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 for I vapor and 3.78 g g for I (KI/I) aqueous solution. It also showed a high K of 8.94 g g h for I vapor and 3.16 g g h for I solution. Due to its high thermal stability in I vapor leading to good reusability, it still exhibited an iodine uptake of 4.23 g g and was able to release 97.2 % of this iodine in the seventh cycle. Interestingly, after the saturated adsorption of I, TA-PDA COP displayed an ultra-high adsorption capacity for I vapor (8.89 g g), with the total adsorption capacity reaching up to 12.67 g g. 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.