NonCovalent Aggregation-Driven D-Band Engineering in Nickel Cocatalysts for Efficient CO₂ Photoreduction

Efficient CO₂ activation remains a pivotal challenge in photocatalytic CO₂ reduction, necessitating precise electronic modulation of catalytic centers to overcome kinetic limitations. In this work, we engineer Ni(bpy)₃Br₂ cocatalyst aggregates via noncovalent self-assembly and systematically unravel the role of aggregation in governing photocatalytic performance. A synergistic combination of experimental and theoretical analyses demonstrates that symmetry disruption within the aggregates induces localized charge redistribution. Such a charge redistribution triggers a 0.6 eV upshift in the Ni d-band center, which delivers lower Gibbs free energies for the formation of *CO₂ and *COOH. The optimized aggregates achieve a record-high quantum yield of 26.84% at 450 nm with 99.3% CO selectivity, representing the highest performance reported to date for visible-light-driven CO₂-to-CO conversion systems. Importantly, the d-band center of the Ni sites can be precisely modulated by varying the aggregation degree of Ni(bpy)₃Br₂. This work not only advances a novel d-band center modulation strategy for electronic configuration engineering but also provides in-depth atomic-level insights into the aggregation-induced symmetry-regulated d-band center.