Unveiling the Remarkable Stability and Catalytic Activity of a 6-Electron Superatomic Ag-30 Nanocluster for CO2 Electroreduction

Nanocluster catalysts face a significant challenge in striking the right balance between stability and catalytic activity. Here, we present a thiacalix[4]arene-protected 6-electron [Ag-30(TC4A)(4)((PrS)-Pr-i)(8)] nanocluster that demonstrates both high stability and catalytic activity. The Ag-30 nanocluster features a metallic core, Ag-10(4+), consisting of two Ag-3 triangles and one Ag-4 square, shielded by four {Ag-5@(TC4A)(4)} staple motifs. Based on DFT calculations, the Ag-10(4+) metallic kernel can be viewed as a trimer comprising 2-electron superatomic units, exhibiting a valence electron structure similar to that of the Be-3 molecule. Notably, this is the first crystallographic evidence of the trimerization of 2-electron superatomic units. Ag 30 can reduce CO2 into CO with a Faraday efficiency of 93.4% at -0.9 V versus RHE along with excellent long-term stability. Its catalytic activity is far superior to that of the chain-like Ag-I polymer 8 (1){[H2Ag5(TC4A)((PrS)-Pr-i)(3)]} (Ag-1(8)n ), with the composition similar to Ag-30 . DFT calculations elucidated the catalytic mechanism to clarify the contrasting catalytic performances of the Ag-30 and 8(1)Ag(n) polymers and disclosed that the intrinsically higher activity of Ag-30 may be due to the greater stability of the dual adsorption mode of the *COOH intermediate on the metallic core.