New insight into structural transformations of borocarbonitride in oxidative dehydrogenation of propane

Boron-containing compounds have been discovered as a kind of promising metal-free catalysts for oxidative dehydrogenation (ODH) of alkanes. Herein, we provide a simple method to synthesize a series of BCN catalysts with tunable carbon contents. We reveal that incorporating appropriate amounts of carbon into the hexagonal boron nitride (h-BN) structure can significantly increase the surface area and lead to remarkable enhanced catalytic conversion. The best-performing catalyst shows 82.3% propylene selectivity and 93.8% olefin selectivity at propane conversion of 18.5%. Systematic study indicates that the carbon doping can derive BN with a large number of defective sites, which are prone to form reactive boron-oxygen species during activation. The excess carbon inclusion, however, results in a decreased catalytic conversion, originated from catalyst decomposition and sintering. In situ transmission electron microscopy (TEM) performed under activation and catalytic reaction conditions shows the dynamic process of gas-phase induced structural/compositional transformations, providing direct insights into the origins of catalytic deactivation.