The long-distance charge transfer process in ferrocene-based MOFs with FeO6 clusters boosts photocatalytic CO2 chemical fixation

Metal nodes and organic ligands are important structural units of MOFs, and their properties can profoundly affect the photocatalytic activity. Herein, two ferrocene-based MOFs with FeO6 or AlO6 clusters as the metal nodes and 1,1'-ferrocenedicarboxylic acid (H2FcDC) as the ligands were successfully synthesized. Comparing with normal organic ligands, ferrocene ligands have longer-lived photogenerated charges due to metal-to-ligand charge transfer (MLCT) process, leading to a better photocatalytic activity of the corresponding ferrocene-based MOFs. In addition, the FeO6 clusters are able to further accept the photogenerated electrons from ferrocene ligands compared to the inert AlO6 clusters, allowing a long-distance charge transfer process, namely the proposed metal-to-ligand-to-metal charge transfer (MLMCT) process, which results in a better performance towards photocatalytic CO2 cycloaddition reaction. This work sheds a light on designing MOFs using ferrocene ligands with high photocatalytic activity.