M. J. Am. Chem. Soc. 200 9 13 1 10394 10396 49. Evans, O.R.; Lin, W. Acc. Chem. Res. 2002 35 511 522. 50. a) Jiang, T.; Zhao, Y. F.; Zhang, X M. Inorg. Chem. Commun. 2007 10 11 94 1197. b) Yu, Z.; Xie, Y.; Wang, S.; Yong, G.; Wang, Z. Inorg. Chem. Commun. 2008 11 372 376. 51. Nouar, F ; Eubank, J F.; Bousquet, T .; Wojtas, L.; Zaworotko, M. J.; Eddaoudi, M. J. Am. Chem. Soc. 200 8 13 0 1833 1835 52. Lee, J. Y.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. B. T.; Hupp, J. T. Chem. Soc. Rev. 2009 38 1450 1459. 53. Horike, S. ; Dinca, M. ; Tamaki K.; Long, J. R. J. Am. Chem. Soc. 2008 130 5854 5855 54. Lu, Y. ; Tonigold, M. ; Bredenktter, B. ; Volkmer, D. ; Hitzbleck J. ; Langstein, G. Z. Anorg. Allg. Chem. 2008 634 2411 2417 55. Shultz, A. M. ; Farha, O. K. ; Hupp J. T. ; Nguyen, S. T. J. Am. Chem. Soc. 2009 131 4204 4205. 56. Suslick, K. S. ; Bhyrappa, P. ; Chou, J. H. ; Kosal, M. E. ; Nakagaki, S. ; Smithenry D W.;Wilson S. R. Acc. Chem. Res. 2005 38 283 291 57. Alkordi, M. H. ; Liu, Y. ; Larsen, R. W. ; Eubank J. F. ; Eddaoudi, M. J. Am. Chem. Soc. 2008 130 12639 12641

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21 58. Ingleson, M. J. ; Barrio, J. P. ; Bacsa, J. ; Dickinson, C. ; Park H.; Rosseinsky, M. J. Chem. Commun. 2008 11 1287 1289 59. Hasegawa, S. ; Horike, S. ; Matsuda, R. ; Furukawa, S. ; Mochizuki, K. ; Kinoshita Y.; Kitagawa, S. J. Am. Chem. Soc. 2007 129 2607 2614 60. Hwang, Y. K. ; Hong, D. Y. ; Chang, J. S. ; Jhung, S. H. ; Seo, Y. K. ; Kim, J. ; Vimont, A. ; Daturi, M. ; Serre C. ; Frey, G. Angew. Chem. 2008 47 4144 4148. 61. Seo, J. S. ; Whang, D. ; Lee, H. ; Jun, S. I. ; Oh, J. ; Jeon Y. J. ; Kim, K. Nature 2000 404 982 986 62. Kepert, C. J. ; Prior T. J. ; Rosseinsky, M. J. J. Am. Chem. Soc. 2000 122 5158 5168. 63. Bradshaw, D. ; Prior, T. J. ; Cussen, E. J. ; Claridge J. B. ; Rosseinsky, M. J. J. Am. Chem. Soc. 2004 126 6106 6114. 64. Lin, Z. ; Slawin A. M. Z. ; Morris, R. E. J. Am. Chem. Soc. 2007 129 4880 4881. 65. Zhang, J ; Chen, S. M. ; Wu, T. ; Feng P. Y. ; Bu, X. H. J. Am. Chem. Soc. 2008 130 12882 12883. 66. Wu, C. D. ; Lin, W Angew. Chem. 2005 44 1958 1961. 67. Ma L.; Lin, W. J. Am. Chem. Soc. 2008 130 13834 1835. 68. Ma L ; Abney C ; Lin W Chem. Soc. Rev. 2009 38 1248 12 56. 69. Evans, O. R. ; Ngo H. L. ; Lin, W. J. Am. Chem. Soc. 2001 123 10395 10396. 70. Hu, A. ; Ngo H. L. ; Lin, W. Angew. Chem. 2003 42 6000 6003. 71. Tanaka, K. ; Oda S. ; Shiro, M. Chem. Commun. 2008 820 822. 72. Vaidhyanathan, R. ; Bradshaw, D. ; Rebilly, J. N. ; Barrio, J. P. ; Gould, J. A. ; Berry N. G. ; Rosseinsky, M. J. Angew. Chem. 2006 45 6495 6499. 73. Ingleson, M. J. ; Barrio, J. P. ; Bacsa, J. ; Dickinson, C. ; Park H. ; Rosseinsky, M. J. Chem. Commun. 2008 11 1287 1289. 74. Ma S. ; Sun, D. ; Simmons, J. M. ; Collier, C. D. ; Yuan D. ; Zhou, H. C. J. Am. Chem. Soc. 2008 130 1012 1016 75. Ma, S.; Zhou, H. C. Chem. Commun. 2010 46 44 53.

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22 76. Wang, B ; Cote, A P.; Furukawa, H. ; O'Keeffe, M ; Yaghi, O M. Nature 2008 453 207 211. 77. Millward A. R. ; Yaghi, O. M. J. Am. Chem. Soc. 2005 127 17998 17999 78. Bourrelly, S. ; Llewellyn, P. L. ; Serre, C. ; Millange, F. ; Loiseau, T.; Ferey, G. J. Am. Chem. Soc. 2005 127 13519 13521 79. Llewellyn, P. L. ; Bourrely, S. ; Serre, C. ; Vimont, A. ; Daturi, M. ; Hamon, L. ; Weireld, G. D. ; Chang, J. S. ; Hong, D. Y. ; Hwang, Y. K. ; Jhung S. H. ; Frey, G. Langmuir 2008 24 7245 7250 80. Park, M. ; Moon, D. ; Yoon, J. W. ; Chang J. S. ; Lah, M. S. Chem. Commun. 2009 15 2026 2028. 81. Ma, S. Q. ; Wang, X. S. ; Yuan D. Q.; Zhou, H. C. Angew. Chem. 2008 47 4130 4133. 82. Chen, B. L. ; Ma, S. Q.; Zapata, F. ; Fronczek, F. R. ; Lobkovsky E. B. ; Zhou, H. C. Inorg. Chem. 2007 46 1233 1236 83. Ma, S. Q.; Sun, D.; Wang, X. S.; Zhou, H. C. Angew. Chem. 2007 46 2458 2462 84. Matsuda, R ; Kitaura, R ; Kitagawa, S ; Kubota, Y .; Belosludov, R. V.; Kobayashi, T C.; Sakamoto, H. ; Chiba, T ; Takata, M ; Kawazoe, Y ; Mita, Y. Nature 2005 436 238 241 85. Kitaura, R. ; Seki, K. ; Akiyama G. ; Kitagawa, S. Angew. Chem. 2003 42 428 431. 86. Chen, B. ; Liang, C. ; Yang, J. ; Contreras, D. S. ; Clancy, Y. L. ; Lobkovsky, E. B. ; Yaghi O. M.; Dai, S. Angew. Chem. 2006 45 1390 1393. 87. Bourrelly, S.; Llewellyn, P. L.; Serre, C.; Millange, F.; Loiseau T.; Frey, G. J. Am. Chem. Soc. 2005 127 13519 13521 88. Chen, B. ; Zhao, X. ; Putkham, A. ; Hong, K. ; Lobkovsky, E. B. ; Hurtado, E. J. ; Fletcher A. J.; Thomas, K. M. J. Am. Chem. Soc. 2008 130 6411 6423 89. Horcajada, P ; Chalati, T ; Serre, C ; Gillet, B ; Sebrie, C ; Baati, T ; Eubank, J F.; Heurtaux, D ; Clayette, P ; Kreuz, C ; Chang, J S ; Hwang, Y K ; Marsaud, V ; Bories, P Nhi ; Cynober, L ; Gil, S ; Ferey, G .; Couvreur, P. ; Gref, R Nature Mat. 2010 9 172 178.

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23 90. Horcajada, P.; Serre, C.; Vallet Regi, M.; Sebban, M.; Taulelle, F.; Ferey, G. Angew. Che m. 2006 45 5974 597 8 91. Horcajada, P.; Serre, C.; Maurin, G.; Ramsahye, N. A.; Balas, F.; Vallet Regi, M.; Sebban, M.; Taulelle, F.; Ferey, G. J. Am. Chem. Soc. 2008 130 6774 67 80 92. Rieter, W. J.; Pott, K. M.; Taylor, K. M. L.; Lin, W. J. Am. Chem. Soc. 2008 130 11584 1158 5. 93. Allendorf, M. D.; Bauer, C. A.; Bhakta, R. K.; Houk, R. J. T Chem. Soc. Rev. 2009 38 1330 1352. 94. Kurmoo, M Chem. Soc. Rev. 2009 38 1353 1379 95. Wang, Z ; Cohen, S M Chem. Soc. Rev. 2009 38 13 15 13 29 96. Spokoyny, A M.; Kim, D ; Sumrein, A ; Mirkin, C A Chem. Soc. Rev. 2009 38 1218 1227 97. Uemura, T ; Yanai, N ; Kita gawa, S Chem. Soc. Rev. 2009 38 1328 1336 98. Zacher, D ; Shekhah, O ; Woell, C ; Fischer, R A Chem. Soc. Rev. 2009 38 1418 1429

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24 Chap ter 2. Introduction to Physis orption and Hydrogen Storage in P orous Metal Organic Materials 2.1. Introduction to Physisorption Nanoporous materials are a subset of porous materials that have porosity greater than 0.4 and pore diameters 1 100nm 1 With the purpose of standardizing of procedures and terminology, the International Union of Pure and Applied Chemistry (IUPAC) published a manual with classifications and definitions concerning physisorption, determination of surface area and porosity. 2 Ac cordingly, porous materials have been classified according to their pore sizes. Pores with dimensions smaller than 2 nm are thus called micropores, pores with dimensions between 2 nm and 50 nm are named mesopores and pores of dimensions greater than 50 nm are called mesopores. Many methods to characterize the porosity of solids are available and an exhaustive list has been published in the pure and applied chemistry reports. 3 However, gas adsorption remains the most popular method for surface area and pore size determination. In fact, gas adsorption permits the analysis of a wider range of porous materials i.e. from pore sizes of 0.35 nm to > 100 nm; this is therefore a method of choice for characterizing microporous, mesoporous and some macroporous material s. Adsorption can be defined as

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25 the enrichment of one or more components in an interfacial layer (gas/solid interface for gas adsorption) 2,4,5 The solid is referred to the adsorbent, the adsorbable gas is the adsorptive and the fluid in the adsorbed state is the adsorbate. Sorption phenomenon can be classified as chemisorption when chemical interactions are comparable in strength to chemical bonds and as physisorption when weak interactions are involved. For a heterogeneous surface, calculation of surface area can be problematic if strong bonding occurs between the molecules adsorbed and specific sites on that surface. Indeed, surface area can be evaluated after the number of molecules adsorbed on a surface is determined and the cross section area of that m olecule, i.e. the effective area covered by each adsorbate on the surface, is known. 6 However, chemisorbed molecules localized to specific sites can result in spacing between molecules on the surface and therefore result in erroneous evaluation of the surface. Unlike chemisorption, physisorption involves weakly adsorbed molecules that are not restricted to specific sites and are therefore able to cover the entire surface. Also, physisorption is a reversible phenomenon, the equilibrium is rapidly reached and accordingly adsorption and desorption processes can be studied. 6 Consequently, p hysi sorption is a more appropriate method for surface area determination. 2.1.1. Adsorption Forces The principal forces involved in physisorption are the van der Waals forces. The dispersion forces or London forces contribute the most to the total van der waa ls forces. In contrast to other types of forces, they are always present in physical adsorption. The

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26 origin of these forces resides in the fact that, for a non polar entity such as argon for example, at any instant a finite dipole moment exists due to the instantaneous positions of the electrons. These dipoles are able to generate an electric field and therefore induce a dipole in a neighboring atom. The interactions between the two dipoles result in finite instantaneous attractive forces between the atoms. Other types of forces that can occur in physisorption involve a permanent dipole that induces a dipole in another molecule; these forces are called induction forces or Debye forces. Attractive forces can also occur between a charged solid and a polar mol ecule, between a permanent dipole in a molecule and another permanent dipole in another molecule, or between polar molecules and quadrupoles present in molecules such as carbon dioxide and nitrogen for example. 7 2.1.2. Adsorption Isotherms and Isotherm sh apes Sorption isotherms can be defined as plots of the weight of adsorbate versus the pressure at a constant temperature. Indeed, the amount adsorbed depends on the temperature, the pressure and the interaction potential between the adsorbate and the adsor bent. Typically, for pore size characterization, the temperature used for recording isotherms is the temperature of the boiling point of the adsorptive i.e. ~77.3 K for nitrogen or ~87.3 K for argon. Therefore, at pressures below the saturation pressure (i .e. P/P 0 <1 and the saturation pressure: P 0 is 760 mmHg for Ar and N 2 ), a dense monolayer of adsorbate can be formed on the surface and consecutively, a multilayer of increasing thickness can be formed when the pressure increases and approaches P 0 At low pressure, the adsorbed phase coexists with the bulk phase. However, at sufficiently low

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27 temperatures, the gas density in the bulk phase is far lower than the gas density near the surface and thus can be neglected. The density of the bulk phase is no longer negligible at temperatures above the boiling point of the adsorptive due to weaker interactions that occur, and usually higher pressures are needed to achieve a significant coverage. In this case, the adsorbed amount can be determined as the surface exces s 8 and corresponds to the excess amount above the amount that would be present in a reference system of the same volume and wher e the density of gas in the bulk phase and in the surface phase are equal. 9 For gas storage studies, such as hydrogen storage, h igher temperatures are used (usually temperatures of liquid nitrogen or liquid argon) and for high pressure measurement, the density of the bulk phase is not negligible. Therefore, the uptake is reported as excess adsorption and total adsorption. As discus sed above, typically for porosity analysis, the temperatures used are the boiling point temperatures of the adsorptive molecules Sorption isotherms are essential in characterizing porous materials and shapes of isotherms provide valuable insight. The sha pe of the isotherms is in fact due to (i ) the coexistence of the strength of fluid wall interactions and the fluid fluid interactions and (ii ) in the case of the presence of narrow pores, the effect on the state and thermodynamic stability of fluids. The most common sorption isotherms can be classified into six groups according to their respective shapes (figure 2.1). 2 The first types are the reversible type I isotherms also called Langmuir isotherms; these isotherms are characteristic of microporous solids with rather low external surface (compared to internal surface area). The shape of the isotherms is concave to the relative pressure and the amount adsorbed

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28 approaches a limiting value as P/P 0 increases to 1. Here the limiting uptake is due to the a ccessible pore volume (micropore filling) rather than by the internal surface area. High uptakes are obtained at relatively low pressure and can be explained by the fact that the dominant interactions occur between the adsorbate and the adsorbent and since the pores are narrow, the adsorption potentials of the opposite walls are overlapping. Other types of isotherms are obtained for non porous or macroporous solids, and are named reversible type II isotherms. In this case, unrestricted monolayer/multilayer adsorption occurs. In Figure 2.1, point B is used to show the stage where monolayer coverage is achieved and multilayer adsorption starts Figure 2.1. Types of sorption isotherms (IUPAC) 2

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29 Reversible type III isotherms, which are relatively uncommon, are convex to the relative pressure axis over the entire range. The shape of the isotherm suggests that the adsorbate adsorbate interactions are dominant and the adsorbate adsorbent interactions are rather weak. Type IV isotherms have characteristic hyster esis loops; they are typically obtained for mesoporous materials. In this case, the fluid wall interactions are no longer dominant and the interaction between fluid molecules plays an important role that is associated to capillary or pore condensation. Als o, these isotherms exhibit limiting uptake over a high relative pressure range until a critical film thickness is reached in which pore condensation starts and the uptake increases drastically until a plateau that corresponds to a complete pore filling. Th e initial part of the type IV isotherms resembles the initial part present in type II isotherms Type IV isotherms and their respective hysteresis loops types will be further discussed in section 2.1.5. The last type is the type VI isotherm; these isotherm s are represented by stepwise multilayer adsorption on a uniform non porous solid. The height of the steps is associated with the monolayer capacity for each adsorbed layer. 2.1.3. Surface Area E valuation 2.1.3.1. Evaluation by Sorption Isotherms Surface area can be evaluated using sorption isotherms and different methods based on certain assumptions In this chapter we will discuss the two mostly used methods of surface area evalu ation for MOFs, i.e. the Langmuir method and the BET method. In the early 20 th century, Irving Langmuir was able, using a kinetic approach, to describe the

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30 type I isotherm with the assumption that adsorption is limited to a monolayer of adsorbate. 10 The Langmuir theory implies that all sites are equivalent, i.e. the adsorption ene rgy is uniform over the entire surface and t he ability of a molecule to adsorb at a given site is independent of the occupation of the neighboring sites. It is also assumed that the energy of adsorption for the first layer is considerably larger than for t he second and higher layers, therefore, multilayer adsorption is only possible at much greater pressures. 11 The Langmuir equation can be written as: = + where P is the pressure, W and W m are the weight adsorbed at a certain pressure and the weight adsorbed in a completed monolayer respectively, and K is the Langmuir adsorption constant (related to the strength of adsorption). Therefore, a plot of P/W versus P generates a straight line with 1/KW m as the intercept and with a slope of 1 /W m The surface area (S t ) can then be calculated as : = = where N m is the number of molecule of adsorbate in a completed monolayer of unit area, A x and are the cross section area and the molecular weight of the adsorbate respec tively and is the Avogadro number. However, later Brunauer Em mett and Teller extended the Langmuir kinetic theory to multilayer adsorption and consequently a BET equation was proposed to evaluate the surface area. 12 In fact, the BET theory enables the determination of the number of molecules required to form a monolayer even if a complete monolayer is never achieved. Indeed, it is thought that even if the surface sites covered by one, two or more layers vary, the num ber of molecules in each layer remains constant. Here assumptions are that

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31 the energy of adsorption is the same for any layers and a new layer can form before another one is finished. The equation is as follow: [ ] = + Th ere fore, a plot of 1 ( ( 0 / ) 1 ) versus P/P o results in a straight line (figure 2.2) with a slope: = C 1 C and an intercept: i = 1 C W m can then be calculated: = 1 + 1 and as a result the surface area can be evaluated ( = ). The BET constant (C) is related to the energy of adsorption in the first adsorbed layer ( indication of the magnitude of the adsorbent adsorbate interactions). The applicability of the BET theory is limited to t he pressure region in which a straight line ca n be obtained, i.e. the boundary region between monolayer and multilayer adsorption has been determined to be between relative pressures of 0.01to 0.35 for most solids and between 0.01 and 0.05 for microporous solids. Figure 2.2. Schematic of a typical BET plot where the intercept and the slope can be used for surface area evaluation 1 ( ( 0 / ) 1 ) P/P 0 i s

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32 2.1.3.2 Evaluation by Geometrical Means Randall Snurr and Tina Duren, researcher at Northwestern university, developed a method to evaluate the surface area for MOF materials. 13,14 The calculated surface area is referred to as the accessible surface area, in fact, a software was designed to calculate the surface area from a Monte Carlo integration technique using a probe molecule t hat rolls over the framework surface. In contrast to other simulated methods to evaluate the surface area (e.g. Connolly surface area), the accessible surface area is designed to give close values than the one given by common adsorptive (see figure 2.3 ). Figure 2.3. Schematic depicting the accessible surface area (green), the connolly surface area (red ), and the van der Waals surface area (blue ) (from figure 1 in ref.14) The software reads the coordinates of the atoms in the material (a xyz format for the crystallographic data is needed). Other information needed to run the software are, the density of the MOF, the unit cell parameters and the diameter of the atoms present in the

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33 material. 15 The authors reported experimental surface area values of several materials that they compare with the data obtained from their software. A strong correlation was demonstrated between BET experimental surface area and simulated accessibl e surface area. 14 2.1. 4 Pore Volume and Pore Size Characterization 2.1.4 .1. Pore Volume E valuation The total pore volume is often evaluated by assuming that the pores are filled with liquid adsorbate (e.g. nitrogen or argon) at a relative pressure close to unity. The volume adsorbed (V ads ) can then be easily converted to a liquid volume (V liq ): = . Pa and T are the ambient pressure and temperature, respectively, V m is the molar volume of the liquid adsorbate (e.g. 34.7 cm 3 /g for nitrogen) and R is the roentgen constant. 2.1.4.2 Pore Size C haracterization Various models have been proposed to appropriately evaluate the pore size and to assess the pore size distribution. 16 26 For example, the Barrett, Joyner and Halenda (BJH) m ethod 16 the Dollimore and Heal (DH) method 17 the t method of Halsey 18 the de Boer method 19 the Dubinin radushkevitch (DR) method 20 the Dubinin astakhov (DA) method 21 the Horvath kawazoe (HK) method 22 the Saito foley (SF) method 23 or the density functional theory (DFT) and monte carlo simulation methods 24 26 The DFT and

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34 Monte carlo methods, for instance, are considered to lead to a much more accurate pore size analysis and permits characterization ranging from micropores to mesopo res. 6 A generalized adsorption isotherm equation is used to interpret the relation between experimental and simulated isotherms. It is assumed that the total isotherm consist of a number of individual single pore isotherms multiplied by their relative dist ribution over a range of pore sizes. 2.1. 5 Mesoporous Materials and Hysteresis loops Type IV isotherms, which are common for mesoporous materials, usually exhibit hysteresis that is associated to capillary condensation. However, a wide variety of hysteresis loop shapes are possible ( figure 2.3). Figure 2.4 Types of hysteresis loops (IUPAC) 2

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35 Although the origin of hysteresis is not clearly understood, it is established that a clear correlation exist between the shape of the hysteresis and the s tructure of a mesoporous compound, i.e. the geometry of the pores, the pore size distribution or the interconnectivity between the pores for example. 1 Type H1 hysteresis exhibit two branches that are almost vertical and parallel and is often related to well defined pore channels or agglomerate of uniform sphere like pores materials. In type H2 hysteresis, in which the two branches are not parallel, is o ften associated to materials that are disordered and where the distribution of pore size and shape is not well defined. Materials that display type H3 hysteresis typically possess slit shaped pores and materials that exhibit type H4 hysteresis contain also slit shaped pores but include pores in the microporous region. 2.1. 6 Isosteric Heat of Adsorption The process of adsorption is exothermic i.e. heat is usually released when a gas molecule is adsorbed on a surface. This can mainly be explained by the l oss of molecular motion of the gas molecules when they adsorb on a surface. Therefore, stronger adsorbent adsorbate interactions are associated with larger amounts of heat. The differential heat of adsorption can be defined as the heat released as small in crements of adsorptive molecules are added to the surface. The amount of the heat released depends on the strength of the adsorbate adsorbent interaction and the degree of which the surface is already covered with adsorbate. However, since the heat often v aries with surface coverage ( ), it is more convenient to express the heat as an isosteric heat of adsorption

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36 ( Q st ), that is, at constant surface coverage and different temperatures. 6 The method of calculating Qst is based on the Cl ausius Clapeyron equation, i.e. = ln ( 1 / ) where R is the gas constant, P is the pressure and T is the temperature. As a result, at least two isotherms at two different temperatures are needed to evaluate Qst Values of isosteric heat of adsorption at ea ch coverage can be determined by extrapolating the pressure values from the isotherms recorded at dif ferent temperatures (figure 2.4 ). Finally, a plot of the isosteric heat of adsorption vs. coverage values can be generated. Figure 2.5 a) A plot of two isotherms at two different temperatures: If two isotherms recorded at temperature T 1 and T 2 respectively are considered, the isosteric heat of adsorption at a given coverage is: Qst = R((ln P 2 ln P 1 )/((1/T 2 ) (1/T 1 ))). b) A plot of Qst vs the amount adsorbed. For gas storage by physisorption applications, the measure of isosteric heats of sorption in Metal Organic Frameworks (MOFs) is particularly important since it permits to evaluate the adsorbent adsorbate strength and therefore allows a performance comparison of the materials. The next section intends to give a brief overview on hydrogen storage in MOFs by physisorption. a) b)

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37 2.2. Hydrogen S torage by P hysisorption in Metal Organic Frameworks 2.2.1. Introduction to Hydrogen Storage Increasing research efforts are being pursued in order to address some of the major environmental concerns facing the world today. Hydrogen (H 2 ) is regarded as a clean alternative fuel which would permit to overcome several energy concerns. 27 However seve ral conditions need to be met in order for hydrogen to be practical. Indeed, intensive research related to hydrogen production, hydrogen storage, hydrogen delivery or fuel cell technology is being pursued. One of the most challenging problems is the safe a nd efficient storage of hydrogen under mild temperatures and pressures. 28 Since hydrogen contains three times the energy of gasoline per unit mass, in order to lead to the same driving range than gasoline tanks, the US Department Of Energy (DOE) has set capacity targets based on a storage system that would contain 5 kg of H 2 In fact, the complete system, i.e. may include material, tank, regulators, valves, piping, mounting brackets, 2 amounts to permit a driving range greater than 300 miles (480 km). The 2010, 2015 and ultimate targets are as follow: 0 .045 kg H 2 / kg system, 0.055 kg H 2 / kg system and 0.075 kg H 2 / kg system respectively for gravimetric capacities and 0.028 kg H 2 /L 0.040 kg H 2 /L and 0.070 kg H 2 /L for volumetric capacities. Several other parameters also need to be addressed such as system storage cost, minimum and maximum delivery temperature ( 30c to 50c for 2010 and 2015), cycle life (from 1000 to 1500 cycles for 2010 and 201 5 respectively), maximum delivery pressure of around 100 atm for 2010 and 2015, charging and discharging rates (system fill time for 5kg of 3 min for 2 010 and 2.5 min for 2015). In order to satisfy the

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38 space/weight requirement s and efficiently reduce the H 2 volume, the density of hydrogen needs to be greatly increased while minimizing the mass of the system However, under ambient conditions, 5 kg of hydrogen would occupy a volume of up to 60 m 3 which would correspond to a cube of ~3.9 m X 3.9 m X 3.9 m. I t is then clear that the task is extremely challenging. Several pathways involving different kinds of materials have been pursued. This section will focus on some of the work achieved on hydrogen storage by physisorption in Metal Organic Frameworks (MOFs) Metal Organic Frameworks ( MO Fs) are indeed, regarded as a new class of materials that have the potential to overcome many issues related to various applications. Indeed, their facile tunability or the capability to vary the pore size and functionality al most s for such applications. Different parameters that influence the gas uptake will be discussed. 2.2. 2 Current Technology Current technology includes compressed hydrogen gas and liquid hydrogen tanks. C ompressed hydrogen gas tanks are already in use in some prototype hydrogen powered vehicles. Complex reinforced materials are employed to allow a pressure range inside the system of 5000 10000 psi (~344 690 bar). However, safety, volumetric capacity and co st are the major disadvantages. Hydrogen can also be stored in a liquid state. Therefore, more hydrogen can be stored than in high pressure tank s However, the constant boil off, the energy required to liquefy hydrogen and therefore the cost are the m ain drawbacks.

