Topology engineering of COFs via localized 1D–2D unit interconnection to facilitate interfacial electron transfer for efficient gold recovery from e-waste leachates

Abstract

Developing cost-effective adsorbents for gold recovery from electronic waste (e-waste) is crucial. Here, we report a dimensional engineering strategy to fabricate covalent organic framework (COF) heterostructures with locally interconnected dimensions, enabling highly efficient host–guest recognition of Au(III) in e-waste leachates. The heterostructures feature local interconnections between 2D and 1D units, introducing additional electron transport pathways. This structural innovation optimizes the electron transport kinetics essential for adsorptive redox reactions. Experimental results demonstrate that the locally interconnected dimensional architecture of TpaIda-2DCOF achieves a static saturation adsorption capacity of 3601 mg g⁻¹ for Au(III) among the highest reported, which reaches an unprecedented 6900 mg g⁻¹ under ultrasonic assistance. A fixed-bed system processes 35 L of e-waste leachate, yielding 23.98 karat gold via in situ reduction while retaining a material cost below 10 CNY g⁻¹—establishing it as one of the most cost-effective COF-based adsorbents reported to date. Theoretical calculations and spectral analyses reveal that the additional charge transport channels created by the heterostructure facilitate the directional conversion of Au(III) to Au(0) through a stepwise single-electron reduction mechanism, thus constructing a closed-loop process for gold capture and recovery.