| Polyoxovanadate clusters are an important branch of polyoxometalates chemistry,and their research depth and breadth are far less than polyoxomolybdate clusters and polyoxotungstate clusters.However,it has attracted much attention due to its excellent catalytic performance.Although classical POVs as catalysts have good catalytic activity,there are problems such as easy dissolution in polar solvents and difficult separation and recovery,and easy agglomeration in non-polar solvents and difficult catalytic activity.In this thesis,three metal-organic frameworks based on mixed valence{?16}clusters were synthesized by one-step solvothermal method using triethylenediamine as organic ligand.The catalytic activities of these compounds were studied through olefin epoxidation.The main innovations of this paper are as follows:1.Three isomeric metal-organic frameworks based on mixed valence{?16}clusters were synthesized by one-step solvothermal method,[Na(N2C6H12)2]2[?5???11O38Cl]·3H2O(1),[K(N2C6H12)2]2[?5???11O38Cl]·3H2O(2),[Li(N2C6H12)2]2[?5???11O38Cl]·3H2O(3).They all have Td symmetry and are cubic.These compounds showed good thermal stability,acid-base stability and solvent stability.Cationic metal organic frameworks({[Na(N2C6H12)2]2}2+,{[K(N2C6H12)2]2}2+,{[Li(N2C6H12)2]2}2+)exhibit adamantane-like structure.As we know,this is the first case of adamantane-like metal-organic framework constructed by alkali metals and organic ligands.2.The catalytic activity of compound 1 as heterogeneous catalyst for olefin epoxidation was studied.With oxygen as oxidant,compound 1 can catalyze the oxidation of a series of olefins to epoxy compounds,showing good catalytic activity and universality.Compound 1 has good reusability,and the catalytic activity and selectivity for the product have no obvious change after five cycles.As a green and sustainable catalyst,compound 1 is expected to be applied in the preparation of epoxy compounds. |
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