Copper‒Chloride Semiconductor Nanoclusters for High-Efficiency Photocatalysis

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, [Cu₄₀Cl₁₂(ClC₆H₄CH₂S)₂₂(PPh₃)₉H₂] (denoted as Cu₄₀Cl₁₂, where ClC₆H₄CH₂SH is 4‑chlorobenzyl mercaptan and PPh₃ is triphenylphosphine), which possesses a covalent framework constructed through copper-chloride bonds. The synthesis of Cu₄₀Cl₁₂ 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 μ₆-coordinated chlorides significantly modulate the cluster electronic structure and contribute to the formation of the electron-hole pairs in the photoexcitation process of the Cu₄₀Cl₁₂ cluster. Ultrafast spectroscopic studies reveal that Cu₄₀Cl₁₂ sustains longer‑lived charge‑separated states and exhibits superior charge separation efficiency upon photoexcitation compared to chloride‑free analogues. As a result, a Cu₄₀Cl₁₂/TiO₂ 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 TiO₂ 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.