Water-induced defect engineering in metal-organic frameworks toward enhanced gas-sensing performance

Defect engineering is regarded as an effective strategy for enhancing gas-sensing performance in metal-organic frameworks (MOFs). However, precise control over defect types and their specific impact on gas-sensing properties remains a significant challenge. Herein, we propose a representative water-treatment approach to induce and regulate different defect types in various MOFs. Comparative structural analysis of ZIF-8 and ZIF-67, differing in metal centers, before and after water treatment, reveals that water molecules disrupt metal-ligand bonds, leading to metal defects in ZIF-8 via metal detachment and ligand defects in ZIF-67 through partial ligand loss. Gas-sensing results demonstrate that defect concentrations and gas-sensing capabilities in MOFs can be effectively modulated by controlling water treatment time. Notably, the presence of metal defects enhances the NO2 response of ZIF-8 (20 ppm) by 2.63 times, while ligand defects improve the C2H4 response of ZIF-67 (25 ppm) by 3.96 times. Additionally, metal defect formation in MOF-74 is evidenced by a 2.97-fold enhancement in its response to 100 ppm acetone. Density functional theory calculations confirm that the defect sites enhance gas adsorption and sensing performance. This study offers new insights into defect engineering in MOFs, expanding the potential of defect-engineered MOFs for diverse applications.