Electrochemical and chemical cascade catalysis for efficient hexamethylenetetramine synthesis over mesoporous copper nanotips.

Catalytic carbon-nitrogen (C-N) coupling reactions offer a sustainable and environmentally friendly route for the production of high value-added hexamethylenetetramine (HMTA). However, it still suffers from limited chemisorption, low activation kinetics, and unfavorable thermodynamics, resulting in low HMTA Faradaic efficiency (FEHMTA) and yield rate. Here, by physically constructing hierarchically tip and mesoporous structure, copper mesoporous nanotips (Cu MNTs) realize efficient HMTA synthesis by an electrochemical-chemical cascade catalysis. Unlike traditional catalysts, tip-enhanced site of Cu MNTs electrochemically favors NO3- chemisorption and further electroreduction into *NH3 radicals, while its confined mesoporous nanoreactor ensures cascade chemical C-N coupling and subsequent cyclization to HMTA. With minor byproducts, Cu MNTs deliver a FEHMTA of 94.2% and a yield rate of 0.227 mmol h-1 cm-2. Moreover, this route enables efficient HMTA synthesis in a flow cell electrolyzer with high economic feasibility and market potential for industrial application. This work thus deepens the physical design strategies of hierarchically structural catalysts that promote electrochemical-chemical cascade C-N coupling reactions for efficient synthesis of various important chemicals and feedstocks.