Versatile polycationic imidazolium hyper-crosslinked polymers for efficient removal of radioactive iodide and adsorption of metallo-anions

Abstract

In support of Sustainable Development Goal 6 (Clean Water and Sanitation), we report the synthesis of polycationic imidazolium hyper-crosslinked polymers (P-Imi∙X, X = OTs, Cl, Br, I) as efficient adsorbents for hazardous anionic contaminants. The parent material, P-Imi∙OTs, was prepared via one-step nucleophilic substitution of tosylated hyper-crosslinked polymers (P-OTs), followed by anion exchange. Structural and physicochemical properties were comprehensively characterized using FTIR, MAS ¹³C NMR, TGA, zeta potential, CHNS, XRF, and SEM analyses. These materials exhibited rapid and high-capacity adsorption of diverse anionic pollutants, including organic dyes, metallo-anions, and radioactive iodide (¹³¹I⁻). Mechanistic insights from ¹H NMR and DFT calculations reveal that anion binding is driven by charge-assisted hydrogen bonding and electrostatic interactions at the densely functionalized imidazolium-rich surfaces. P-Imi∙OTs achieved an adsorption capacity of 861 mg·g⁻¹ for methyl orange and 198 mg·g⁻¹ for KAuCl₄ within 6 min. Notably, P-Imi∙Cl exhibited the highest uptake of radioactive Na¹³¹I at 1.31 GBq·g⁻¹. These results highlight the potential of polycationic imidazolium HCPs as scalable, fast-acting, and versatile adsorbents for industrial wastewater treatment and radioactive waste remediation.