A novel hybrid containing two kinds of polyoxometalates <?A3B2 pi6?>for catalyzing olefin epoxidation

Vanadium-substituted Keggin-type polyoxometalates exhibit a higher negative charge compared to parent polyoxometalates, which not only enhances their ability to coordinate with metals but also endows them with significant potential for oxidative catalysis due to the intrinsic high oxidative catalytic capacity of vanadium. In this study, by incorporating vanadium-substituted Keggin-type polyoxometalates and sodium molybdate, an inorganic-organic hybrid compound, [Cu6(phen)6(Mo6O22)(HPMo10V2O40)·H2O] (phen = 1,10-phenanthroline), was successfully constructed under hydrothermal conditions. This compound is composed of two kinds of polyoxometalates, [PMo10V2O40]5− and [Mo6O22]8−, in which {PMo10V2} and {Mo6} represent [PMo10V2O40]5− and [Mo6O22]8−, respectively. In the catalytic epoxidation of olefins, this hybrid efficiently oxidized cyclooctene to 1,2-epoxycyclooctane within 4 hours at 35 °C using oxygen as the oxidant (conversion rate of 98.6% and a selectivity greater than 99%). Moreover, it retained high catalytic activity after five successive cycles and demonstrated broad substrate scope, effectively catalyzing the epoxidation of various olefins.