Direct immobilization of self-assembled polyoxometalate catalyst in layered double hydroxide for heterogeneous epoxidation of olefins

摘要

We present a novel method for the fabrication of immobilized polyoxometalate catalysts that directly use a self-assembled polyoxometalate solution without isolation and purification.Specifically,self-assembled [WZn3(ZnW9O34)2]~(12-) catalyst can be selectively immobilized into layered double hydroxides in the presence of undesired anions.The material thus obtained demonstrates high dispersion and good hy-drothermal stability.The heterogenized catalyst exhibits excellent activity (turnover frequency up to 18,000 h~(-1) at 50°C) in the epoxidation of allylic alcohols with aqueous H2O2 and can be readily recycled with no apparent loss of performance.