Electrosynthesis of propanol via CO electrochemical reduction (COER) offers a green route to produce highly value-added chemicals while achieving negative carbon emission. Combining density functional theory calculations and constant-potential implicit solvent model, Cu 3 @C 2 N was demonstrated to be highly active and selective toward the production of propanol via the COER. On one hand, Cu is known to exhibit high activity for the C–C coupling; on the other hand, the anchor of Cu 3 ensemble creates a microenvironment for the formation of C 3 products. In a wide potential window of [−1.95, −0.92 V/SHE], propanol can be generated through a one-shot nonelectrochemical C–C–C coupling process with a surmountable kinetic barrier and electrochemical proton-coupled electron transfer processes with a low onset potential. After checking 27 kinds of transition-metal ensembles, the high catalytic performance was found to originate from the well-defined structure of the substrate and the moderate CO adsorption strength. Our study not only proposes an excellent catalyst for the electrosynthesis of propanol but also provides an advanced strategy to address the electrochemical reaction mechanism.