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39 Insulation is needed which in turn reduces the volumetric and the gravimetric capacities. Efforts are currently being pursued in new hybrid tanks which would combine both gas and liquid storage and as a result temperatures required would not be as low and the evaporation would be reduced. 2.2. 3 Physisorption versus Chemisorption Two strategic avenues have mostly been pursued to address the hydrogen storage challenges. Systems based on chemisorption offer high gravimetric capacities however high temperatures are required for hydrogen desorption and non reversibility is a major problem. Physisorption based materials permit, in contrast, reversibility but their gravimetric uptake is far less than that possible with chemisorption. Meta l hydrides and chemical hydrides adsorb hydrogen by a chemisorption process that is, involving strong interactions (>50 kJ/mol) where dissociation of dihydrogen molecules takes place. These types of materials are capable of storing large amounts of hydrog en, thus resulting in high gravimetric uptakes that sometimes surpass the DOE targets. However, facile reversibility is a serious hurdle. Indeed, the energy cost required to regenerate H 2 make s these materials impractical in their present form. 29 On the other hand, physisorption based materials have a significant advantage over chemisorption based materials. Indeed, adsorption and desorption are readily reversible which preclude the need for chemical reactions or high temperatures to release the stored ga s. 30 However, physisorption based materials, including the majority of MOFs, are involved in weak interactions with hydrogen (~ 5 kJ/mol) 31,32 and therefore not strong

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40 enough to store adequate gas amounts i.e. low capacities are usually achieved. As a res ult, gravimetric and volumetric DOE targets at working temperature and pressure are not likely to be achieved. However, extensive efforts are in progress to develop new classes of physisorption based materials with the potential to provide superior perform ance for hydrogen storage. Approaches involving reversible sorption of hydrogen with interactions much stronger than mere physisorption but less than chemisorption are desirable. In fact, to reach H 2 storage DOE targets it has been estimated that a sorptio n based storage system would need H 2 adsorbent binding energies in the range of 15 25 kJ/mol. 33 Several key parameters need to be tuned in order to increase the current binding energy by factors of three to five and improve sorption uptakes at room tempera ture by a factor of around ten These parameters include : 1) availability of significant numbers of accessible open metal binding sites; 2) tunability of organic links to contain more highly polarizable atoms without altering the overall framework structur e; 3) the introduction of a strong electrostatic field in the cavity by having a charged framework, along with extra framework cations (as in zeolites); and, finally, 4) a narrow range of pore sizes (~1 nm), which would allow each H 2 molecule to interact w ith more atoms than on a simple surface. All of these requirements must be accomplished whil e maintaining high surface area without an appreciable increase in framework density (necessary for high loading to maintain higher volumetric and gravimetric uptak es), which points towards light weight constituents and substitutions. Indeed, m ajor current research efforts are thus aimed at making physisorption based hydrogen storage practical. A brief overview of the current investigations will be discussed in the following parts.

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41 2.2. 4 Factors Influencing Hydrogen Storage in MOFs 2.2. 4 .1. Surface Area and Pore V olume As stated above, surface area is a critical parameter to consider. Indeed, the more available surface for H 2 to interact with, the more poten tial for the material to achieve higher performance. There is a clear positive correlation for MOFs between surface area and pore volume (as shown in figure 2.6 a). It seems also that materials of high surface area (and high pore volume) h ave lower densiti es (Figure 2.6 b) Figure 2.6 Correlation between surface area (BET or Langmuir ) and a) pore volume; b) density A complete study on adsorption regimes related to pressure has shown that the uptake of H 2 is mostly dependent on the adsorbate adsorbent binding energy at low pressures (i.e. at pressures below 1 atm). At medium to high pressure, it has been found that the uptake correlates positively with surface area and pore volume. 13 A graph of gravimetric uptake data at high pressure versus sur face area is shown in figure 2.7 It should be noted that for most of the MOFs, the high pressure uptake corresponds in fact to the saturation uptake.

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42 Figure 2.7 Some MOFs gravimetric uptake data at high pressure versus surface area (black for BET surface area and red for Langmuir surface area) The highest surface area recorded to date is for UMCM 2 with 5200 m 2 /g (BET) and 6060 m 2 /g (Langmuir). 34 This surface area surpasses the surface area for MOF 177 35 (4750 m 2 /g and 5640 m 2 /g BET and Langmuir surface area respectively) 36 and for MIL 101 37 (4280 m 2 /g and 5500 m 2 /g BET and Langmuir surface area respectively) 38 H owever, this usually results in materials with lower densities Sorption information on select MOFs with high surface area is given in table 1; it seems that most of the frameworks are neutral and have low densities. It is also worth mentioning that the Q st values obtained are rather low for neutral MOFs that do not have potential open metal binding sites and contain pores with sizes greater than 15 (see the following sections) such as UMCM 2, IR MOF1 or MOF177. For those MOFs, the gravimetric uptake at low pressure is indeed quite low (~1.3 wt %). However, as expected due to the high pore volumes, the gravimetric uptake obtained at high pressure reaches or surpasses 7 wt %.

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43 Table 2.1. Sorption data in select MOFs with high surface area MOFs C. Pore size S.A. BET m 2 /g S.A. Lang m 2 /g d. g/cm 3 P.v. cm 3 /g H 2 77K, 1atm wt% H 2 77K, P>10 atm wt% H 2 77K, P>10 atm g/L Qst kJ/mol ref. UMC M 2 N ~15 27 5200 6060 0.383 1.3 0 6.9 27.5 ~6.4 34 MOF 177 N ~10 15 4746 5640 0.427 1.59 1.25 7.52 32.1 ~4.4 36 MIL 101 N > 25 4230 5500 0.428 1.9 0 2.5 0 6.1 0 26.1 ~10 38 IR MOF20 N ~15 20 4024 4593 0.511 1.53 1.35 6.67 34.1 31,39 IR MOF1 N ~10 15 3800 4400 0.590 1.18 1.32 7.1 0 41.7 ~4.8 40 41 rht like PCN 66 N 13 20 4000 4600 0.411 1.63 42 NOT 112 N 10 20 3800 0.503 1.69 2.3 0 7.07 ~ 5.6 43 PMOF 2 N 3730 4180 0.561 2.21 5 .00 ~9.2 44 PCN 61 N 13 20 3000 3500 0.561 1.36 42 rht 1 C 13 20 2847 3223 0.688 1.01 2.4 0 ~ 9.5 45 IR MOF6 N ~10 15 2476 3263 0.71 0 1.14 1.48 4.9 0 34.9 31 PCN 6 N ~10 15 3800 0.528 1.45 1.9 0 46 C.: Charge of the framework, N for neutral and C for charged; S.A.: Apparent surface area calculated using BET or Langmuir (Lang.) model; Densities (d.) were calculated from completely degassed materials i.e. free of solvent in the cavities or coordinated ; P.v.: Pore volume; Q st is reported as the isosteric heat of adsorption calculated at the lowest coverage; volumetric capacities (g/L) = gravimetric capacity (g/g) x density (g/ d m 3 ). Cells left blank when data was not reported 2.2. 4 .2. Accessible Metal Sites An evidence of an open metal site in a MOF was reported by Yaghi et al. in 2000. A MOF containing M 2 (O 2 CR) 4 paddlewheel building blocks (see figure 2.8 1 ) was built and thermal removal of axial ligands was proven to be successful by single X ray dif fraction methods. 47 The binding of hydrogen molecules to a metal center in a Metal Organic Framework (MOF) was first experimentally demonstrated in 2006 by Bordiga and co workers. 48 The MOF employed for this study was the so called HKUST or Cu 2 BTC 3 (BTC: 1 ,3,5 benzene tricarboxylate) containing M 2 (O 2 CR) 4 paddlewheel building blocks. 49 IR spectroscopy was indeed used to observe the stretching band of H 2 adsorbed into the MOF at 4100 cm 1 48 Later, another group performed low temperature powder

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44 neutron diffraction experiments on HKUST, six sites were evidenced with the most favorable being at close proximity to the copper site of the M 2 (O 2 CR) 4 paddlewheel building block. 50 The Cu 2+ D 2 distance was determined to be 2.39 . Another powder neutron d iffraction study on a Manganese based MOF with a sod topology Mn 3 [(Mn 4 Cl) 3 (BTT) 8 (CH 3 OH) 10 ] 2 (BTT: 1,3,5 benzenetristetrazolate) containing M 4 Cl(N 4 CR) 8 building blocks, revealed that the Mn 2+ D 2 distance is shorter, i.e. 2.27 (figure 2. 8 4 an d table 2.2 ). 51 Figure 2.8 Pictures of selected building blocks that possess potential open binding sites. 1 : M 2 (O 2 CR) 4 ; 2 : M 3 O(O 2 CR) 6 ; 3 : M 3 O(N 4 CR) 3 ; 4 : M 4 Cl(N 4 CR) 8 ; 6 : M 3 (N 4 CR) 6 ; 5 and 7 : Chain like motifs Potential H 2 biding sites are represented as yellow spheres; green, blue, red, grey, light blue, purple and orange represent the metal, N, O, C, Cl, Na and S, respectively. These distances are consistent with the observation that H 2 binds stronger in the Manganese based compound than in the HKUST. 31 Indeed, the low coverage isosteric

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45 heats of adsorption for the copper and for the Mn compound are 6.8 kJ/mol and 10.1 kJ/mol respectively. It should be noted that this Mn based MOF is a r are example of a MOF with surface area lower than 2500 m 2 /g and yet a quite high gravimetric capacity at high pressure, i.e. 5.1 wt%. Later, a copper based MOF with sod topology (HCu [( Cu 4 Cl) 3 (BTT) 8 ] 3.5 HCl) isostructural to the Mn based compound was synth esized and neutron diffraction studies showed that Cu 2+ D 2 distance is 2.47 . 52 Here, the heat of adsorption recorded at low coverage was lower (9.5 kJ/mol). However, the heat was higher over the entire pressure range. Several strategies to incorporate metal sites within a MOF were reported. One way to incorporate metal sites in a MOF is to practice ion exchange 53 55 In fact, Long et al. conducted studies on the Manganese based compound and subsequent ion exchanged materials in the form of M 3 [(Mn 4 Cl) 3 ( B TT ) 8 (CH 3 OH) 10 ] 2 xMCl 2 (M=Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ ; x= 0 2) suggested that the isosteric heat of adsorption at low coverage ranges from 8.5 kJ/mol for the Cu exchange compound to 10.5 kJ/mol for the Co exchanged MOF (see table 2.2 ). Other neutron diffraction experiments included the use of MOF 74 where the Zn 2+ D 2 distance was estimated to be 2.6 . 56 The authors suggested that the presence of open metal sites lead to high hydrogen surface packing, and D 2 D 2 distances of 2.85 , which are even shor ter than intermolecular distances in solid hydrogen (i.e. 3.6 ), have been reported. 60 I sosteric heat s of adsorption have been reported for o ther selected MOFs with potential accessible open metal sites and are listed in table 2.2 (see also figure 2. 8 for the list of building blocks (BB) involved).

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46 Table 2.2. Sorption data in select MOFs containing potential open metal sites MOFs Other names BB S.A. BET m 2 /g S.A. Langmuir m 2 /g Qst kJ/mol H 2 77K, 1atm wt% H 2 77K, P>10 atm wt% ref Zn 3 (BDC) 3 .Cu(Pyen) 12.29 1.55 64 Co 3 [(Mn 4 Cl) 3 (BTT) 8 1.7 CoCl 2 4 2096 2268 10.5 0 2.12 a 54 NaNi 3 (OH)(SIP) 2 7 700 10.4 0 0.94 57 Fe 3 [(Mn 4 Cl) 3 (BTT) 8 FeCl 2 4 2033 2201 10.2 0 2.21 a 54 Mn 3 [(Mn 4 Cl) 3 (BTT) 8 (CH 3 OH) 10 ] 2 4 2057 2230 10.1 0 2.23 a 5.1 51 Cr 3 OF( BDC ) 3 MIL 101 2 4230 5500 10.0 0 2.5 0 6.1 37 Mn 3 [(Mn 4 Cl) 3 (BTT) 8 ] 2 0.75CuPF 6 4 1911 2072 9.9 0 2.0 0 a 54 Zn 3 [(Zn 0.7 Mn 3.3 Cl) 3 ( BTT ) 8 ] 2 2ZnCl 2 4 1927 2079 9.6 0 2.1 0 a 54 Cu 6 O(TZI) 3 (NO 3 ) rht 1 1,3 2847 3223 9.5 0 2.4 0 45 HCu[(Cu 4 Cl) 3 ( BTT ) 8 ] 3.5HCl 4 1710 1770 9.5 0 2.42 a 4.2 52 Ni 2.75 Mn 0.25 [(Mn 4 Cl) 3 ( BTT ) 8 ] 2 4 2110 2282 9.1 0 2.29 a 54 Li 3.2 Mn 1.4 [(Mn 4 Cl) 3 ( BTT ) 8 ] 2 0.4 LiCl 4 1904 2057 8.9 0 2.06 a 54 Zn 3 ( BDT ) 3 6 640 8.7 0 1.46 a 58 Cu 3 [(Cu 2.9 Mn 1.1 Cl) 3 ( BTT ) 8 ] 2 2CuCl 2 4 1695 1778 8.5 0 2.02 a 54 Mn 3 ( BDT ) 3 6 290 8.4 0 0.97 58 Zn 2 (DHTP) MOF 74 5 783 1132 8.3 0 1.77 2.3 31 Cu 3 (BTC) 2 HKUST 1 1507 2175 6.8 0 2.5 0 31 [In 3 O(ABTC) 1.5 ](NO 3 ) Soc MOF 2 1417 6.5 0 2.61 a 59 a at 1.2 bar; S.A.: Apparent surface area; BB: Building blocks with potential open metal sites; BTT: 1,3,5 benzenetristetrazolate ; SIP: 5 sulfoisophthalate ; TATB: s triazine 2,4,6 triyltribenzoate ; BDC: 1,4 benzenedicarboxylate ; TZI: 5 tetrazolylisophthalate ; BDT: 1,4 benzeneditetrazolate ; DHTP: 2,5 dihydrox yterephthalate ; BTC: 1,3,5 benzenetricarboxylate ; ABTC: The table shows that indeed, the presence of metal binding sites is important to improve the hydrogen molecule MOF interactions T he reported data at low pressure indicate s that higher gravimetric uptake can be achieved as opposed to neutral MOFs without open metal binding sites where high gravimetric uptakes are usually obtained only at high pressure (i.e. > 50 bars). It should be noted that for most of the MOF s in table 2 .2 surface area s are lower than 2500 m 2 /g except for rht 1 and MIL101. These are

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47 rare examples of MOFs that combine potential metal binding sites and high surface areas, the low pressure gravimetric uptakes are equal or higher than 2.4 wt%. It is also important to realize that the heat of adsorption values reported are obtained at very for low surface coverage, i.e. from data at very low pressure which does not necessarily reflect the overall effect over the full pressure range. Therefore, in these case isosteric heat of adsorption could be erroneous. Indeed, for soc MOF, a MOF build from M 3 O(O 2 CR) 6 (figure 2.8 2 the reported Qst is 6.5 kJ/mol and this value is relatively stable over the entire range of pressure. 59 In fact, one of the highest low pressure gravimetric uptakes was reported for this MOF, i.e. 2.61 wt% and a density of H 2 inside the pores as high as 0.05 g /cm 3 has been calculated which approaches the density of liquid H 2 at 20K (0.0708 g/cm 3 ). This high gravimetric uptake was in fact attributed to the combined effects of potential metal binding centers, high localized charge density and narrow pores. 61,62 However, due to the rather low surface area and pore volume (0.5 cm 3 /g), the performance at higher pressure is expected to be lower than 6 wt%. Another material constructed from M 2 (O 2 CR) 4 paddlewheel building blocks, named PCN 12, shows the highest record ed gravimetric uptake achieved at low pressure (1 bar and 77K). 63 A value of 3.05 wt% at 1 bar and 77K was obtained and was attributed to close packing alignment of the metal binding sites. It is suggested that not only the presence of metal sites, but als o their orientation and close packing, is an important strategy to improve the overall binding affinities between H 2 and the MOF and therefore, increase the gravimetric uptakes at low pressure. Surface area

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48 and pore volume were recorded (Langmuir: 2425 m 2 g 1 BET: 1943 m 2 g 1 ; Pore volume: 0.94 cm 3 /g), however, the isosteric heat of adsorption was not reported. An isosteric heat of adsorption of 12.29 kJ/mol was reported for a MOF with the formula: Zn 3 (BDC) 3 This high value was achieved by incorporating metal binding sites in the ligand. However, this value is not only attributed to open metal centers but also to narrow pore sizes present (see following sections). 64 It is therefore acknowledged that the presence of potential metal bindin g sites in a MOF will have a positive effect on the gravimetric uptakes at low pressure. Several strategies were chosen to introduce unsaturated metal sites in MOFs, and the most predominant is to build a MOF from bridging metal clusters that possess termi nal ligands that can be removed. Other strategies include the construction of anionic MOFs and introduction of metal species by ion exchange, and using bridging ligands that can incorporate metal centers. It should also be mentioned that orientation and ef ficient packing of the open metal sites while maintaining high surface areas and pore volumes could play a major role in the overall performance of the MOFs. For instance, Thomas et al. from Zinc and salen type schiff base of pyridine de rivative in which Copper metal sites were incorporated; the high heat of adsorption of 12.29 kJ/mol was attributed to the presence of metal binding sites but also to the small pore sizes. 64 So far, for most of the MOFs with potential metal binding sites an d high H 2 uptakes at low pressure, the surface area and pore volumes are rather low. And therefore, these storage materials are expected to saturate quickly, i.e. high pressure gravimetric uptake are or are expected to be lower than 6 wt%.

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49 2.2. 4 3 Polariz able Ligands Another approach to enhance the hydrogen molecule MOF interaction is to use polarizable ligands that should permit to induce a dipole in the hydrogen molecule and therefore increase the binding affinities. Systematic studies on polariza ble ligands and the subsequent effect on heat of adsorption are very rare. For example, a systematic study was attempted by Kimoon Kim and coworkers, a series of MOFs was synthesized using linkers with different functionalities (e.g. Fluorine derivatives). 65 It has been reported, however, that the overall performances were in fact very similar. Other studies by Yaghi et al. involved a series of IRMOFs and it has been concluded that functionalization does not have a significant influence on the amount adsorb ed. 31 Theoretical studies by Mulder and coworkers indicated that the substitution of ligands with halogen has little effect and the weight added may be detrimental to the overall performance. 66 However, a true correlation between isostructures with functi onalized ligands and the effect on the performance i.e. the effect on Qst values (at low or high loadings) is still unclear. Therefore, more sim ulation and experimental studie are needed to clearly understand the effect of functionalization on H 2 storage. 2.2. 4 4 Pore Size Another critical parameter to consider is pore size. MOFs with large pores will often produce empty space, away from the walls, that will contribute little to the overall H 2 uptake of the MOF at pressure and temperature close to ambient and often lead to poor volumetric performance. In order to maximize the H 2 MOF interactions and therefore

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50 increase the uptake capacity, MOFs with smaller pore sizes are beneficial. Indeed, sma ller pore sizes would enable H 2 to interact with more atoms than on a simple surface and improve the overall affinities by enabling the adsorption potentials in opposite walls to overlap. In fact, studies on pure carbon materials demonstrated that hydrogen binding energy of up to 15 kJ/mol can be obtained and are correlated to confined geometry effects. 67 Other simulation studies on single walled carbon nanotubes and idealized carbon slit pores have demonstrated that the highest H 2 uptake at 77K are correla ted with optimized pore size of 6 for low pressure and 9 for high pressure. 68 In MOFs systematic studies on the correlations between pore size as a single varying parameter and heat of adsorption are lacking. Multiple parameters, such as geometry of pores or presence of counter ions, do not permit a simple and direct correlation. For instance, desorption studies of hydrogen in some selected Metal Organic Frameworks have shown that hydrogen adsorbed in cavities of different sizes is desorbed at differ ent temperatures. 69 It has been concluded that at high hydrogen concentrations, the heat of adsorption is mainly correlated to pore size. The reduction of pore sizes while maintaining high surface area and pore volume is therefore favorable. Different path ways have been pursued to produce MOFs with reduced pore sizes. The most predominant strategy being the so Organic Frameworks the interpenetration of two or more frameworks. This method can be used to generate reduced pore sizes and free volume materials at the same time. However, controlling interpenetration is very challenging and examples of the synthesis of interpenetrated MOFs with non interpenetrated counterparts are very rare. 70 A systematic

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51 stud y on the effect of interpenetration on hydrogen uptake was reported by Zhou et al. in 2007. 71 Two MOFs: PCN 6 for the interpenetrated framework and PCN interpenetrated framework, based on copper paddlewheel and 4,4 ,4 s triazine 2,4,6 triyl tribenzoate linkers were synthesized. The interpenetrated MOF shows 41% increase in surface area, 29% increase of the gravimetric uptake at low pressure and 77K and 133% increase of the volumetric uptake. Other approaches involved the use of bulky groups carborane based ligands were used in attempts to form MOF 5 structural analogues with reduced pore size. 72 However, other MOFs with low surface area were obtained and a systematic st udy on pore size was undertaken. The gravimetic uptake at low pressure for the MOF with the smallest pores (~ 5) was 2.1 wt%, which is high for a MOF with a surface area of only 152 m 2 /g. Other work on hydrogen affinity and pore size correlations include the studies from Thomas et al. 64 Recently, a MOF constructed from cadmium and ethyl tetrazolate 5 carboxylate was reported where a record heat of adsorption of 13.3 kJ/mol was reporded. It was suggested that the high binding affinity of hydrog en is due to the small pore size and to the tetrazolyl ring decorated surface of the pores. 73 T ab le 2.3 lists some selected MOFs in which work was involved on reducing pore size (i.e. < 1nm) to enhance the hydrogen binding affinities. However, reports on MOFs involving systematic studies on pore size as a single parameter and the effect on the heat of adsorption are very rare.

