Tailoring the Asymmetric Structure of NH2 -UiO-66 Metal-Organic Frameworks for Light-promoted Selective and Efficient Gold Extraction and Separation.

Designing adsorption materials with high adsorption capacities and selectivities is highly desirable for precious metal recovery. Desorption performance is also particularly crucial for subsequent precious metal recovery and adsorbent regeneration. Herein, a metal-organic framework (MOF) material (NH2 -UiO-66) with an asymmetric electronic structure of the central zirconium oxygen cluster has an exceptional gold extraction capacity of 2.04 g g-1 under light irradiation. The selectivity of NH2 -UiO-66 for gold ions is up to 98.8 % in the presence of interfering ions. Interestingly, the gold ions adsorbed on the surface of NH2 -UiO-66 spontaneously reduce in situ, undergo nucleation and growth and finally achieve the phase separation of high-purity gold particles from NH2 -UiO-66. The desorption and separation efficiency of gold particles from the adsorbent surface reaches 89 %. Theoretical calculations indicate that -NH2 functions as a dual donor of electrons and protons, and the asymmetric structure of NH2 -UiO-66 leads to energetically advantageous multinuclear gold capture and desorption. This adsorption material can greatly facilitate the recovery of gold from wastewater and can easily realize the recycling of the adsorbent.