Low‐Coordination Triangular Cu3 Motif Steers CO2 Photoreduction to Ethanol

Photoreduction of CO2 using copper‐based multi‐atom catalysts (MACs) offers a potential approach to achieve value‐added C2+ products. However, achieving MACs with high metal contents and suppressing the thermodynamically favored competing ethylene production pathway remain challenging, thus leading to unsatisfactory performance in ethanol production. Herein, we developed a ‘pre‐locking and nanoconfined polymerization’ strategy for synthesis of an ultra‐high‐density Cu MAC with low‐coordination triangular Cu3 motifs (Cu3 MAC) on polymeric carbon nitride mesoporous nanofibers. The Cu3 MAC with Cu contents of 36 wt% achieves a high reactivity of 117 μmol·g‐1·h‐1 for ethanol production from CO2 and H2O, with a remarkable selectivity of 98% under simulated sunlight irradiation, representing one of the highest performances in ambient conditions without sacrificial reagents. The superior catalytic efficiency is attributed to the triangular Cu3 configuration, in which both Cu(I) and Cu(II) coexist, predominantly as Cu(I). Such Cu3 motifs act as strong alkaline sites that effectively chemisorb and activate CO2, extend visible‐light absorption range, while accumulating high‐density electrons and favoring 12‐electron‐transfer products. An accelerated asymmetric C‐C coupling with adsorption configuration of the bridge‐adsorbed *CO at paired Cu sites and atop‐adsorbed *CO at adjacent single Cu atom was observed, enabling preferential formation of *CHCHOH intermediates to produce ethanol.