Physically hybrid Zr(OH)4 + CuO catalyzed selective aniline oxidation: A new Ph‐N˙$$ \dot{\mathbf{N}} $$OH mediated mechanism

Abstract

AbstractDeveloping the sustainable and cost‐effective heterogeneous catalytic system for controlling chemoselectivity holds substantial importance in fine organic chemicals. Herein we construct a unique Zr(OH)4 + CuO physically hybrid system for selective oxidation of anilines. Zr(OH)4 alone leads to azoxybenzene formation, and Zr(OH)4 + CuO shifts the reaction favorably toward nitrosobenzene. The proximity study indicates Zr(OH)4 + CuO outperforms its counterparts synthesized through methods like ball‐milling, loading, and coprecipitation, because the closer proximity exhibits stronger chemical interaction, restricting the activity of Zr‐OH hydroxyl sites. Through mechanistic experiments, in situ DRIFT‐IR and DFT calculations, a new Ph‐OH intermediate mechanism is firstly proposed. Two Ph‐OH self‐condensate to form azoxybenzene for only Zr(OH)4, whereas Zr(OH)4 + CuO could promote rapid transformation of Ph‐OH to nitrosobenzene on CuO through a hydrogen transfer process. Moreover, Zr(OH)4 + CuO displays good recyclability and robust scalability. This is the first report demonstrating the utilization of a physically hybrid catalyst to adjust the selectivity of the aniline oxidation reaction.