Atomically Precise [Cu23H4(SC7H7)18(PPh3)6] Nanocluster: Structural Integration of Johnson Solids through a Cu(0) Center and Electrocatalytic Functionality

In recent years, the synthesis of copper (Cu) nanoclusters (NCs) has attracted significant attention due to their promis-ing catalytic applications. However, the high reactivity of Cu(0) often renders these NCs unstable, limiting the synthe-sis primarily to Cu(I)-based NCs. This limitation also restricts the utility of these NCs in catalysis. Here, we present a synthetic strategy to fabricate a stable Cu(0)-containing, [Cu₂₃H₄(SC₇H₇)₁₈(PPh₃)₆] NC, where the Cu(0) center is atomically protected by two Cu(I)-based Johnson solids and stabilized by the additional Cu(I) units, thiolate ligands and interstitial hydrides. Although neutral PPh₃ ligands are present, their attachment is positioned away from the Cu(0) center, primarily serving to stabilize the overall geometry and prevent further structural distortions. This ro-bust architectural framework enables the NC to maintain exceptional structural stability and catalytic performance in electrochemical CO₂ reduction reactions, facilitating a consistent selectivity for the end product over time. Additionally, theoretical calculations corroborate the experimental findings, confirming a preference for HCOOH formation over CO. This is attributed to a lower limiting potential for the formation of *HCOO compared to *COOH at the active site, which favors HCOOH as the primary product.