Irreversible Sulfur Cyclization to Construct a D–A Type Covalent Organic Framework with Ultrastability for Photoenhanced Gold Recovery

Covalent organic frameworks (COFs) have witnessed rapid development as gold adsorption materials in recent years, while the construction of COFs with large adsorption capacity, high selectivity, and superior stability in strong acid is still one of the great challenges. Here, we designed and synthesized a novel COF-Py-BTP and further constructed an ultrastable thiazole-linked COF-Py-BTP-NS. The thiazole ring not only synergistically captured Au(III) with the pyridine groups on the pore walls but also enhanced charge separation and transfer capabilities. Under light-assisted conditions, the gold recovery capacity was substantially improved from 2845 mg g^-1 of COF-Py-BTP to 4374 mg g^-1 of COF-Py-BTP-NS, meanwhile the recovery efficiency remained above 99% in the presence of various competitive cations and anions. Importantly, due to its high stability, COF-Py-BTP-NS exhibits long-term cycling stability under acidic conditions and can selectively extract Au from the leachate of waste electronic devices.