A Z-Scheme CuWO4/Poly(heptazine imide) Interface Coupled With Asymmetric Cu2+/Cu+ Sites Enables Efficient Photocatalytic CO2-to-Ethanol Conversion.

Selective photocatalytic reduction of CO2 into multicarbon products remains challenging because constructing uniform C─C coupling centers while maintaining their stability under reaction conditions is difficult. Here, we report a Z-scheme CuWO4/poly(heptazine imide) heterojunction featuring asymmetric Cu2+/Cu+ dual sites for CO2-to-ethanol conversion. Site-selective oxygen vacancies in CuWO4 trigger generation of structurally identical, charge-asymmetric neighboring Cu sites, which enhance CO2 activation and stabilize adjacent *CO intermediates, thereby facilitating C─C bond formation. Meanwhile, an atomically bonded O─W─N heterointerface enables directional Z-scheme charge transfer, supplying photogenerated electrons to the CuWO4 surface and stabilizing the asymmetric Cu2+/Cu+ dual sites throughout photocatalysis. Consequently, the optimized photocatalyst achieves an ethanol production rate of 244.5 µmol g-1 h-1 in pure water without sacrificial reagents. Advanced synchrotron spectroscopies identify the asymmetric Cu2+/Cu+ dual sites and the chemically bonded heterointerface, while operando spectroscopies record the dynamic evolution of active sites and the *CO─*CO coupling pathways upon illumination. Density functional theory calculations reveal that the synergy between asymmetric catalytic centers and the atomically bonded heterointerface promotes the C─C coupling process. This work establishes a strategy for constructing and stabilizing asymmetric catalytic centers through atomic engineering of crystal structure and heterointerface, providing a photocatalyst design paradigm for selective multicarbon solar fuel synthesis.