Dynamic Structural Engineering of Ferrocene-Functionalized Ag20 Nanoclusters for Enhanced CO2 Electroreduction Performance

The integration of organometallic motifs with metal nanoclusters offers a powerful strategy for constructing hybrid catalysts with precisely tunable active sites. Here, we report the synthesis of a 20-silver nanocluster, Ag20-Fc, via cooperative coordination between thiacalix[4]arene (TC4A) and ferrocenylacetylene ligands. The cluster adopts a distinctive sandwich-like architecture, featuring two Ag5@TC4A units flanking a ferrocenyl-stabilized Ag10 core, and exhibits excellent structural tunability. Ligand engineering allows replacement of the ferrocenylacetylene units with methoxyphenylacetylene (Ag20-OPh) or phenylacetylene (Ag20-Ph), while preserving the core framework. Electrospray ionization mass spectrometry reveals dynamic structural reorganization in solution, where Ag₅@TC4A fragments are capable of capturing Ag–alkyne species and reassembling into sandwich-type clusters—a process substantiated by the structural features of Ag24, Ag12, and Cu2Ag11. Ag20-Fc generates a locally electron-rich environment and conjugated ethynyl bridges that facilitate directional charge transfer, delivering outstanding electrocatalytic CO2 reduction. It achieves over 98% Faradaic efficiency for CO across a wide potential range (–1.0 to –1.8 V vs. RHE) and maintains operational stability for 48 h, significantly outperforming Ag20-OPh and Ag20-Ph. Density functional theory calculations uncover a dual enhancement mechanism in which orbital hybridization between ferrocenyl groups and silver atoms tunes the electronic structure at active sites, resulting in a 0.28 eV reduction in the energy barrier for *OCHO intermediate formation compared to Ag20-Ph.