Constructing nanotraps in covalent organic framework for uranium sequestration

Nuclear wastes include sludges and supernatant liquids containing toxic uranium radionuclides (235U and 238U). Concerns about the potentially hazardous impact of uranium on the environment motivate the development of new technologies for selectively removing uranium radionuclides from polluted water and groundwater. We demonstrate herein the enormous potential of covalent organic frameworks (COFs) as a low-cost platform for the construction of adsorbents for uranium radionuclide capture and nuclear waste management. Using amidoxime groups together with carbonyl electron donors as chelating sites, COFs demonstrating fast adsorption kinetics, high adsorption capacities, and selectivity toward uranyl adsorption were successfully synthesized. A particular COF, COF-DBD-AO, was capable of rapidly decontaminating uranium-contaminated potable water to drinking water levels within 120 min. The presence of nearby carbonyl groups improved the affinity of amidoxime groups for uranyl ions, thus enhancing the selectivity for uranyl ion adsorption over other common cations.