Dynamic structural engineering of ferrocene-functionalized Ag20 nanoclusters for enhanced CO2 electroreduction performance

Abstract

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 24 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 *COOH intermediate formation compared to Ag₂₀-Ph.