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.