Mo2C-derived molybdenum oxycarbides afford controllable oxidation of anilines to azobenzenes and azoxybenzenes

Abstract

The catalytic synthesis of aromatic azo compounds via oxidative coupling of anilines still faces great challenges due to the difficulty in controlling product selectivity. In this study, we have pioneered the application of Mo₂C as a pre-catalyst for the selective oxidation of aniline using H₂O₂ to produce azobenzenes and azoxybenzenes. Both experimental and theoretical studies reveal that H₂O₂ induces the formation of Mo oxycarbides (MoC_xO_y) on the surface of Mo₂C during the reaction, which subsequently activates H₂O₂ to generate active sites (Mo⋯O) essential for the oxidative coupling of anilines. Furthermore, the kinetics of the critical conversion from Ph-NH₂ to Ph-NHOH over MoC_xO_y can be adjusted by modulating the solvent, thereby enabling controlled product selectivity between azobenzenes and azoxybenzenes. This work elucidates the structural evolution of Mo₂C to MoC_xO_y in a H₂O₂ system and its catalytic oxidation capabilities, potentially paving the way for broader applications of MoC_xO_y in various oxidation reactions.