Unveiling the Remarkable Stability and Catalytic Activity of a 6-Electron Superatomic Ag 30 Nanocluster for CO 2 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 ( i PrS) 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 CO 2 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 ∞ 1 {[H 2 Ag 5 (TC4A)( i PrS) 3 ]} ( ∞ 1 Ag 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 ∞ 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.