Highly efficient and selective capture of uranium from groundwater by using an ultrathin 2D MOF nanosheet with pocket-like cavities

Highly efficient and selective removal of uranium from aqueous media is crucial for the sustained development of nuclear energy. Herein, we utilized the intrinsic advantages of two-dimensional (2D) metal–organic frameworks (MOFs) and developed an ultrathin 2D MOF nanosheet with cavity structure. The preconcentration of the pocket-like cavities on the MOF nanosheet and sufficient interactions with the adsorption sites in the cavity structure realized highly efficient removal of uranium from water. Even in the low concentration range of 0.05–1 ppm, relatively high removal ratios and fast adsorption kinetics still can be achieved. Additionally, the MOF nanosheet exhibited extremely high anti-interference capability, which can efficiently reduce uranium pollution (0.05–1 ppm) in acid groundwater to the safe level (≤30 ppb) recommended by World Health Organization, and the removal performance was comparable to that in deionized water. The adsorption mechanism was thoroughly studied by Fourier transform infrared analysis, X-ray photoelectron spectroscopy, and density functional theory calculations, which revealed that the interactions between uranyl ions and the carboxylate groups dominated uranium adsorption, and the H-bonding interactions in the pocket-like cavities played an important role in uranium extraction.