Quantitative Relationships between Lewis Acidity and Catalytic Activity in Atomically Precise Copper Nanoclusters

Atomically precise metal nanoclusters (APMNCs) provide an ideal platform for investigating structure-activity relationships (SARs) in catalysis. Although significant progress has been made in elucidating SARs, the development of quantitative structure-activity relationships (QSARs) in cluster catalysis─particularly those incorporating fundamental physicochemical descriptors such as Lewis acidity (LA)─remains limited and mechanistically unclear. To address this gap, we synthesized a tailored series of isostructural [X@Cu₁₄(C₂₄H₂₇P)₄(SCH₂C₆H₄R)₁₂] nanoclusters (R = OMe, CH₃, H, Cl, F). Critically, this series enables exclusive modulation of LA via ligand electronic effects while maintaining identical core geometry and surface structure. Through combined experimental measurements and density functional theory (DFT) calculations of electrocatalytic hydrogen evolution reaction (HER) performance, a strong correlation within this series between LA and catalytic activity was established. A smaller LA promotes more efficient electron donation to the adsorbed hydrogen species, which lowers the reaction energy barrier and enhances HER activity. Based on this established correlation, the top-performing catalyst of [X@Cu₁₄(C₂₄H₂₇P)₄(SCH₂C₆H₄OMe)₁₂] was further optimized, enabling the design of an integrated photovoltaic-electrolysis system for water splitting. This work not only establishes LA as a meaningful electronic descriptor for nanocluster catalyst design but also demonstrates the pioneering application of APMNCs in establishing QSARs for nanocatalysis.