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52 Table 2.3 Sorption data in selected MOFs with reduced pore sizes MOFs Other names S.A. BET m 2 /g S.A. Langmuir m 2 /g Qst kJ/mol H 2 77K, 1atm wt% H 2 77K, P>10 atm wt% ref Cd 5 (Tz) 9 (NO 3 ) 3 310 338 13.3 0 0.75 73 Zn 3 (BDC) 3 .Cu(Pyen) 12.29 1.55 64 Cu 3 [(Cu 4 Cl) 3 (TPB 3TZ) 8 ] 2 11CuCl 2 1120 1200 8.2 0 2.8 74 [Zn 3 (OH)( p CDC) 2.5 152 7 .00 2.1 0 72 [In 3 O(ABTC) 1.5 ](NO 3 ) Soc MOF 1417 6.5 0 2.61 a 59 Cu 3 (TATB ) 2 PCN 6 3800 2.9 0 71 Tz = tetrazolate; BDC : 1,4 benzenedicarboxylate ; CDC: 1,12 dihydroxycarbonyl 1,12 dicarba closo dodecaborane ; TPB: 1,3,5 tri p (tetrazol 5 yl)phenylbenzene ; ABTC: azobenzene 3,3 ,5,5 tetracarboxylate ; TATB: 4,4 ,4 s triazine 2,4,6 triyltribenzoate Although i t is clearly acknowledge d that reduced pore size will increase the binding affinities the challenge is however to construct materials with small pore sizes that still maintain h igh surface areas and not too high densities. As discussed above, platforms are needed to perform full studies and demonstrate clearly th e correlation between pore size and heat of adsorption in MOFs. 2.2. 4 .5 Electrostatic Field The positive effect of an electrostatic field in the cavities of zeolites on hydrogen molecule material binding affinities has been known for years. 75,76 However, reports on the importance of an electrostatic field in MOFs are rare. For instance, researchers in my group highligh ted the importance of the highly localized charge density in soc MOF. 59 The superior performance of this material, at 77K and 1 atm, has been also attributed to narrow pore sizes and presence of open metal sites. Later, simulation studies on the same mater ial demonstrated that indeed the presence of charges is partly responsible of the

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53 high density of H 2 in the MOF. 61 The high performance was also attributed to the high polarizability of the azo benzene ligands. In a more recent report, a study on electrost atics and the effect of H 2 material interactions was undertaken by us with the so called zeolite like MOFs. 55 It was indeed demonstrated, as in inorganic zeolites, that the presence of an electrostatic field in the c avity is largely responsible for the imp roved heat of adsorption by as much as 50% when compared to neutral MOFs. This full study will be further discussed in chapter 4. 2.2. 5 Other Modifications 2.2. 5 1 S pillover S pillover can be defined as the dissociative chemisorption or adsorption of hydrogen molecule on a metal and the migration of atomic hydrogen to the surface of a support (e.g. alumina, silica or carbon). 77 ,78 Recently, Ralph T. Yang and coworkers from the department of chemical engineering at University of Michigan applied the concept of spillover in MOFs. It has been proposed that the generation of bridges (activated carbon) between the metal (Pt) and the sup port (the MOF) enhances spillover. 79 82 Table 2.4 summarizes the results obtained by spillover in comparison to data recorded after typical sorption experiments and by different investigators. The authors demonstrated that their carbon bridge technique lea ds to superior performance on some select MOFs. Indeed, the hydrogen uptake can be increased by a factor 8 for IRMOF 8 reaching a record uptake at room temperature of 4 wt%. 80

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54 Table 2.4. Sorption data obtained from spillover experiments in MOFs compared to the data from typical experiments. MOFs Regular experiment Spillover experiment H 2 uptake wt%, 298K r ef. H 2 uptake wt%, 298K r ef. IRMOF 8 0.4 0 (30 bar) 83 4 .00 (100 bar) 80 IRMOF 1 0.45 (60 bar) 83 3 .00 (100 bar) 80 MOF 177 1.5 0 (100 bar) 81 MIL 101 0.43 (80 bar) 38 1.43 (100 bar) 82 HKUST 0.35 (65 bar) 84 1.12 (100 bar) 82 T he bridge formation and the mechanism of hydrogen storage via spillover are still unclear. 27b However; this new approach stimulated significant worldwide interests and indicates the capability of MOFs to perform at ambient temperature. 27a Future experiments on other materials may lead to even higher uptakes. 2.2. 5 .2. Sample Activation P roper sample activatio n prior to sorption studies is essential. Indeed, obtaining accurate and reproducible data is critical. It permits to achieve optimized results, to compare and to assess correctly performances among the MOFs. 2.2.5.2. 1. Solvent Exchange T he solvent exchange method has been typically employed and corresponds to the replac ement of the solvent molecules inside the pores of the framework by low boiling point solvents For instance, a report by Eddaoudi and coworkers in 2000 indicated that the guests in the original as synthesized MOF 5 can be fully exchanged with

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55 ch loroform. 85 The chloroform guests were than easily evacuated from the pores without loss of framework periodicity. 2.2.5.2. 2. Supercritical CO 2 A ctivation The unusual chemical and physical properties of carbon dioxide (CO 2 ) permit its use in applications involving preservation and stabilization of delicate structures. Indeed, for sample drying experiments, sudden changes of fluid densities (from liquid to gas) in the bulk of delicate materials is not desirable and could lead to alt eration of the structures due to surface tension forces. In fact, most liquids have a well defined critical point at a specific temperature and pressure at which the densities of the gas and the liquid phase of the transitional fluid are equal and no true phase boundary exist s W ith a critical pressure of 1072 psi (~7.4MPa, 73 bar) and a reasonably low critical temperature of 31C Carbon dioxide is a solvent of choice for activation purpose s Once the critical point transition has taken place, the gas phase can be removed from the sample with no damages from surface tension forces. It was only recently that this technique was applied and used for the activation of MOFs. Traditional activation involved low boiling point solvent evaporation and was successful for many materials. However, some structures lack of robustness and especially those with large pore sizes and often results in framework collapse upon removal of solvent molecules It has in fact supercritical CO 2 activation is a beneficial for such MOFs. 86 Four MOFs have been employed and different activation processes were compared to CO 2 activation. The

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56 authors reported either substantial or spectacular surface area increase (up to 1200 %) that was explained by the inhibition of mesopores collapse This technique has been employed for hybrid microporous/mesoporous rht MOFs and lead to impressive results (see chapter 3). 2.2.6 Conclusion Hydrogen storage by physisorption in MOFs is still under investigation. Indeed fundamental understanding of hydrogen phy sis orption process is still lacking. 27a Although the gravimetric and volumetric uptakes are still far below the DOE targets, there is still room for many results that may prove the advantages of MOFs over ot her materials However, systematic studies to enhance the understanding are too rare. Platforms are needed and should enable a better understanding of hydrogen physisorption in these materials. During my research, new isoreticular MOFs were synthesized and preliminary data demonstrates that they can be used as platforms for many studies related to various application s and especially hydrogen storage. These platforms will be described in chapter 3. Other existing platforms based on MOFs with zeolitic topology were employed and systematic studies were performed and will be discussed in chapter 4.

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57 2.3. References Cited 1. Lu, G. Q.; Zhao, X. S. Nanoporous Materials Science and Engineering Vol. 4, Imperial College Press, London 2004 2. Sing, K. S. W.; Everett, D. H.; Haul, R. A. W.; Moscou, L.; Pierotti, R. A.; Rouquerol, J.; Siemieniewska, T. Pure and Appl. Chem 1985 57 603 6 19. 3. Rouquerol, J.; Avnir, D.; Fairbridge, C. W.; Everett, D. H.; Haynes, J. H.; Pernicone, N.; Ramsay, J. D. F.; Sing, K. S. W.; Unger, K. K. Pure and Appl. Chem 19 94 66 1739 1758 4. Everett, D. H. Pure and Appl. Chem 19 72 31 577 638 5. Burwell, R. L. Pure and Appl. Chem 19 76 46 71 90 6. Lowell, S.; Shields, J. E.; Thomas, M. A.; Thommes, M. Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density Kluwer Academic Publishers Dordrecht 2004 7. Israelachvili, J. N. Intermolecular and Surface Forces with Applicatioins to Colloidal and Biological Systems Academic Press, London 1985 8. Gibbs, J. W. The Collected Works Vol.1, Yale University Press New, Haven 1957 9. Everett, D. H. Pure and Appl. Chem 19 72 31 579 10. Langmuir I. J. Am. Chem. Soc. 1918 40 1361 1402 11. Rouquerol, F.; Rouquerol, J.; Sing, K. Adsorption by Powders and Porous Solids: Principles, Methodology and Applications Academic Press, San Diego 1999 12. Brunauer, S. ; Emmett, P. H.; Teller, E J. Am. Chem. Soc. 19 38 6 0 309 319 13. Frost, H. ; Dren, T. ; Snurr, R.Q. J. Phys. Chem. B 2006 110 9565 9570 14. Duren, T.; Millange, F. ; Ferey, G ; Walton, K S.; Snurr, R Q. J. Phys. Chem. C 200 7 111 15350 15356. 15. Rappe, A. K.; Casewit, C. J.; Colwell, K. S.; Goddard, W. A.; Skiff, W. M. J. Am. Chem. Soc. 1992 114 10024 10035. 16. Barrett, E. P. ; Joyner L. G. ; Halenda, P.P. J. Am Chem. Soc. 1951 73, 373 380. 17. Dollimore, D.; Heal, G. R J. Appl. Chem. 1964 14 109 1 14.

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58 18. Halsey, G J Chem Phys. 1948 16 931 937. 19. de Boer, J. H.; Linsen, B. G.; van der Plas, Th.; Zondervan, G. J. J. Catal. 1965 4 649 653. 20. Dubinin, M. M.; Radushkevich, L. V. Dokl. Akad. Nauk. SSSR 1947 55 327 32 9. 21. Dubinin, M. M.; Astakhov, V. A Adv. Chem. Ser. 1971 102 69 85. 22 Horvath, G. ; Kawazoe, K J. Chem. Eng Jpn 1983 16 470 47 5. 23. Saito, A.; Foley, H. C. AIChE J. 1991 37 429 4 36. 24. Evans, R.; Marconi, U. M. B.; Tarzona, P. J. Chem. Soc. Faraday Trans. II 1986 82 1763 25. Ravikovitch, P. I.; Vishnyakov, A.; Neimark, A. Phys. rev. E 2001 64 011602. 26. Neimark, A V.; Ravikovitch, P I.; Vishnyakov, A. J. Phys.: Condens. Matter 2003 15 347 365. 27. a) Satyapal, S. 2009 Annual Progress Report DOE Hydrogen Program, Washington 2009 Available online at: http://www.hydrogen.e nergy.gov/; b) Gross, K.J.; Carrington, R.K.; Ba rcelo, S.; Karkamkar, A.; Purewal, P.; Parilla, P., Hyd 2009 V2 64 U.S. D.O.E. Hydrogen Program, available online at: http://www1.eere.energy.gov/hydrogenandfuelcells/ c) Hydrogen Program, 2009 Annual Merit Review and Peer Evaluation Report, Arlington May 18 22, 2009 Available online at: http://www.hydrogen.energy.gov/ 28. DOE Office of Energy and Efficiency and Renewable Energy. Hydrogen Storage Technical Plan, April 2009 : http://www1.eere.energy.gov/hydrogenandfuelcells / 29. Schlapbach L; Zuttel A. Nature 2001 414 353 358. 30. Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Kim, J.; O'Keeffe, M.; Yaghi, O. M. Science 2003 300 1127 1130. 31. Rowsell, J. L. C.; Yaghi, O. M. J. Am. Chem. Soc. 2006 128 1304 1315. 32. Sagara, T.; Klassen, J.; Ortony, J.; Ganz, E. J. Chem. Phys. 2005 123 014701/1 014701/4. 33. Myers, A. L. Langmuir 2006 22, 1688 1700.

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59 34. Koh, K.; Wong Foy, A. G., Matzger, A. J. J. Am. Chem. Soc. 2009 131 4184 4185. 35. Chae, H. K.; Siberio Perez, D. Y.; Kim, J.; Go, Y. B.; Eddaoudi, M.; Matzger, A. Nature 2004 427 523. 36. H. Furukawa, M. A. Miller and O. M. Yaghi, J. Mater. Chem. 2007, 17 3197 3204. 37. Ferey, G.; Mellot Draznieks, C.; Serre, C.; Millange, F.; Dutour, J.; Surble, S.; Margiolaki, I. Science 2005 309 2040 2042. 38. Latroche, M.; Surble, S.; Serre, C.; Mellot Draznieks, C; Llewellyn, P. L.; Lee, J. H.; Chang, J. S.; Jhung, S. H.; Ferey, G Angew. Chem. 2006 45 8227 8231 39. Wong Foy, A. G.; Matzger, A. J.; Yaghi, O. M. J. Am. Chem. Soc. 2006 128 3494 3495. 40. Rowsell, J. L. C.; Millward, A. R.; Park, K. S.; Yaghi, O. M. J. Am. Chem. Soc. 2004, 126 5666 5667. 41. Kaye, S. S.; Dailly, A.; Yaghi, O. M.; Long, J. R. J Am. Chem. Soc. 2007, 129 14176 14177. 42. Zhao, D.; Yuan, D.; Sun, D.; Zhou, H. C. J. Am. Chem. Soc. 2009 131 9186 9188. 43. Yan, Y.; Lin, X.; Yang, S.; Blake, A. J.; Dailly, A.; Champness, N. R.; Hubberstey, P.; Schroeder, M. Chem. Commun. 2009 9 1025 1027. 44. Hong, S.; Oh M.; Park, M.; Yoon, J. W.; Chang, J. S.; Lah, M. S. Chem.Commun. 2009 36 5397 5399. 45. Nouar, F., Eubank, J. F., Bousquet, T., Wojtas, L., Zaworotko, M. J.; Eddaoudi, M. J. Am. Chem. Soc. 2008 130 1833 1835. 46. Ma, S. Q.; Sun, D. F.; Ambrogio, M.; Fillinger, J. A.; Parkin S.; Zhou, H. C. J. Am. Chem. Soc. 2007 129 1858 1859. 47. Chen, B. L.; Eddaoudi, M.; Reineke, T. M.; Kampf, J. W.; O'Keeffe M.; Yaghi, O. M. J. Am. Chem. Soc. 2000 122 11559 11560 48. Prest ipino, C.; Regli, L.; Vitillo, J. G.; Bonino, F.; Damin, A.; Lamberti, C.; Zecchina, A.; Solari, P. L.; Kongshaug, K. O.; Bordiga, S. Chem. Mater. 2006 18 1337 1346.

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60 49. Chui, S. S. Y.; Lo S. M. F.; Charmant, J. P. H.; Orpen, A. G.; Williams, I. D. Scie nce 1999 283 1148 1150. 50. Peterson, V. K.; Liu, Y.; Brown, C. M.; Kepert, C. J. J. Am. Chem. Soc. 2006 128 15578 15579. 51. Dinca, M. ; Dailly, A. ; Liu, Y. ; Brown, C. M. ; Neumann, D. A. ; Long, J. R. J. Am. Chem. Soc. 2006 128 16876 16883 52. Dinca, M ; Han, W S ; Liu, Y ; Dailly, A ; Brown, C M.; Long, J R Angew. Chem. 2007 46 1419 1422. 53. Liu Y ; Kravtsov, V. Ch.; Larsen, R. ; Eddaoudi M Chem. Commun. 2006 14 1488 14 90. 54. Dinca, M. ; Long, J. R. J. Am. Chem. Soc. 2007 129 11172 11176 55. Nouar, F ; Eckert, J ; Eubank, J F.; Forster, P ; Eddaoudi, M J. Am. Chem. Soc. 2009 131 2864 2870. 56. Liu, Y. ; Kabbour, H. ; Brown, C. M. ; Neumann, D. A. ; Ahn, C. C. Langmuir 2008 24 4772 4777. 57. Forster, P M.; Eckert, J ; Heiken, B D.; Parise, J B.; Yoon, J W ; Jhung, S H ; Chang, J S ; Cheetham, A K J. Am. Chem. Soc. 200 6 128 16846 16850. 58. Dinca, M ; Yu, A F.; Long, J R J. Am. Chem. Soc. 200 6 128 8904 8913. 59. Liu, Y ; Eubank, J F.; Cairns, A J.; Eckert, J. ; Kravtsov, V Ch.; Luebke, R ; Eddaoudi, M. Angew. Chem. 2007 46 3278 3283. 60. Silvera, I F Rev. Mod. Phys. 1980 52 393 452. 61. Belof, J L.; Stern, A C.; Eddaoudi, M ; Space, B J. Am. Chem. Soc. 2007 129 15202 15210. 62. Moellmer, J.; Celer, E. B.; Luebke, R.; Cairns, A. J.; Staudt, R.; Eddaoudi, M.; Thommes, M. Microporous Mesoporous Mater. 2010 129 345 353. 63. Wang, X. S. ; Ma, S ; Forster, P M.; Yuan, D ; Eckert, J ; Lopez, J J.; Murphy, B J.; Parise, J B.; Zhou, H C. Angew. Chem. 2008 47 7263 7266. 64. Chen, B ; Zhao, X ; Putkham, A ; Hong, K ; Lobkovsky, E B.; Hurtado, E J.; Fletcher, A J.; Thomas, K. M J. Am. Chem. Soc. 200 8 1 30 6411 6423. 65. Chun, H. ; Dybtsev, D. N. ; Kim H. ; Kim, K. Chem. Eur. J. 2005 11 3521 3529.

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61 66. Mulder, F. M. ; Dingemans, T. J. ; Wagemaker M. ; Kearley, G. J. Chem. Phys. 2005 317 113 118. 67. Benard, P ; Chahine, R Scr. Mater. 2007 56 803 808. 68. Wang, Q ; Johnson, J. K J. Chem. Phys. 1999 110 577 586. 69. Panella, B. ; Hoenes, K ; Mueller, U ; Trukhan, N ; Schubert, M ; Puetter, H ; Hirscher, M Angew. Chem. 2008 47 2138 2142. 70. Zhang, J ; Wojtas, L ; Larsen, R W.; Eddaoudi, M ; Zaworotko, M J. Am. Chem. Soc. 200 9 1 31 17040 17041. 71. Ma, S ; Sun, D ; Ambrogio, M ; Fillinger, J A.; Parkin, S ; Zhou, H. C. J. Am. Chem. Soc. 200 7 1 29 1858 1859. 72. Farha, O K.; Spokoyny, A M.; Mulfort, K L.; Hawthorne, M. F ; Mirkin, C A.; Hupp, J. T. J. Am. Chem. Soc. 2007 129 12680 12681. 73. Zhong D. C.; Lin, J. B.; Lu, W. G.; Jiang, L.; Lu, T. B. Inorg. Chem. 2009 48 8656 8658. 74. Dinca, M ; Dailly, A ; Tsay, C ; Long, J R. Inorg. Chem. 2008 47 11 13. 75. Nicol, J M.; Eckert, J.; Howard, J J. Phys. Chem. 1988 92 7117 71 21. 76. Eckert, J ; Nicol, J M.; Howard, J.; Trouw, F R J. Phys. Chem. 19 96 100 10646 10651 77. Srinivas, S. T.; Rao, P. K. J. Catal. 1994 148 470 477. 78. Robell, A. J.; Ballou, E. V.; Boudart, M. J. Phys. Chem. 1964 68 2748 2753. 79. Li Y. W. ; Yang, R. T. J. Am. Chem. Soc. 2006 128 726 727. 80. Li Y. W. ; Yang, R. T. J. Am. Chem. Soc. 2006 128 8136 8137. 81. Li, Y. W.; Yang, R. T. Langmuir 2007 23 12937 12944. 82. Li, Y. W.; Yang, R. T. AICHE J. 2008 54 269 279. 83. Dailly, A. ; Vajo, J. J. ; Ahn, C. C. J. Phys. Chem. B 2006 110 1099 1101 84. Panella, B. ; Hirscher, M. ; Ptter H. ; Mller, U. Adv. Funct. Mater. 2006 16 520 524. 85. Eddaoudi, M.; Li, H.; Yaghi, O. M. J. Am. Chem. Soc. 200 0 12 2 1391 1397.

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62 86. Nelson, A P.; Farha, O K.; Mulfort, K L.; Hupp, J T. J. Am. Chem. Soc. 200 9 1 31 458 460.

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63 Chap ter 3. Hetero F unctional Tetrazolate/Carboxylate L igands f or the Design and Synthesis of P orous Metal Organic Material s Solid state materials with suitable physical and chemical properties are of great interest and are already established as an important class of materials involved in various relevant technologies However, t he design and synthesis of functional materials remains very challenging. The Molecular Building Block (MBB) approach has recently been employed as a strategy to design a nd construct solid state materials. 1 4 In the context of solid assembly of atoms, ions or molecules which, by condensation of the groups of others (identical or different), give rise to the final solid, whatever the sym metry and/or the dimensionality 2 A simple analogy with architecture can be made where building blocks of different shape and size are used to construct larger monuments (stone building units used to construct Egyptian pyramids for example ) In fact, the concept of building units in crystal chemistry originated in 1929 with studies of complex ionic crystals by Linus Pauling. 5 The MBB strategy has proven to be successful in the rapidly academic and i ndustrial growing subset of solid state materials 6 i.e. Metal Organic Materials (MOMs),

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64 where desired attribute s can be introduced at the molecular level prior to the assembly process. 7 8 3.1. From Molecular Building Blocks (MBBs) to Supermolecular Building Blocks (SBBs) Rigid or flexible MBBs consisting of coordination clusters and/ or organic ligands, of specific geometry and connectivity are readily accessible and can be used to construct structures in which the points of extension of the MBBs define the Secondary Building Units (SBUs) that serve to augment the vertices of a given net. 9 12 However, it remain s very challenging to absolutel y predict the network topology of the constructed framework al specific building block leads to a specific predetermined structure, which is the only poss ibility for that building block 9 Therefore, the ability to target nets that are exclusive for a combination of building blocks 1 3 presents greater potential toward prediction, design, and synthesis of the resultant framework. Nevertheless, the use of simple MBBs is limited when targeti ng nets that could only be generated upon using building blocks of connectivity higher than 8 ( the building blocks need to have a greater number of points of extension i.e. conventional building blocks usually only result in SBUs with 8 vertices or less ). As a result, another level of complexity for molecular building blocks is desi rable. These building blocks can be referred to as Supermolecular Building Blocks (SBBs) and since linking the point of extensions of the MBBs results in SBUs, Tertiary Building Units (TBUs) are obtained by linking the point of extensions of the SBBs Indeed, the strategy involves the use of externally functionalized Metal Organic Polyhedra (MOPs)

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65 that serve as SBBs for edge transitive nets that are unique, specifically nets with vertex figures of high connectivity. The design of such structures involves the use of SBBs with a high degree of symmetry and connectivity where enhanced directional and structural information is already built in. S everal examples were reported in which MOPs were used as nodes to construct diverse types of material s 14 For instance, MOPs can be employed as SBBs that serve as tetrahedra, cubes, cuboctahedra or rhombicuboctahedra in the final net (figure 3.1) 15 20 Figure 3.1. Schematics depicting some select SBBs that can be used as nodes for the constr uction of the framework: a) a t etrahedron SBB (ref. 15 ) ; b) a cube SBB (ref. 16 ) ; c) cuboctahedron SBB (ref. 17 ) and; d) rhombicuboctahedron SBB ( ref. 18 20 ) SBBs of particular interest for this dissertation employ a metal cluster MBB that serve s as a square SBU In fact, there are only 3 possible ways to link squares with one kind of edge into a polyhedron 21 T herefore, when using MBBs in which the point s of e xtension lie in the vertices of a square, only three types of MOPs can be generated a) b) c) d)

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66 (figure 3.2 ). In fact, there are no examples yet of MOPs based on the sma ll rhombidodecahedron. However, the use of isophthalate moieties functionalized in the 5 position permitted the formation of linked cubohemioctahedra SBBs where the structure can be interpreted as a 12 connected fcu net. 17 F igure 3.2 Linking squares at their vertices results in three types of faceted polyhedra: a) cubohemioctahedron, b) small rhombihexahedron, c) small rhombidodecahedron Another type of polyhedra that can be formed when using isophthalate moieties are the small rhombihexahedra 22 2 3 ( also called nanoballs and can be viewed as a truncated cuboctahedron) E x ed on using these building blocks as nodes to construct much larger structures. 2 3 Indeed, the feasibility of this strategy was later demonstrated. 18 19 F unctionalized nan o balls w ere used as SBB s and bcu or pcu like nets were obtained after a judicious choice of ligands. One example, shown in figure 3.3, illustrate the pcu like arrangement of the SBBs. Reaction of copper nitrate and 1,3 bis(5 methoxy 1,3 benzene dicarboxylic acid)benzene resulted in the assembly of quadruple cross linked nanoballs. a) b ) c )

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67 Figure 3. 3 Schematic depicting a pcu like net that was formed by employing a ligand that contain s the necessary features to cross link the nanoball s (shown in red and green). Each nanoball is linked to six nanoballs through four ligands (shown in yellow and green) 3.2. Design and S ynthesis of (3,24) C onnected rht N et s As stated above, externally functionalized Metal Organic Polyhedra (MOPs) can be employed as SBB s to target nets with vertex figures of high connectivity The use of functionalized nanoballs seems to be an excellent choice to target such nets. In fact, t hese MOPs possess the ne cessary structural information directionality and the pot ential for high connectivity. A judicious choice of functionalization in the 5 position of isophthalate ligand s could in principle permit maximize d connectivity when using these molecules as SBBs. In fact, the only possibility of generating 24 connected nets when using nanoballs as SBBs is to link them via triangular building units.

