Electronegative Strategic Positions in Covalent Organic Frameworks: Unlocking High-Efficiency Gold Recovery

Abstract

Gold (Au) concentrations accumulated from electronic waste (e-waste) and industrial leachates far surpass those found in natural ores, a highly valuable resource if efficient recovery methods can be developed. Despite advancements in covalent organic frameworks (COFs), achieving adsorbents with high selectivity, large capacity, and rapid adsorption kinetics remain challenging because of limitations in partial pore wall sites. Here, we present hexaazatriphenylene-based COFs (HATP-COFs) with an electronegative skeleton, specifically designed for selective Au recovery. The hexaazatriphenylene centers, imine linkages, and pyridine linkers within the COFs introduce electron-rich sites that extend across strategic positions-vertex, linkages, and linkers-thereby enhancing the overall structural integrity. These features facilitate efficient Au capture through electrostatic interactions, achieving an exceptional adsorption capacity exceeding 2366 mg g-1 with rapid kinetics, making HATP-COFs one of the most efficient pure COFs reported to date. Moreover, these HATP-COFs demonstrate remarkable selectivity, stability, and scalability. Theoretical calculations reveal that the electronegative skeleton introduces critical binding sites, promoting strong electrostatic interactions with Au3+ ions and improving adsorption kinetics. This work highlights the potential of charge-interface engineering in COFs as a transformative strategy for developing next-generation materials.