Formation of the Most Iodine-Rich Polyiodide [I13]− in Pore-Partitioned Metal-Organic Frameworks for Efficient Iodine Capture

Radioactive iodine produced from nuclear fission in power plants presents substantial environmental risks and requires effective remediation measures. Metal-organic frameworks (MOFs) containing specifically designed pore geometries with stable skeletons that allow dense packing of guest molecules are sought after for iodine capture. Here, 14 new MOFs were developed through reticular chemistry for a comprehensive study of the iodine capture behavior. Remarkably, one of this family of materials, JOU-20(FeCo₂), exhibited an exceptional static vapor iodine uptake capacity of 3.08 g/g at 80°C and a high iodine storage density of 4.69 g/cm³. Significantly, single-crystal X-ray diffraction revealed the adsorbed iodine in JOU-20(FeCo₂) forming an unusual aggregation of the giant trigonal antiprismatic polyiodide anion [I₁₃]⁻. To the best of our knowledge, this is the first time that the polyiodide [I₁₃]⁻ was structurally resolved in a crystalline framework, and it represents the most iodine-rich polyiodide species ever discovered experimentally. Combined spectroscopy and theoretical calculation methods demonstrated that nitrogen/sulfur sites and metal nodes play critical roles in stabilizing [I₁₃]⁻. This work introduces a pore partition strategy to create a confined space with specific pore geometry for the formation of unusual polyiodide [I₁₃]⁻, and multiple binding sites for stabilizing it, which significantly enhances the iodine adsorption performance of MOFs.