Oxygen-Bridged Copper Dual-Metal Sites Dispersed on Carbon Nitride for Highly Efficient and Selective Photoreduction of CO2 to Acetic Acid in Pure Water

The development of dual-metal-atom catalysts (DACs) represents a promising strategy for efficient and selective CO2 photoreduction to C2 fuels. Herein, a polymeric carbon nitride-based catalyst featuring oxygen-bridged Cu atomic pairs (CuDAC) was synthesized via a straightforward pyrolysis of a layered supramolecular precursor comprising the paddlewheel complex Cu2(p-O2NC6H4CO2)4 (Cu2Ph4), melamine and cyanuric acid. In pure water, the optimized CuDAC exhibited an impressive CH3COOH formation rate of 62.94 μmol h–1 g–1 and a product selectivity of 98.18%. These metrics were superior to those of polymeric carbon nitride and Cu single-atom counterparts. Experimental and theoretical analyses revealed the pivotal roles of Cu–O–Cu sites in driving the high performance of CuDAC. Essentially, Cu–O–Cu centers enhanced solar light utilization, accelerated charge transfer, increased CO2 uptake capacity, and promoted favorable surface-CO interactions. Furthermore, the synergistic effects of charge accumulation, electronic delocalization, and the structurally favorable configuration of the Cu–O–Cu motifs stabilized the intermediates, promoted the C–C coupling step, and lowered the reaction barriers. This work provides valuable insights into the design of dual-metal-atom photocatalysts and elucidates their underlying mechanisms, paving the way for the advancement of metal-atom-site catalysts in energy conversion and storage applications.