Defect engineering via monodentate ligands creates large-pore UiO-66-SH for ultrafast and high-capacity Hg(II) removal

Defect engineering in metal-organic frameworks (MOFs) is critical for enhancing their adsorption performance. Herein, a “large-pore” UiO-66-SH (LP-UiO-66-SH) was successfully synthesized by introducing the monodentate ligand 3-amino-4-hydroxybenzoic acid (3,4-AHBA) into UiO-66-SH. This strategy generates ligand defects and creates opens metal vacancies, thereby enhancing the porous structure and the density of active sites. Consequently, LP-UiO-66-SH exhibited significantly superior adsorption kinetics and capacity compared to micro-UiO-66-SH, achieving a maximum Hg(II) uptake of 1180 mg g −1 (versus only 560 mg g −1 for micro-UiO-66-SH under comparable conditions) and rapidly reducing the Hg(II) concentration in seawater to the drinking water standard (0.002 mg L −1 ) within 8 min. DFT and molecular dynamics (MD) simulations further revealed that S H, -NH₂ and -OH groups cooperatively participate in Hg(II) binding, while the presence of a porous architecture significantly improved adsorption kinetics across a wide range of initial Hg(II) concentrations. This study provides a defect-engineering strategy for designing efficient porous adsorbents for mercury-contaminated water remediation and, through combined experimental and theoretical analyses, elucidates the intrinsic coupling mechanism between defect-induced binding sites and ion transport within the engineered framework.