Imidazole Cationic-Bridged Pillar[5]arene Polymer as a Recycle Adsorbent for Iodine Capture

Developing efficient and recyclable iodine adsorbents is crucial for addressing radioactive iodine pollution. An imidazole cation-bridged pillar[5]arene polymer (P5–P5I) was synthesized via a salt formation reaction. P5–P5I exhibited a high iodine vapor capture capacity of 2130.0 mg/g and a maximum adsorption capacity of 1935.3 and 942.4 mg/g for I2 and I3– in solution, respectively. The adsorption kinetics of I2 and I3– on P5–P5I in aqueous solution followed a pseudo-second-order kinetic model, reaching adsorption equilibrium within a few minutes. P5–P5I demonstrated the ability to selectively capture I2 and I3– in the presence of competing anions (10–1000-fold), removing over 97.1% of iodine from various environments. Meanwhile, under extreme conditions (strong acids, strong bases, and high temperature), P5–P5I still has a superior adsorption performance and cycling ability for I2 and I3–. Molecular modeling revealed that P5–P5I could synergistically enhance iodine capture through multiple weak interactions, including host–guest, C–H···I hydrogen bond, and electrostatic interactions. This study indicates that P5–P5I has promising applications for rapid and efficient iodine uptake from vapor and various aqueous media.