Atomically precise high-nuclearity Cu nanoclusters (Cu atom number > 50) with both Cu(I) and Cu(0) species have been rarely reported due to the inherent instability of Cu(0) species. Herein, we report a C₃ symmetric alkynyl-protected [Cu₆₇(C≡CPh)₂₄(OAc)₁₈]⁻ (Cu₆₇; Ph and OAc refer to phenyl group and acetate, respectively) superatomic nanocluster, which possesses a hierarchical metal core structure of Cu₅@Cu₂₆@Cu₃₆. Cu₆₇ was synthesized by a one-pot reduction strategy in which phenylacetylene drives the assembly of a nested architecture stabilized by synergistic μ-coordinated alkynyl ligands (μ₄/μ₅ modes) and κ²-bridged acetates. Remarkably, when Cu₆₇ is used for electrochemical CO₂ reduction reaction (eCO₂RR), deeply reduced hydrocarbon chemicals, especially the C₂₊ products, with high selectivity are acquired. Specifically, Cu₆₇ achieves a Faradaic efficiency (FE) of 56.32% for the total C₂₊ products at −0.9 V vs. reversible hydrogen electrode (RHE), among which the FE of ethylene ( ${\text{FE}}_{{\mathrm{C}}_2{\mathrm{H}}_4}$) is 39.01%. The excellent catalytic performance from Cu₆₇ is superior to most of the recently reported Cu nanocluster-based catalysts. In-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) study reveals the reaction pathway and identifies the key intermediate *COCHO for yielding C₂₊ products. Density functional theory (DFT) calculations systematically elucidate the reaction mechanism of eCO₂RR on Cu₆₇ to generate CO and C₂H₄, where the transformation from *CO to *CHO is the rate-determining step for generating the C₂₊ products. This work not only enriches the family members of alkynyl-protected high-nuclearity superatomic Cu nanoclusters, but also provides atom-level mechanistic insights on employing Cu nanoclusters for eCO₂RR to produce highly valuable products.

Electrochemical nitrate reduction reaction (NtrRR) has been emerging as an appealing route for both water treatment and NH₃ synthesis. Herein, we report the structure analysis and electrocatalytic performance of a novel homoleptic alkynyl-protected Ag₂₀Cu₁₂ nanocluster (Ag₂₀Cu₁₂ in short) with atomic precision, which has eight free electrons and displays characteristic absorbance feature. Single crystal X-ray diffraction (SC-XRD) discloses that, it adopts a Ag₁₄ kernel capped by three Ag₂Cu₄(C≡CAr^F)₈ metal–ligand binding motifs in the outer shell. Ag₂₀Cu₁₂ exhibited excellent catalytic performance toward NtrRR, as manifested by the superior NH₃ Faradaic efficiency (FE, 84.6%) and yield rate (0.138 mmol·h⁻¹·mg⁻¹) than the homoleptic alkynyl-protected Ag₃₂ nanoclusters. Additionally, it demonstrates good catalytic recycling capability. Density functional theory (DFT) calculations revealed that, the de-ligated Ag₂₀Cu₁₂ cluster can expose the available AgCu bimetallic sites as the efficient active sites for NH₃ formation. In particular, the participation of Cu sites greatly facilitates the initial capture of NO₃⁻ and simultaneously promotes the selectivity of the final product. This study discovers a novel homoleptic alkynyl-protected AgCu superatom, and offers a great example to elucidate the structure–performance relationship of bimetallic catalyst for NtrRR and other multiple protons/electrons coupled electrocatalytic reactions.

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.