Abstract
A key challenge in the field of environmental remediation is the design of adsorbent materials bearing an abundance of accessible chelating sites with high affinity, to achieve both rapid uptake and high capacity for the contaminants. In this work, we demonstrate how two dimensional covalent organic frameworks (COFs) with well-defined mesopore structures display the right combination of properties to serve as a scaffold for decorat-ing coordination sites to create ideal adsorbents for toxic metal species decontamination. The proof-of-concept design is illustrated by modifying sulfur derivatives on a newly designed vinyl-functionalized mesoporous COF (COF-V) via thiol-ene “click” reaction. Representatively, the material, synthesized by treating COF-V with 1,2-ethanedithiol (COF-S-SH), exhibits high efficiency in removing mercury from aqueous solutions and the air, affording a Hg2+ capacity of 1350 mg g-1 and Hg0 vapor capacity up to 863 mg g-1, surpassing all thiol and thi-oether functionalized materials reported thus far. More significantly, COF-S-SH can rapidly reduce the Hg2+ concentration from 5 ppm to an extremely low level of less than 0.1 ppb, well below the acceptable limit in drinking water (2 ppb), and gives rise to an initial adsorption rate as high as 143 mg g-1 min-1. We attribute the high capacities, rapid sorption, and outstanding removal efficiency to the synergistic effects arising from dense-ly populated flexible chelating groups with a strong binding ability within ordered mesopores that allow rapid diffusion of mercury species throughout the material. The results presented here thus reveal the exceptional potential of COFs for high-performance environmental remediation.