Phosphorus-doped h-boron nitride as an efficient metal-free catalyst for direct dehydrogenation of ethylbenzene

Abstract

Direct dehydrogenation (DDH) of ethylbenzene to styrene catalyzed by metal-free materials is one of the most challenging topics in the chemical industry. We demonstrate that phosphorus-doped h-boron nitride (PBN) exhibits outstanding catalytic activity with a styrene production rate of 6.63 mmol_ST g⁻¹ h⁻¹ and a styrene selectivity of 95% even after 100 h in the DDH of ethylbenzene under steam-free conditions. The characterization and DFT calculations indicate that the N₂PO and N₃P–OH sites of PBN synergistically catalyze the reaction: the N₂PO sites promote ethylbenzene C–H bond breaking, and the N₃P–OH sites significantly lower the energy barrier of hydrogen associative desorption. The characterization of fresh and used catalysts indicates that the coverage of the N₃P–OH sites by carbonaceous species is the main reason for the deactivation. This work facilitates the utilization of BN-based materials in the direct dehydrogenation of alkanes under steam-free reaction conditions.