379365 Approaches to Synthesize New Zeolitic Imidazolate Framework Type Metal Organic Frameworks
Zeolitic imidazolate frameworks (ZIFs) are subclass of metal organic frameworks (MOFs) which are structurally comprised of ditopic imidazolate linkers and tetrahedrally coordinated transition metal ions as nodes. As metal-linker-metal bonds of ZIFs make the same angle as Si-O-Si of zeolites, 145°, the ZIFs can attain the same topologies of zeolites. In addition of high surface area which is typical property of MOFs, ZIFs exhibit prominent thermal and chemical stability. Therefore, they are proper candidates for industrial applications like gas separation and storage. Alike to other MOFs, solvothermal method is common de novo approach to produce ZIFs by which large number of ZIFs have been synthesized by variation of metal salt, imidazole, and solvent. This approach has inherent challenges when:
- The linker solubility in the solvent is limited,
- The linker is not chemically or thermally stable at reaction condition,
- Side reaction between functional group of the linker and metal ion leads to exclusion of MOF formation (especially when multi-functional linker is used),
- The reaction lead to formation of kinetic product (i.e. less stable polymorph) rather than thermodynamic product.
Post synthesis methods are capable of mitigate these shortcomings and enable one to achieve an MOF with desired linker, metal, and/or topology. In post synthesis method linker or metallic node can be modified (post synthesis modification) or exchanged by solvent assisted linker exchange and transmetalation methods, respectively. The main future of post synthesis methods is preserving the topology of the parent MOF in the modified one. The goal of this study is to synthesize new ZIF type MOFs by applying de novo and post synthesis approaches.
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