Isolated Tin(IV) Active Sites for Highly Efficient Electroreduction of CO₂ to CH₄ in Neutral Aqueous Solution

The development of efficient electrocatalysts with non-copper metal sites for electrochemical CO₂ reduction reactions (eCO₂ RR) to hydrocarbons and oxygenates is highly desirable, but still a great challenge. Herein, a stable metal-organic framework (DMA)₄ [Sn₂ (THO)₂ ] (Sn-THO, THO^6- = triphenylene-2,3,6,7,10,11-hexakis(olate), DMA = dimethylammonium) with isolated and distorted octahedral SnO₆ ^2- active sites is reported as an electrocatalyst for eCO₂ RR, showing an exceptional performance for eCO₂ RR to the CH₄ product rather than the common products formate and CO for reported Sn-based catalysts. The partial current density of CH₄ 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 SnO₆ ^2- active site favors the formation of key *OCOH species to produce CH₄ and can greatly inhibit the formation of *OCHO and *COOH species to produce *HCOOH and *CO, respectively.