Accurate Thermal Resection of Atomically Precise Copper Clusters to Achieve Near-IR Light-Driven CO₂ Reduction.

Abstract

Atomically precise copper clusters are desirable as catalysts for elaborating the structure-activity relationships. The challenge, however, lies in their tendency to sinter when protective ligands are removed, resulting in the destruction of the structural integrity of the model system. Herein, a copper-sulfur-nitrogen cluster [Cu₈(S^tBu)₄(PymS)₄] (denoted as Cu₈SN) is synthesized by using a mixed ligand approach with strong chelating 2-mercaptopyrimidine (PymSH) ligands and relatively weak monodentate tert-butyl mercaptan ligands. A precise thermal-resection strategy is applied to selectively peel only the targeted weak ligands off, which induces a structural transformation of the initial Cu₈ cluster into a new and more stable Cu-S-N cluster [Cu₈(S)₂(PymS)₄] (denoted as Cu₈SN-T). The residual bridging S^2- within the metal core forms asymmetric Cu-S species with a near-infrared (NIR) response, which endows Cu₈SN-T with the capability for full-spectrum responsive CO₂ photoreduction, achieving a ≈100% CO₂-to-CO selectivity. Especially for NIR-driven CO₂ reduction, it has a CO evolution of 42.5 µmol g^-1 under λ > 780 nm. Importantly, this work represents the first NIR light-responsive copper cluster for efficient CO₂ photoreduction and opens an avenue for the precise manipulation of metal cluster structures via a novel thermolysis strategy to develop unprecedented functionalized metal cluster materials.