Phosphine‐Triggered Structural Defects in Au44 Homologues Boost Electrocatalytic CO2 Reduction

The systematic induction of structural defects at the atomic level is crucial to metal nanocluster research because it endows cluster-based catalysts with highly reactive centers and allows for a comprehensive investigation of viable reaction pathways. Herein, by substituting neutral phosphine ligands for surface anionic thiolate ligands, we establish that one or two Au₃ triangular units can be successfully introduced into the double-stranded helical kernel of Au₄₄ (TBBT)₂₈ , where TBBT=4-tert-butylbenzenethiolate, resulting in the formation of two atomically precise defective Au₄₄ nanoclusters. Along with the regular face-centered-cubic (fcc) nanocluster, the first series of mixed-ligand cluster homologues is identified, with a unified formula of Au₄₄ (PPh₃ )_n (TBBT)_28-2n (n=0-2). The Au₄₄ (PPh₃ )(TBBT)₂₆ nanocluster having major structural defects at the bottom of the fcc lattice demonstrates superior electrocatalytic performance in the CO₂ reduction to CO. Density functional theory calculations indicate that the active site near the defects significantly lowers the free energy for the *COOH formation, the rate-determining step in the whole catalytic process.