Copper‒Chloride Semiconductor Nanoclusters for High‐Efficiency Photocatalysis

ABSTRACT Research on atomically precise copper nanoclusters is ongoing, with particular attention paid to cluster systems that possess novel structural motifs and distinctive properties. Herein, we report a binary copper–chloride semiconductor nanocluster, [Cu 40 Cl 12 (ClC 6 H 4 CH 2 S) 22 (PPh 3 ) 9 H 2 ] (denoted as Cu 40 Cl 12 , where ClC 6 H 4 CH 2 SH is 4‑chlorobenzyl mercaptan and PPh 3 is triphenylphosphine), which possesses a covalent framework constructed through copper–chloride bonds. The synthesis of Cu 40 Cl 12 benefits from immediate separation during assembly in poor solvents and this synthetic approach is applicable to the corresponding copper–bromide and copper–iodide analogues. As revealed by theoretical calculations, the μ 6 ‐coordinated chlorides significantly modulate the cluster electronic structure and contribute to the formation of the electron‐hole pairs in the photoexcitation process of the Cu 40 Cl 12 cluster. Ultrafast spectroscopic studies reveal that Cu 40 Cl 12 sustains longer‑lived charge‑separated states and exhibits superior charge separation efficiency upon photoexcitation compared to chloride‑free analogues. As a result, a Cu 40 Cl 12 /TiO 2 composite demonstrates a remarkable solar‑driven hydrogen evolution rate of ∼9000 µmol g −1 h −1 under simulated sunlight irradiation and with methanol serving as a sacrificial agent, outperforming TiO 2 composites incorporating conventional metal nanoclusters. This work not only highlights the potential of copper–chloride semiconductor nanoclusters for photochemical transformation, but also emphasizes the broader prospects of copper nanoclusters in advancing research in chemical and materials science.