Sulfhydryl functionalized covalent organic framework as an efficient adsorbent for selective Pb (II) removal

A key challenge in environmental remediation is the design of adsorbents with appropriate pore size and accessible sorption sites to achieve the rapid uptake and high capacity for the removal of their target pollutants. Covalent organic framework (COF) materials with adjustable pore size and designed skeleton structure are a new class of adsorbent materials for environmental remediation. Here, a novel COF was synthesized by a mild solvothermal solution-suspension method for efficient Pb (II) removal from aqueous solution. The prepared COF material displayed a typical lamellar structure , and the sulfhydryl groups on the COFs skeleton were confirmed to behave as active adsorption sites for Pb (II) capture. Sulfhydryl functionalized COF (COF-SH) reached adsorption equilibriums within 48 h and had a maximum adsorption capacity for Pb (II) of 239 mg/g based on Langmuir fitting. The adsorption capacity of COF-SH for Pb (II) removal is much higher than that of other conventional adsorbents, such as shell activated carbon and resin. Moreover, the selective adsorption performance of COF-SH to Pb (II) in the presence of coexisting heavy metal is superior, and its unique properties are derived from its soft sulfur-based chelating groups allowing selective capture of soft or relatively soft metal ions . The results presented here reveal the exceptional potential of COFs for high performance in environmental remediation.