Optimizing *CO/CO Supply by Atomically Dispersed Fe Sites for High-rate CO2-to-C2H4 Conversion Under Visible Light.

Visible light driven carbon dioxide (CO2) reduction to ethylene (C2H4) is a promising pathway to obtain renewable fuels and valuable chemicals. However, the insufficient supply of *CO/CO severely limits the rate of C-C coupling toward C2H4. Herein, we present a synergistic engineering strategy to construct a Fe0.2/H-MOF-1 composite catalyst by anchoring high-density iron single atoms sites (Fe SAs) onto a pyridinic nitrogen rich metal-organic framework (H-MOF-1). Under visible light, the catalyst achieves an exceptional C2H4 yield of 1056.2 µmol·g-1·h-1. This performance surpasses state-of-the-art systems for visible light driven CO2-to-C2H4. The X-ray absorption fine structure (XAFS) analysis, CO adsorption experiments and density functional theory (DFT) calculations demonstrate that the Fe-N active sites in the Fe0.2/H-MOF-1 catalyst not only significantly reduce the energy barrier from *COOH to *CO but also maintain abundant *CO/CO for C-C coupling through strong CO adsorption, thus efficiently promoting the rapid generation of C2H4. This study provides insights into the rapid generation of C2H4 through photocatalytic CO2 reduction, paving the way for visible light-driven CO2 reduction reactions.