Synthesis And Catalytic Properties Of Heterogeneous Catalysts Based On Zeolitic Imidazolate Frameworks

Zeolitic imidazolate frameworks?ZIFs?are a subclass of metal-organic frameworks?MOFs?comprised of ordered networks which are formed by imidazole or imidazole derivatives and inorganic transition metal cations?Zn/Co?.ZIFs have the advantages of large specific surface area and pore volume,regular pore structure,species diversity,high thermal and chemical stabilities and so on.ZIFs possess highly desirable properties of both conventional zeolites and MOFs and it has potential applications in adsorption,separation,catalysis.RHO-ZIFs is an ideal heterogeneous catalyst support material.with large cages and small“windows”.At present,the application of ZIFs material mostly focused on the gas adsorption,separation,storage,and the reports on their catalytic application is scarce.In this paper,using RHO-ZIF as research subject,we successfully prepared compounds in which POMs are enclosed in the cages of ZIFs by using ball-milling method.We afforded three distinct compounds,H₄PMo₁₁VO₄₀@RHO-ZIF,H₅PMo₁₀V₂O₄₀@RHO-ZIFand H₆PMo₉V₃O₄₀@RHO-ZIF.Compared with the traditional synthetic methods,mechanochemical method is more widely used as a simple,green and efficient synthesis strategy.The structure of the catalyst was investigated by PXRD?FT-IR?SEM?ICP-AES?SEM,and the stability of the catalyst was tested by UV-Vis spectroscopy.The results show that all members of these series have intact RHO-ZIF crystalline structures and the POM are intentionally‘trapped'inside the well-defined cages of RHO-ZIF.The materials are stable in different solvents and POMs molecules are not easy to flow from the frameworks.We chose the methyl phenyl sulfide oxidation as model reaction and the catalytic properties of this kind of composite catalyst was investigated.As a result,the products sulfone or sulfoxide can be selectively obtained under different reaction conditions.As heterogeneous catalysts,compounds As heterogeneous catalysts,compounds H₄PMo₁₁VO₄₀@RHO-ZIF exhibit excellent catalytic performance in the oxidation of sulfides and it can be simply separated by filtration to achieve the recovery of the catalyst without obvious lose of its activity.