MOFs-derived (Fe3O4/Fe2O3)OH@C-X in-situ form frustrated Lewis acid-base pairs for visible-light-driven photocatalytic CO2 reduction

Abstract

Frustrated Lewis pairs (FLPs) have demonstrated their capacity to capture and react with CO2, presenting a novel method for CO2 reduction. Despite this, their practical application remains limited due to a complex preparation process, poor stability, and regeneration challenges. We address these issues in this study by pyrolyzing a metal-organic framework (MOF) to form in-situ FLPs on an iron oxide surface. The resulting (Fe3O4/Fe2O3)OH@C-400 composite exhibits a significantly improved CO2 reduction rate of 173.3 μmol g−1 h−1, which is approximately 13.4 times higher than that of Fe2O3 and 10.9 times higher than that of Fe3O4. Both theoretical and experimental findings confirm that the creation of heterostructured hollow spheres and in-situ FLPs enhances visible light absorption, improves the separation and transfer of photogenerated carriers, and increases the photocatalytic efficiency for CO2 reduction. The H/D kinetic isotope effect suggests that water plays a crucial role in the limiting step of CO2 photoreduction. In-situ FTIR results corroborate the formation of COOH* as a critical intermediate in photocatalytic CO2 reduction over (Fe3O4/Fe2O3)OH@C-X. This research provides a novel insight into catalyst material design and mechanism research for photocatalytic CO2 reduction.