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68 Indeed, a (3,24) connected rht net 2 0 was constructed by using metal organic truncated cuboctahedral SBBs generated in situ that serve as rhombicu boctahedral TB Us (see figure 3.4 ). Figure 3.4 The 5 position of the isopthalate ligands in the truncated cuboctahedron ( green ) SBB sits directly on the vertices of the rhombicuboctahedron (yellow/orange frame), serving as the TBU The SBB consists of twelve copper paddlewheels joined by twenty four 1,3 Benzene dicarboxyl ate (1,3 BDC ) linkers so that the 5 position of the bent bridging ligand (120 angle) lies exactly on the vertices of the rhombicuboctahedron, the 24 connected vertex figur e for the (3,24) connected rht net (figure 3.4 and 3.5 ). 24 Thus, functionalization at this 5 position with an organic moiety that permits the form ation of a rigid triangular MBB, i.e. the SBU is the 3 connected vertex figure, lead to the assembly of a MOF having rht like network topology (figure 3.6)

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69 Figure 3.5 The (3,24) connected rht net and the two vertices and corresponding vertex figures w hen augmented This MOF, to the best of our knowledge, is the only edge transitive net known for the assembly of 24 and 3 connected vertices. 13 Figure 3.6 Schematic showing the corresponding strategy from MBBs to SBBs (generated all together in situ ) to the resulting framework : rht 1 the 5 position of the 1,3 BDC ligand is highlighted in orange; the yellow spheres indicate the cavity of truncated cuboctahedra; some spheres, all solvent molecules and all hydrogen atoms have been omitted for clarity (C = gray, N = blue, O = red, Cu = green)

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70 3.3. Tetrazolyliso phthalic Acid L igand and rht 1 S ynthesis 3.3.1. Tetrazolylisophthalic Acid S ynthesis (H 3 TZI) H 3 TZI was obt ained pure as confirmed by NMR from 5 cyanoisophthalic acid with a 33.3% yield using the Demko Sharpless method. 25 The 5 cyanoisophthalic acid was synthesized from 5 aminoisophthalic acid ( figure 3.7 and section 3. 8.1 ) 26 Figure 3.7 Schematic of the synthesis of H 3 TZI from 5 aminoisophthalic acid 3.3.2. rht 1 S ynthesis S olvothermal reaction between 5 tetrazolylisophthalic acid and Cu(NO 3 ) 2 2.5H 2 O in an N,N dimethylformamide /ethanol solution yields a homogeneous crystalline material ( see section 3.8 .2 ) purity confirmed by similarities betwee n simulated and experimental X Ray Powder D iffraction (XRPD) patterns (Figure 3.33 ). The as synthesized compound, characterized by single crystal X ray diffraction as [Cu 6 O(TZI) 3 (H 2 O) 9 (NO 3 )] n (H 2 O) 15 (section 3.8.4) reveals a crystal structure consisting of truncated cuboctahedra (twenty four functionalized isop h thalate ligands connected by twelve copper dimer centers ( Cu 2 (O 2 CR) 4 paddlewheels) connected to trigonal Cu 3 O(N 4 CR) 3 trimers through each tetrazolate (N 4 CR) moiety, which is unprecedented

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71 for tetrazolate ligands (t o the best of our knowledge, the Cu 3 O(N 4 CR) 3 trimer has never been obs erved, but the Cu oxo trimer is known for similar azolates) 27 Each inorganic paddlewheel MBB is dinuclear and consists of two copper ions with a square pyramidal geometry, each coordinated to four oxygen atoms of four carboxylates and one axial water molecule, CuO 5 Both carboxylate moieties of the triply deprotonated TZI ligand coordinate in a bis monodentate fashion to two copper atoms to form t he Cu 2 (O 2 CR) 4 MBBs, which combine to form the finite truncated cuboctahedron. Each tetrazolate moiety also coordinates in a bis monodentate fashion to two copper atoms of the Cu 3 O(N 4 CR) 3 trimer. Each copper atom of the trimer is coordinated to two nitrogen atoms (one from each of two tetrazolates), an oxygen (oxo) core, one oxygen atom of an equatorial water molecule, and one oxygen atom of an axial disordered water molecule to give square pyramidal geometry, CuN 2 O 3 The formation of the oxo trimer with the tetrazolate po rtion of the TZI ligands result in a 24 connected rhombicuboctahedral TBU, formed via the isop h thalate portion, linked to twelve neighboring TBUs through twenty four 3 connected trigonal SBUs (metal tetrazolate trimers). This results in a (3 ,24) connected MOF having rht like topology that has only recently been depicted by Delgado rhombicuboctahedral and trigonal building units (figure 3.8 ) 24 It should be noted that the present framework can also be interpreted topologically as a novel three dimensional (3,3,4) connected ternary net, i.e. trinodal, based on the assembly of three different basic SBUs (Figure 3.9 ). 13

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72 Figure 3. 8 T he (3,24) connected rht net The first MBB, copper paddlewheel Cu 2 (CO 2 ) 4 decorates 28 the 4 connected vertex; the second is the trigonal Cu 3 O(N 4 CR) 3 trimer that decorates the first 3 connected vertex; and the third, the tritopic ligand that was designed to be hetero functional to accommodate two types of metal clusters at each of the two types of coordination functionalities (tetrazolate and carboxylate), decorates the second 3 connected vertex. The SBB approach involving multifunctional ligands is a suitabl e way to design and assemble ternary nets in MOFs. 29 In fact, this trinodal topology has not been encountered in MOM chemistry nor experimentally/theoretically predicted.

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73 Figure 3.9 The unprecedented ternary topology of the compound: a) schematic of the 3 MBBs and the corresponding 3 SBUs b) Pictur e of the augmented ternary net (Topological terms for each node: (a) 6.6.8.8.8(2).8(2), Coordination Sequence: 4, 8, 18, 29, 52, 61, 106, 120, 170, 187 TD 10 755(0.654); (b) 6.8(3).8(3), Coordina tion Sequence: 3, 8, 15, 29, 40, 69, 81, 131, 146, 206 TD 10 : 728(0.630); (c) 8(3).8(3).8(3), Coordination Sequence: 3, 6, 18, 24, 42, 63, 84, 93, 183, 175; TD 10 : 691(0.598).) It is also worth mention ing that the connectivity can be alternatively interpreted to be related to inorganic zeolite A with lta topology and to r eo.e net (Figure 3.10 ). 13,30 The overall cationic framework, where one NO 3 per three Cu cations balances the charge, consists of three different types of open cages (Figure 3.11 ) with the truncated octahedral cages, ha ving a 22.87 diameter (19.83 including van der Waals (vdw) radii and assuming a sphere that can fit in the cage), delimite d by eight Cu 3 O(N 4 CR) 3 trimers and twenty four Cu 2 (O 2 CR) 4 paddlewheel MBBs, and therefore sur rounded by six rhombicuboctahedral cages and eight truncated tetrahedral cages.

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74 Figure 3.10 The present framework can also be interpreted as a) lta blue; and d4R : red) and reo e (rhombicuboctahedron: yellow, green; cuboctahedron: blue ; and d4r: red ) nets The truncated tetrahedra l cage, with a diameter of 15.30 (12.50 vdw sphere), is delimited by four Cu 3 O(N 4 CR) 3 trimers and twelve Cu 2 (O 2 CR) 4 paddlewheel MBBs, each is, as a result, surrounded by four rhombicuboctahedra and four of the truncated octahedral cages; the rhombicuboctahedron w ith a diameter of 15.90 (13.10 vdw sphere) are delimited by twelve Cu 2 (O 2 CR) 4 paddlewheel MBBs, surrounded by six of the truncated octahedral cages and eight of the truncated tetrahedral cages.

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75 Figure 3.11 Schematic represent ing the arrangement of the different cage s in the structure The total solvent accessible volume for rht 1 was estimated to be ~75% by summing voxels more than 1.2 away from the framework using PLATON software. 31 Combined with a low calculated density for the fully evacuated framework (0.702 g/cm 3 ), the large accessible windows, open cavities, and c harged nature make this framework seemingly prospective for gas storage, specifically H 2 3.4. Sorption S tudies on rht 1 In order to assess the sorption properties of rht 1, the guests were exchanged with ethanol. The crystalline material was then loaded into the sample cell, where it was outgassed first at room temperature and then at 85C for 6 hours. Argon and nitrogen isotherms can be regarded as pseudo type I isotherms (Figure 3 .12 a ) and the apparent surface area was estimated using Langmuir a nd BET methods (N 2 : 3223 m 2 /g and 2847

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76 m 2 /g, respectively); the total pore volume was found to be 1.01 cm 3 /g (N 2 ). An interesting feature of the isotherms can be observed for pressures between 0.01 atm to 0.1 atm, where a second slope appears. This phenome non is attributed to the three different cage diameters, where the largest cages, i.e. the truncated octahedral cages approach mesoporous range; the smallest cages are first to be covered, the largest are subsequently covered at higher pressure Figure 3 12 rht 1 sorption graphs a) Nitrogen and argon sorption isotherms at 78K and 87K, respectively. b) Hydrogen sorption isotherms at 77K and 87K. c) Graph of the isosteric heat of sorption a) b) c)

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77 Hydrogen capacity was assessed for rht 1, measured at 77K and 87K at atmospheric pressures (Figure 3 .12 b), with up to 2.4 wt% at 77K. The isosteric heat of sorption has an estimated value of 9.5 kJ/mol at the l owest coverage (Fig ure 3. 12 c) This indicates a higher strength of H 2 interactions compared to other MOFs. 32 37 Nevertheless, the isosteric heat falls to 4.7 kJ/mol at higher loadings, which is in accordance with the large size of the cavities filled at hi gher loading. With a combined large surface area and accessible free volume, rht 1 offers great potential for higher H 2 uptake at 77K and higher pressures (estimated up to 6%). 3.5. I soreticular rht L ike S tructures 3.5.1. Design of rht L ike N ets The uniqueness of rht net s is beneficial to the practice of isoreticular chemistry, where higher surface areas and larger free volumes can be easily achieved through expansion of the bifunctional organic linker. Indeed, it is possible to construct new isor eticular MOFs based on rht topology from a variety of bifunctional ligands as well as various tritopic hexacarboxylate ligands where the Cu oxo trimer can be replaced by tritopic organic building blocks. In fact, t he judicious choice of ligand s with differ ent functionalities will lead to diverse rht like structures with cages of different sizes and propertie s. Therefore, the possibilities to form new rht like structures with various pores sizes that contain features for specific applications such as gas sto rage and separation, drug delivery, sensor technology and catalysis are almost limitless.

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78 Figure 3.1 3 rht 1 was used as a blueprint for the design of new rht nets where the length of H 3 TZI has been increased by additional benzene rings in the X dire ction to lead to rht 2 and rht 6 and in t he Y direction to lead to rht 3 (using TBPDC, TBBD and TTPDC ligands respectively to construct rht 2, rht 6 and rht 3 respectively) A series of rht like MOFs is reported using a variety of ligands from our library of ligands designed to contain the attributes needed to build rht type structures (figure 3.13) 38 Furthermore, the present rht like nets do not allow for interpenetration 13 and therefore permit the assembly of frameworks of various dimensionalities i.e. materials with large pore sizes, such as mesoporous sizes could be easily assembled. We therefore, designed new tetrazolate ligands of different length s that lead to rht structures containing various cage size s. 3.5.2. Synthesis of rht L ike Structures rht 2, rht 3 and rht (1H tetrazol 5yl)biphenyl 3,5 dicarboxylic acid (TBPD C ) (1H tetrazol 5yl) terphenyl dicarboxylic acid (TTPD C ) (4 (1 H tetrazol 5

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79 yl)benzamido)benzene 1,3 dioic acid (TBBD), respectively (Figure 3. 13 ; synthesis schemes in section 3.8.1 figure s 3. 30, 3.31 and 3.32 ) and c opper nitrate ( see section 3.8.2 ) Purity wa s confirmed by XRPD (figure 3.34, 3.37 and 3.38 ). With a formula unit: CuL 0.5 (NO 3 ) 0.167 (O 2 ) 0.167 (Z = 192) (simplified formula: Cu 6 OL 3 (NO 3 )), tetrazolate based structures of rht 1, rht 2, rht 3 and rht 6 are cationic MOFs in which nitrates balance the charge. It should be noted that rht 3 contains unprecedented truncated cuboctahedron cages connected through Cu 3 O(N 4 CR) 3 trimer s assembled from t erphenyl dicarboxylic moieties as large as 27.52 , almost double the size of traditional truncated cuboctahedro n cages built from isophthalate moieties (~13.1 0 ). It is obvious that structures with rht topology can be built from different tritopic hexacarboxylate ligands where the oxo trimer is replaced by a triangular organic moiety such as 6 member ring derivat ives for example. Based on this strategy, several new ligands have been designed. 38 As an example, two MOFs with rht topology have been synthesized (figure 3 .1 4 ). Indeed, solvothermal re actions between copper nitrate and [1,3,5 phenyltri(methoxy)] tri isophthalic acid (PTMOI) or copper nitrate and triazine 2,4,6 triyl)triimino]triisophthalic acid (TTIMI) lead to rht 4 and rht 5 respectively. With a general formula unit of: CuL 1/3 (Z = 96), rht 4 and rht 5 are neutral MOFs.

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80 Figure 3 .1 4 rht 1 was used as a model for the design of new rht nets where the Cu oxo trimer was replaced by b enzene and triazine derivatives 3.5.3. Sorption S tudies of rht L ike S tructures Preliminary gas sorption studies on rht 2, rht 3 showed that rht materials are highly porous. Nevertheless, t he large cages in rht 2 and rht 3 render ed the activation process problematic Indeed previous activation attempts, involving common methods of low boiling solvent evaporation processes 39 were unsuccessful i.e. porosity values obtained were lower than expected and attributed to framework collapse upon removal of solvent molecules in the bulk materials However, careful activation s using supercri tical CO 2 lead to highly porous structure s As discussed in chapter 2 due to its unique properties, supercritical CO 2 fluid has been beneficial for the activation of MOFs 40 Indeed, after activation (see section 3.8.3 ) an a rgon isotherm was recorded for rht 2 (figure 3.15 a ). The recorded isotherm p resents interesting features. First, a second slope appears at pressure between 0.01 and 0.2 atm. As for rht 1, this phenomenon is attributed to the

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81 three different cage diameters where the smaller cages ar e the first to be covered and the largest are covered at higher pressures Here the step is shifted to higher pressure s when compared to rht 1 due to cages larger in rht 2 Second, the shape of the isotherm between pressure 0.4 and 1 atm appears to follow a path characteris tic to mesoporous materials with a typical hysteresis. Hysteresis appearing in this region is usually associated with capillary condensation in mesopores and the hysteresis loop may display a wide variety of shapes. The present isotherm exhibit s a hysteresis loop that resembles type H4, i.e. remains nearly horizontal and relatively parallel (when compa red to the other extreme type H1 hysteresis) over a wide range of pressure (see chapter 2, figure 2.1 and 2.4 ) 41 Therefore, t he isotherm ap pears to be a mixture of microporous and mesoporous type s with a clear microporosity shape, i.e. the low pressure uptake follows a sharp path ( similar than for rht 1) and mesoporosity features evidenced by a typical H4 hysteresis loop at higher pressure s. The uniqueness of rht type frameworks allow for mixed cage dimensionalities (microporous and mesoporous) to be present in the same material, for instance in rht 2 ~27 .21 for the largest cages along with ~13.1 0 and ~15.73 for the other cages, and may therefore account for this unusual phenomenon for MOF materials. The apparent BET surface area was estimated to be ~ 4 780 m 2 /g with a pore volume of 1.2 0 cm 3 /g. The hydrogen capacity was also measured, with a value of 1.2% a t 77K and 1 atm (figure 3.15 b) was lower than values obtained for rht 1 (2.4%).

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82 Figure 3.1 5 S orption data on rht 2 after supercritical CO 2 activation a) Argon isotherm; b) Low pressure h ydrogen isotherm at 77K and 87K ; c) Isosteric heat of sorption plot However, it is expected that due to the higher pore volume, the hydrogen wt% at higher pressure will surpass the capacity of rht 1. On the other hand, the isosteric heat of adsorption, calculated after re cording an isotherm at 87K, is very similar to rht 1 a t low coverage, i.e. around 9.2 kJ/mol (figure 3.15 c) Pore size distribution was calculated from the argon isotherm using the DFT & Monte Carlo mod el (figure 3.16 ). a) b) c)

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83 Figure 3.16 Pore size distribution in rht 2 (calculated from the Ar isotherm) using DFT & Monte Carlo method (spherical/cylindrical model ) Dimensions of ~ 11.7 0 , ~17.15 and ~27.15 can be extracted and can be compared to the dimension calculated from the crystal structure as shown in figure 3.17 (13.1 0 , 15.73 and 27.2 1 ). The distribution is in accord with the expected number of cages and their respective contribution to the total volume however, it appears that the rhombicuboctahedral cage dimensions are underestimated (11.7 0 vs. 13.1 0 ) and the truncated tetrahedral cage dimensions overestimated (17.15 vs. 15.73 ).

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84 Figure 3.17 Schematics of the three types of cages (from left to right: truncated octahedral, truncated tetrahedral and rhombicuboctahedra) present in rht 1, rht 2 and rht 3. Cavities d imensions are shown on top of each cages and windows (triangular or quadrangular) are shown on the side. The rht 3 framework was also activated using supercritical CO 2 and an argon isotherm recorded ( figure 3.18 ). The shape of the isotherm is typical to mesoporous compounds and, in contrast to rht 1 and rht 2, does not exhibit microporosity features. In fact, the isotherm recorded resembles that of type IV isotherms (see chapter 2, figure 2.1 ). 41 In fact, type IV isotherms characteristic features, representative to mesoporous materials, are the hysteresis loops associate d to capillary condensation that occur in the mesopores. Due to weaker interactions with the adsorbent, the uptake at low pressure is relat ively weak and this persists to relatively high p/p 0

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85 Figure 3.18 S orption data on rht 3 after supercritical CO 2 activation: Argon isotherm. At a certain relative pressure, pore condensation begins and the uptake increases significantly until a plateau is reached which corresponds to a pore completely filled In the present case, this step appears to be at ~0.7 0 atm and the plateau is reached at ~ 0.8 5 atm. The argon isotherm for rht 3 exhibit a hysteresis loop that can be attributed to H1 types ( the two branches are almost vertical and parallel, see chapter 2 section 2.4 ) which is often indicative to the presence of well defined pore channels or agglomerate of uniform sphere like pores materials An apparent BET surface area of 851 m 2 /g and a pore volume of 1.64 cm 3 /g were extracted from the isotherm. A pore size distribution was also calculated using the DFT & Monte Carlo method (figure 3.19 ). A sharp peak appears at ~94.7 0 along with a broad peak of low intensity at ~18 24 . In fact, the dimensions of the 3 different cages in rht 3 are very comparable and above the microporous range : ~ 25.36 , 23.6 1 and 27.5 2 for the octahedral, the truncated octahedral and the

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86 rhombicuboctahedral cage s respectively. However, the value of 94.7 0 obtained from the calculated pore size distribution is far higher than the sizes obtained from the crystal structure. The other peak at ~18 24 is broad and the pore volume that it is associated with is also far below expected. Figure 3.19 Pore size distribution in rht 3 (calculated from the Ar isotherm) using DFT & Monte Carlo method (spherical/cylindrical model) Therefore, the shape of the isotherm, even though expected to exhibit mesoporosity, appears to be characterist ic of a mesoporous material with an average pore size that is far above the pore sizes in rht 3. In order to gain more information on the structure, single crystal X ray crystallography was attempted. However, the diffraction was so weak that a ray powder diffraction trials were also unsuccessful i.e. ible to compare the experimental data with the calculated powder pattern from the crystal structure of rht 3.

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87 Figure 3.20 S orption data on rht 3 after supercritical CO 2 activation a) Low pressure hydrogen isotherm at 77K and 87K; b) Isosteric heat of sorption plot H 2 isotherms were also recorded and the isosteric heat was ca lculated as shown in figure 3.20 was found to be 0.63 wt% and the low coverage isosteric heat of adsorption was ~8.5 9 kJ/mol which is lower than the low coverage heat of adsorption measured for rht 1 and rht 2. The experiment was repeated using a different batch of rht 3 crystals. The same activation procedure was tentatively followed. However, it appeared that the supercritical fluid step was sho rter in time i.e. the bleed rate was faster than for the first attempt and was attributed to a faulty o ring Another argon isotherm was recorded (figure 3.21 ). Although the shape of the isotherm is similar to the previous attempt, the pressure in which t he pore condensation step begins is shifted to a lower value of ~ 0.55 atm. The por e size distribution (figure 3.22 ) indicate d a pore of ~68 which is lower than the value of 94.7 0 obtained after the previous attempt. a) b )

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88 Figure 3.21 S orption data on rht 3 after supercritical CO 2 activation (s e cond attempt) : Argon isotherm. Figure 3.22 Pore size distribution in rht 3 (calculated from the Ar isotherm) using DFT & Monte Carlo method (spherical/cylindrical model) after the second attempt

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89 It seem s that the present sorption results might suggest a possible correlation to the time in which the crystals remained in the supercritical CO 2 fluid. In order to verify this hypothesis, a third experiment was performed. After activation an argon isotherm was recorded (figure 3.23 ) and exhibit s the same features as the one recorded after the two previous activations. However, it seems this time that the shape of the isotherm resembles the shape o f the isotherm obtained after the first CO 2 activation trial i. e. the pore condensation step starts at a relative pressure of ~0.65 0.7 atm and the plateau is reached at a pressure of ~ 0.8 atm. However, a pore size distri bution was measured (figure 3.24 ) and depicts an average pore size of ~ 84 which is lower than the value obtained after the first activation (94 .70 ). Nevertheless, in contrast to the two previous attempts, the peak at ~ 24 is sharper and the volume associated with it is greater. Thi s indicates that the contribution of these pores to the whole material is significant. Figure 3.23 S orption data on rht 3 after supercritical CO 2 activation (third attempt): Argon isotherm.

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90 Figure 3.2 4 Pore size distribution in rht 3 (calculated from the Ar isotherm) using DFT & Monte Carlo method (spherical/cylindrical model) after the third attempt Although the isotherm shapes recorded for rht 3 framework accounting to the sizes of the pores, are expected to be of mesoporous types the pressure at which pore condensation presumably starts seem s to be shifted to higher pressure s Indeed, pore size distribution indicates pores with greatly overestimated siz es. Therefore, the current results do not permit, at this time, to fully explain the reasons of these unexpected isotherm shapes. 3.5. 4 rht L ike Structures from other Groups Other structures with a 3,24 connected rht like topology have been reported. 43 46 In fact, the first example of an rht like net with a benzene derivative that replaces the copper oxo trimer was reported by Myoung Soo Lah and coworkers shortly after the rht 1 (figure 3.25 a ) w a s reported 43 The structure contains ligand s with amide functionalities and zinc

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91 paddlewheel building blocks S orption experiments were attempted however, the activation was unsuccessful and the authors reported that the framework wa s nonporous. Later, Schroder et al. reported a 3,24 connected rht net referred to as NOTT 112, after reacting copper ions and a more rigid ligand (figure 3.25 b). 44 Argon and nitrogen isotherms were recorded and it was mentioned that the shape resembles the shape of the argon isotherm in rht 1. The apparent BET surface area was estimated to be around 3800 m 2 /g and the pore volume ~1.62 cm 3 /g. Low pressure hydrogen isotherms were also recorded and a gravimetric uptake of 2.3 % was reported, which is close to the value obtained for rht 1. High pressure hydrogen experiments indicated that the framework can store up to 7.07 % (excess) and 10 % gravimetric total uptake. Later, Zhou and coworkers reported 3 rht like structures based on i) the ligand shown in figure 3.25 c with zinc ii) the liga nd shown in figure 3.25 c with co pper and i ii) the ligand shown in figure 3. 25 d with copper that are referred to as PCN 60, PCN 61 and PCN 66 respectively. 45 Surface area and pore volume were evaluated for PCN 61 (BET surface area: 3000 m 2 /g and Langmuir surface area: 3500 m 2 /g; pore vo lume: 1.36 cm 3 /g) and PCN 66 (BET: 4000 m 2 /g and Langmuir: 4600 m 2 /g; pore volume: 1.63 cm 3 /g). It was found that the zinc based MOF, PCN 60, was not porous. Very shortly after, Soo Lah et al. reported two structures (with zinc and with copper ions), referred to as PMOF 2(Zn) and PMOF 2(Cu) respectively, ba sed on the ligand in figure 3.25 c. 46

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92 Figure 3.25 Schematics of the ligands that have been used to construct rht like structures. a) [1,3,5 benzenetriyltris (carbonylimino)]tris 1,3 benzenedicarboxylic acid (from ref. 4 3 ); b) 1,3,5 biphenyl] 4 yl)benzene (from ref. 44 ); c) benzene 1,3,5 triyltris(1 ethynyl 2 isophthalate) (from ref. 45 and ref. 46 ) and d) nitrilotris(benzene 4,1 diyl)tris(ethyne 2,1 diyl))triisophthalate (f rom ref. 45 ) Nitrogen isotherms indicated that PMOF 2 (Zn) was not porous and surface areas of 3780 m 2 /g (BET) and 4180 m 2 /g (Langmuir) were obtained for PMOF 2(Cu). The surface areas reported here are more than 20 % higher than the one reported by Zhou et al. for the same compound. Hydrogen isotherms were also recorded and a low pressure gravimetric uptake of 2.29 % was obta ined. High pressure isotherms indicated that the MOF can store up to 5% (excess uptake) and 7% (total uptake) at 50 bar. The increasing number of reports of materials based on rht topology indicate s that s tructures based on the 3,24 connected topology are an important class of MOMs. a) b ) c ) d )

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93 Indeed, the potential to construct diverse structures with rht topology is significant. These materials are light, a large variety of structures with different functionalities and various pore sizes distribution can be obtained and therefore numerous applications can be targete d 3.5. 5 Encapsulation of Porphyrin Derivatives As stated above, rht 1, rht 2, rht 3 and rht 6 are cationic frameworks. With cag es of different dimensions (mesoporous (>20) and microporous (<20), rht type structures can be employ ed as host s for a variety of anionic molecules. A first trial of encapsulating porphyrin derivatives with sizes of ~ 24 (VDW ), in rht 2 was a ttempted S olvothermal reaction of c (1H tetrazol 5yl)biphenyl 3,5 dicarboxylic acid (TBPDC) and meso Tetra(4 sulfonatophenyl)porphine (SPP) in DMF yielded red crystals of rht 2 and the purity of the crystals was confirmed by XRPD ( section 3.8.2, figure 3.35 ). Single crystal X ray experiments were also attempted and although the unit cell parameters of rht 2 were confirmed, it was not possible to crystallographically locate the porph yrin derivative. Solid state and liquid state U V visible spectroscopy was used to confirm the presence of the SPP in rht 2 ( section 3.8.2, f igure 3. 36 ) Solid crystals were used and the spectrum obtained was compared to the spectra of solutions of free base SPP and copper metallated SPP respectively. The spectra indicate that the SPP is metal l ated with copper ions in the framework. This clearly demonstrates the possibilities to use rht compounds as platforms for studies relevant to various applications such as catalysis or hydrogen storage.

