Sulfhydryl functionalized chitosan-covalent organic framework composites for highly efficient and selective recovery of gold from complex liquids.

Developing candidate adsorbents with high capacity and selectivity for adsorption is a critical approach to recover gold from secondary sources such as electronic waste (e-waste). This measure not only contributes to the recycling of valuable resources but also benefits environment protection and mitigates the detriment to the ecosystem. Traditional covalent organic frameworks (COFs) have garnered great potential in various fields owing to their unique structures and innate functional sites. However, the construction of specific functionalized COFs and their application in efficient gold extraction are still in their nascent stages. Herein, inspired by the photo-induced thiol-ene click reaction, a novel chitosan-modified COFs material (DhaTab-V@chitosan-SH) was first demonstrated by choosing a precursor COF (DhaTab-V) abundant with vinyl groups to crosslink with a thiol-functionalized chitosan (chitosan-SH). Significantly, the coexistence of imine, amide, hydroxyl and thioether groups in the skeleton could serve as functional adsorption sites to combine with the Au (III) via electrostatic interaction and coordination, imparting DhaTab-V@chitosan-SH with prominent adsorption potential for swift, selective and efficient gold capture (970.15 mg·g). Additionally, DhaTab-V@chitosan-SH exhibited superior reusability, and realized real gold capture from the leaching solution of e-waste.