MoFs (METAL-ORGANIC FRAMEWORKS)

Introduction of MoF compounds and comparison of statistical data of these compounds with zeolites.

1. 1

2. MOF, METAL-ORGANIC FRAMEWORKS: A VERSATILE CLASS OF ADVANCED MATERIALS Presented by Mahsa Ehsani nia PhD ( Inorganic Chemistry ) RAZI Uni Supervisor: Dr. Mohammad Joshaghani 2

3. Title and Content Layout with List Introduction Nanoporous Materials ( What are?, and types) Review of Metal-Organic Frameworks Basic structure Structural features Important of pore size Preparation of MOFs Common ligands used for MOFs Properties of MOFs For better application Synthesis method Chemistry of MOFs Applications of MOFs Literature review Conclusion and Scope for future work for MOFs 3

4. INTRODUCTION: NANOPORUS MATERIALS Consist of a regular organic or inorganic structure, supporting a periodic porous system. 4

5. 5

6. ZEOLITES:( INORGANIC NANOPOROUS COMPOUNDS) Zeolites are microporous crystalline solids with well-defined structures. Generally they contain silicon, aluminium and oxygen in their framework and cations, water and/or other molecules within their pores. Zeolites form with many diffrenet crystalline structures, which have large open pores ( sometimes referred to as cavities) in a very regular arrangement and roughly the same size as small molecules. The most interesting thing about zeolites is their open, cage-like framework structure and the way it can trap other molecules inside it. 6

7. POFs : ( ORGANIC NANOPOROUS COMPOUNDS) POFs are composed of different organic moieties linked by covalent bonds, resulting in ordered and rigid structure. Exceptional Thermal stabilities and low Frameworks D ensities. Exibit permanent porosity and specific surface areas. Application: Gas storage, Separation, Catalysis and etc. 7

8. MOFs: ( HYBRID ORGANIC-INORGANIC NANOPOROUS COMPOUNDS) Metal-Organic Framework, abbreviated to MOF, is a Coordination Polymer ( or alternatively Coordination Network) with an open framework containing potential voids. MOFs are self-assembled metal clusters with organic ligands, are well known for their structure, permanent porosity, and tunable properties and have shown great prospect for various applications. 8

9. Review of Metal-Organic Frameworks: Basic structure MOFs structures made up of inorganic nodes, which can either be single ions or clusters of ions, and organic linkers. 9

10. Structural features They contain potential voids which can be used for various application. Very low density Crystalline Large voids Significant van der waals interaction Complex unit cell 10

11. Important of pore size 11

12. 12

13. Preparation of MOFs 13

14. 14 The coordination complex formed by the metal ions and the donor atoms of the linker, termed the secondary building unit (SBU), dicates the final topology of the MOF framework .

15. Common ligands used for MOFs 15

16. Properties of MOFs The backbone of the compound is constructed from metal ions which act as connectors and organic bridging ligands as linkers. Readily accessible porosity. The coexistence of inorganic ( hydrophilic) and organic ( hydrophobic) moieties in structure may influence on adsorption properties. Although most of MOFs are electrical insulators, several materials in this class have recently demonstrated excellent electrical conductivity and high charge mobility. The thermal stability of MOFs is determined by the coordination number and local coordination environment instead of framework topology In general MOFs are poor thermal conductors with thermal conductivity that is similar to concrete. 16

17. For better application Surface Area: MOFs with higher surface area are more desirable. Pore Size: MOFs must have the proper pore size to allow uptake and release of analytes . Stability: MOFs must exhibit reasonable stability upon exposure to oxygen, moisture, the analytes of interest or changes in temperature. Solubility: MOFs shoud be insoluble in aqueos media. Analyte interaction: MOFs may exhibit special structural characteristics that may facilitate selective uptake and release of analytes . 17

18. Synthesis Different methods of synthesis of MOFs have been described: I] non- solvothermal ( open flasks, below the solvent boiling point, at atmospheric pressure) A) Traditional synthesis: II] Hydrthermal / solvothermal ( special closed chemical reactors, boiling temperature of the solvent or above this boiling point, elevated pressure caused by solvent vapour or produced by a pump.) Notice: method I] dose not require complex equipment method II] Solvothermal synthesis affords higher yields and better crystallinity of the product. but requires special equipment (autoclaves or sealed containers that can withstand increased pressure); in addition, the duration of the process should be taken into account (the synthesis can continue for several weeks and even months). 18

