Chemically Robust Cationic Porous Organic Polymer (POP) for Selective Detection and Removal of ReO₄⁻ as a Surrogate of Radioactive ⁹⁹TcO₄⁻

The efficient removal of ⁹⁹TcO₄ ^- from alkaline nuclear waste is vital for optimizing nuclear waste management and safeguarding the environment. However, current state-of-the-art sorbent materials are constrained by their inability to simultaneously achieve high alkali resistance, rapid adsorption kinetics, large adsorption capacity, and selectivity. In this study, we synthesized a urea-rich cationic porous organic polymer, IPM-403, which demonstrates exceptional chemical stability, ultrafast kinetics (~92 % removal within 30 seconds), high adsorption capacity (664 mg/g), excellent selectivity, along with multiple-cycle recyclability (up to 7 cycles), making it highly promising for the removal of ReO₄ ^- (surrogate of ⁹⁹TcO₄ ^-) from nuclear wastewater. Notably, after exposure to 1 M NaOH solution for 24 hours, IPM-403 maintained a high adsorption capacity of 421.3 mg/g for ReO₄ ^-. Furthermore, IPM-403 acts as an efficient sensor for ReO₄ ^-, exhibiting a turn-on response and a detection limit as low as 78.8 ppb.