Adsorption of Radioiodine Species by a Microporous Rare-Earth-Organic Framework

Rare-earth-organic frameworks (REOFs) have been extensively investigated as promising adsorbents for radioactive nuclides, owing to the diverse coordination environments and robust bonding structures of rare-earth ions and the tunable large-pore architectures of frameworks. Herein, a yttrium-based REOF (Y-NH₂-BTB) featuring microporous and hierarchical channels (pore volume of 0.2625 cm³ g^-1) is reported as an efficient platform for capturing radioactive iodine vapor─a highly radiotoxic fission product released during nuclear fuel reprocessing. A maximum adsorption capacity of 1238 mg g^-1 was achieved via vapor diffusion experiments. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations identified the preferred adsorption sites of iodine within the microporous structure. The high uptake capacity is primarily attributed to halogen bonding and charge-transfer interactions between the I₃^- species and the NH₂-functionalized ligand in addition to the structural confinement offered by the microporous channels. Furthermore, cyclic adsorption tests demonstrated the excellent reusability of Y-NH₂-BTB. This study highlights the potential of microporous REOFs for radioactive species separation, combining high adsorption capacity with excellent recyclability through the use of a lighter rare-earth element.