Structural reconstruction of Sn-based metal-organic frameworks for efficient electrochemical CO2 reduction to formate

MOF-based materials have been widely explored in electrochemical CO₂ reduction reactions for the production of valuable chemicals. Understanding the reconstruction of those catalysts under working conditions is crucial for the identification of active sites and clarification of reaction mechanism. Herein, a series of six N coordinated Sn-based metal-organic frameworks (Sn-N6-MOFs) are newly developed for electrochemical CO₂ reduction (CO₂RR). 2% Sn-N6-MOF achieves the optimal catalytic performance with a formate Faradaic efficiency of ~85% and a current density of 23 mA·cm^-2 at -1.23 V vs. RHE. In-situ Raman results combined with ex-situ ¹¹⁹Sn Mössbauer measurements reveal the structural reconstruction of Sn-N6-MOFs during CO₂RR, generating tin nanoclusters as the real active sites for CO₂ electroreduction to HCOOH.