Decorating Covalent Organic Frameworks with High-density Chelate Groups for Uranium Extraction

The extraction of uranium from aqueous solution is highly desirable for sustaining the increasing demand for environmental safety and nuclear fuel. Herein, we report a strategy using a two-step covalent modification for the synthesis of covalent organic frameworks(COFs) with high-density amidoxime chelate groups at periphery. The introduction of dense amidoxime groups plays a pivotal role in uranium adsorption. The resulting COF exhibits strong affinity with the distribution coefficient of 5.2×104 mL/g and a high adsorption capacity of 319.9 mg/g. The strategy could be expanded to identify and remove different contaminants by introducing special functional groups.