Boosting Solar‐Driven CO2 Conversion to Ethanol via Single‐Atom Catalyst with Defected Low‐Coordination Cu‐N2 Motif

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AbstractCu‐based catalysts have been shown to selectively catalyze CO2 photoreduction to C2+ solar fuels. However, they still suffer from poor activity and low selectivity. Herein, we report a high‐performance carbon nitride supported Cu single‐atom catalyst featuring defected low‐coordination Cu‐N2 motif (Cu‐N2‐V). Lead many recently reported photocatalysts and its Cu‐N3 and Cu‐N4 counterparts, Cu‐N2‐V exhibits superior photocatalytic activity for CO2 reduction to ethanol and delivers 69.8 μmol g−1 h−1 ethanol production rate, 97.8 % electron‐based ethanol selectivity, and a yield of ~10 times higher than Cu‐N3 and Cu‐N4. Revealed by the extensive experimental investigation combined with DFT calculations, the superior photoactivity of Cu‐N2‐V stems from its defected Cu‐N2 configuration, in which the Cu sites are electron enriched and enhance electron delocalization. Importantly, Cu in Cu‐N2‐V exist in both Cu+ and Cu2+ valence states, although predominantly as Cu+. The Cu+ sites support the CO2 activation, while the co‐existence of Cu+/Cu2+ sites are highly conducive for strong *CO adsorption and subsequent *CO‐*CO dimerization enabling C−C coupling. Furthermore, the hollow microstructure of the catalyst also promotes light adsorption and charge separation efficiency. Collectively, these make Cu‐N2‐V an effective and high‐performance catalyst for the solar‐driven CO2 conversion to ethanol. This study also elucidates the C‐C coupling reaction path via *CO‐*CO to *COCOH and rate‐determining step, and reveals the valence state change of partial Cu species from Cu+ to Cu2+ in Cu‐N2‐V during CO2 photoreduction reaction.