Iodine crystallization-promoted efficient capture of iodine by nonporous covalent organic polymer

The development of efficient iodine capture methods is essential for the safe utilization of nuclear energy. Here, a nonporous triazine-phenylenediamine covalent organic polymer (TA-PDA COP) with abundant nitrogen atoms and a π-conjugated system was used to capture iodine. The as-prepared adsorbent exhibited an iodine uptake of 5.65 g g^-1 for I₂ vapor and 3.78 g g^-1 for I₃^- (KI/I₂) aqueous solution. It also showed a high K_80% of 8.94 g g^-1 h^-1 for I₂ vapor and 3.16 g g^-1 h^-1 for I₃^- solution. Due to its high thermal stability in I₂ vapor leading to good reusability, it still exhibited an iodine uptake of 4.23 g g^-1 and was able to release 97.2 % of this iodine in the seventh cycle. Interestingly, after the saturated adsorption of I₃^-, TA-PDA COP displayed an ultra-high adsorption capacity for I₂ vapor (8.89 g g^-1), with the total adsorption capacity reaching up to 12.67 g g^-1. The ultra-high adsorption capacity of TA-PDA COP was ascribed to the formation of iodine crystals as well as the interactions between N-rich groups and π-conjugated systems with iodine. This study reveals a new phenomenon that can be utilized to promote iodine capture, offering a strategy for the efficient adsorption of iodine.