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.