Photocatalytic oxidative dehydrogenation of cyclohexane to cyclohexene over oxygen-deficient tungsten trioxide

Abstract

Oxidative dehydrogenation of cyclohexane (C6H12) to cyclohexene (C6H10) suffers from low selectivity due to its over-dehydrogenation and oxidation to other products like benzene or cyclohexanol. In this study, we report that oxygen-deficient tungsten trioxide (WO3-x) can realize photocatalytic oxidative dehydrogenation of C6H12 with high C6H10 selectivity (∼99 %) and stability. Experimental results and theoretical calculations revealed that the introduction of oxygen vacancy favored the adsorption of C6H12 over tungsten trioxide and the low-coordinated W atom of WO3-x would donate electrons to the C atom of C6H12, weakening its CH bond. During the photocatalysis, the photogenerated holes acted as oxidative species for the dehydrogenation of C6H12 along with the H2O formation through the combination with adjacent O atom in WO3-x. Meanwhile, the product C6H10 could easily desorb from the surface of WO3-x to avoid the over-dehydrogenation and oxidation, contributing to the high selectivity.