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.