Inter-clusters synergy in iron-organic frameworks for efficient CO2 photoreduction

Abstract It is extremely desirable to explore molecular catalysts with precise structure for in-depth exploring structure-activity relationship of CO2 photoreduction. Herein, we demonstrate the precise encapsulation of dual-nuclear clusters {Fe2(H2O)6(triazole)3} into metal-organic frameworks (MOFs) via ligand substitution strategy, resulting in two Fe2@Fe3-MOF composites (Fe3-Fe2 and NH2-Fe3-Fe2). The fixed distance between two adjacent Fe3(µ3-O)Cl(H2O)2 nodes in the MOF matrix allows the Fe2-Tri clusters to be fixed at a predetermined distance to unveil the critical role in improving the activity and selectivity for CO2 reduction. The performance of Fe3-Fe2 and NH2-Fe3-Fe2 can reach to 309.3 and 395.5 µmol g-1 h-1 respectively, much superior to most of the state-of-the-art MOF catalysts. Such high activity and selectivity for formate generation can be attributed to the inter-clusters synergy mediated via in situ formed H-bonds and the cluster-framework cooperativity, supported by the results of DFT calculations and systemic experimental characterizations.