Tuning Electrocatalytic Water Oxidation Activity: Insights from the Active-Site Distance in LnCu 6 Clusters.

Atomically precise metal clusters serve as a unique model for unraveling the intricate mechanism of the catalytic reaction and exploring the complex relationship between structure and activity. Herein, three series of water-soluble heterometallic clusters LnCu 6 , abbreviated as LnCu 6 -AC (Ln = La, Nd, Gd, Er, Yb; HAC = acetic acid), LnCu 6 -IM (Ln = La and Nd; IM = Imidazole), and LnCu 6 -IDA (Ln = Nd; H 2 IDA = Iminodiacetic acid) are presented, each featuring a uniform metallic core stabilized by distinct protected ligands. Crystal structure analysis reveals a triangular prism topology formed by six Cu 2+ ions around one Ln 3+ ion in LnCu 6 , with variations in Cu···Cu distances attributed to different ligands. Electrocatalytic oxygen evolution reaction (OER) shows that these different LnCu 6 clusters exhibit different OER activities with remarkable turnover frequency of 135 s -1 for NdCu 6 -AC, 79 s -1 for NdCu 6 -IM and 32 s -1 for NdCu 6 -IDA. Structural analysis and Density Functional Theory (DFT) calculations underscore the correlation between shorter Cu···Cu distances and improves OER catalytic activity, emphasizing the pivotal role of active-site distance in regulating electrocatalytic OER activities. These results provide valuable insights into the OER mechanism and contribute to the design of efficient homogeneous OER electrocatalysts.