Exploiting the nodes of metal-organic framework by grafting functional organic molecules for synergistic uranium extraction

Abstract

High-efficiency elimination of uranium was a research hotspot from the aspect of nuclear energy development. Metal chelators and porous materials were two cutting-edge technologies for the recovery and separation of uranium from wastewater. However, there was only limited success in transferring the metal coordination function of metal chelators to chemically stable host materials. Herein, oxamic acid (OxA) and glycine (Gly) functionalized MOF-808 were prepared by a simple solvent-assisted ligand incorporation method and used for uranium removal. The ordered porous structure of MOFs provided rapid diffusion channels, and the introduction of amino acids on Zr₆ nodes endowed MOF-808 channels more functional groups with strong binding ability and high hydrophily. The MOF-808@OxA exhibited higher elimination ability (q_max = 370.76 mg·g⁻¹), rapider elimination rate (∼40 min), and higher selectivity than those of MOF-808@Gly and original MOF-808 at pH = 5. Particularly, density functional theory calculations revealed that MOF-808@OxA had a stronger affinity for uranium compared to MOF-808@Gly due to the synergistic effect of C = O and –NH₂ groups. Thus, this study provided a feasible strategy for modifying MOFs and a promising prospect for MOF-based materials to eliminate uranium from wastewater.