Leveraging Photothermal Effect in 1D Covalent Organic Frameworks for Efficient, Rapid, and Selective Gold Recovery

The recovery of gold from electronic waste is a sustainable and eco-friendly resource recycling strategy. However, simultaneously achieving high adsorption capacity, rapid kinetics, and exceptional selectivity remains a significant challenge. Herein, a novel approach was presented for efficient gold recovery by photothermal effect in one-dimensional covalent organic frameworks (1D-COFs), and TN-COF and TC-COF were designed and synthesized for such studies. Under visible light irradiation, they exhibited excellent AuCl₄ ^- adsorption capacity (3489 and 3340 mg g^-1), ultrafast adsorption kinetics (over 99% gold removal within 20 s), good recyclability (> 25 cycles) and high selectivity (K_d > 1.0 × 10⁶ mL g^-1, S_q > 9.0 × 10³), which enable about 99% gold recovery from waste central processing unit (CPU) leachates with only 17 ppm Au(III), ranking among the highest values reported for COF-based adsorbents to date. Mechanistic results revealed that Au(III) was adsorbed by electrostatic and coordination interactions with multiple N and O sites, while both protonated ─NH group and photogenerated electrons efficiently reduced the adsorbed Au(III) to Au(0). By leveraging the photothermal properties of the COFs, a synergistic photoreduction-thermal promotion strategy was established to surpass traditional exothermic adsorption, enabling rapid and high-capacity gold recovery via an endothermic-reduction-driven equilibrium shift under visible light.