A generalized approach to adjust the catalytic activity of borocarbonitride for alkane oxidative dehydrogenation reactions

Abstract

The borocarbonitrides (BCNs) have exhibited enormous potential as non-metallic catalysts for alkane oxidative dehydrogenation (ODH) reactions. However, the poor electron transportation ability in BCN leads to a low reactivity of oxygen functional groups (CO and BOH). Herein, we present a generalized strategy to promote the catalytic activity of BCN through in situ encapsulation of transition-metal (Fe, Co, Ni) nanoparticles within BCN nanotubes (BCNNTs). Among them, individual metal particles themselves do not contribute directly on ODH reactions and mainly serve as electron modulators to tune the electron density of CO and BOH active sites on BCNNTs. As a result, catalytic activities of all metal@BCNNTs catalysts surpass pure BCN in ethylbenzene (EB) ODH reactions, among which Fe@BCNNTs displays a significant activity enhancement with 36 % EB conversion with the styrene (ST) selectivity remaining >98% under gentle reaction conditions. Structural and kinetic analyses proved that the promotion effect originated from the strong interactions between metal nanoparticles and BCNNTs. The theoretical calculations disclosed that the enhanced ODH activity was due to the electron transfer from the encapsulated metal to BCNNTs, which increases the electron transportation ability and electron density of BCNNTs, thus promoting the nucleophilicity of CO and BOH active sites, leading to the reduced activation energy barrier for CH bond dissociation. The present work sets forth the structure-function relationship, identifying opportunities for rational design of highly efficient BCN catalysts for ODH reactions.