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94 3.6. H etero F unctional Ligands for the C onstruction of Multinodal Nets 3.6.1. Introduction Hetero functional ligands contain at least two types of atoms that can serve as donor s for coordination bonds (for example O donor and N donor). The presence of multiple donors within a single ligand could be beneficial since a larger variety of building blocks can be potentially formed and should permit the construction of diverse materials. For instance, several binary or ternary nets have been discovered and are based on various combinations of building blocks that can be used as blue prints for the design of MOMs. 42 In fact, it should be advantageous to use ligands with built in features allowing at least two different building blocks to be for med in situ The use of hetero functional tetrazolate/carboxylate ligands may then be very useful in targeting nets with heterogeneous building units since some of the possible highly symmetrical building blocks that form with azolates and carboxylates are known. 20, 47 56 For example, the use of azolate based ligands has led to the formation of buildi ng blocks of various geometries, i.e. triangular or cubic SBUs, 47 52 and the use of carboxylate permitted the formation of tetrahedral, square trigonal prism or octahedral SBUs. 53 56 3.6.2. Structures B ased on Tetrazolylisophthalate 3.6.2.1. sra N et First attempts involved reactions of 5 tetrazolylisophthalic acid ligand and zinc nitrate. The choice of zinc was driven by its possibility of forming metal clusters of various geometries with carboxylates (e.g. tetrahedral, square or octahedral units) and tetrazolates (e.g. trigonal units) However, forming t wo different clusters in situ w as in

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95 fact quite challenging. A uninodal net based on tetrahedral nodes was formed ( figure 3.26 ) Indeed, solvothermal reaction of 5 tetrazolylisophthalic acid and zinc nitr ate in a DMF /water solution resulted in a structure with sra (SrAl 2 ) or zeolite ABW topology (see section 3.8.2 ) The ligands and the metal ions both formed tetrahedral nodes to produce an anionic s tructure with unit cell formula Zn 4 (C 9 O 4 N 4 H 3 ) 4 (C 2 NH 8 ) + 4 in which dimethylamonium cations balance the charge. Figure 3.26 Schematics of Zn TZI structure: sra net ( zeolite ABW topology ) depicting a) the ligand and b) the metal as tetrahedral nodes in the structure; c) v iews of the structure in the x, z and y directions (from left to right). Hydrogen atoms have been omitted for clarity. Zn, C, O and N are shown in violet, grey, red and blue respectively. 3.6.2.2. sqc Trinodal Net Other trials involved metals with potentially high coordination number such as yittrium. In fact, a CCDC analysis indicated the possibility of forming tetrahedral nodes with azolates. Therefore, reactions with 5 tetrazolylisophthalic acid were attempted to form a tetrahedral building unit with the tetrazolate moiety and a sq uare building unit c ) a) b )

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96 with the carboxylate moiety in situ Indeed, solvothermal reaction s with yittrium nitrates resulted in the assembly of both building units. A structure with sqc 5588 topology (3 nodal net) was obtained (figure 3. 27 ) The unit cell consist s of 10 yittrium and 8 ligands that result in a cationic framework in which 6 nitrates balance the charge. Figure 3.27 Schematic of the structure with sqc topology. a) a view in the z axis; b) left: four ligands assembl e to form a ~ 10.2 cage (vdw) and right: a 6.6 window (vdw ) ; c) a vue in the x axis; d) the tetrahedral arrangement around the metal with the tetrazolate moieties (left) and the square arrangement around the metal cluster and the carboxylates. Hydrogen atoms have been omitted for clarity. Y, C, O and N are shown in turquoise, grey, red and blue respectively. 3.6.3. Structures Based on 4 Tetrazolylbenzoate 4 tetrazolylbenzoate (TZB) is a linear tetrazolate/carboxylate ligand that has be en emplo yed to construct several types of MOMs 57 61 However, as in rht type structures, for example, it should be possible to form Cu 2 (O 2 CR) 4 paddlewheels and trigonal a) b) c) d)

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97 Cu 3 O(N 4 CR) 3 trimers when using copper as the metal ion and 4 tetrazolylbenzoic acid as the ligand I f formed in situ the assembly of these building unit s sh ould lead to a structure related to HKUST, with bcu k topology. 13 However, several other building blocks c an potentialy be formed and structures with various topology can be obtained. 42 The ligand was synthesized using protocols that are similar than for the synthesis of 5 tetrazolylisophthalic acid (see experimental section 3.8.1 ) and used with copper nitrate. Two 3 dim ensional structures were obtained. 3.6.3 .1 A New Bin odal Net Solvothermal reactions of 4 tetrazolylbenzoic acid and copper nitrate in dimethylformamide resulted in a structure with a new binodal topology. Figure 3. 28 depicts schematic pictures of the structure. The unit cell contains 18 copper ions and 20 ligands which produces an anionic framework in which 4 dimethylamonium cations balance the charge. In fact, the metal ion clusters in the network arrange as a zig za g chain (figure 3. 28 c)

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98 Figure 3.28 Schematic pictures depicting the Cu TZB structure with a binodal topology a) a view in the y, z and x direction (from left to right respectively); b) a partial view of a cage like arrangement and c) a top view of (b). Hydrogen atoms have been omitted for clarity. Cu, C, O and N are shown in orange, grey, red and blue respectively. 3.6.3 .2 lvt Net Other reactions of 4 tetrazolylbenzoic acid and copper nitrate resulted in a polar structure with lvt topology (figure 3.29 ) The structure is neutral and there are 4 copper ions and 4 ligands in one unit cell. In fact, the specific arrangement of the ligands i n the same direction lead to polarity in the structure. The network consist s of channels in one direction T he chain arrangement of the metal clusters is illustrated in figure 3. 29 b, the tetrazolate moieties and the carboxylate moeties alternate and coordinate to the metal ions in a bis monodentate fashion. a) b ) c )

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99 Figure 3 .29 Schematic pictures illustrating the polar Cu TZB structure. a) a view in the x direction ( left ) describing the arrangement of the channels in the structure (yellow rods represent the void available space in the channels, dimensions and angles in the channels are given (right) b) a portion of the structure depicting the arrangement of the chain like arrangement of the ligands c) a view in the y direction (top) and a view in the z direction (down) showing windows of ~ 3.3 (vdw) Hydrogen atoms have been omitted for clarity. Cu, C, O and N are shown in orange, grey, red and blue respectively. 3.7 Conclusion Here, a novel approach to construct highly porous MOFs based on the hierarchical bottom up assembly of SBBs is described This represent s a new pathway for the assembly of pre determined highly coordinated building blocks based on supermolecules, as well as an alternate route to construct multinodal nets based on pre designed heterofunctional ligands and metal clusters. The use of 5 tetraz olyliso pthalate has been particularly beneficial in the construction of a family of MOFs with a new type of topology, i.e. the 3,24 coordinated rht like net. Preliminary studies have shown the strong potential of these structures to be used as platforms fo r various types of applications. In fact, rht type structures may be industrially a) b ) c )

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100 relevant in the near future These hetero functional ligands also permitted the construct ion of a variety of relevant structures with different topologies. In fact, these het ero functional ligands should lead to the construction of numerous novel MOFs, especially binary and ternary nets. Perhaps, even higher coordination and more complex nets (e.g. quaternary) are capable of being achieved. 3.8 Experimental Section 3.8 .1. Organic Syntheses 5 cyanoisophthalic acid: This intermediate was obtained from published procedures. 26 Copper cyanide and sodium cyanide were dissolved in water and heated to 60 70 C A cold diazonium salt was then separately prepared with 5 amino isophthalic that was added very slowly to a solution of sodium nitrate, HCl (6N) and water. The mixture was always kept to temperatures close to 0 C The diazonium salt was then slowly added to the warm cyanide solution. The solution was heated afterward t o boiling for ~1H. Several filtration extraction evaporation steps were necessary to finally obtain a solid with ~60% yield. 5 t etrazolylisophtalic acid: 5 cyanoisophtalic acid ( 1.9 g 10 mmol), sodium azide (0.72 g, 11 mmol) and zinc bromide (2.25 g, 10 mmol) were added to a 20 mL water solution. The reaction mixture was reflux ed for 2 days with vigorous stirring. HCl (3N, 15 mL) and 50 mL ethyl acetate were the n added to the mixture. More HCl was added

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101 until a pH of 1 was achiev ed in the aqueous layer. T he product was collected by filtration and washed several times with water. 2.29 g of a white solid wa s obtained with ~ 98% yield ( 1 H NMR ( d DMSO, 400MHz): ppm 8 59 (s, 1 H), 8.81 (s, 2H). 4 cyanobenzoic acid: The synthesis was performed following the same protocol as the one for 5 cyanoisophthalic acid. The diazonium salt involved 4 aminobenzoic acid. 4 tetrazolylbenzoic acid: A S harpless reaction was performed using 4 cyanobenzoic acid and following a similar protocol as for 5 tetrazolylisophthalate. The product was obtained with ~ 85 % yield ( 1 H NMR ( d DMSO, 400MHz): ppm 7.6 (d 2 H), 8.1 (d 2H). T he following procedures (from compound (1) to (7)) were design ed by post doctoral fellow Till Bousquet Figure 3. 30 S chematic of the synthesis of (1H tetrazol 5yl)biphenyl 3,5 dicarboxylic acid (TBPD C ) cya nobiphenyl 3,5 d icarboxylate (1) see figure 3.30 : A solution of dimethyl 5 iodoisophthalate (6 g, 18.75 mmol, 1 eq.), 4 cyanophenylboronic acid (2.95 g, 19.68 mmol, 1.05 eq.) and Na 2 CO 3 (7.95 g, 74.98 mmol, 4 eq.) in 400 mL of MeOH is

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102 degassed by 4 thaw freeze pump cycles. Then 1.3 g of 5% Pd/C is added and nitrogen gas is bubbled through the solution for 10 min. The reaction under stirring is carried out at 80C for 1h. Then, the mixture is filtered and washed with EtOH and CH 2 Cl 2 All organic solvents are removed under vacuum and aqueous layer is extracted 4 times with CH 2 Cl 2 the recombined organic layer are washed once with H 2 O, dried over MgSO 4 filtered and evaporated under va cuum. An off white solid is obtained with 85% yield. 1 H NMR ( d DMSO, 400MHz): ppm 4.00 (s, 6H), 7.79 (br s, 4H), 8.47 (s, 2H), 8.73 (s, 1H). (1H tetrazol 5yl)biphenyl 3,5 dicarboxylate (2) see figure 3.30: A solution of dimethyl 4 cyano phenyl dicarboxylate (4.8 g, 17.96 mmol, 1 eq.), sodium azide (2.3 g, 35.92 mmol, 2 eq.), ZnBr 2 (2 g, 8.98 mmol, 0.5 eq.) in 75 mL of H 2 O/iPrOH (2/1) is warmed to 100C for 48h. Then, 200 mL of AcOEt and 150 mL of HCl 3N is added. The aqueous layer is extr acted 3 times with 50 mL of AcOEt and the organic layers recombined are dried, filtered and solvent is removed, providing a white solid (99% yield). (1H tetrazol 5yl)biphenyl 3,5 dicarboxylic acid (3) see figure 3.3 0: A solution of dimethyl 4 tetrazoyl phenyl dicarboxylate in 1N aqueous solution of NaOH and ethanol is heated at 80C for 2h. After removing the ethanol under vacuum, the solution is filtered in order to remove the starting material. Then, the solutio n is acidified with 2N aqueous solution HCl until pH 3. The precipitate formed is collected by filtration, well washed with a 0.5N aqueous solution of HCl, and dried for 2h in an oven connected to

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103 the vacuum at 80C. A white solid is obtained with 99% yiel d. 1 H NMR ( d DMSO, 400MHz): ppm 7.91 (d, J = 7.8 Hz, 2H), 8.17 (d, J = 7.8 Hz, 2H), 8.46 (s, 2H), 8.48 (s, 1H). Figure 3. 31 S chematic of the synthesis of (1H tetrazol 5yl) terphenyl dicarboxylic acid (TTPD C ) cyano terphenyl dicarboxylic acid (4) see figure 3.3 1: A solution of 3,5 dibromocyanobenzene (3 g, 11.5 mmol, 1 eq.), 4 carboxyphenyl boronic acid (4 g, 24.1 mmol, 2.1 eq.) and Na 2 CO 3 (9.8 g, 92 5 mmol, 8 eq.) in 200 mL of EtOH is degassed by 4 thaw freeze pump cycles. Then 1.5 g of 5% Pd/C is added and nitrogen gas is bubbled through the solution for 10 min. The reaction under stirring is carried out at 80C for 1h. Then, the mixture is filtered and washed with EtOH and CH 2 Cl 2 All organic solvents are removed under vacuum and aqueous layer is extracted 4 times with CH 2 Cl 2 the recombined organic layer are washed once with H 2 O, dried over MgSO 4 filtered and evaporated under vacuum. An off white solid is obtained with 85% yield. 1 H NMR ( d DMSO, 400MHz): ppm 8.02 (d, J = 8.1 Hz, 4H), 8.06 (d, J = 8.1 Hz, 4H), 8.27 (s, 2H), 8.37 (s, 1H), 13.10 (s, 2H).

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104 (1H tetrazol 5yl) terphenyl dicarboxylic acid (5) see figure 3.3 1: A solution of 3,5 bis(4 carboxyphenyl) 1 (4 cyanophenyl)benzene (1 g, 2.86 mmol, 1 eq.), sodium azide (0.378 g, 5.8 mmol, 2.03 eq.), NH 4 Cl (0.329 g, 6.2 mmol, 2.15 eq.) in 20 mL of dimethylformamide is warmed to 100C for 24h. Then, after cooling 3N aqueous solution of HCl is added until pH 1 2, the solid remaining is collected by filtration, well washed with H 2 O and dried in the oven under vacuum at 80C for 2h. A white solid is obtained quantitatively. 1 H NMR ( d DMSO, 400MHz): ppm 8.03 (d, J = 7.9 H z, 4H), 8.11 (d, J = 7.9 Hz, 4H), 8.28 (s, 1H), 8.43 (s, 2H), 13.09 (s, 2H). Figure 3. 32 S chematic (4 (1 H tetrazol 5 yl)benzamido)benzene 1,3 dioic acid respectively (TBBD) 5 (4 cyanobenzamido)benzene 1,3 dioic acid (6) see figure 3.3 2: To a solution at 5C of 5 aminoisophthalic acid (1.5 g, 8.3 mmol, 1 eq.) in 16.6 mL of 1N aqueous NaOH is added 8.3 mL of 1N aqueous NaOH and 4 cyanobenzoyl chloride (1.37 g, 8.3 mmol, 1 eq.) in 4 mL of acetone simultaneously The mixture is stirred at r.t. for 7h then acidified with diluted aqueous HCl. The solid is collected by filtration, well washed with H 2 O and

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105 dried in the oven (80C) under vacuum for 2h. Purification by recrystallisation (DMF/H 2 O ) affords a white solid with 64% yield (m p=328.8C using DSC). (4 (1H tetrazol 5 yl)benzamido)benzene 1,3 dioic acid (7) see figure 3.3 2: A solution of N (3,5 dicarboxy)phenyl 4 (5 tetrazolyl) benzamide (0.8 g, 2.58 mmol, 1 eq.), sodium azide (0.34 g, 5.2 mmol, 2.03 eq.) and ammonium chloride (0.3 g, 5.5 mmol, 2.15 eq.) in DMF is heated at 100C for 24h. Then the mixture is diluted with water, acidified with diluted HCl and the solid is filtered and washed with water. Purification is carried out by recrystallisation (DMF/H 2 O) and a white solid is quantitatively afforded 1 H NMR ( d DMSO, 400MHz): ppm 8.22 (br s, 5H), 8.69 (s, 2H), 10.76 (s, 1H), 13.30 (s, 2H). 3.8 .2. Metal Organic Frameworks (MOFs) syntheses rht 1 synthesis: In a typical protocol, a solution of Cu(NO 3 ) 2 2.5H 2 O (0.08 mmol) and H 3 TZI (0.056 mmol) in 1.5 mL of DMF and 0.5mL of ethanol was prepared. The solution was then heated to 85C for 12 h, pu re blue crystals were obtained and purity was confirmed by XRPD In an alternative protocol, a solution of Cu(NO 3 ) 2 2.5H 2 O ( 0.1 68 mmol) and H 3 TZI ( 0.112 mmol) in 1 mL of DMF was prepared. The solution was then heated to 75C for 40 h pure blue crystals were obtained and purity was confirmed by XRPD (figure 3. 33 ).

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106 Single crystal X ray data (see section 3.8.4 ) Formula: Cu(C 9 H 3 N 4 O 4 ) 0.5 (NO 3 ) 0.167 (O 2 ) 0.167 (Z=192 unit cell Mw= 36888.768 g/mol ) Density: 0.7 02 g/cm 3 (after removal of solvent molecules and terimanal ligands) Free volume: 76.4 % (estimated) Figure 3. 33 C alculated and experimental XRPD s for rht 1 rht 2 synthesis : A solution of Cu(NO 3 ) 2 2.5H 2 O (0.168 mmol) and 3 (0.112 mmol) in 1 mL of DMF was prepared. The soluti on was then heated to 75C for 4 0 h, blue crystals were obtained and purity confirmed by XRPD (figure 3. 34 ) Single crystal X ray data (see section 3.8.4 ) Formula: Cu(C 15 H 7 N 4 O 4 ) 0.5 (NO 3 ) 0.167 (O 2 ) 0.167 (Z=192 unit cell Mw= 44193.536 g/mol ) Density: 0.448 g/cm 3 (after removal of solvent molecules and terimanal ligands) Free volume: 83.1 % (estimated)

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107 Figure 3. 34 C alculated and experimental XRPD s for rht 2 S P P rht 2 synthesis: A solution of Cu(NO 3 ) 2 2.5H 2 O (0.168 mmol) 3 (0.112 mmol) and meso Tetra(4 sulfonatophenyl)porphine (SPP) (0.013 mmol) in 1 mL of DMF was prepared. The soluti on was then heated to 75C for 4 0 h, red crystals were obtained and purity was confirmed by XRPD (figure 3. 3 5 ). Single crystal X ray data was collected and the unit cell of rht 2 was confirmed. However, the porphyrine derivative could not be located.

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108 Figure 3. 35 C alculated and experimental XRPD s for SPP rht 2 Solid state and liquid UV vis spectroscopy was used to confirm the presence of SPP in rht 2 (figure 3. 3 6 ) For clarity, the Soret bands (at ~ 420 nm) are not shown (the absorbencies are too high). In the spectrum of the SPP free base (green), bands at 515 nm, 550 nm, 590 nm and 650 nm are attributed to the Q bands. The Cu metallated SPP and the rht 2 encapsulated SPP spectra show a decrease in the number of Q bands (an apparent peak at 540 nm) which is typical for metalloporphyrins. Another broad peak appea rs in the ~630 nm 800 nm region and can be attributed to the Cu ligand absorbencies of the framework.

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109 Figure 3. 36 UV vis spectra of the SPP (green), Cu metallated SPP (blue) compared with the spectrum of CuSPP rht 2 (red). Only the visible region is shown When compared to the Q bands, too large intensities are associated with the Soret band s (at ~ 420 nm) this wavelength region is not shown in the graph rht 3 synthesis: A solution of Cu(NO 3 ) 2 2.5H 2 O (0.1 26 mmol) and 5 (0. 028 mmol) in 1 mL of DMF was prepared. Th e solution was then heated to 80C for 4 0 h blue green crystals were obtained and purity was confirmed by XRPD (figure 3.3 7 ) Single c rystal X ray data (see section 3.8.4 ) Formula: Cu(C 21 H 11 N 4 O 4 ) 0.5 (NO 3 ) 0.167 (O 2 ) 0.167 (Z=192, unit cell Mw= 51498.368 g/mol ) Density: 0.327 g/cm 3 (after removal of solvent molecules and terimanal ligands) Free volume: 86.5 % (estimated)

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110 Figure 3.37 C alculated and experimental XRPD for rht 3 rht 6 synthesis: A solution of Cu(NO 3 ) 2 2.5H 2 O (0.168 mmol) and 7 (0.112 mmol) in 1 mL of DMF was prepared. The solution was then heated to 75C for 20 h then to 85 C for 12h blue crystals were obtained and purity was confirmed by XRPD (figure 3. 3 8 ) Single crystal X ray was attempted and data was collected. However, low resolution data was collected and did not allow the structure to be solved However, the unit cell parameters could be determined: a = b = c = 58.06 ; F m 3 m) Expected f ormula: Cu( C 16 H 8 N 5 O 5 ) 0.5 (NO 3 ) 0.167 (O 2 ) 0.167 (Z=192, unit cell Mw= 48323 456 g/mol)

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111 Figure 3. 38 C alculated and experimental XRPD for rht 6 Zn TZI (sra topology) synthesis: A solution of Zn (NO 3 ) 2 6 H 2 O (0. 0 168 mmol) and 5 tetrazolylisophthalic acid (0. 0336 mmol) in 2 mL of DMF and 1 mL of water was prepared. T he solution was then heated to 85C for 12 h then to 105 C for 23h rod like crystals were obtained and purity was confirmed by XRPD (figure 3. 3 9 ). Topology was assessed with TOPOS40 software : Point (Schlafli) symbol for net: {4 2 ;6 3 ;8} 4 c net; uninodal net ; t opological type: sra SrAl 2 CeCu 2 ABW Single crystal X ray data (see section 3.8.4 )

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112 Figure 3. 39 C alculated and experimental XRPD for Zn TZI (sra) Y and TZI (sqc 5588 topology) synthesis: A solution of Y (NO 3 ) 3 6 H 2 O (0. 03 mmol) and 5 tetrazolylisophthalic acid (0. 04 mmol) in 0.75 mL of DMF and 0.25 mL of water was prepared. T he solution was then heated to 8 5c for 12 h then to 105 c for 23h and finally to 115c for 23h plate like crystals were obtained an d purity was confirmed by XRPD (figure 3. 40 ). Topology was assessed with TOPOS40 software : Point (Schlafli) symbol for net: {6 2 ;8 2 ;10 2 }2{6 2 ;8 4 }{6 3 }4 3,4 c net with stoichiometry (3 c)4(4 c)3; 3 nodal net ; t opological type: sqc5588 (epinet.ttd) Single crystal X ray data (see section 3.8.4 )

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113 Figure 3. 40 C alculated and experimental XRPD for Y TZI (s qc5588 ) Cu and TZB (new topology) synthesis : A solution of Cu (NO 3 ) 2 2.5 H 2 O (0. 084 mmol) and 4 tetrazolyl benzo ic acid (0. 112 mmol) in 1.5 mL of DMF was prepared. T he solution was then heated to 85c for 12 h then to 105c for 23h an impure mixture was obtained along with polyhedron crystals Topology was assessed with TOPOS40 software: Point (Schlafli) symbol for net: {4 14 ;5 8 ;6 6 }2{4 4 ;5 2 } 4,8 c net wi th stoichiometry (4 c)(8 c)2; 2 nodal net ; new topology. Single crystal X ray data (see section 3.8.4 ) Cu and TZB ( lvt net ) synthesis : A solution of Cu (NO 3 ) 2 2.5 H 2 O (0. 156 mmol) and 4 tetrazolyl benzo ic acid (0. 105 mmol) in 1 mL of DMF was prepared. T he solution was then heated to 85c for 12 h, rod like crystals were obtained and purity was confirmed by XRPD (figure 3. 41 ).

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114 Figure 3. 41 C alculated and experimental XRPD for Cu and TZB (lvt net) Topology was assessed with TOPOS40 software: Point (Schlafli) symbol for net: {4^2.8^4} 4,4 c net; uninodal net ; t opological type: lvt Single crystal X ray data (see section 3.8.4 ) 3. 8 .3. Supercritical CO 2 activation and Gas Sorption Experiments Typical activation process es : Typical activation processes are performed by replacing the, usually high boiling point, solvent inside the pores by a more volatile solvent (solvent exchange). After periods varying from 1 day to ~ a week, during which successive refreshin g of the solution is preferable. The sample can then be dried and loaded to a sorption cell (slightly wet samples are loaded when moisture sensitive materials are involved )

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115 Supercritical CO 2 activation : Supercritical CO 2 activation experiments were performed using a TOUSIMIS Samdri PVT 3D instrume nt In a typical experiment, around 50 mg of crystalline materials were washed with the mother liquor prior to s olvent exchange using 200 proof ethanol for a period of 7 to 10 days (refreshing the solution every day). The crystals are then loaded into a gl ass cell and covered with ~1mL of 200 proof ethanol. The cell is finally transferred to the instrument chamber. After cooling the chamber to temperatures between 0 and 10C the cell is filled with liquid CO 2 followed by a 15 min purge. The material is then left to soak in liquid CO 2 for 2 hours (temperature should al ways be kept between 0 and 10C during purges and soaks times). After 2 hours, the cell is again purged for 10 min and so a ked in fresh liquid CO 2 I n order to eliminate traces of ethanol, s everal purges are scheduled (a total of ~6 purges every 2 hours). After the last purge, the heat is turned on to automatically reach supercritical temperatures (> 32 C ) After reaching supercritical temperature and pressure (>1100 psi) the sample is left for 30 min in the supercritical fluid environment. The system is then allowed to slowly breed overnight. During the breed time, the pressure will decrease very slowly to ~ 200 psi (the heater should be left on until the end of the experiment). The dry samp le is now ready for sorption analysis Gas Sorption : All s orption isotherms were record ed using a volumetric Autosorb I instrument.

