Design, synthesis and Applications of Metal Organic Framework

Hu, Moqing

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Design, synthesis and Applications of Metal Organic Framework

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Porous materials have been a focus of researchers for their applications as molecular storage, molecular sensing, catalysis, asymmetric synthesis and host materials. Metal-organic frameworks (MOFs) represent a promising new class of porous crystalline solids because they exhibit large pore volumes, high surface areas, permanent porosity, high thermal stability, and feature open channels with tunable dimensions and topology. We are currently investigating the design, synthesis, and structures of a new family of MOFs derived from transition metals complexes of 4-(imidazole-1-yl)benzoic acids. Here we present our effort in continuing design and synthesis MOFs composed of 4-(imidazole-1-yl)benzoic acids to expand our knowledge about 4-(imidazole-1-yl)benzoic acid MOF family. A series of ligands are synthesized and Cu MOF-3N, 4, 5 and Cd MOF-3 were synthesized, structure determination found out metal-ligand complex follows our proposal, while Cu MOF-4,5 exhibit porous framework structure via absolute structure determination. Sorption behavior is a key focus in MOF application because the great potential applications MOF bears. Here we carry out a fundamental study about MOF texture and selectivity on MOF-5 and Cd MOF-2. Non-polar polyaromatic hydrocarbons such as naphthalene, phenanthrene, and pyrene, polar molecules such as 2-naphthol, ibuprofen were selected to test our hypothesis that sorption is influenced by the degree of tight fitting, and guest-host interaction such as van der waals and hydrogen bonding. By determining Langmuir isotherms of selected guest molecules, we are able to demonstrate our hypothesis that tighter the fit of the guest molecule and the pores, the higher the amount it would sorb. The sorption difference of non-polar and polar molecules suggest hydrogen bonding is not involved in guest sorption and the dominating force of sorption is hydrophobic interaction. Polymorphism is an interesting phenomenon that bears great value in pharmaceutical industry. Here we report the first case for MOF to serve as a heterogeneous surface that induced nucleation of indomethacin. It is also a first report of this polymorph form of indomethacin. PXRD, DSC, TGA, NMR are conducted as our initial investigation effort. This polymorph exhibits exceptionally thermal stability and low solubility, indicating an unusual tight binding between indomethacin and ethanol solvate.

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