Nanoconfined Polycarbene@Covalent Organic Frameworks for Efficient Gold Trapping from Electronic Waste

Abstract

Gold, often recognized as a luxury jewelry, plays an important role in diverse fields because of its specific physical and chemical properties. However, the limited supply and lack of abundance of gold led to continuous competition for its use. Therefore, industries have developed various techniques for gold mining and recycling, e.g., gold recovery from electronic waste (e-waste, commonly referred to as the gold bonanza). To address this challenge, a novel poly(ionic liquid)@covalent organic framework (PIL@COF) nanotrap for highly efficient gold recovery from e-waste is reported. The orderly arrangement of PIL facilitated by COF nanochannels, coupled with the strong binding affinity of PIL to gold (generated by its polycarbene intermediate) and the highly ordered porous COF architecture results in the rapid and selective capture of gold ions. This polycarbene@COF material achieves a gold adsorption capacity of up to 1.9 g g⁻¹ and exhibits excellent sorption kinetics of 90% gold adsorption within 10 min while simultaneously reducing Au³⁺ to metallic Au⁰, which enables direct gold recovery and reuse. The high selectivity and efficiency of the gold recovery of this composite material are further confirmed by theoretical calculations. In addition, this polycarbene@COF nanotrap demonstrates high effectiveness across a wide pH range and maintains stability over multiple adsorption‒desorption cycles, highlighting its potential as a sustainable and robust platform for the recovery of precious metals.