Optimizing Strategy for Enhancing the Stability and ⁹⁹TcO₄ ^- Sequestration of Poly(ionic liquids)@MOFs Composites

Metal-organic frameworks (MOFs) are a class of promising sorbents for effective sequestration of radioactive ⁹⁹TcO₄ ^- anions. However, their poor stability and slow sorption kinetics in the industrial condition pose a great challenge. Herein, we demonstrate an optimizing strategy via in situ polymerization of ionic liquids (ILs) encapsulated in the pores of MOFs, forming polyILs@MOFs composites with greatly enhanced TcO₄ ^- sequestration compared with the pristine MOFs. Notably, the cross-linked polymerization of ILs facilitates the formation of both the inside ionic filler as the active sites and outside coating as the protective layers of MOFs, which is significantly beneficial to obtain the optimized sorption materials of exceptional stability under extreme conditions (e.g., in 6 M HNO₃). The final optimized composite shows fast sorption kinetics (<30 s), good regeneration (>30 cycles), and superior uptake performance for TcO₄ ^- in highly acidic conditions and simulated recycle stream. This strategy opens up a new opportunity to construct the highly stable MOF-based composites and extend their applicability in different fields.