Formulation of Poly(ionic liquids)@COF Nanotrap for Efficient Perrhenate Sequestration from Alkaline Nuclear Waste

It is of great challenge to develop the effective and stable sorbents for 99TcO4– sequestration from alkaline nuclear waste. In this work, we demonstrate a general strategy for the design of poly(ionic liquids)@COF composites, via in situ polymerization of imidazolium-based ionic liquids (ILs) encapsulated in the pores of covalent–organic frameworks (COFs). With regard to the polyILs@COF composites, the cross-linking polyILs endow the alkali-stable COF framework with numerous ionic fillers as the anion-exchange sites. Compared with the pristine COF, the optimized composite not only enhances the alkali resistance but also shows the excellent ReO4– (a surrogate of 99TcO4–) removal performances of fast exchange kinetics, high uptake capacity, superior selectivity, and good reusability, even in simulated high-level waste stream at the U.S. Savannah River Site (a typical alkaline nuclear waste). The alkaline stability and selectivity of the optimized composite can be further verified by the density functional theory (DFT) calculations, indicating its unique chemical recognition of TcO4– over other anions with higher charge density.