In Situ Synthesis of MXene–Perovskite Interfaces in 3D Carbon Catalysts Boosts Aerobic Oxime Oxidation

The development of heterogeneous catalysts for liquid-phase aerobic oxidation is of great interest. Herein, we report the synthesis of 3D porous graphitic carbon spheres incorporating M _n+1C _n -type MXenes (M = Ti, V, Nb), prepared by delaminating MXene nanosheets in chitosan-based aerogels, followed by pyrolysis. In the case of Nb₂C, a heterojunction with a NaNbO₃ perovskite forms within the carbon matrix, leading to the highest catalytic performance. This 3D Nb₂C/NaNbO₃ structure achieved a 100% yield in the aerobic oxidation of cyclohexanone oxime to cyclohexanone within 6 h, with negligible metal leaching. Structural analysis revealed the partial oxidation of Nb₂C to NaNbO₃ during synthesis, leading to a Nb₂C-NaNbO₃ heterostructure. Control experiments confirmed that this interface is essential for the high activity, as neither Nb₂C nor NaNbO₃ alone on the porous carbon matrix reached a similar performance. Mechanistic studies based on hot filtration tests, quenching experiments, and EPR spectroscopy demonstrated that the reaction involves reactive oxygen species, mainly superoxide and hydroperoxyl radicals, generated and acting on the catalyst surface. This work provides a promising strategy for designing efficient and robust MXene-based catalysts for sustainable oxidation processes.