Redox‐Active Two‐Dimensional Covalent Organic Frameworks (COFs) for Selective Reductive Separation of Valence‐Variable,Redox‐Sensitive and Long‐Lived Radionuclides

We report the first example of 2D covalent organic framework nanosheets (Redox‐COF1) for the selective reduction and in situ loading of valence‐variable, redox‐sensitive and long‐lived radionuclides (abbreviated as VRL nuclides). Compared with sorbents based on chemical adsorption and physical adsorption, the redox adsorption mechanism of Redox‐COF1 can effectively reduce the impact of functional group protonation under the usual high‐acidity conditions in chemisorption, and raise the adsorption efficiency from the monotonous capture by pores in physisorption. The adsorption selectivity for UO₂²⁺ reaches up to unprecedented ca. 97 % at pH 3, more than for any analogous adsorbing material.