Introgression of Lone Electron Pairs into π-Conjugated Structures Resulting in Giant Electron-Rich Clusters with High Trapping Capacity for Iodine Molecules

Abstract

Effective removal of radioactive iodine from fission is of great importance, whereas adsorption of iodine by porous organic polymers provides an effective adsorption method and remains an active research topic. Here, three porous organic polymers (POPs), were designed and synthesized by introducing N, S heteroatomic groups using Schiff base condensation reaction to examine their iodine adsorption ability. Excellent iodine adsorption capacity was demonstrated for the three prepared POPs, not only in the fast and reversible volatile iodine uptake of up to 510–543 wt % but also in the cyclohexane solution with high iodine adsorption capacity of 504.4, 664.6, and 537.4 mg g^–1, respectively. Nitrogen and sulfur elements, as well as the π-conjugated structure of sp² hybridization, formed huge electron-rich clusters, enticing the attraction of electron-deficient I₂ molecules to form polyiodide anions (I₃^– and I₅^–). On top of that, the lone pair of electrons and π-conjugation of the heteroatoms led to a high binding capacity between the adsorbent and the iodo Lewis acid molecules, contributing to a significant increase in the adsorption rate and removal efficiency of I₂. In conclusion, this is a useful strategy for developing POPs to remove iodine.