Engineering Single Ni Sites on 3D Cage‐like Cucurbit[n]uril Ligands for Efficient and Selective CO2 Photocatalytic Reduction

Solar‐driven CO2 selective reduction with high conversion is a challenging task yet holds immense promise for both CO2 neutralization and green fuel production. Enhancing CO2 adsorption at the catalytic centre can trigger a highly efficient CO2 capture‐to‐conversion process. Herein, we introduce cucurbit[n]urils (CB[n]), a new family of molecular ligands, as a key component in the creation of a 3D cage‐like metal (nickel, Ni)‐complex molecular co‐catalyst (CB[7]‐Ni) for photocatalysis. It exhibits an unprecedented CO yield rate of 72.1 µmol· h‐1 with a high selectivity of 97.9% under visible light irradiation. To verify the origin of the carbon source in the products, a straightforward isotopic tracing method is designed based on tandem reactions. The catalytic process commences with photoelectron transfer from Ru(bpy)32+ to the Ni2+ site, resulting in the reduction of Ni2+ to Ni+. The locally enriched CO2 molecules in the cage ligand CB[7] undergo selective reduction by the Ni+ nearby to form CO product. This work exemplifies the inspiring potential of ligand structure engineering in advancing the development of efficient unanchored molecular co‐catalysts.