Engineering Heteroatomic Nanotraps in Vinyl-Benzazole COFs: Record Capacity and 99% Selectivity for Photocatalytic Gold Recovery From E-Waste.

Abstract

The recovery of gold from electronic waste is a critical environmental and technological challenge for a circular and sustainable economy. Conventional methods for gold recovery often suffer from low efficiency, poor selectivity, and reliance on harsh chemicals. In this work, we engineered three vinyl-azole-bridged covalent organic frameworks (COFs), systematically controlling heteroatom motifs to elucidate the structure-activity relationships behind gold ion adsorption and photocatalytic reduction. This strategic incorporation of azole-based units yielded hydrogen-bonded nanotraps along the pore walls, thereby maximizing active-site density and enhancing electrostatic interactions for the selective capture of gold ions. We found that all these COFs show gold adsorption capacities exceeding 3600 mg g^- ¹, with the thiazole-containing COF-featuring both nitrogen and sulfur-exhibiting the highest binding affinity and photocatalytic efficiency to a record value of 4658.1 mg g^- ¹ under optimal conditions and a 99.2% efficiency for gold extraction. These results are confirmed by density functional theory (DFT) calculations, x-ray photoelectron spectroscopy, and real e-waste recovery experiments. The highly conjugated framework facilitates synergistic photoreduction of Au(III) to Au(0), exploiting the unique interplay between heteroatom chemistry, microenvironment engineering, and light-driven redox processes. This work introduces a new class of COF photocatalysts engineered with heteroatomic nanotraps, achieving exceptional gold recovery efficiency.