Dipropyne‐Modified N‐Heterocyclic Carbene Stabilized Atomically Precise Copper(I) Nanocluster Catalysts for CO₂ Electroreduction

Abstract Atomically precise copper(I) nanoclusters with stable active sites are highly sought‐after catalysts for the electrocatalytic CO₂ reduction reaction (CO₂RR), providing an exceptional platform to elucidate structure–activity relationships. However, the rational synthesis of robust copper nanoclusters as effective electrocatalysts and understanding the relationship between a more realistic active site and its performance remain a significant challenge due to their inherent instability. Here, a novel dipropyne‐modified NHC ligand is elaborately devised to synthesis two atomically precise copper nanoclusters, [Cu 17 H 6 (NHC H ) 4 (dppm) 4 ] 3+ ( Cu17a ) and [Cu 17 H 6 (NHC Ph ) 4 (dppm) 4 ] 3+ ( Cu17b ), both exhibiting a distinct unique square orthobicupola Cu 17 H 6 core ( J 28 , Johnson solid). The robust σ‐ and π‐bonding between copper and the NHC ligands imparts ultrahigh stability of nanoclusters, while the unique coordination pattern ( μ 7 ‐ η σ 1 : η σ 1 : η σ 1 : η σ 1 : η σ 1 : η π 2 : η π 2 ) of NHC ligands facilitates exposure of neighboring copper atoms, generating accessible catalytic sites. Electrocatalytic CO 2 reduction experiments show that Cu17a achieves the highest Faradaic efficiency for ethylene production among reported nanoclusters. The active sites and tandem catalytic reaction mechanism of the CO 2 RR are elucidated through a combination of theoretical calculations with attenuated total reflection‐surface‐enhanced IR absorption spectroscopy (ATR‐SEIRAS). This work not only introduces dipropyne‐modified NHC ligands for synthesizing stable copper nanoclusters but also offers critical insights into molecular design principles for CO 2 RR catalysts.