Fluorine-induced enhancement of the photocatalytic activity in Ti-based Metal-Organic Frameworks

[Display omitted] •Ti-based Metal-Organic Framework, ACM-1, fluorination mediated by trifluoroacetic acid is presented.•The presence of F-species enhances the photocatalytic activity in the hydrogen evolution reaction.•Improved activity was attributed to the extended light absorption and increased charge capacitance. Defect engineering has emerged as a promising strategy to enhance the photocatalytic properties of metal–organic frameworks (MOFs). In this study, we investigate the influence of the introduction of defects into a Ti-based MOF, ACM-1, on its photocatalytic activity for hydrogen evolution reaction. Through solid-state NMR and XPS analysis, we define the structural defects as a fluoride inclusion. Our results demonstrate a remarkable 5-fold increase in photocatalytic activity compared to pristine ACM-1. Density functional theory (DFT) calculations reveal that the presence of fluorine atoms stabilizes titanium orbitals, leading to a reduced band gap. This reduction in the band gap is identified as the key mechanism underlying the enhanced photocatalytic activity. Our findings highlight the efficacy of defect engineering through TFA-mediated fluoride inclusion in improving the photocatalytic performance of Ti-based MOF ACM-1.