Acceleration of Molecular Oxygen Activation in m-Xylene Oxidation at Low-Temperature through Building the Cu-O-Mn...

The limitations of pure Mn₃O₄ catalysts in oxygen activation and electron transfer impeded their efficiency for low-temperature catalytic oxidation of m-xylene. Herein, a Cu-substitution strategy was employed to construct the Cu-O-Mn electron bridge in Mn₃O₄, enabling tailored electronic redistribution and enhanced molecular oxygen activation. A series of characterizations and DFT calculations revealed that the substitution of Cu decreased the electron density around the Mn atoms, generated abundant oxygen vacancies, and elevated the Mn⁴⁺ concentration, improving oxidative capacity. The optimized CuMn₂O₄ catalyst achieved 90% conversion of m-xylene at 246 °C, which was 12 °C lower than that of Mn₃O₄. The investigation of the mechanism demonstrated that the synergistic effect of Cu⁺ species and oxygen vacancies accelerated molecular oxygen activation and dynamically replenished the consumed lattice oxygen. Furthermore, the Cu-O-Mn bridge facilitated interfacial electron transfer, weakening Mn-O bonds and lowering oxygen vacancy formation energy, which promoted surface lattice oxygen mobility. Additionally, the CuMn₂O₄ catalyst exhibited excellent stability and water tolerance. This work provided new insights into electron regulation to accelerate molecular oxygen activation, which was beneficial for the targeted design of highly efficient catalysts for refractory m-xylene.