Stability and adsorption performance of UiO-67 for uranium(VI) in solution

Based on the stable Zr6O4(OH)4 metal clusters, UiO-67 was first applied to the adsorption of U(VI), and its stability and adsorption performance for U(VI) were compared with UiO-66. As the organic ligand was lengthened, UiO-67 had a larger specific surface area and pore volume than UiO-66. The adsorption capacity of UiO-67 for uranium was 1.68 times that of UiO-66 under the same conditions. The chemical stability of UiO series decreased with the extension of organic ligands; for example, the crystalline structure of UiO-67 disintegrated in methanol, ethanol and water. Through the infrared spectra, adsorption isotherms and kinetics fitting, it is concluded that the carboxyl groups of UiO-67 participated in the chemisorption of U(VI), and uranyl ions adsorbed on UiO-67 were not desorbed with the collapse of UiO-67 crystal. This work represents the extension of organic chains reduces the chemical stability of MOFs but improves the adsorption performance of U(VI), which may be applied to predict the structural stability and adsorption capacity of other MOFs containing aromatic dicarboxylate organic linkers.