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.