Synthesis And Catalytic Properties Of Metal Organic Frameworks Modified By Amine And Metal Salen

Metal-Organic Frameworks （MOFs） are porous meterials with regular network structure,constructed by inorganic metal centers （metal ions or metal clusters） and organic multidentateligands through a self-assembled formation. MOFs have porous, tunable frameworks andunsaturated metal coordination sites, making it potencial in many applications, including gasstorage and adsorption, molecule separation, heterogeneous catalysis, drug delivery andapplication prospect of optical, electrical, magnetic properties.Post-Synthetic Modification （PSM） is an efficient method to produce functionalizedmaterials which contain the intrinsic characteristics of MOFs. The chemical modification isperformed on the fabricated material, rather than on the molecule precursors. According to thetype of chemical bond that is formed or broken during the approach, PSM is divided intocovalent PSM and dative PSM.In this thesis, we have synthesized MOF-based heterogeneous catalysts by theimmobilization of homogeneous catalytic active group into MOFs through post-syntheticapproach.In chapter2, two rare earth MOFs with basic framework as Er（btc） and Tm（btc） weresynthesized by solvothermal method, and the structure, composition and stability of themwere characterized. Three diamines with different volume size （ethylenediamine, piperazineand1,4-diazabicyclo[2.2.2]octane） were grafted onto the coordinatively unsaturated metalions in the channels of the desolvated framework. The framework structure and thermalstability of the modified materials remained. Compound3, with75%loading rate ofethylenediamine on Er（btc）, exhibited high catalytic activity (>99%of conversion and1.33min^-1of TOF value) and reusability for Knoevenagel condensation reaction. Leaching testshowed that no catalytic active group migrated from MOF during the course of the reactionand contributed to the catalytic activity, indicating that3acted as solid base catalyst. Thecatalytic mechanism was proposed based on the size-selective catalysis that in the reactionprocess, active methylene compound available to access the channels is the key procedure.Only the volume size of active methylene compound is small enough to access the channelsof MOF, the reaction can proceed.In chapter3, MIL^-101was synthesized by solvothermal method, and the structure,composition and stability were characterized. Employing the methodology of “ship in abottle”, the materials with small volume were transported into the cage to form the Salen-Mn（Ⅲ） complex, which was too large to filter through the window of the cage and therefore immobized in the framework. The modified material retained the same framework structure,thermal stability and porosity of MIL^-101. The content of Salen was0.29mmol·g^-1and Mnwas0.28mmol·g^-1. Compound9could be used as heterogeneous catalyst for epoxidation ofolefins. The total conversion of substituted olefins and terminal olefins were excellent, whilethe former had a higher yield of epoxide product. E-stilbene performed the best of83%epoxide among the substrates. This catalyst could be reused at lease five times withoutdecrease in catalytic activity. Leaching test also showed that Mn（Ⅲ） did not migrated fromthe framework during the reaction process. That is, this postsynthetic approach couldeffectively improve the stability, separation and reusability of catalytic active group Salen-Mn（Ⅲ） complex.