Synergistic C─N Coupling for Efficient Cyclohexanone Oxime Synthesis from Ambient Air by Supported Molecular Catalysts

Abstract

Abstract Electrocatalytic synthesis of cyclohexanone oxime from rich nitrogen resources is a promising alternative to traditional industrial processes. However, the difficulties in unraveling atomic‐scale catalytic mechanisms and managing selective C─N coupling still pose great challenges to realizing considerable yield and selectivity, and therefore rational catalyst design to boost collaborative C─N coupling for oxime synthesis is particularly attractive. In the present work, molecular catalysts are demonstrated to be unique for oxime synthesis under mild conditions, i.e., iron bis(pyridyl)amine‐bipyridine (FeBPAbipyH) modified MWCNTs@CP (multi‐walled carbon nanotubes coated carbon fiber paper) cathodes produced cyclohexanone oxime from NO 2 − and cyclohexanone, attaining mass‐specific efficiency of 87.00 mg h −1  cm −2  mg cat −1 , Faradaic efficiency (FE) of 77.3%, and exclusive carbon selectivity, which is the best efficiency known to date in H‐cell. Mechanistic studies showed that the FeBPAbipyH molecular skeleton exhibited intimate interaction with both cyclohexanone and NO 2 − , and catalyzed selective NO 2 − ‐to‐NH 2 OH reduction for C─N bond in situ. The in‐depth understanding of substrate‐catalyst interactions and synergic C─N coupling from molecular points of view offers valuable insights to boost collaborative synthesis of organic nitrogen compounds. Further integrating plasma‐driven N 2 oxidation and electrocatalysis enabled cyclohexanone oxime formation at 61.73 mg h −1  cm −2  mg cat −1 on the FeBPAbipyH/MWCNTs@CP electrode, and the whole synthetic and separation process is projected to be profitable with a promising cost of $2709 ton −1 , which is much lower than the breakeven point (∼$10 000 ton −1 ), representing a sustainable pathway to nitrogenous chemical synthesis from abundant resources under ambient conditions.