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116 3.8 .4 Single C rystal Structural Analysis and Refinement 3.8.4.1. Crystal data and structure refinement for rht 1 Empirical formula C27 H15 Cu6 N12 O1 6 Formula weight 258.5 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group c ubic F m 3m Unit cell dimensions a = 44.358(8) alpha = 90 b = 44.358(8) beta = 90 c = 44.358(8) gamma = 90 Volume 87280(27) 3 Z, Calculated density 32 0.93 Mg/m 3 Absorption coefficient 1.207 mm 1 F(000) 24046 Crystal size 0.20 x 0.20 x 0.20 mm Theta range for data collection 2.05 to 19.23 deg. Limiting indices 5<=h<=41, 31<=k<= 40, 38<=l<=37 Reflections collected / unique / observed 9092 / 1702 / 1265 [R(int) = 0.1309] Completeness to theta = 19.98 92.0 % Refinement method Full matrix least squares on F 2 Data / restraints / parameters 1702 / 0 / 197 Goodness of fit on F^2 1.084 Final R indices [I>2sigma(I)] R1 = 0.0787, wR2 = 0.1781 R indices (all data) R1 = 0.1085, wR2 = 0.1933 Largest diff. peak and hole 0.754 and 0.552 e. 3

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117 3.8.4.2. Crystal data and structure refinement for rht 2 Empirical formula C45 H27 Cu6 N12 O16 Formula weight 1414.98 Temperature 293(2) K Wavelength 1.54178 Crystal system, space group cubic, Fm 3m Unit cell dimensions a = 54.3898(16) alpha = 90 b = 54.3898(16) beta = 90 c = 54.3898(16) gamma = 90 Volume 160899(8) 3 Z, Calculated density 32, 0.467 Mg/m 3 Absorption coefficient 0.890 mm 1 F(000) 22432 Crystal size 0.1 x 0.1 x 0.1 mm Theta range for data collection 2.30 to 36. 42 deg. Limiting indices 10<=h<=41, 31<=k<=29, 41<=l<=30 Reflections collected / unique 19637 / 1950 [R(int) = 0.1149] Completeness to theta = 36.42 99.6 % Refinement method Full matrix least squares on F 2 Dat a / restraints / parameters 1950 / 0 / 75 Goodness of fit on F 2 1.329 Final R indices [I>2sigma(I)] R1 = 0.1358, wR2 = 0.3591 R indices (all data) R1 = 0.1759, wR2 = 0.3802 Largest diff. peak and hole 0.585 and 0.430 e. 3

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118 3.8.4.3. Crystal data and struc ture refinement for rht 3 Empirical formula C63 H39 Cu6 N12 O16 Formula weight 1739.25 Temperature 100(2) K Wavelength 1.54178 Crystal system, space group cubic, Fm 3m Unit cell dimensions a = 63.931(3) alpha = 90 b = 63.931(3) beta = 90 c = 63.931(3) gamma = 90 Volume 261298(20) 3 Z, Calculated density 32, 0.354 Mg/m 3 Absorption coefficient 0.590 mm 1 F(000) 27808 Crystal size 0.10 x 0.10 x 0.10 mm Theta range for data collection 1.95 to 38.86 deg. Limiting indices 51<=h<=51, 8<=k<=50, 35<=l<=35 Reflections collected / unique 34866 / 3498 [R(int) = 0.2215] Completeness to theta = 38.86 97.0 % Max. and min. transmission 0.9434 and 0.9434 Refinement method Full matrix least squares on F 2 Data / restraints / parameters 3498 / 2 / 91 Goodness of fit on F 2 1.014 Final R indices [I>2sigma(I)] R1 = 0.1209, wR2 = 0.2571 R indices (all data) R1 = 0.2441, wR2 = 0.3233 Largest diff. peak and hole 0.341 and 0.499 e. 3

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119 3.8.4.4. Crystal data and structure refinement for Zn TZI (sra) Empirical formula C11 H13 N5 O5 Zn Formula weight 360.63 Temperature 100(2) K Wavelength 0.71073 Crystal system, space group monclinic, P21 /c Unit cell dimensions a = 10.079(3) alpha = 90 b = 12.698(4) beta = 105.145(6) c = 10.954(3) gamma = 90 Volume 1353.2(7) 3 Z, Calculated density 4, 1.770 Mg/m 3 Absorption coefficient 1.849 mm 1 F(000) 736 Crystal size 0.15 x 0.10 x 0.10 mm Theta range for data collection 2.09 to 25.03 deg. Limiting indices 11<=h<=10, 13<=k<=9, 13<=l<=10 Reflections collected / unique 3598 / 2229 [R(int) = 0.0398] Completeness to theta = 25.03 93.7 % Max. and min. transmission 0.8367 and 0.7689 Refinement method Full matrix least squares on F 2 Data / restraints / parameters 2229 / 0 / 242 Goodness of fit on F 2 1.061 Final R indices [I>2sigma(I)] R1 = 0.0519, wR2 = 0.1061 R ind ices (all data) R1 = 0.0719, wR2 = 0.1154 Largest diff. peak and hole 0.759 and 0.449 e.A 3

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120 3.8.4.5. Crystal data and structure refinement for Y TZI ( sqc ) Empirical formula C36 H12 N16 O30 Y5 Formula weight 1593.17 Temperature 183(2) K Wavelength 0.71073 Crystal system, space group tetragonal, P 4 Unit cell dimensions a = 19.692(5) alpha = 90 b = 19.692(5) beta = 90 c = 14.554(8) gamma = 90 Volume 5644(4) 3 Z, Cal culated density 2, 0.938 Mg/m 3 Absorption coefficient 2.594 mm 1 F(000) 1550 Crystal size 0.05 x 0.05 x 0.05 mm Theta range for data collection 1.74 to 20.81 deg. Limiting indices 12<=h<=14, 19< =k<=11, 14<=l<=0 Reflections collected / unique 6213 / 4601 [R(int) = 0.0723] Completeness to theta = 20.81 90 % Max. and min. transmission 0.8812 and 0.8812 Refinement method Full matrix least squares on F 2 Data / re straints / parameters 4601 / 0 / 188 Goodness of fit on F 2 0.935 Final R indices [I>2sigma(I)] R1 = 0.0766, wR2 = 0.1920 R indices (all data) R1 = 0.1057, wR2 = 0.2059 Largest diff. peak and hole 0.537 and 0.491 e.A 3

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121 3.8.4.6. Crystal data and structure refinement for Cu TZB (new topology) Empirical formula C95.50 H40 Cu9 N46.50 O28 Formula weight 2858.60 Temperature 163(2) K Wavelength 0.71073 Crystal system, s pace group orthorhombic, Pnnm Unit cell dimensions a = 30.075(12) alpha = 90 b = 13.588(6) beta = 90 c = 19.622(8) gamma = 90 Volume 8019(6) 3 Z, Calculated density 2, 1.184 Mg/m 3 Absorption coefficient 1.236 mm 1 F(000) 2847 Cryst al size 0.05 x 0.04 x 0.03 mm Theta range for data collection 1.94 to 23.41 deg. Limiting indices 33<=h<=16, 15<=k<=6, 20<=l<=20 Reflections collected / unique 13051 / 5802 [R(int) = 0.0863] Completeness to theta = 23.41 95.5 % Max. and min. transmission 0.9639 and 0.9408 Refinement method Full matrix least squares on F 2 Data / restraints / parameters 5802 / 6 / 380 Goodness of fit on F 2 1.002 Final R indices [I>2sigma(I)] R1 = 0.0974, wR2 = 0.2697 R indices (all data) R1 = 0.1478, wR2 = 0.3031 Largest diff. peak and hole 0.961 and 0.700 e.A 3

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122 3.8.4.7. Crystal data and structure refinement for Cu TZB (lvt) Em pirical formula C11 H4 Cu N5 O3 Formula weight 317.73 Temperature 293(2) K Wavelength 1.54178 Crystal system, space group orthorhombic, Ima2 Unit cell dimensions a = 7.1215(2) alpha = 90 b = 9.0777(3) beta = 90 c = 21.5374(5) gamma = 90 Volume 1392.32(7) A 3 Z, Cal culated density 4, 1.516 Mg/m 3 Absorption coefficient 2.367 mm 1 F(000) 632 Crystal size 0.20 x 0.07 x 0.06 mm Theta range for data collection 4.11 to 58.87 deg. Limiting indices 7<=h<=6, 7<=k<=6, 12<=l<=23 Reflections collected / unique 1350 / 515 [R(int) = 0.0184] Completeness to theta = 58.87 75.4 % Max. and min. transmission 0.8710 and 0.6489 Refinement method Full matrix least squares on F 2 Data / restraints / parameters 515 / 25 / 103 Goodness of fit on F 2 1.140 Final R indices [I>2sigma(I)] R1 = 0.0488, wR2 = 0.1303 R indices (all data) R1 = 0.0500, wR2 = 0.1318 Largest diff. peak and hole 0.871 and 0.400 e.A 3

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123 3.9 References Cited 1. Stein, A.; Keller, S. W. and Mallouk, T. E. Science 1993 259 1558 1564 2. Frey, G. J. Solid State Chem 2000 152 37 48. 3. Yaghi, O. M. Science 2002 295 469 472. 4. Kitagawa, S.; Kitaura, R.; Noro, S. I. Angew. Chem. Int. Ed 2004 43 2334 2375. 5. Pauling, L. J. Am. Chem. Soc. 1929 51 1010 1026 6. Mueller, U.; Lobree, L.; Hesse, M.; Yaghi, O. M. and Eddaoudi, M. 2003 US 6624318. 7. Moulton, B. and Zaworotko, M. J. Chem. Rev. 2001 101 1629 1658. 8. Yaghi, O. M. Acc. Chem. Res. 2001, 34 319 330. 9. Ockwig, N. W.; Delgado Friedrichs, O.; O'Keeffe, M. and Yaghi, O. M. Acc. Chem. Res. 2005 38 176 182. 10. Liu, Y.; Kravtsov, V. C.; Beauchamp, D. A.; Eubank, J. F. and Eddaoudi, M. J. Am. Chem. Soc. 2005 127 7266 7267. 11. Brant, J. A.; Liu, Y.; Sava, D. F.; Beauchamp, D. and Eddaoudi, M. J. Mol. Struct. 2006 796 160 164. 12. Liu, Y.; Kravtsov, V. Ch.; Larsen, R. and Eddaoudi, M. Chem. Commun. 2006 14 1488 1490. 13. Resource ( http://rcsr.anu.edu.au/ ). 14 Perry, J. J.; Perman, J. A. ; Zaworotko, M. J. Chem. Soc. Rev. 2009 38 1400 1417. 15. Sudik, A. C.; Ct, A. P.; Wong Foy, A. G.; O'Keeffe, M. and Yaghi, O. M. Angew. Chem. 2006 45 2528 2533. 16. Alkordi, M H.; Brant, J A.; Wojtas, L ; Kravtsov, V Ch.; Cairns, A J.; Eddaoudi, M. J. Am. Chem. Soc. 2009 131 17753 17755. 17. Cairns, A. J.; Perman, J. A.; Wojtas, L.; Kravtsov, V. Ch.; Alkordi, M. H.; Eddao udi, M.; Zaworotko, M. J. J. Am. Chem. Soc. 200 8 130, 1560 1561.

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124 18. McManus, G J.; Wang, Z ; Zaworotko, M J. Cryst Growth Des 2004 4 11 13. 19. Perry, J J., IV; Kravtsov, V Ch.; McManus, G J.; Zaworotko, M J. Am. Chem. Soc. 2007 129 10076 10077. 20. Nouar, F., Eubank, J. F., Bousquet, T., W ojtas, L., Zaworotko, M. J.; Eddaoudi, M. J. Am. Chem. Soc. 2008 130 1833 1835 21. Holden, A. Shapes, Space, and Symmetry ; Columbia University Press: New York 1971. 22. Eddaoudi, M.; Kim, J.; Wachter, J. B. Yaghi, O. M. J. Am. Chem. Soc. 2001 123 4368 4369. 23. Moulton, B.; Lu, J.; Mondal, A.; Zaworotko, M. Chem. Commun. 2001 863 864 24. Delgado Friedrichs, O. ; O'Keeffe M. Acta Cryst 2007 A63 344 347. 25. Demko, Z. P.; Sharpless, K. B. J. Org. Chem. 2001 66 7945 7950. 26. Ritzn, A.; Frejd, T. Eur. J. Org. Chem. 2000 22 3771 3782. 27. a) Mezei, G.; McGrady, J. E. and Raptis, R. G. Inorg.Chem. 2005 44 7271 7273. b) Zhai, Q.; Lu, C.; Chen, S.; Xu, X. and Yang, W. Cryst.Growth Des. 2006 6 1393 1398. 28. Y aghi, O. M.; O'Keeffe, M.; Ockwig, N. W.; Chae, H. K.; Eddaoudi, M.; Kim, J. Nature 2003 423 705 714. 29. Wang, Z.; Kravtsov, V. Ch. ; Zaworotko, M. J. Angew. Chem. Int. Ed. 2005 44 2877 2880. 30. Atlas of zeolite framework types ( www.iza structure.org/databases/ ). 31. Spek, A. L. Acta Cryst 1990 A46 c34. 32. Rowsell, J. L. C.; Yaghi, O. M. J. Am. Chem. Soc. 2006 128 ,1304 1315. 33. Dinca, M.; Han, W. S.; Liu, Y.; Dailly, A.; Brown, C. M.; Long, J. R. Angew. Chem. Int. Ed. 2007 46 1419 1422. 34. Dinca, M. and Long, J. R. J. Am. Chem. Soc. 2007 129 11172 11176. 35. Mulfort, K. L. and Hupp, J. T. J. Am. Chem. Soc. 2007 129 9604 9605. 36. Li u, Y.; Eubank, J. F.; Cairns, A. J.; Eckert, J.; Kravtsov, V. Ch.; Luebke, R.; Eddaoudi, M. Angew. Chem. Int. Ed. 2007 46 3278 3283.

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125 37. Hayashi, H.; Cote, A. P.; Furukawa, H.; O'Keeffe, M.; Yaghi, O. M. Nat. Mater. 2007 6 501 506. 38. Eddaoudi, M., Nouar, F. ; Eubank, J. F.; Bousquet, T.; Wojtas, L.; Zaworotko, M. J. U.S. Pat. Publ. 20090143596 2009 39. Eddaoudi, M.; Li, H.; Yaghi, O. M. J. Am. Chem. Soc. 200 0 1 22 1391 1397 40 Nelson, A P.; Farha, O K.; Mulfort, K L.; Hupp, J T J. Am. Chem. Soc. 2009 131 458 460. 41. Sing, K. S. W.; Everett, D. H.; Haul, R. A. W.; Moscou, L.; Pierotti, R. A.; Rouquerol, J.; Siemieniewska, T Pure Appl. Chem 1985 57(4), 603 6 19. 42. Delgado Acta Cryst. 2006 A 62 350 355 43. Zou, Y ; Park, M ; Hong, S ; Lah, M Soo. Chem. Commun. 2008 20 2340 2342. 44. Yan, Y ; Lin, X ; Yang, S ; Blake, A J.; Dailly, A ; Champness, N R.; Hubberstey, P ; Schroeder, M Chem. Commun. 200 9 9 1025 1027 45. Zhao, D ; Yuan, D ; Sun, D ; Zhou, H C J. Am. Chem. Soc. 2009 131 9186 9188 46. Hong S ; Oh M ; Park M ; Yoon J W ; Chang J S ; Lah M S Chem. Commun. 200 9 36 5397 5399 47. Zhang, J. P.; Horike, S.; Kitagawa, S. Angew. Chem. Int. Ed. 2007 46 889 892. 48. Zhang, J. P ; Kitagawa, S J. Am. Chem. Soc. 2008 130 907 917. 49. Mircea D ; Yu, A. F.; Long, J.R. J. Am. Chem. Soc. 2006 128 8904 8913. 50. Mircea D .; Dailly, A.; Liu, Y.; Brown, C. M.; Neumann, D.; Long, J. R. J. Am. Chem. Soc. 2006 128 16876 16883 51. Dinca, M ; Han, W S ; Liu, Y ; Dailly, A .; Brown, C. M.; Long, J R Angew. Chem. Int. Ed. 2007 46 1419 1422. 52. Dinca, M ; Dailly, A .; Tsay, C. ; Long, J R Inorg Chem 2008 47 11 13. 53. Watanabe, S. Nature 1949 163 225 226. 54. Koyama, H.; Saito, Y. Bull. Chem. Soc. Jpn 1954 27 112 114. 55. V an Niekerk, J. N.; Schoening, F. R. L. Acta Cryst. 1953 6 227 232.

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126 56. Figgis, B. N.; Robertson, G. B. Nature 1965 205 694 695 57. Yu Z P.; Xiong, S. S.; Yong, G. P.; Wang Z. Y. J.Coord.Chem. 2009 62 242 248 58. Li, Y ; Xu, G ; Zou, W Q ; Wang, M S ; Zheng, F K. ; Wu, M. F. ; Zeng, H. Y. ; Guo, G. C. ; Huang, J. S. Inorg. Chem. 2008 47 7945 7947. 59. Zhang, J. Y.; Wang, Y. Q.; Peng, H. Q. ; Cheng, A. L. ; Gao, E. Q. Struct. Chem. 2008 19 535 539. 60. Yu, Z ; Xie, Y ; Wang, S ; Yong, G ; Wang, Z. Inorg. Chem. Commun. 2008 11 372 376. 61. Jiang, T.; Zhao, Y. F.; Zhang, X. M. Inorg. Chem Commun. 2007 10, 1194 1197.

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127 Chapter 4 Post S ynthetic M odification s of Zeolite L ike Metal Organic Frameworks 4 .1. Introduction Zeolites are microporous alumino silicate minerals. The t erm zeolite, from the Greek zeo (boil) and lithos (solid), originated in 175 6 when Axel Fredrik Cronstedt a Swedish mineralogist, observed that when heated, the material s generated large amount s of steam from water adsorbed in the solid s The unique combination of properties makes zeolites a significant class of porous materials of broad academic and industrial interests. 1 So far more than 190 frameworks types are recognized by the International Zeolite Association (IZA) as zeolites. 2 Their specific conformation does not allow for interpenetration and permit larger free volume to be generated. Zeolites, built from tetrahedral building components linked through oxygen atoms linkers are anionic materials and their charge is balanced by counter ion s present in the cages It is therefore possible, via ion exchange, to tune the properties of the materials toward desirable functions and specific applications These porous compounds can for example, act as molecular sieves, i.e. their ordered pores and openings enable them to selec tively separate molecules based on their respective size s The y are also widely used as catalysts in the petrochemical field Moreover, zeolites are commonly e mployed as detergent or adsorbent desicc ant. However, they are difficult to alter in ter m of structure and composition and because they

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128 have cavities smaller than 1nm, their application is limited to applications involving small molecules. 3 It is therefore a great challenge to design and synthesize new porous solids topologically related to zeolites, with extra large cavities and functional organic building units. 4 Recently, a new class of metal organic materials with zeolitic topology was introduced and referred to as Zeolite like Metal Organic Frameworks (ZMOFs). 5 4 .2. Zeolite L ike Metal Orga nic Frameworks (ZMOFs): Design S trategy The design of Metal Organic Frameworks with nets topologically related to zeolites and with extra large cavities could in theory be achieved by i) employing decorated tetrahedral building units (replacing the vertex by a group of vertices) and/or by ii) using expanded linkers (increasing the spaces between the vertices) i.e. replacing the oxygen linker by larger building units. The design of so called zeolite like Metal Organic Framework s (ZMOFs) involves exp ansion of the oxygen link er, found in inorganic zeolites ( Si O Si ) by replacing it with an organic molecule linker that possess the necessary attributes to construct zeolite like frameworks with extra large cavities. The ligand i s judiciously chosen to b e rigid and to contain the necessary chelating and bridging functionalities Here, the single metal ion based Molecular Building Blocks (MBBs) strategy was employ ed, i.e. each hetero coordinated single metal ion, formed in situ is rendered rigid and directional using ligands that allow the completion of the metal ion coordination sphere via a hetero chelating functionality. 6 7 Accordingly, the ligand 4,5 imidazoledicarboxylic acid (H 3 ImDC) was used as the linker. It is rigid and contains the necessary bridging and chelating attributes to construct ZMOF s. The nitrogen groups

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129 direct the framework topology upon coordination to the metal, the carboxylate groups, position relative to nitrogen groups, secure the geometr y of the metal by locking it into its position through the formation of rigid five membered rings via N O hetero chelation. Also, the nitrogen atoms in the ligand permit adequately position ing of the tetrahedral building units at an angle similar to the T O T angle (i.e.: ~140) observed in inorganic zeolites. The chosen metal, e.g. Indium, allow s the formation of high coordination complexes (coordination number between 6 and 8) and therefore, MN 4 O 2 and MN 4 O 4 MBBs can be formed Solvothermal reactions of indium nitrate and H 3 ImDC in the presence of different Structure Directing Agents (SDAs) afforded two anionic microcrystalline materials referred to as sod ZMOF with a simplified formula: In(C 5 N 2 O 4 H 2 ) 2 (C 3 N 2 H 5 ) (Z = 96) and rho ZMOF with a simplified formula : In(C 5 N 2 O 4 H 2 ) 2 (C 7 N 3 H 15 ) 0.5 (Z = 48) In sod ZMOF, each indium is coordinated to 4 nitrogen atoms (from 4 different ligands) and two oxygen atoms (from 2 different ligands) to form 6 coordinated InN 4 (C O 2 ) 2 MBBs. In rho ZMOF, each indium is coordinated to 4 nitrogen atoms and 4 oxygen atoms from 4 different ligands to form 8 coordinated InN 4 (CO 2 ) 4 MBBs. The rho ZMOF unit cell contains 48 indium metal ions and 96 ligands where the negatively charged framework ([In 48 HImDC 96 ] 48 ) is ne utralized by 24 doubly protonated hexahydro 2H pyrimido[1,2 a]pyrimidine (HPP). The unit cell volume of the resulting framework is up to 9 times higher than the aluminosilicate rho analogue (figure 5.1). The rho ZMOF material contains extra large cavities consisting of cages in which spheres of 18.5 (VDW) in diameter can fit The cages are interconnected through double 8 membered rings (D8R) (figure 4 .2).

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130 Figure 4 .1 Schematic representation showing the building blocks necessar y for the assembly of inorganic RHO zeolite (left) and rho ZMOF (right). rho zeolite formula is: | (Na + ,Cs + ) 12 | [ Al 12 Si 36 O 96 ] RHO where Silicon and Aluminum ions arrange as tetrahedra linked by oxygen atoms forming a ~140 angle. rho ZMOF, with a formula | ( HPP 2 + ) 24 | [ In 48 (C 5 N 2 O 4 H 2 ) 96 ] rho ZMOF, consist in the assembly of Indium tetrahedra linked by 4,5 Imidazole dicarboxylates resulting in a framework with a volume up to 9 times higher than inorganic rho zeolite O, C, N, H and In are shown in red, grey, blue, white and green respectively The synthesis of new materials, topologically related to zeolites, with new features that could widen the range of use is of scientific and major industrial interests. Zeolite like Metal Organic Frameworks (ZMOFs) are anionic microporous crystalline materials with zeolite features, designed to contain larger sized cavities.

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131 Figure 4 .2 Rep resentation of a zeolite with rho cages (green and blue) containing 8, 6 and 4 member ed rings, are connected through double 8 membered rings (D8R) (red) (left) View of 1 cage in rho ZMOF O, C, N, H and In are shown in red, grey, blue, white and green respectively (right) Other ZMOFs were synthesized in my research group, 8, 9 however, the focus of my work was mainly on tuning the properties of rho ZMOFs via multiple synthetic modifications with the objective of gaining more control over the properties and accessing more information that would help target various applications. The following sections will focus on different types of modification and the emphasis will mainly be toward hydrogen storage. Indeed, a s discussed in chapter 2, extensive research is involved toward the development of physisorption based materials with improved performance for hydrogen storage. So far, the gravimetric and volum etric targets set by the U.S. Department Of Energy (DOE) are far from being achieved. In order to increase the current sorption uptakes, the H 2 material binding affinities need to be greatly enhanced. In fact, several key parameters need to be tune d in ord er to increase the existing binding affinities at room temperature. These parameters include: 1) availability

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132 of important numbers of accessible open metal binding sites; 2) highly polarizable atoms in the organic links ; 3) the introduction of a strong ele ctrostatic field in the cavity by having a charged framework, along with extra framework cations (as in zeolites); and, finally, 4) a narrow range of pore sizes (~1 nm), which would allow each H 2 molecule to interact with more atoms than on a simple surfac e. All of these requirements must be accomplished while maintaining high surface area and pore volume without an appreciable increase in framework density (necessary for high loading to maintain higher volumetric and gravimetric uptakes), which points towards light weight constituents and substitutions. Platforms are needed to develop a porous material with optimized properties that could reach the targets set by the DOE. The r ho ZMOF seems to be an excellent candidate to investigate these key parameter s separately. Indeed, the possibility to tu ne the material by ion exchange, encapsulation using various cations or by other post synthetic modifications and study the effect on H 2 storage could lead to crucial information that will help material scientists to design and synthesize new porous materials with improved H 2 storage performance. The next part is related to ion exchange and the effect on hydrogen storag e. A systematic study pertaining to ion exchange and the effect on H 2 ( rho ZMOF ) interactions was pursued and will be fully described in the next part.

