Isolated Tin(IV) Active Sites for Highly Efficient Electroreduction of CO 2 to CH 4 in Neutral Aqueous Solution.

The development of efficient electrocatalysts with non-copper metal sites for electrochemical CO 2 reduction reactions (eCO 2 RR) to hydrocarbons and oxygenates is highly desirable, but still a great challenge. Herein, a stable metal-organic framework (DMA) 4 [Sn 2 (THO) 2 ] (Sn-THO, THO 6- = triphenylene-2,3,6,7,10,11-hexakis(olate), DMA = dimethylammonium) with isolated and distorted octahedral SnO 6 2- active sites is reported as an electrocatalyst for eCO 2 RR, showing an exceptional performance for eCO 2 RR to the CH 4 product rather than the common products formate and CO for reported Sn-based catalysts. The partial current density of CH 4 reaches a high value of 34.5 mA cm -2 , surpassing most reported copper-based and all non-Cu metal-based catalysts. Our experimental and theoretical results revealed that the isolated SnO 6 2- active site favors the formation of key *OCOH species to produce CH 4 and can greatly inhibit the formation of *OCHO and *COOH species to produce *HCOOH and *CO, respectively.