Caprolactam (CPL), a monomer of nylon-6 widely used in automotive, machinery, and electronics, is traditionally synthesized from cyclohexanone (CYC) through a complex process that generates low-value ammonium sulfate, leading to environmental pollution. In contrast, electrochemical methods offer a safer, greener one-pot synthesis of CPL from waste NO3 -, but currently, the coupling of CYC and NO3 - primarily produces cyclohexanone oxime (CHO), and the direct generation of CPL is challenging. Here, we report for the first time the electrochemical conversion of CYC and NO3 - to high-value CPL in a one-pot process under ambient conditions. Using Ag-Ag4Sn-SnO2 nanoparticle catalysts, we achieved a remarkable 96% yield and 97% selectivity for CPL electrosynthesis. In situ characterizations, control experiments, and theoretical calculations suggested the importance of balanced activation of NO3 - and CYC substrates on the Ag-Ag4Sn-SnO2 catalysts for achieving high-efficient CPL electrosynthesis. The method also exhibits broad versatility in synthesizing various amide compounds, including paracetamol for antipyretic. Notably, scaling up the reactor enabled a high CPL production rate of 3.41 g h-1 gcat -1 with a 90.5% isolated yield, highlighting the potential of this technique for large-scale electrosynthesis.
Xue et al. (Tue,) studied this question.