Ambient One-Pot Electrocatalytic Synthesis of Caprolactam From Cyclohexanone and Nitrate Over Ag-Ag₄Sn-SnO₂...

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 g_cat ^-1 with a 90.5% isolated yield, highlighting the potential of this technique for large-scale electrosynthesis.