Redox-Driven Selective Gold Recovery from Electronic Waste Using Functionalized Polyhedral Oligomeric Silsesquioxane

The growing demand for sustainable alternatives to conventional mining has highlighted urban mining as a key strategy for recovering valuable metals from secondary resources. Herein, two functionalized polyhedral oligomeric silsesquioxanes (POSSs), BMPA@POSS and PTMA@POSS, were evaluated for the selective recovery of Au(III) from multicomponent solutions, including electronic waste leachates. Characterization by FTIR, solid-state ²⁹Si and ¹³C NMR, TGA, and elemental analysis confirmed successful functionalization. Among the adsorbents, PTMA@POSS exhibited outstanding selectivity for Au(III), achieving a maximum adsorption capacity of 341 mg g⁻¹ for gold and maintaining its performance over four adsorption–desorption cycles. Mechanistic studies and DFT calculations revealed an intrinsic redox process involving alcohol oxidation and Au(I) disproportionation, leading to the in situ formation of Au(0) nanoplates. The material also demonstrated excellent performance with a real electronic waste leachate, highlighting its strong potential for practical urban mining applications.