Hydroxyl and pyrrole functionalized polymeric frameworks for efficient aqueous and gaseous iodine sequestration

Abstract

Radioactive iodine, including I129 and I131, poses significant environmental and health risks due to its high volatility, long half-life, and water solubility, making the effective capture and storage of these substances crucial for environmental remediation and nuclear waste management. In this context, adsorption-based capture of radioiodine by porous solids has gained considerable attention. Here, we present three chemically robust pyrrole-based porous organic polymers, IISERP-POF15, IISERP-POF16, and IISERP-POF17, for efficient gaseous and solution-phase (aqueous and non-aqueous) iodine sequestration. IISERP-POF17 exhibits a high iodine uptake of 3.07 g/g in the gas phase at 70 °C, as well as effective performance in a non-aqueous medium (hexane), with an uptake of 0.47 g/g at room temperature. In aqueous solution, IISERP-POF15 shows the highest iodine uptake, reaching 2.20 g/g at room temperature. These polymers hold high chemical stability and can be readily recycled with intact iodine capacity. X-ray photoelectron spectroscopy (XPS) analysis evidenced the occurrence of I2 and polyiodides (I3–/I5–) in the post iodine-adsorbed polymers. Infrared spectroscopic investigation of the polymers upon iodine adsorption indicated a strong interaction of I2 with -OH and pyrrolic -NH of the framework. The observed I2-framework interactions were further backed by molecular simulation using Density Functional Theory (DFT) calculations.