A functionalized metal-organic framework decorated with O^- groups showing excellent performance for lead(ii) removal...

Heavy metal ions are highly toxic and widely spread as environmental pollutants. New strategies are being developed to efficiently remove these toxic ions. Herein, we use the intrinsic advantages of metal-organic frameworks (MOFs) and develop a porous Zn(ii)-based MOF decorated with O^- groups for the removal of Pb²⁺. Benefiting from its multiple porosity, sufficient adsorption sites and strong affinity, the activated MOF material exhibits an ultrahigh Pb²⁺ uptake capacity (616.64 mg g^-1), surpassing all those of reported MOF adsorbents. Moreover, it can selectively capture Pb²⁺ with high efficiency (>99.27%) against background ions. Even in the presence of a high concentration of competitive ions, such as Ca²⁺ or Mg²⁺, effective removal (>99.21%) can also be achieved in a short time. The excellent removal performance demonstrates the strong electrostatic attraction and coordination interaction between the highly accessible O^- groups and Pb²⁺. The possible adsorption mechanism was systematically verified by zeta potential, FT-IR and XPS studies. Our work reveals the enormous potential of functionalized MOFs as an appealing platform to construct sorbent materials.