A cucurbit[6]uril-based supramolecular framework material for highly effective iodine adsorption

Abstract

Capturing radioactive iodine is critical for the effective disposal of nuclear waste and environmental safety. Herein, a novel supramolecular complex (Q[6]-(2-AP)) for the removal of radioactive iodine was constructed from cucurbit[6]uril (Q[6]) and 2-aminopyrimidine (2-AP). The single-crystal X-ray diffraction (SCXRD) analysis revealed that Q[6]-(2-AP) formed through intricate hydrogen bonding interactions, involving four 2-AP molecules and the cavity, ports, and the outer surface of Q[6]. Experimentally testing the iodine capture ability demonstrated the remarkable iodine vapor adsorption of Q[6]-(2-AP), with an adsorption capacity of 2.59 g g⁻¹ at 75 °C and 2.23 g g⁻¹ at room temperature; furthermore, Q[6]-(2-AP) effectively adsorbed iodine from an n-hexane iodine solution, exhibiting an adsorption capacity of 1.19 g g⁻¹. The adsorption process was studied using kinetic and isotherm models, revealing that the adsorption behavior followed the pseudo-second-order kinetics and the Langmuir isotherm model. Further analyses using FT-IR, XPS, RM, and SCXRD demonstrated that abundant hydrogen bonding interactions between Q[6]-(2-AP) and iodine anions (I⁻ and I₃⁻) were the main driving force for the adsorption of iodine onto Q[6]-(2-AP). Conclusively, Q[6]-(2-AP), synthesized using a convenient and cost-efficient method, exhibited an outstanding iodine adsorption ability, making it a reliable material for long-term iodine storage.