Anchored Ag+ sites on a thiacalix[4]arene-stabilized Ti-oxo cluster enable efficient CO2-to-CO electroreduction

Abstract

Electrochemical CO₂ reduction (eCO₂RR) provides a promising route for converting CO₂ into value-added carbon monoxide (CO), a key feedstock for chemical synthesis. Silver-based catalysts are among the most effective materials for this process; however, their practical development is often hindered by the poorly defined nature of their active sites, which limits precise structure–activity correlations. Herein, we report the synthesis of a structurally well-defined Ag⁺/Ti⁴⁺ bimetallic titanium-oxo cluster, Ti₆Ag₆, stabilized by thiacalix[4]arene ligands. The cluster adopts a distinctive linear architecture comprising three types of surface-exposed Ag sites. When applied to eCO₂RR, Ti₆Ag₆ exhibits outstanding catalytic performance, delivering over 90% faradaic efficiency for CO across a wide potential window. DFT calculations reveal that the central bridging Ag site exhibits the highest intrinsic activity, attributed to its superior ability to stabilize the *COOH intermediate.