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133 4 .3. Zeolite L ike Lithium and Magnesium Ion E xchange and H 2 ( rho ZMOF) Interaction S tudies 4 .3. 1 Li and Mg Ion E xchange in rho ZMOF It is possible, via ion exchange and/or encapsulation experiments to introduce various extra framework cations in the ZMOF cavities and therefore creat e H 2 sorption sites. As with the inorganic rho material, the rho ZMOF exhibit s facile ion exchange ability. Indeed it has been demonstrated that the organic cations (HPP) in the cavities can be fully exchanged at room temperature after 24 hours. 5 The present work focuses on ion exchange and the effect of the electrostatic field on the binding of H 2 in the porous (In H ImDC) based rho ZMOF. 10 T he effect of several extra framework cations (DMA + (dimethylamonium) Li + Mg 2+ ) on the H 2 sorption energetics and uptake will be discussed The choice of lithium as a cation for this study was driven by its known high affinity for H 2 11, 12 as well as its interesting behavior in conventional inorganic zeolites, 1 0 where zeolite LiX is used in air separation. In addition, lithium cations are light and have a small ionic radius compared to most inorganic cations, which results in a red uced framework density and still maintains large enough voids for H 2 storage. The other cation of interest is magnesium also because of its high affinity for H 2 11, 12 and because only half as many of the divalent cations are needed to balance the framework charge. Magnesium is relatively similar in size to the monovalent lithium and therefore an excellent complementary cation for charge/space comparison studies of electrostatic effects on sorption energetics and uptake of H 2 The ion exchange studies indica te that the organic cations in the cavities can be fully exchanged at room temperature after 15 to 24 hours (depending on the inorganic cation used), as shown by atomic absorption studies (see

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134 experimental section 4 3 .6 ). The fully exchanged compounds were found, by optical microscopy and powder X ray diffraction (PXRD), to retain their morphology and crystallinity, respectively (Figure 4 .3) In order to obtain the (In ImDC) based rho ZMOF on a larger scale than previously reported, 5 the original reaction co nditions were slightly modified Reaction of H 3 ImDC and In(NO 3 ) 3 2H 2 O in DMF yields a microcrystalline material referred to as DMA rho ZMOF. Single crystal X ray diffraction studies confirmed the framework structure and correspondi ng unit cell parameters; however, the extra framework organic cations and their locations could not be determined on account of the large volume of the cavities and large number of guest molecules. Figure 4 .3. Experimental PXRD spectra of DMA rho ZMOF, Mg rho ZMOF, Li rho ZMOF compared to the original HPP rho ZM OF (experimental and simulated)

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135 4 .3.2. Mg rho ZMOF Single Crystal X ray D iffraction Single crystal X ray diffraction studies were also performed on Mg rho ZMOF on the microcrystal diffraction beamline 11.3.1 at the Advanced Light Source in order to determine the locations of the extra framework cations The Mg(II) cation was located as the str ongest peak in the Fourier map in the solution of the framework structure by direct methods and least squares refinement. Three crystallographically unique oxygen atoms were subsequently located which formed an octah edron around the Mg(II) cation. These oxygen atoms were refined to chemically reasonable positions without any constraints other than the sym me try imposed by the space group. Hydrogen atoms on the aqua ligands could not be reliably extracted from the Fourier map, and were not included in the final model. Inspection of the displacement parameters suggests either the presence of considerable diso rder or partia l occupancy of the cation site. Positional disorder is consistent with the ligand O101 and the free carboxylate oxygen atom O2. It is likely that the cation prefers a site with one shorter hydrogen bond, but disorder and symmetry constraints lead to a model containing an averaged superposition for multiple possible geometries with correspondingly large anisotropic displacement parameters. Positional disorder is further favored by the lack of any peaks consistent with a Mg(II) cation elsewhere in the structure. However, each magnesium cation w as found to be in the form of a hexaaqua complex, [Mg(H 2 O) 6 ] 2+ in Mg rho ZMOF, [Mg(H 2 O) 6 ] 2+ 24 [In 48 (HImDC) 96 ] Each hydrogen bonds well within the expected range for such

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136 interactions ) between four of the six aqua ligands ) and carboxylate oxygen atoms of the framework (Figure 4 .4 ). The two remaining aqua ligands with longer are less strongly bound to the metal. Figure 4 .4 Top: A fragment of the single crystal structure of Mg rho cages (green) and th e cubohemioctahedral arrangement (shown as a yellow polyhedron) of the twelve [Mg(H 2 O) 6 ] 2+ per cage. All H atoms have been omitted for clarity. Bottom: hexaaqua magnesium complex is loca ted near each of the twelve 4 cage, interacti ng with the framework through hydrogen bonds (shown as black dotted lines, Oxygen to oxygen distance is ~2.9 ) with four of the aqua ligands. Intra m the closest 4 membered ring) is 6.532 . O, C, N, H, In and Mg are shown in red, grey, blue, white green and yellow respectively

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137 a) b ) 4 .3.3. Sorption D ata on DMA Mg and Li rho ZMOF H 2 adsorption isotherms were recorded after complete evacuation a t 115C of the fully exchanged ( with acetonitrile ) materials (Figure 5.5 a ). Hydrogen loadings are reported in terms of H 2 /In to directly compare the three materials on a structural basis, as well as directly correlate the isotherms to the loading dependence of the Inelastic Neutron Scattering spectra. For example, a loading of 1 H 2 /In corresponds to 0.40, 0.41, and 0.43 wt % for Li Mg and DMA rho ZMOF, respectively. Gravimetric capacities and other sorption related properties for the three materials are g iven in Table 4 1. The Li + exchanged material, Li rho ZMOF, can store slightly more H 2 molecules per indium at 1 atm than both Mg rho ZMOF and the parent DMA rho ZMOF framework, namely 2.28, 2.21, 2.21 molecules, respectively. Fig ure 4 .5 a) H 2 adsorption isotherms for DMA Mg and Li rho ZMOF at 78 K. b) E nlarged view o f the low pressure range in (a)

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138 We note that recent studies on lithium ion exchange in other MOFs have shown that the effect on the overall hydrogen storage capacity was not significant, 13 and enhanced H 2 uptake via framework reduction and doping with Li 0 /Li + has been largely attributed to displacement of interpenetrated frameworks. 14, 15 It is also notewort hy that a group recently reported a higher H 2 gravimetric capacity for a Li + exchange pts like MOF compared to the parent framework that was attributed to an increase of the accessible pore volume on the Li + exchanged compound. 16 At pr essures below 0.02 atm (Figure 4 .5 b), we find that the Li rho ZMOF and Mg rho ZMOF isotherms appear to have a steeper rise than the isotherm of the parent compound. Table 4 1 Sorption data for DMA Mg and Li rho ZMOF Material H 2 wt% H 2 per In Isosteric heat of adsorption (kJ/mol) DMA rho ZMOF 0.95 2.21 8.0 Mg rho ZMOF 0.91 2.21 9.0 Li rho ZMOF 0.91 2.28 9.1 H 2 wt% and H 2 per In values measured at 0.95 atm and 78 K; Isosteric heat of adsorption given for low surface coverage. This is in accord with the isoster ic heats of adsorption (Figure 4 .6 ) calculat ed from the isotherms (H 2 sorption isotherms were also recorded at 87 K for calculation of the isosteric heats of adsorption), where Li rho ZMOF and Mg rho ZMOF exhibit higher values (9.1 and 9.0 kJ/mol, r espectively) at low loading than the parent compound (8.0 kJ/mol). It is important to note that the slightly higher value for Li rho ZMOF contrast s to results observed in previous Li + exchanged MOFs, which show no evidence for strong

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139 H 2 Li + interaction(s). 1 3 16 In addition, the values for all three compounds are considerably higher than those observed in most neutral MOFs (typically 5 6 kJ/mol), 17 20 and comparable to some neutral MOFs with open metal sites. 21, 22 Figure 4 .6 Isosteric heats of adsorption for DMA Mg and Li -rho ZMOF calculated from the corresp onding isotherms at 78 and 87 K These high values associated with the rho ZMOFs must primarily be the result of having a charged framework along with the compensatin g cations. A similar comparison may be made between H 2 adsorbed in zeolites and on various (neutral) carbons, where the isosteric heat of adsorption is up to 50 % higher in the former depending on the extra framework cation. 23 31 The similarity of the adsorption isotherms of the three materials strongly suggests that the extra framework metal cations may not be directly accessible for binding the adsorbed hydrogen molecules, since much larger differences between the ion exchanged r ho ZMOF (Li + or Mg 2+ ) and the parent compound would be expected.

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140 Single crystal X ray diffraction data on Mg rho ZMOF suggest that two of the aqua ligands could in principle, be removed to create open metal binding sites on the extra framework cation. How ever, even at the highest temperature used for activation of this material (115C), we do not observe removal of any aqua ligands (heating beyond this temperature results in progressive degradation of the framework, see section 5. 3.6. ). This can be expecte d, since water molecules coordinated to extra framework cations in ion exchanged zeolites normally require temperatures well over 300C for removal. 1 We may consequently assume that the Li + cation in Li rho ZMOF also is fully coordinated with aqua ligands, most likely in a tetrahedral geometry (tetraaqua lithium complex), 32 so that the adsorbed H 2 molecules cannot, in either case (Mg 2+ or Li + ), interact directly with the extra framework cations, but most likely with the H atoms on the coordinated water mole cules. The similarity of the adsorption properties of the three materials can thereby readily be accounted for. This, in turn, leads to the conclusion that the enhanced isosteric heats of adsorption for these materials may largely be attributed to the pres ence of the electrostatic field in the cavity from the charged framework and counterions, and not from a direct interaction with the cations. The fact that the isosteric heats of adsorption for H 2 are highest in the ion exchanged rho ZMOFs for most of the range of loadings is likely a reflection of a higher electrostatic field in the cavities because of the large charge/size ratio of the Mg 2+ and Li + cations. This hypothesis is supported by the fact that the Li rho ZMOF isosteric heats of adsorption value is higher than Mg rho ZMOF, as there is a higher concentration of Li + cations per unit cell (i.e. larger distribution of the electrostatic field).

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141 4 .3.4. Inelastic Neutron S cattering (INS) D ata on DMA Mg and Li rho ZMOF Inelastic Neutron Scattering ( INS) is a phenomenon in which neutrons either gain or lose energy after colliding with atomic nuclei In contrast to other scattering methods that monitor interactions between photons and the electrons of the sample ( e.g. X ray crystallography ) INS monitors interactions between neutron s and n uclei of the sample W hen neutrons are considered, the strength of the interaction is dependent on the nuclei involved. When studying the hydrogen molecule binding sites in MOFs, INS spectroscopy is a very sensi tive technique that permit s a direct study of the interactions between hydrogen molecule adsorbate and the adsorbent 10,33 36 This method has been used to study the interactions of H 2 in various porous materials. 37 46 In fact, t he neutron scattering cross section of 1 H is very large and neutrons can be used to observe transitions in the hydrogen molecules that involve a change in the nuclear spin of the molecule which make this method particularly attractive for these studies Th e lowest rotational transition for the free H 2 molecules between para and ortho H 2 occurs at 14.7 meV. However, when H 2 is sorbed, the interaction with the adsorbent gives rise to a barrier to rotation which results in a strong decrease of this transition frequency. In fact, t he lowest transition frequency for the hindered rotor decreases approximately exponentially with increasing barrier height, which makes this technique very sensitive to small differences in barrier height. For the current study, the p eaks in the INS spectra are assigned on the basis of a previously reported model 33 36 namely that of a hindered rotor with two angular degrees of freedom. In the case of the free hydrogen molecule, the rotational energy levels can be expressed by the rel ation E = B(J + 1), where B is the

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142 rotational constant and J the rotational quantum number. The application of a barrier to rotation removes some of the degeneracy of the J levels and changes the level spacings. 47,48 The spacing of the two lowest energy le vels (labeled as 0 1) is strongly dependant and very sensitive to small difference in the barrier height Inelastic Neutron Scattering (INS) experiments were thus performed to provide information on binding sites for hydrogen in DMA Mg and Li rho ZMOF. All spectra exhibit some reasonably well defined, but broad, peaks that are tentatively assigned using the model discussed above (table 4 2) Table 4 .2 : Assignments for DMA Mg and Li rho ZMOF INS data. Material Transition energy (meV) Barrier ( V/B ) 0 1 0 2 1 2 DMA rho ZMOF 4.3 26.5 22.2 7.4 8.0 20.0 12.0 4.0 10.8 11.0 17.0 17.2 6.0 6.2 2.0 2.1 13.5 15.3 1.8 0.6 Mg rho ZMOF 7.2 21.2 14.2 4.8 (8.0) 10.5 17.4 6.9 2.3 12.0 16.2 4.2 1.45 13.0 15.6 2.6 0.9 14.0 15.0 1.0 0.35 Li rho ZMOF 3.0 31.0 28.0 9.45 4.5 26.1 21.6 7.2 7.3 20.8 13.3 4.5 9.5 18.3 8.8 2.9 11.0 17.0 6.0 2.0 (12.0) 16.2 4.2 1.4 14.0 15.1 1.1 0.4 Blue = observed peaks; Red = weak peaks; Green = calculated peaks; Shoulders are shown in parentheses.

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143 The INS spectra of hydrogen at different loadings in the 3 compounds show some similarities as expected from their respective hydrogen sorption properties (figure 4.7, 4.8 and 4.9) The spectra also reveal some very broad intensity underneath that must be due to a wide distribution of non specific binding sites. Figure 4 .7 INS spectra of DMA rho ZMOF at 0.5, 1, 1.5 and 3 H 2 per In Figure 4 .8 INS spectra of Mg rho ZMOF at 0.25, 0.5, 1 H 2 per In

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144 Figure 4 9. INS spectra of Li rho ZMOF at 0.5, 1, 2 and 4 H 2 per In At least four reasonably well defined binding sites for H 2 appear at the lowest loading for each of the compounds. Very useful structural information from previous INS studies on Li + exchanged zeolites are available elsewhere 49, 50 In fact, the enhanced affinity of zeolites for hydrogen when compared to neutral materials (i.e. carbons) is a consequence of the presence of an electrostatic field in the cavities and the interaction of H 2 with the extraframework cations. Valuable data on well characterized Li + exchange zeolites can thus be us ed to explain the enhanced H 2 binding in rho ZMOFs. Indeed, INS studies on Li + exchanged zeolite FAU (LiX) and Li + exchanged zeolite LTA (LiA) demonstrated the presence of multiple H 2 binding sites depending on the location of extraframework lithium cations in the framework cavities. For instance, H 2 adsorbed on Li + sites located in the six membered ring windows of LiX (type II) or LiA (type I) indicate a rotational transitions broad band at around 7.5 meV whereas for type III cations in LiX, a sharp transition is observed at 1 meV. The Li + cations located in the six

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145 membered ring si tes in these zeolites are presumably not fully accessible to hydrogen molecules because of the surrounding oxygen atoms from the windows. Therefore, the transition at 7.5 meV can be explained by more interactions of hydrogen with the oxygen atoms. In contr ast, i t is very likely that the Li + cations located in the type II sites are more 2 which explains the band observed at 1 meV. In the case of Li rho ZMOF, this strong peak at very low energy is not present which suggest s that indeed Li cations are not fully accessible to hydrogen. As discussed above, Mg 2+ cations in Mg rho ZMOF are in the form of a hexaaqua complex and we can assume that Li + cations are in the form of a tetraaqua complex in Li rho ZMOF. Rot ational transitions closer to the one associated to the six membered ring sites in zeolites are indeed observed for Li rho ZMOF in the range of 6 to 10 meV. Comparison of the spectra in DMA rho ZMOF and Li rho ZMOF at a loading of 1 H 2 per In show s for th e Li material, an additional broad intensity in the 6 10 meV range (figure 4 .10). Figure 4 .1 0. The INS spectra of Li rho ZMOF (red) and DMA rho ZMOF (black) at a loadings of 1 H 2 /In

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146 It is therefore apparent that the weight of the INS spectrum of H 2 in Li rho ZMOF is shifted to lower frequ encies i.e. stronger H 2 /host interactions around the Li + aqua complex; this persi sts at higher loadings (Figure 4 .9 ). We can therefore assume that the reason may arise from Li + cations in Li rho ZMOF being in a tetrahedral form and thus are more accessible to hydrogen in contrast to Mg 2+ cations in Mg rho ZMOF where the cation is in a n octahedral geometry This slightly stronger interaction in Li rho ZMOF can also be explained by the higher electrost atic field in Li rho ZMOF versus Mg rho ZMOF that may arise from the higher number of sites in Li rho ZMOF (24 versus 12 per cage for Mg rho ZMOF) On the other hand, comparison of the INS spectra of Mg rho ZMOF and DMA rho ZMOF show that they are somewhat similar except at low loading s that is at 0.5 H 2 per Indium (figure 4.7 and 4 .8). It seems also that the weight of the INS spectrum is greater for Mg rho ZMOF at frequencies below 10 meV which indicate the presence of some stronger binding sites than in DMA rho ZMOF. The isosteric heat of adsorption plots for Mg rho ZMOF, when compared to DMA rho ZMOF (figure 4 .6), indeed indicates stronger interaction at low loading for Mg rho ZMOF and similar interactions at higher loadings. A comparison can be made wit h previous studies of H 2 adsorption on the surface of MgO where a well defined peak at 11 meV is observed for the layer of H 2 51 This peak was attributed to H 2 located over a Mg position surrounded by an intervening layer of oxygen atoms. It can therefore be concluded that in Mg rho ZMOF, with values below 11 meV observed at low loading, the H 2 host interactions are stronger than on a MgO surface or on DMA rho ZMOF which could be explained by the presence of electrostatic effects.

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147 4 3.5. Summary and C onclusion T he current study on lit hium and magnesium ion exchange and H 2 ( rho ZMOFs) interaction s clearly demonstrates that the presence of an electrostatic field in the cavities of the host is mostly responsible of the increased isosteric heat of adsorpti on by around 50% when compared to neutral Metal Organic Frameworks. Indeed, the magnesium and lithium cations are not fully accessible to hydrogen molecules and are instead in the form of aqua complexes. 4 .3.6. Experimental S ection Synthesis : 4,5 Imidazoledicarboxylic acid (H 3 ImDC, 0.029 g, 0.174 mmol), In(NO 3 ) 3 2H 2 dimethylformamide (DMF, 4 mL) were added, respectively, to a 40 mL Parr acid digestion vessel, which was sealed and heated to 120C at a rate of 1C/min f or 3 days, then cooled to room temperature at a rate of 1C/min. The colorless polyhedral crystals were collected and air dried, yielding 0.0425 g DMA rho ZMOF with formula: (DMA + ) 48 [In 48 (HImDC) 96 ] ( 82% based on In(NO 3 ) 3 2H 2 O ) where DMA represents the dim ethylammonium extra framework cations (generated in situ from degradation of DMF). Ion e xchange : C rystals of DMA rho ZMOF were washed several times with the mother liquor, then with a mixture of ethanol (EtOH) and water (0.75:0.25). The crystals were then soaked in a solution containing NaNO 3 (1M in EtOH/water (0.75:0.25) and washed to replace all 48 DMA cations with Na + Then, the Na + exchanged compound

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148 was soaked in a solution containing LiNO 3 ( 1M in EtOH/water (0.75:0.25)) The crystals were then washed several times with an EtOH/water (0.75:0.25) solution to remove excess salt, and incorporation of Li + ions was followed by atomic absorption (AA) experiments. After 18 hours, all 48 Na + ions were completely exchanged with the Li + ions, as proven by the ab sence of any residual Na + to give Li rho ZMOF. In the case of the Mg 2+ exchanged compound, crystals of DMA rho ZMOF were washed several times with the mother liquor, and then with EtOH/water (0.75:0.25). The crystals were then soaked in a solution contain ing Mg(NO 3 ) 2 (0.75M in EtOH/water (0.75:0.25)) and washed to remove excess salt. The incorporation of Mg 2+ ions was followed by atomic absorption experiments, and, after 15 hours, all 48 DMA cations were completely exchanged ( AA: Mg/In ratio (calculated) = 0.5; Mg /In ratio (found) = 0.49) to give Mg rho ZMOF. Hydrogen Sorption : Samples of DMA rho ZMOF, Mg rho ZMOF, and Li rho ZMOF were activated by soaking the crystals in CH 3 CN for 12 hours. Approximately 45 mg of each activated sample was placed in a glass sample cell, evacuated at room temperature for 12 hours, and then at 115C for 6 hours. All sorption experiments were performed on a Quantachrome Autosorb 1. Inelastic Neutron Scattering (INS) : Fresh samples were placed in a minimal amount of CH 3 CN, sealed (to prevent evaporation of the solvent), and shipped to the Intense Pulsed Neutron Source (IPNS) at Argonne National Laboratory (ANL). The samples

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149 a) b ) were air dried on site at the IPNS facility, and subsequently evacuated at room temperature followed by evacuation at 115C in a vacuum tube furnace acc ording to the sorption protocol Each guest free (blank) sample was transferred (under He atmosphere) to a separate aluminum sample container, sealed under He, and connected to an external gas dosing syste m on the spectrometer. INS spectra for each sample were collected on the Quasi Elastic Neutron Spectrometer (QENS) at IPNS mostly in neutron energy loss. 2 ), H 2 was adsorbed in situ at various loadings with the sample at approximately 78 K, and equilibrated before cooling to the data collection temperature of approximately 15 K. TGA: Thermal gravimetric analysis graphs were recorded for the exchanged samples and are shown in figure 4.11. Figure 4 .1 1. TGA spectra of a) Li rho ZMOF and b) Mg rho ZMOF showing (for both compounds) a loss of acetonitrile at temperatures below 100C; at temperatures above 250C, a loss of water and framework degradation are observed

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150 Single Crystal X ray Diffraction : Data of Mg rho ZMOF were collected at the Small Molecule Crystallography beamline (11.3.1) at the Advanced Light Source (Berkeley, CA). A data collection strategy was specifically designed to pr ovide high quality data for weak, high scattering vector reflections. One scan for strongly diffracting, low scattering vector reflections was collected using 1 s. The detector was moved out to higher scattering vectors only, and 7 s. scans were used to co llect a full hemisphere of data. Data out to 0.75 1 were used for the final refinement. Crystal data and structure refinement for Mg rho ZMOF is: Identification code Mg rho ZMOF Empirical formula C20 H20 In2 Mg N8 O22 Formula weight 974.36 Temperature 296(2) K Wavelength 0.77490 Crystal sy stem, space group cubic, Im 3m Unit cell dimensions a = 30.9840(2) alpha = 90 b = 30.9840(2) beta = 90 c = 30.9840(2) gamma = 90 Volume 29744.9(3) 3 Z, Calculated density 24, 1.305 Mg/m 3 Absorption coefficient 1.012 mm 1 F(000) 11472 Crystal size Theta range for data collection 4.54 to 31.10 deg.

