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

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 mmolST 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 N2P = O and N3P-OH sites of PBN synergistically catalyze the reaction: the N2P = O 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.