19. I ] microwave method II] electrochemical method III] mechano chemical method B) Non-traditional methods: IV] sono -chemical method V] microemulsion method 19

20. But most of the time, MOFs are synthesized by combining organic ligands and metal salts in solvothermal reactions at low temperatures (below 300° C), that: Polar solvent: Water, dialkyl formamides , dimethyl sulfoxide or acetonitrile. The most important parameters of solvothermal : temperature, the source and concentration of metal salt and ligand (which can be varied across a large range), the solubility of the reactants in the solvent, the PH of the solution, reaction time and etc. 20

21. Chemistry of MOFs The organic linkers used in MOFs are capable of connecting two metal oxide clusters ( ditopic linkers). Linkers with higher dimensionality can also be used. Organic ligands with rigid backbones are often preferred, because the rigidity makes it easier to predict the network geometry, and in addition the rigidity also helps to sustain the open pore structure after the removal of the included solvent . Transition metal ions are often used as the inorganic components of MOFs. Different metal ions are well known to prefer different coordination numbers and geometries, such as linear, T- or Y-shaped, tetrahedral, square-planar, square-pyramidal, trigonal- bipyramidal , octahedral, trigonal-prismatic, and pentagonal- bipyramidal . The bonds formed between the metal ions and donor atoms of the linker are strong and as a result, the extended network structure in the MOF is quite robust. 21

22. Careful selection of MOF constituents can yield crystals of ultrahigh porosity and high thermal and chemical stability. These characteristics allow the interior of MOFs to be chemically altered for use in gas separation, gas storage, and catalysis, among other applications. Active sites on MOFs are located at the metal nodes, functional linker on the crystalline structure and guest species; when the reaction occurs, the framework protects their active sites and increases the efficiency. 22

23. By using appropriate system it possible to synthesis extended polymeric structures. MOFs containing large spaces may result in the formation of interpenetrating structures. Formation of interpenetrating networks can be inhibited by choosing suitable organic ligands. 23

24. Applications of MOFs 24

25. Literature review 25

26. R esults 1. Number of publications on zeolites and MOFs: 26

27. 2. Population and representative researches in research countries: zeolites MOFs 27

28. 28 26% 13% 8% 7% 5% 3% 2% 3. Research area population 11% 7%

29. 29 37% 22% 11% 8% 7% 5% 2% 1% 1% 1%

30. 4. Next C lassify of Research Domain for Zeolites and MOFs We next classify the research domain using the four stages defined in Scheme 2 . 30

31. Figure 6 summarizes the percentages and representative large domains for zeolites and MOFs. The research area for zeolites has been focused on “properties” and “applications”, whereas that for MOFs has been focused on “synthesis” and “applications”. 1 2 1 2 31

32. 1) Synthesis (the synthesis stage proposes new type or new derivatives of MOF and zeolites.) Synthesis of zeolites: Around 200 framework types of zeolites have been synthesized and reported. Primarily, zeolites have been synthesized using hydrothermal methods. The lower number of framework structures of zeolites is due to the low number of building unites and mystery in the self-assembly processes of zeolites. In general, the synthesis of new framework structures is difficult to achieve. Synthesis of mofs : The synthesis of new MOFs is widely studied because of the variety in combinations of metal ions and bridging ligands. These structures are important with regard to the surface area. Likewise, the incorporation of functional building unites basically allows their molecular functionality to be adopted by porous materials. Most of these are synthesized using hydrothermal methods, along with microwave or ionothermal synthetic methods. Interest in them is also due to their topological structures, which are not found in inorganic salt or molecular crystals. 32

