A thiol-functionalized zirconium metal-organic cage for the effective removal of Hg2+ from aqueous solution

摘要

The mercury ions in waste water have threatened public health and environmental protection. In this sense, novel materials with outstanding performances for removal of Hg2+ are imperative. Herein, we demonstrate a thiol-functionalized zirconium metal-organic cage (MOC-(SH)(2)) with excellent dispersion displays ideal properties for Hg2+ capture. MOC-(SH)(2) exhibits the ability of removing Hg2+ in aqueous solutions with a capacity of 335.9 mg(Hg2+)/g(MOC-(SH)2), which surpasses that of classical Zr-based metal-organic framework Uio-66-(SH)(2) by 1.89 folds. The higher loading capacity of MOC-(SH)(2) is probably owing to the excellent dispersion of the discrete cage, which makes the accessibility of binding sites (thiol) easier. Additionally, 99.6% of Hg2+ can be effectively captured by MOC-(SH)(2) with the concentration decreased from 5 to 0.02 ppm reaching the permissible limit for Hg2+, outperforming the performance of Uio-66-(SH)(2). The excellent absorption property of MOC-(SH)(2) is also achieved in terms of superior selectivity under the presence of competitive metal ions. Meanwhile, the regenerated MOC-(SH)(2) can be reused without apparent loss of Hg2+ loading capacity. UV-vis absorption spectra, IR spectra and emission spectra further verified the strong chemical affinity between Hg2+ and the thiol of MOC-(SH)(2). The study lays the groundwork for using Zr-MOCs in the removal of toxic metal ions and environmental sustainability.