High-Efficiency Removal of Pb(II) Ions in the Aqueous Phase via a Functionalized MOF

The contamination of water resources by toxic heavy metal ions, particularly lead (Pb(II)), poses serious threats to human health, driving considerable interest in developing innovative chelating adsorbents for effective decontamination. In this study, we designed a novel pillar-layered cadmium-based metal-organic framework (MOF), designated as TMU-90, featuring multifunctional groups with defined orientation along its pillar backbone to achieve rapid, efficient, and selective Pb(II) removal from polluted water. The structure was comprehensively characterized using single-crystal X-ray crystallography, PXRD, FT-IR, XPS, BET, and SEM. The effects of initial substrate concentration, adsorbent dosage, and pH on the Pb(II) adsorption capacity and removal efficiency were systematically examined. The maximum adsorption capacity of TMU-90 reached 1500 mg·g-1 within 60 min at room temperature and the optimal pH of 5.5, with the highest removal efficiency of 92% observed at an initial Pb(II) concentration of 50 mg·L-1. The adsorption mechanism, along with uptake kinetics and thermodynamic behavior toward Pb(II), was systematically investigated. TMU-90 was successfully recycled for at least four cycles without any loss in adsorption capacity or crystallinity. This study demonstrates that incorporating multifunctional linkers bearing free amide and amine groups into MOFs offers a simple and effective strategy for enhancing wastewater remediation performance compared to nonpillared structures.