Enhanced Selectivity of Photocatalytic CO₂ Reduction to Formate via Tailoring the Metal Site

Photocatalytic reduction of CO2 to liquid fuel HCOOH is an ideal strategy for addressing environmental and energy problems, but it still remains a challenge to design photocatalysts with high HCOOH selectivity. Herein, the coordinated O atom in iron-based MOFs (Fe-BDC) was partially replaced by the N atom to afford a special FeO4N2 metal site. Comprehensive experimental and calculation results suggest that the introduction of a N atom increases the asymmetry of electron distribution with a higher electron density in the Fe site, which affects the formation and desorption of the key *HCOOH intermediate and consequently optimizes the CO2-to-formate reaction pathway. As a result, the synthesized Fe-PYC presents a higher formate selectivity (93%) with a formation rate of 238 μmol g–1 h–1 compared to that of Fe-BDC (54%, 175 μmol g–1 h–1). This work provides deeper insight into the interplay between the coordination geometry of metal sites and the selectivity of CO2 photoreduction.