A novel hybrid containing two kinds of polyoxometalates for catalyzing olefin epoxidation

Vanadium-substituted Keggin-type polyoxometalates exhibit a higher negative charge compared to their 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 high oxidative catalytic capacity of vanadium element. In this study, by incorporating vanadium-substituted Keggin-type polyoxometalates and sodium molybdate, an inorganic-organic hybrid compound, [Cu6(phen)6(Mo6O22)(H5PMo10V2O40)·H2O] (phen = 1,10-phenanthroline) (1), was successfully constructed under hydrothermal conditions. Compound 1 is composed of two kinds of polyoxometalates, [PMo10V2O40]5- and [Mo6O22]8- ({PMo10V2} = [PMo10V2O40]5-, {Mo6} = [Mo6O22]8- ). In the catalytic epoxidation of olefins, compound 1 successfully 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 of >99%). After five cycles, compound 1 maintained its catalytic activity. Furthermore, compound 1 exhibited broad applicability, effectively catalyzing the epoxidation reactions of various olefin substrates.