Iodine Capture and Transformation at a Hydrogen-Bond-Stabilized Dimethylammonium Site within a Uranyl-Based MOF

Due to its high volatility and long half-life, iodine poses a serious threat to the environment and human health. Therefore, trapping radioactive iodine is of significant importance. In this study, a novel uranyl-based metal-organic framework (MOF) material, IHEP-103, was synthesized via a solvothermal process by combining Schiff base ligands with uranyl cations. IHEP-103 features 1D rhombic channels functionalized by dimethylamine, uranyl acyl oxygen atoms, imine nitrogen atoms, aromatic rings, and alkyl hydrogen moieties. The structural characteristics of IHEP-103 (such as its multiple functional groups) give it potential applications in iodine capture, while the dimethylammonium cation further enhances iodine adsorption through electrostatic interactions and intermolecular C-H···I interactions. The results from XPS, Raman spectroscopy, and single-crystal X-ray diffraction reveal an evolution of the iodine species surrounding the dimethylamine group with increasing iodine loading: from the (I₂·I₃)^- supramolecular complex structure to the polyiodide anions I₅^-.