Hierarchical redox-engineered thiolate-bridged MOF@CNT sponge for sustainable gold recovery and catalytic hydrogen generation from E-wastewater

Gold recovery from waste remains challenging due to the lack of materials that can simultaneously coordinate, reduce and stabilize Au species. Herein, we report a hierarchical redox-engineered copper(II) benzenehexathiol metal-organic framework (BHT MOF) featuring six thiolate coordination sites, uniformly grown on a three-dimensional carbon nanotube sponge (BHT MOF@CNT sponge), for the selective recovery of waste gold ions and their direct conversion into catalytically active gold nanoparticles (Au NPs). The hybrid material exhibits high gold adsorption capacity of 647.9 mg g −1 at pH 1.0 and 50 °C, coupled with outstanding selectivity, showing only a 5–10% decrease in Au uptake in the presence of 11 competing metal ions and achieving a total gold recovery efficiency exceeding 90% in both binary and multicomponent systems. The conformal growth of the BHT MOF on the conductive CNT sponge generates a hierarchical porous architecture with sulfur-rich active sites that provide strong Au-S coordination and thermodynamically favorable binding. Simultaneously, the redox-active thiolate ligands facilitate spontaneous in situ electron transfer, driving the reduction of Au(III) to metallic Au(0) and enabling the formation of uniformly dispersed Au NPs confined onto the hybrid matrix, without the need for external reducing agents or post-synthetic treatments. The resulting Au-BHT MOF@CNT catalyst exhibits an enhanced hydrogen generation rate and excellent cycling stability, benefiting from the synergistic interplay between thiolate-based redox engineering, strong metal-support interactions and accelerated electron transport through the CNT network. This work demonstrates a scalable waste-to-energy platform that integrates waste gold recovery and hydrogen production within a single multifunctional material, providing a sustainable strategy for precious metal recycling and clean energy generation.