"Ship-in-a-Bottle" Integration of Ditin(IV) Sites into a Metal-Organic Framework for Boosting Electroreduction of CO in Acidic Electrolyte.

The electrochemical CO reduction reaction (eCORR) under acidic conditions has become a promising way to achieve high CO utilization because of the inhibition of undesirable carbonate formation that typically occurs under neutral and alkaline conditions. Herein, unprecedented and highly active ditin(IV) sites were integrated into the nanopores of a metal-organic framework, namely , by a "ship-in-a-bottle" strategy. delivers nearly 100% formic acid Faradaic efficiency at an industry current density of 260 mA cm with a high single-pass CO utilization of 95% in an acidic solution (pH = 1.67). No obvious degradation was observed over 15 hours of continuous operation at the current density of 260 mA cm, representing the remarkable eCORR performance in acidic electrolyte to date. The mechanism study shows that both oxygen atoms of the key intermediate *HCOO can coordinate to the two adjacent Sn atoms in a ditin(IV) site simultaneously. Such bridging coordination is conducive to the hydrogenation of CO, thus leading to high performance.