Homoleptic alkynyl-protected Ag₃₂ nanocluster with atomic precision: Probing the ligand effect toward CO₂ electroreduction and 4-nitrophenol reduction

We report a superatomic homoleptic alkynyl-protected Ag₃₂L₂₄ (L = 3,5-bis(trifluoromethylbenzene) acetylide, Ag₃₂ for short) nanocluster with atomic precision, which possesses eight free electrons. Ag₃₂ is formed by an Ag₁₇ core with C₃ symmetry and the remaining 15 Ag atoms bond to each other and coordinate with the 24 surface ligands. When applied as electrocatalyst for CO₂ reduction reaction (CO₂RR), Ag₃₂ exhibited the highest Faradaic efficiency (FE) of CO up to 96.44% at −0.8 V with hydrogen evolution being significantly suppressed in a wide potential range, meanwhile it has a reaction rate constant of 0.242 min⁻¹ at room temperature and an activation energy of 45.21 kJ·mol⁻¹ in catalyzing the reduction of 4-nitrophenol, both markedly superior than the thiolate and phosphine ligand co-protected Ag₃₂ nanocluster. Such strong ligand effect was further understood by density functional theory (DFT) calculations, as it revealed that, one single ligand stripping off from the intact cluster can create the undercoordinated Ag atom as the catalytically active site for both clusters, but alkynyl-protected Ag₃₂ nanocluster possesses a smaller energy barrier for forming the key *COOH intermediate in CO₂RR, and favors the adsorption of 4-nitrophenol. This study not only discovers a new member of homoleptic alkynyl-protected Ag nanocluster, but also highlights the great potentials of employing alkynyl-protected Ag nanoclusters as bifunctional catalysts toward various reactions.