Cu₃₄S₆(PFBT)₂₂(PPh₃)₆: A Cu₁₂S₆ Core‐Based Nanocluster with Long‐Lived Phosphorescent Crystallization‐Induced Emission Enhancement for Selectively Acetonitrile Sensing

Abstract Atomically precise copper nanoclusters with crystallization‐induced emission enhancement (CIEE) have garnered significant academic interests‐ but the rational design of high‐nuclearity Cu nanoaggregates with precise atomic structures and the CIEE effect remains a long‐standing challenge. Herein, a new atomically precise copper nanocluster co‐protected by thiolate, phosphine, and S²⁻ ligands, formulated as Cu₃₄S₆(PFBT)₂₂(PPh₃)₆ (Cu₃₄, PFBT = pentafluorobenzenethiol, PPh₃ = triphenylphosphine), is reported, which possesses a typical Cu₁₂S₆ core and a Cu₂₂S₂₂P₆ shell. Under photoexcitation at 505 nm, Cu₃₄ exhibits strong red‐light emission with a photoluminescence quantum yield of 4.1%. DFT calculations confirm that the emission stems from the ligand‐to‐metal charge transfer (LMCT) transition. This nanoaggregate shows a strong CIEE effect, with the crystalline form exhibiting an 800‐fold enhancement in emission intensity compared to its solution form. An in‐depth structural investigation of the ligand shell reveals that the extensive C−H···F, C−H···π, and π···π interactions significantly restrict the intra‐ and inter‐molecular rotations and vibrations, accounting for the CIEE phenomena. The red emission of Cu₃₄ can be selectively quenched by CH₃CN, with a lower detection limit of 9.36 µM (0.38 ppm). This study advances the development of high‐nuclearity copper nanocluster with the CIEE effect and holds significant potential for applications in selectively sensing volatile organic compounds (VOCs).