33. 2) Process (the process stage focuses on efficient methods to synthesize in terms of cost, time and number of steps for synthesis) Process of zeolites Processing in zeolite synthesis mainly includes two topics: 1) synthesizing zeolites from low-cost starting materials and 2) control zeolite morphologies. The starting materials for zeolites are relatively cheap, with a cost of approximately $ 200 to produce 1 kg of typical zeolite Y. For SiO2, using industrial wastes such as coal fly ash and asbestos has been well studied. Process of MOFs Processing of MOFs is a minor topic in this research area. The chemicals needed for syntheses, such as organic ligands and solvents, are more expensive than the building blocks for zeolites. In case of MOF-5, which could be the most famous class of MOFs, this cost is more than $14,000 to produce 1 kg. This is because of the requirement for expensive organic solvents such as DMF and chloroform. Industrial researchers are still investigating the processing strategy. BASF started the electrolysis of Cu for the synthesis of HKUST-1 [ Cu3( btc )2]n ( btc = 1,3,5-benzenetricarboxylate ), and some researchers have started to use organic waste such as PET bottles as a route for MOF syntheses. 33

34. 3) Properties ( the properties stage focuses on investigation of properties of synthesized materials.) Properties of zeolites One of the most important properties of zeolites is their acidity. Zeolites have Brønsted acidic proton sites as counterparts to anionic frameworks, which can be introduced by the isomorphous substitution of Si(IV) by Al(III) atoms in the TO4/2 (T = Si, Al) tetrahedral . Properties of mofs Adsorptive properties are tunable in terms of pore functionalization. MOF-74 [M2( dobdc )]n ( dobdc = 2,5-dioxido-1,4-benzenedicarboxylate) can be synthesized with a variety of metal centers such as Zn2 +, Ni2 +, Mn2+, Co2+, and Fe2 +. The H2 adsorption heat is also tunable. These tunabilities in relation to the adsorption energy are particularly important for gas separation based on interactions. The flexibility of the framework is specific for MOFs and has been shown as unique porous properties. This is because such porous materials change their structures in response to guest adsorption , making these materials useful for some applications. 34

35. 4) Applications ( the applications stage focuses on the applications of a synthesized materials for practical use.) Application of zeolites Catalytic applications are more ideal for zeolites because of the use of robust frameworks and their acidic sites compared with MOFs. Acidic sites provide various organic reactivity such as cracking and isomerization. Tons of zeolites have been used for the fluid catalytic cracking of heavy oils. Redox active sites are introduced using metal site substitutes such as Ti and Sn. The redox activity can be used for epoxidation, and so on. Extra-framework cations such as Cu2+ and encapsulated clusters such as Pt clusters can also be catalytic reaction sites. Application of mofs Gas adsorption applications as portable storage are more suitable for MOFs because of the light composition of formula weights. Hydrogen and methane gases are the general targets for gas storage as a demonstration of energy transport. Because of their high surface area and strong interaction with guest molecules, they already exceed the theoretical limits for zeolites and carbon-based materials. Gas separation applications have also been studied. Syn -gas can be contaminated with CO2. Therefore, CO2/CH4 or C2H6/CH4 separation has been studied. 35

36. 5. Well-cited research areas from citation network analysis high impact areas of research by analyzing what types of research areas are acceptable to high-impact journals (HIJs) on average. High impact areas of research for zeolites High impact areas of research for mofs 36

37. 6. Research area preferences by country A. zeolites Membrane reactor Nanosheet -based catalysis Cation exchange and the basic spectroscopic characterization of zeolites Cation exchange and the basic spectroscopic characterization of zeolites 37

38. B. MOFs Synthesis of MOFs Gas storage Catalysis, semiconductors and films Synthesis of MOFs and battery- basedapplications 38

39. Conclusion and Scope for future work for MOFs The research area of zeolites has been application-oriented compared with that on MOFs because of their solid acid and ion-exchange properties with robust frameworks. Designable zeolite synthesis based on the physical properties and framework structures will be a future challenge. On the other hand , research areas of MOFs are still being developed . Their structural design ability leads to the control of physicochemical properties. Structural robustness of MOFs will be required for the future development of industrial applications and processes . Basically, the research areas classified as “application” in the zeolite area, such as harsh catalytic reactions, have not been examined in the MOF area. Similarly, the application areas for MOFs are seldom investigated in contrast to zeolites. This tendency seems to reflect the longer research history for zeolites compared to MOFs, with many studies in the “application” stage. Referring to the future applications of zeolites will be beneficial for MOFs. Here, we propose possible research areas for zeolites and MOFs, as listed. 39

40. 40