Anion Modulation of Ag‐Imidazole Cuboctahedral Cage Microenvironments for Efficient Electrocatalytic CO2 Reduction.

How to achieve CO2 electroreduction in high efficiency is a current challenge with the mechanism not well understood yet. The metal‐organic cages with multiple metal sites, tunable active centers, and well‐defined microenvironments may provide a promising catalyst model. Here, we report self‐assembly of Ag4L4 type cuboctahedral cages from coordination dynamic Ag+ ion and triangular imidazolyl ligand 1,3,5‐tris(1‐benzylbenzimidazol‐2‐yl) benzene (Ag‐MOC‐X, X=NO3, ClO4, BF4) via anion template effect. Notably, Ag‐MOC‐NO3 achieves the highest CO faradaic efficiency in pH‐universal electrolytes of 86.1 % (acidic), 94.1 % (neutral) and 95.3 % (alkaline), much higher than those of Ag‐MOC‐ClO4 and Ag‐MOC‐BF4 with just different counter anions. In situ attenuated total reflection Fourier transform infrared spectroscopy observes formation of vital intermediate *COOH for CO2‐to‐CO conversion. The density functional theory calculations suggest that the adsorption of CO2 on unsaturated Ag‐site is stabilized by C−H⋅⋅⋅O hydrogen‐bonding of CO2 in a microenvironment surrounded by three benzimidazole rings, and the activation of CO2 is dependent on the coordination dynamics of Ag‐centers modulated by the hosted anions through Ag⋅⋅⋅X interactions. This work offers a supramolecular electrocatalytic strategy based on Ag‐coordination geometry and host–guest interaction regulation of MOCs as high‐efficient electrocatalysts for CO2 reduction to CO which is a key intermediate in chemical industry process. [ABSTRACT FROM AUTHOR]