Amorphous phase-engineered Cr-based coordination polymers for efficient gold recovery in highly acidic environments.

There is an urgent need to develop innovative materials for the high-efficiency and selective recovery of gold from electronic waste. In this work, we pioneer a novel amorphous chromium-glyoxal bis-(2-hydroxyanil) coordination polymer (Cr-GBHA aCPs) through rational molecular engineering of metal-organic coordination systems. Distinguished from conventional crystalline adsorbents, the deliberately designed amorphous architecture enables unprecedented exposure of multifunctional active sites, achieving gold adsorption capacity of up to 4242 mg/g at 55 °C. The Cr-GBHA aCPs demonstrates exceptional acid tolerance (pH = 2.62) and cycle stability, maintaining 100 % recovery efficiency through 8 successive adsorption-desorption cycles, a critical advancement for practical industrial applications. A unique synergistic multimode adsorption mechanism was revealed. The electron-rich phenolic hydroxyl/amine moieties facilitate selective Au(III) recognition via electrostatic interaction, followed by chelation-induced coordination and simultaneous reduction to Au(0) species. This triple-action mechanism establishes a new paradigm in metal recovery material design, overcoming the limitations of single-mode adsorption systems. Overall, this work opens new avenues for developing smart adsorption platforms through amorphous phase engineering of coordination polymers, and provides a feasible scheme for the recovery of precious metals in e-waste.