Tailoring d‐Band Center of Single‐Atom Nickel Sites for Boosted Photocatalytic Reduction of Diluted CO2 from Flue Gas

Photocatalytic reduction of diluted CO₂ from anthropogenic sources holds tremendous potential for achieving carbon neutrality, while the huge barrier to forming *COOH key intermediate considerably limits catalytic effectiveness. Herein, via coordination engineering of atomically scattered Ni sites in conductive metal-organic frameworks (CMOFs), we propose a facile strategy for tailoring the d-band center of metal active sites towards high-efficiency photoreduction of diluted CO₂. Under visible-light irradiation in pure CO₂, CMOFs with Ni-O₄ sites (Ni-O₄ CMOFs) exhibits an outstanding rate for CO generation of 13.3 μmol h^-1 with a selectivity of 94.5 %, which is almost double that of its isostructural counterpart with traditional Ni-N₄ sites (Ni-N₄ CMOFs), outperforming most reported systems under comparable conditions. Interestingly, in simulated flue gas, the CO selectivity of Ni-N₄ CMOFs decreases significantly while that of Ni-O₄ CMOFs is mostly unchanged, signifying the supremacy for Ni-O₄ CMOFs in leveraging anthropogenic diluted CO₂. In situ spectroscopy and density functional theory (DFT) investigations demonstrate that O coordination can move the center of the Ni sites' d-band closer to the Fermi level, benefiting the generation of *COOH key intermediate as well as the desorption of *CO and hence leading to significantly boosted activity and selectivity for CO₂-to-CO photoreduction.