Hydroxyl-induced structural defects in metal-organic frameworks for improved photocatalytic decontamination: Accelerated exciton dissociation and hydrogen bonding interaction

The introduction of structural defects can improve the charge separation efficiency of metal-organic frameworks (MOFs)-based photocatalysts, which however come with suboptimal decontamination performance, due to steric hindrance and limited binding capacity of the involved modulators. In this work, hydroxyl group capturing the advantages of both worlds was utilized as new modulator to improve the photocatalytic performance of Fe-based defective MOFs. Benefited from its low steric effect and strong coordination bonding capability, hydroxyl-induced defects in Fe-MOF contributed to a nearly 8-fold increase of rate constant for the photocatalytic removal of hexavalent chromium (Cr(VI)) compared to that of pristine one, which also exceeded the defective one induced by acetic acid as modulator. A combination of characterizations and theoretical calculations suggests that hydroxyl-induced structural defects fostered faster kinetics of exciton dissociation and optimal charge separation. The higher electron utilization through hydrogen bonding interaction between these hydroxyl-induced structural defects and contaminant was further confirmed by ab initio molecular dynamics (AIMD) simulations. This work presents a simple yet robust strategy for the generation of defective MOFs, upon which efficient photoreduction systems toward Cr(VI) removal are anticipated.