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151 Limiting indices 36<=h<=41, 30<=k<=41, 37<=l<=41 Reflections collected / unique 107309 / 3482 [R(int) = 0.0634] Completeness to theta = 31.10 99.2 % Absorption correction SADABS Ref inement method Full matrix least squares on F^2 Data / restraints / parameters 3482 / 0 / 131 Goodness of fit on F^2 1.097 Final R indices [I>2sigma(I)] R1 = 0.0543, wR2 = 0.1846 R indices (all data) R1 = 0.0622, wR2 = 0.1944 Largest diff. peak and hole 0.834 and 1.200 e. 3 4 .4. Zeolite like M : E ncapsulation and H 2 Storage Studies 4 .4.1. Introduction Previous studies show that it is possible to encapsulate large molecules in rho ZMOF (in the present context, encapsulation can be defined as the confinement of a molecule within a larger one). The rho ZMOF possesses cavities of at least 18.5 interconnected through windows of ~ 9. Therefore, ion exchange involving molecules larger than 9 is not possible and such molecules could only be included in the material via encapsulation. In fact, encapsulati on of positively charged ruthenium complexes (i.e. t ris(4,7 diphenyl 1, 10 phenanthroline)ruthenium(II); t ris(1, 10 phenanthroline)ruthenium(II) and bipyridyl) ruthenium(II)) as well as encapsulation of a cationic porphyrin derivative (i.e. 5,10,15, 20 tetrakis(1 methyl 4 pyridinio)porphyrin ) was successful and could be

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152 explained by directing electrostatic interactions that allow a one step construction of the anionic host and the cationic guest molecule s in situ 52 Pore size is one of the key parameters to be tuned in order to improve the current H 2 binding affinity with MOFs. In fact, as discussed in chapter 2, MOFs with large pores will often produce empty space away from the walls and will contribute little to the overall H 2 uptake of the MO F. Smaller pores (i.e. ~1nm) would be beneficial to enable hydrogen molecules to interact with more atoms than on a simple surface. In fact, a MOF with optimized pore sizes while maintaining high surface area and pore volume should lead to increased H 2 binding affinities higher H 2 density in the pores and therefore, better overall performance at temperature s close to ambient. Experimental systematic studies on the correlations between pore size and heat of adsorption are crucial but nevertheless very rare. Therefore, to perform systematic studies and gain more information on H 2 sorption behavior in MOF materials, platforms are needed. The possibility to tune the properties of zeolite like Metal Organic Frameworks (ZMOFs) such as rho ZMOF offer a grea t advantage toward the synthesis of new physisorption based porous materials with binding energies in the range of 20 kJ/mol that could be suitable for H 2 storage. In this context, a study of the effect of pore size and hydrogen storage on rho ZMOF was attempted. In fact, reducing the pore size in rho ZMOF could in principle be achieved by introducing large molecule s in the cages i.e. molecule s that c ould increase the surface area per unit volume by occup ying the space that does not contribu te to the overall uptake under the experiment conditions

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153 4 .4.2. Encapsulation of F ullerene Derivatives Previous attempt s in our group on encapsulating neutral C 60 fullerenes in rho ZMOF were unsuccessful. As discuss ed above, rho ZMOF is anionic and electrostatic interactions may favor a one step construction of the host material and the guest molecules in situ Therefore, fullerene derivatives were synthesized in order to be used as cationic guests of the rho ZMOF host (figure 4 .12) A brown powder, characteristic of the Tetra(N methyl piperazine)C 60 product was obtained after 20 hours of reaction (see experimental section 4 .4.5 ) 53 Figure 4 .1 2. Schematic of the synthesis of Tetra(N methyl piperazine)C 60 epoxide from fullerene C 60 and 1 methylpiperazine in chlorobenzene under open air for 20 hours with a 60 W incandes cent light at room temperature After processing, the final product was used to perform encapsulation experiments. In fact, the initial protocol to obtain pure crystals of rho ZMOF was modified and after several trials, brown polyhedral crystals were obtained. A schematic representing the hos t guest and the available space is shown in figure 4 .1 3 X ray powder diffraction w as used to confirm the identity of the material as rho ZMOF (see figure 5.15) Single X ray

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154 diffraction studies also confirmed the framework structure and corresponding unit cell parameters. However, it was not possible to locate the fullerene derivatives. Ultraviolet visible (UV Vis) spectroscopy was used to identify the fullerene derivative in rho ZMOF crystals; however, the spectra (of the organic product and the host guest crystals) did not show any specific peaks that could be used to confirm the presence of the molecule s in rho ZMOF Therefore, there is no strong evidence of the guest being inside rho ZMOF except for the color of the crystals However, in the following discussion, the material will be referred to as C 60 rho ZMOF for simplicity. Figure 4 .13. Schematic representation of Tetra(N methyl piperazine)C 60 epoxide as it could exist inside the framework Only a portion of a cage in rho ZMOF (18 ligands and 18 metals) is shown for clarity and to depict the available guest host space. The size of a regular C 60 molecule is ~10 ; the longest dimension for the present C 60 derivative is ~ 17 ; dimensions of ~ 4 to 5 separate the host from the guest on average (the shortest distance between the host and guest is ~ 1.5 from the methyl group to a H from the fr amework) and; the size of the cages in rho ZMOF is at least 18.5 VDW are taken into account for all dimensions. In, C, N, O, H are shown in green, grey, blue, red and white respectively.

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155 4 .4.3. Sorption Studies Sorption isotherms were record ed after evacuation of the framework at room temperature. The apparent BET surface area was determined to be around 750 m 2 /g which is close to the value for the parent DMA rho ZMOF material (~ 800 m 2 /g). However, the H 2 uptake was 1.3 % which represents an increase of ~ 30% over the parent framework (figure 4 .14) Figure 4 .14. H 2 sorption isotherm at 77K (left) and; isosteric heat of adsorption for C 60 rho ZMOF (right) Nevertheless, since the densities of the parent and the C 60 rho ZMOF are different, a more appropriate method to compare the two materials would be to calculate the uptakes per unit volume. In fact, if we consider 1 guest per unit cell of the framework, the volumetric uptake is more than 40% higher in the case of C 60 rho ZMOF when compare d to the parent framework (calculations are based on a simple conversion using the gravimetric uptake and the densities of the materials). However, if we consider that the cages of rho ZMOF are half occupied the v olumetric uptake increase is the n 20%. This

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156 result suggests that the density of hydrogen inside the pores is higher in the case of C 60 rho ZMOF The isosteric heat was also m easured and is shown in figure 4 .14. The values are somewhat similar to the one obtained for the Mg and Li exchang ed compounds. At the lowest coverage the isosteric heat of adsorption is ~9.3 kJ/mol which is slightly more than both the Mg and the Li exchanged compound and higher than the parent DMA rho ZMOF (8 kJ/mol). It seems also that, in the low coverage region ( less than 0.1 H 2 wt%) the isosteric heat of adsorption remains more steady than in the case of DMA Li and Mg rho ZMOF which may suggest stronger interactions at low loading and may account for the smaller pore size s 4.4 .4. Summary and Conclusion In summary, there is not enough evidence to conclude that encapsulating the C 60 derivative was successful. However, the sorption results for the so called C 60 rho ZMOF are different than the results of the parent framework and the Li and Mg exchanged compounds and suggest s that the density of H 2 in the pores are higher This c ould be expected and attributed to a decrease in pore size Future direction to be taken should include encapsulation of other cationic organic molecules and especially lighter on es such as other cationic carbon based compounds e.g. other C 60 derivatives that could be detected by UV Vis methods

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157 4 .4 .5 Experimental S ection Organic s ynthesis : The product: Tetra(N methyl piperazine)C 60 epoxide was obtained after one step multiple addition to fullerene C 60 (purple) under photochemical aerobic conditions. After removing the solvent, the brown product was washed several times with hexane ( 1 H NMR ( (150 MHz, CDCl 3 ) ppm 2.38, 2.42, 2.1 2.5, 2.5 3.5) C 60 rho ZMOF sy n thesis : To obtain crystals of rho ZMOF with Tetra(N methyl piperazine)C 60 epoxide guests, the original protocol 5 w as modified. 4,5 Imidazoledicarboxylic acid (H 3 ImDC, 14 mg 0.084 mmol) In(NO 3 ) 3 2H 2 O (15 mg 0.043 mmol), t etra(N methyl piperazine)C 60 epoxide ( 5 mg, 0.0044 mmol) 2 dimethylformamide (DMF) 1 mL of acetonitrile and 0.4 mL of nitric acid (2.2 M) were added to a 40 mL Parr acid digestion vessel which was heated to 85 C at a rate of 1.5 C /min for 12 hours and then cooled to room temperature at a rate of 1 C /min. A clear solution was obtained at this point and the reaction mix ture was further heated to 105C at a rate of 1.5C /min for 23 hours and then cooled to room te mperature at a rate of 1C /mi n. Pure b rown polyhedral crystals were obtained. X Ray Powder Diffraction : The identity of the compound was confirmed by XRPD ( figure 4 .15 )

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158 Figure 4 .15 Experimental PXRD spectrum of TAC 60 rho ZMOF compared to the simulated PXRD spectrum of DMA rho ZM OF UV Vis spectroscopy : In the UV Vis spectra of the tetra(N methyl piperazine)C 60 epoxide product in different solutions and of the brown crystals ( solid and liquid UV vis was attempted ) no peaks were apparent Sorption experiments : The brown crystals were washed several times with DMF th e n exchanged with acetonitrile. After 1 day, the crystals were dried (~30 mg) and loaded into an autosorb cell for N 2 and H 2 analysis.

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159 4 .5. Zeolite like Metal Organic Frameworks (ZMOFs): Other Post S ynthetic Modification s 4 .5.1. Introduction As discuss ed in the previous sections, with typical formula | ( C 2 H 8 N + ) 48 | [ In 48 (C 5 N 2 O 4 H 2 ) 96 ] rho ZMOF material permits the practice of ion exchange or encapsulation of large molecules. T he framework can also be modified by alter ing the ligand In fact, the 4,5 Imidazoledicar boxylic acid molecule exist in the form of a dianion in the structure of rho ZMOF (fig ure 4 .16 ) Figure 4 .16 Imidazole 4,5 dicarboxylic acid dianion present in rho ZMOF structure (the hydrogen bond is shown as a black do tted line) In deed, only one of the two carboxyl ate function al group s is deprotonated resulting in a hydrogen bond between COO and COOH as evidenced in the crystal structure In principle, it should theoretically be possible to protonate the carboxylate by post synthetic addition of protons. The charge in rho ZMOF is in fact the consequence of the dianion ligands coordinated to the trivalent indium cations. Each unit cell contain s 96 ligands and 48 metals which results in a net charge of 48 that is balanced by 48 positive charges (dimethylamonium in the case of the parent framework). I f for instance all the ligands c ould exist in the form of monoanion s the framework would be cationic wit h a

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160 net charge +48 The objective of the present study was to try to control the net charge in rho ZMOF and to post synthetically produce framework s with different properties 4.5.2 rho ZMOF Protonation A prelim inary study on acridine orange (AO) exchanged rho ZMOF (AO rho ZMOF) sample s permitted to verify the proton sensitivity of the material. When small amounts of protons were added to orange colored crystals of AO rho ZMOF in clear ethanol solution, a rapid orange coloration of the solution was observed which should be a consequence of H + /AO ion exchange (see experimental section 4 .5.4 ) In ano ther experiment the pH values were recorded after slow addition s of H + into a water solution containing DMA rho ZMOF crystals (figure 4 .17). An approximate pKa value of 4 can be extracted from the graph (literature pka value for free molecule is ~3.5) 54 A sodium exchanged sample of rho ZMOF (Na rho ZMOF 48 Dimethylam m oni u m cations have been replaced by 48 Na + cations as proven by a tomic absorption studies) was then used to quantify the sodium content of the framework upon acidification. Indeed, slow additions of protons into a deionized water solution containing Na rho ZMOF crystals resulted in slow release of sodium cations In fact, several different samples of Na rho ZMOF were analyze d and the ion exchange reactions were stopped at various stages to measure the sodium content (figure 4 .18) Atomic absorption measurements demonstrated that indeed, the Na + can be exchanged with H + However, a full Na + /H + ion exchange was not possible under these conditions. Therefore, multiple protonations were successively performed on the same Na rho ZMOF sample (figure 4 .19). In this case, it was shown

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161 that after the 5 th experiment, up to 90% of sodium was replaced (from 48 to 5 Na + per unit cell ). 4.5.3 Summary and Conclusion The purpose of this study was to attempt to control the net charge in rho ZMOF. Preliminary data reveals that indeed, the cations that balance the charge in rho ZMOF can be exchanged with protons. However, it is important to gain more information to clearly demonstrate the possibility to use rho ZMOF to practice protonation by post synthetic modifications and therefore producing frameworks with different properties. Other experiments should include other powerful single crystal X ray diffraction, infrared spectroscopy to attempt identifying the site of protonation, TGA to compar e the thermal stability of the framework before and after post synthetic modification, and elemental analysis. 5 5 4 .5. 4 Experimental S ection Acridine orange exchange : rho ZMOF crystals were soaked into a concentrated solution of acridine orange in ethanol for 1 hour. The crystals of AO rho ZMOF were then thoroughly washed with ethanol to eliminate any excess of acridine orange. AO rho ZMOF protonation : The crystals (~ 20 mg ) were put in a solution of water and 50 HNO 3 ( 3 M) was added. The solution turned orange almost instantly. The result was reproduced several times after washing thor oughly the crystals with water.

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162 Moreover, after several cycles, the crystals color changed from deep orange to light orange. Protonation/H + DMA + rho ZMOF ion exchange : 72.7 mg ( ) of D MA rho ZMOF were used and added to a 10 mL solution of water. A nitric acid (0.0158M) solution was prepared and added drop wise to the solution. Figure 4 17 DMA rho ZMOF protonation graph: pH vs. number of milli moles of H + (blue) and blank (red) The pH was than recorded after each addition and after equilibration time. A blank was also recorded to verify that no other species would interfere and cause disturbances in pH measurements, the same volume of water was used (10 mL) and a solution of HNO 3 (0.0158M) was added drop wise (figure 4.17). Protonation/H + Na + i on exchange : A sample of Na rho ZMOF was prepared according to literature. 5 A titration/ion exchange was then performed on Na rho ZMOF

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163 as described above. In order to calculate the percentage of sodium that is exchanged with protons, 4 titration experiments were conducted and stop p ed at different stages (figure 5.18). 11.5 mg ( 0.54 ), 11. 3 mg ( 0.53 ) 12.1 mg ( 0.57 ) and 10.3 mg ( 0.48 ) of crystals were used respec tively for the 4 titrations. Figure 4 .18. Na rho ZMOF protonation graphs: pH vs. number of milli moles of H + ; the percentage loss es of Na+ in the materials are shown for the 4 graphs Multiple protonations /H + Na + ion exchange : Other experiments were performed with 12.5 mg ( ) of Na rho ZMOF crystals. The experiment was done as previously described, after the first protonation experiment; the crystals were thoroughly washed with water before starting the next titration and so on. At the end of the experiments, it was found that around 90% of sodium was lost (from 48 to 5 Na + per unit cell)

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164 Figure 4 .19. Na rho ZMOF protonation graphs: pH vs. number of milli moles of H + ; the same sample was used to perform 5 consecutive protonation experiments 4 .7. References Cited 1. Davis, M. E. Nature 2002 417 813 821. 2. http://www.iza structure.org/databases/ 3 Paillaud, J. L. ; Har buzaru, B.; Patarin, J.; Bats, N. Science 2004 304 990 992. 4. Davis, M ; Chem Eur J 1997 3 1745 1755. 5. Liu, Y ; Kravtsov, V Ch.; Larsen, R ; Eddaoudi, M. Chem. Commun. 2006 14 1488 1490. 6. Liu, Y. ; Kravtsov, V. ; Walsh, R. D. ; Poddar, P. ; Srikanth H. ; Eddaoudi, M. Chem. Commun. 2004 24 2806 2807. 7. Liu Y ; Kravtsov V Ch ; Beauchamp D A ; Eubank J F ; Eddaoudi M J. Am. Chem. Soc. 2005 127 7266 7267 8. Liu, Y ; Kravtsov, V Ch.; Eddaoudi, M. Angew. Chem., Int. Ed. 2008 47 8446 8449. 9. Sava, D F.; Kravtsov, V Ch.; Nouar, F ; Wojtas, L ; Eubank, J F.; Eddaoudi, M J. Am. Chem. Soc. 2008 130 3768 3770.

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166 29. Langmi, H. W.; Walton, A.; Al Mamouri, M. M.; Johnson, S. R.; Book, D.; Speight, J. D.; Edwards, P. P.; Gameson, I.; Anderson, P. A.; Harris, I. R. J. Alloys and Compounds 2003 356 357 710 715. 30. Langmi, H. W.; Book, D.; Walton, A.; Johnson, S. R.; Al Mamouri, M. M.; Speight, J. D.; Edwards, P. P.; Harris, I. R.; Anderson, P. A. J. Alloys and Compounds 2005 404 406 637 642. 31. Bae, D.; Park, H.; Kim, J. S.; Lee, J. b.; Kwon, O. Y.; Kim, K. Y.; Song, M. K.; No, K. T. J. Phys. Chem. Solids 2007 69 1152 1154. 32. CSD search: Of 42 aqua lithium species, 40 are tetraaqua lithium and a large majority is in a tetrahedral arrangement (September 2009) 33. Liu, Y.; Eubank, J.F.; Cairns, A. J.; Eckert, J.; Kravtsov,V. Ch.; Luebke, R.; Eddaoudi, M. Angew. Chem. Int. Ed. 2007 46 3278 3283. 34. Rowsell, J. L. C. ; Spencer, E. C ; Eckert, J.; Howard, J. A. K.; Yaghi, O. M Science 2005 309 1350 1354 35. Rowsell, J. L. C. ; Eckert, J.; Yaghi, O. M J. Am. Chem. Soc. 2005 127 14904 14910. 36. Rosi, N. L.; Eckert, J.; Eddaoudi, M.; Vodak, D. T.; Keeffe, M.; Yaghi, O. M. Science 2003 300 1127 1130. 37. Braid, I. J.; Howard, J.; Nicol, J. M.; Tomkinson, J. Zeolites 1987 7 214 218. 38. Nicol, J. M.; Eckert, J.; Howard, J. J. Phys. Chem. 1988 92 7117 7121. 39. Eckert, J.; Nicol, J. M.; Howard, J.; Trouw, F. R. J. Phys. Chem. 1996 100 10646 10651. 40. MacKinnon, J. A.; Eckert, J.; Coker, D. A.; Bug, A. L. R. J. Chem. Phys. 2001 114 10137 10150. 41. Mojet, B. L.; Eckert, J.; van Santen, R. A.; Albinati, A.; Lechner, R. E. J. Am.Chem. Soc. 2001 123 8147 8148. 42. Forster, P. M.; Eckert, J.; Chang, J. S.; Park, S. E.; Ferey, G.; Cheetham, A.K. J. Am. Chem. Soc. 2003 125 1309 131 2. 43. Fitzgerald, S. A.; Yildirim, T.; Santodonato, L. J.; Neumann, D. A.; Copley, J. R. D.; Rush, J. J., Trouw, F. Phys. Rev. B 1999 60 6439 6451.

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168 Chapter 5 Summary and Conclusion 5 .1. Summary The research presented in this dissertation comprises the design synthesis and post synthetic modifications of functional Metal Organic Materials (MOMs). The use of h etero functional ligands permitted the assembly of e xternally functionalized Metal Organic Polyhedra (MOP), employed as Supermolecular Building Blocks (SBBs) to generate Metal Organic Frameworks (MOFs) with 3,24 connected rht topologies Indeed, the highly connected truncated octahedron or nanoball SBBs possess the necessary structural information and directionality to built frameworks with a topology that is the only edge transitive known for the assembly of 24 and 3 connected vertices The hetero functionality of the ligands permitted to form rigid triangular Molecular Building Blocks (MBBs) unprecedented for tetrazolate ligands, that served to connect the SBBs into rht like nets The frameworks contain in fact, 3 types of cages in wh ich the dimensionalities var y depending on the ligand employ ed. The materials comprise two types of metal clusters that contain potential open metal sites. The three cages can be referred to as truncated octahedral, rhombicuboctahedra, and truncated

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169 tetrahedra With low densities ranging from ~0.3 cm 3 /g to ~0.7 cm 3 /g free volume range s from ~75 % to ~85% and charged nature make these materials prospective for gas storage In fact, s orption studies on rht 1 indicated that this framework is very porous. The apparent surface area was measured to be as high as ~ 3200 m 2 /g (Langmuir) and ~2800 m 2 /g (BET) The argon isotherm shape (pseudo type I), was unusual for MOFs, indeed, steps appeare d in the low pressure reg ion which indicate s pore filling of the largest cages ( approaching mesoporosity) at higher pressure. Hydrogen storage studies indicated that rht 1 can store up to 2.4 wt% at 77K and ~ 1 bar. This value is very high when compared to other large size cavities MOFs. The low coverage isosteric heat of adsorption has an estimated value of ~9.5 kJ/mol which indicates a higher strength of interactions when compared to other MOFs. The uniqueness of rht nets permits to practice isoreticular chemistry where higher surface areas and larger free volumes can be easily achieved through expansion of the bifunctional organic linker as well as various tritopic hexacarboxylate ligands in which the C u oxo trimer can be replaced b y tritopic organic building blocks. The possibilities to construct n ew rht like structures with various pores sizes that contain specific features for different applications are thus almost limitless. For instance, the employment of expanded bifunctional l igands permitted the synthesis of rht 2, rht 3 and rht 6 comprising various cages dimensionalities with some in the mesoporosity range. Sorption studies were attempted using typical activation approaches. However, the large cages in rht 2 and rht 3 rendered the process very problematic where it is believed that framework collapse may have been taking place. Nevertheless, a new CO 2 supercritical drying activation

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170 method was employed. Indeed, sorption measurements on rht 2 and rht 3 indicated that the 1. The shape of the Ar isotherms obtained are very rare in MOFs. Interestingly, the isotherm in rht 2 exhibit features of both, microporous and mesoporous materials. As in rht 1, steps appeared in the isotherm and as expected, the pressure in which the largest pores are being filled is shifted to higher pressure. However, a typical mesoporous hysteresis loop type H4 appears between pressures ~0.4 atm to ~1 atm. A pore size analysis indicated that the experimental v alues more or less match the calculated pore dimensions. The BET surface area was evaluated to be around 4 700 m 2 /g, one among the highest surface area in MOFs. Hydrogen sorption data indicated that rht 2 can store 1.2 wt% which is lower than for rht 1 and can be accounted to the larger pore sizes in rht 2.The isosteric heat of adsorption was estimated to be ~9.2 kJ/mol. The rht 3 MOF argon isotherm indicate a shape that is typical for mesoporous compounds, i.e. ty pe IV isotherm with a typical H1 hysteresis loop. The pore size analysis from the experiment resulted in large discrepancies with values calculated from the crystal structure. However, the recorded pore volume of ~1.63 cm 3 /g, is also among the highest reported for MOFs. This material is still under investigation. The cationic nature and the large cages in rht structures permit to practice anion exchange or to encapsulate large anionic molecules such as porphyrin derivatives. Indeed, a sulfonated porphyrin derivative with a size as large as 24 w as successfully encapsulated in rht 2. Bifunctional ligands can also be employed to construct a large variety of nets with various connectivities A ternary net and a new binary net were indeed assembled.

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171 Moreover, a framewor k with zeolite ABW topology and a polar structure with lvt topology were synthesized. My research also involved the use of platforms with zeolitic topology, e.g. rho ZMOF. A detailed and systematic study on ion exchange and H 2 (rho ZMOF) interactions was undertaken. Structural information of Mg rho ZMOF, atomic absorption, sorption measurements, TGA, INS demonstrate d that in fact, the extra framework cations are fully coordinated with aqua ligands and therefore not accessible to the H 2 molec ules T he isosteric heat of adsorption measured for these compounds are ~ 50% higher than the one measured for neutral MOFs and comparable with MOFs with open metal sites. This clearly demonstrates that the presence of an electrostatic field in the cavities is lar gely responsible for the observed improvement in the isosteric heat of adsorption. The rho ZMOF platform was also employed as a host for larger guests. A cationic fullerene derivative was encapsulated after a one step construction of the anionic host and t he cationic guest molecules in sit u Encapsulation of other cationic C 60 should be used for more studies on hydrogen storage. Other post synthetic modifications included protonation of the framework. The preliminary results indicate that indeed it is possi ble to protonate the carboxylate of the dianion ligand. A titration graph was recorded and a pka~4 was evaluated. To summarize, t he research highlighted in this dissertation permitted to apply new design strategies based on the SBB approach. Isoreticular MOFs with unprecedented 3 24 connected rht topology were synthesized and can serve as platforms for various studies pertaining to different applications. This research also involved a full hydrogen

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172 storage study with other functional platforms with zeolit ic topologies in which encapsulation and post synthetic modifications such as ion exchange and protonation were performed. 5. 2 Conclusion Porous materials have the ability to interact with atoms, ions or molecules not only at their surface but also throughout the bulk. Porous solids are therefore a major class of high scientific and industrial impact. Metal Organic Frameworks (MOFs) are a rapidly growing sub class of porous materials. Their hybrid and ordered nature, very high surface area fine tun ability offer many advantage s and opportunities in very relevant applications This is evidenced by the recent increased industrial interests on some select and very promising MOFs. These materials can be used in applications such as catalysis, gas separat ion and gas storage. MOFs are indeed heading to market! For instance, 3 types of MOFs, from the IR MOFs and the MIL family, are currently manufactured by the BASF Company. It is also believed that many other companies, e.g. Shell Total are investigating MOF materials. However most of them do not reveal details of their research. MOFs with rht topology are a recent class of materials that have been discovered in our group. belief that rht like materials have the potenti al to become a major class of MOF materials A patent on design and synthesis of highly porous Metal Organic Frameworks with rht like topology is pending. These materials have indeed several advantage s over other MOF materials: i) t hey are easy to synthesi ze, the only limitation s are from the

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173 synthesis of the ligands; ii) i nterpenetration is not possible, this therefore permit s the construction of frameworks with various dimensionalities i.e. materials with pore sizes reaching mesoporosity could be easily obtained; iii) the rht frameworks possess three types of cages with tunable sizes, i.e. various combinations of sizes are possible by judicious choice s of ligands; iv) the frameworks properties can be tune by introducing functionalities in the ligands; v) Post synthetic modifications are possible i.e the practice of e ncapsulation and ion e x change is achievable on the charged rht compounds; vi) rht like frameworks have very low densities, high free volumes, high surface area and large pore volumes. These compounds may in fact soon surpass the high pressure H 2 gravimetric records uptakes It is then clear that the formidable rht platform can be employed in various studies pertaining to a wide set of applications f or example gas storage and separation, cat alysis or drug delivery. Future work should include other encapsulations (negatively charged fullerenes and other porphyrin derivatives for example) high pressure hydrogen sorption, catalysis, CO 2 and gas separation experiments. MOFs with zeolitic topolo gy such as rho ZMOF are also an important class of materials This platform allow ed for many different studies related to various applications It is accepted that this platform has high potential and may soon be even marketed.

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About the Author Farid Nouar was born in 1975 in Roussillon, France. He received a Bachelor Degree in Biochemistry in 2001 and a Master in Formulation Engineering in 2003 from Universite Claude Bernard, Lyon I, France He later was admitted to the Ph.D. program at University of South Florida and joined the research group of Mohamed Eddaoudi in 2005. The focus of his research was on the design and synthesis of metal organic materials. He is a member of the American Chem ical Society. He is co author in 6 publications and first author in 2 publications including 1 full article and 1 communication. He is also author in 1 patent and has several other manuscripts pending.