Electron Redistribution-Driven Enhancement of Cu@CN Catalysts for Low-Temperature Ammoxidation of Aldehydes

Ammoxidation of aldehydes to nitriles has garnered significant attention due to the importance of nitriles in fine chemicals and pharmaceuticals. However, achieving this transformation using earth-abundant metal catalysts under mild conditions remains a considerable challenge. In this work, Cu-based nanoparticles supported on N-doped carbon nanosheets (Cu@CN-x, where x denotes the pyrolysis temperature) were synthesized by pyrolyzing a fine mixture of sodium lignosulfonate, melamine, and CuCl2 at different temperatures. Notably, the Cu@CN-900 catalyst exhibited excellent catalytic performance for the ammoxidation of aldehydes at low temperatures (≤50 °C). A wide range of aromatic and aliphatic aldehydes were efficiently converted to the corresponding nitriles with high yields and selectivity. Mechanistic investigations revealed that Cu2+ species and graphitic-N species served as the primary active sites. Crucially, electron redistribution between Cu and N species generated more negatively charged Cu2+ and positively charged graphitic-N, leading to a synergistic enhancement in catalytic activity at temperatures below 50 °C. Beyond the use of earth-abundant metals and mild conditions, another distinctive advantage of Cu@CN-900 is its inactivity toward hydrolysis of the resulting nitriles, thus ensuring high product selectivity. This study offers a rational design strategy for enhancing the catalytic performance of Cu-based systems through interfacial electronic modulation between multiple active sites.