Bridged nitrogen sites in carbon nitride activated by a low-coordination AuN2 configuration for enhanced CO2 photoreduction

Conventional single-atom catalyst (SAC) design anchors metal atoms within a host matrix to create well-defined metal active sites for enhanced catalytic efficiency. Herein, we engineer a novel SAC featuring Au single atoms (AuSAs), which is synergistically enhanced by the coexistence of Au nanoparticles (AuNPs), transcending the conventional design strategy. The AuSAs are stabilized within the carbon nitride (PCN) skeleton via the formation of an unconventional low-coordination AuN 2 configuration, which is achieved through the coordination of each Au atom with one bridged nitrogen atom and one nitrogen from bipyridine motif. This unique configuration activates the once-inert bridged nitrogen while simultaneously modulates the electronic band structure of PCN. Consequently, the optimal AuSAs-PCN/AuNPs catalyst achieves an average CO production rate 3.59 times higher than that of the pristine PCN in aqueous solution. In triethanolamine solution, the CO and CH 4 production rates reach 1.55 and 1.64 times those of PCN, respectively. This work demonstrates a breakthrough that moves beyond traditional SAC design by creating a low metal-coordination configuration to activate adjacent nonmetallic sites, thereby providing a strategic blueprint for a broad class of high-performance catalysts.