Azole-Engineered Covalent Organic Frameworks for Efficient Light-Assisted Gold Recovery from E-Waste

Abstract

Developing COF-based materials capable of integrating AuCl4– enrichment with photocatalytic reduction is highly desirable for sustainable gold recovery from electronic waste. Herein, an azole heterocycle engineering strategy is proposed to construct multifunctional covalent organic frameworks with both multicoordination adsorption sites and electron-regulating centers. A vinyl-functionalized imine-linked COF, TAPT-COF, was postmodified with imidazole and thiazole units via thiol–ene click chemistry, affording TAPT-COF-MI and TAPT-COF-TZ, respectively. The introduced N/S-rich heterocycles not only provide abundant coordination sites for AuCl4– capture, but also modulate the local electronic structure to promote charge separation and electron transfer toward the adsorbed gold species. Benefiting from this synergistic effect, TAPT-COF-TZ delivers a high AuCl4– adsorption capacity of 2791.1 mg g–1 under light irradiation, along with excellent selectivity, good reusability, and promising performance in practical CPU leachate. Mechanistic studies and DFT calculations reveal that thiazole-derived N/S sites enhance AuCl4– binding, interfacial charge redistribution, and in situ reduction to metallic Au nanoparticles. This work provides an effective heterocycle engineering strategy for coupling adsorption and photoreduction in COF-based systems toward selective gold recovery from e-waste.