Safe confinement of fission iodine isotopes for long-term radioactive waste disposal remains a formidable challenge, as conventional sorbents provide inherently weak iodine-host interactions. We report here a novel halogen bond (X-bond) directed strategy to sequester volatile iodine in hydrogen-bonded (H-bonded) frameworks with unprecedented stability. Charge-assisted H-bonded frameworks bearing open halide sites are developed, showing distinctive iodine encapsulation behaviors without compromising the crystallinity. Direct crystallographic evidence indicates the formation of X-bonds, i.e., I–I···Cl⁻ and I–I···Br⁻, within the confined pore channels. Unusual polyhalogen anions, i.e., [I₂Cl₂]²⁻ and [I₂Br₂]²⁻, sustained in H-bonded frameworks are identified for the first time. The X-bond reinforced host-guest interaction affords robust iodine trapping without leaking out even at elevated temperatures up to 180 °C. By integrating the halogen-bond chemistry with H-bonded frameworks, this study offers fresh concepts for developing effective host reservoirs to secure fission iodine isotopes from spent fuel reprocessing off-gases.

This work reports a de novo synthesis of novel bifunctional conjugated microporous polymers (CMPs) exhibiting a synergistic-effect involved coordination behavior to uranium. It is highlighted that the synthetic strategy enables the engineering of the coordination environment within amidoxime functionalized CMP frameworks by specifically introducing ortho-substituted amino functionalities, enhancing the affinity to uranyl ions via forming synergistic complexes. The CMPs exhibit high Brunauer-Emmett-Teller (BET) surface area, well-developed three-dimensional (3D) networks with hierarchical porosity, and favorable chemical and thermal stability because of the covalently cross-linked structure. Compared with the amino-free counterparts, the adsorption capacity of bifunctional CMPs was increased by almost 70%, from 105 to 174 mg/g, indicating evidently enhanced binding ability to uranium. Moreover, new insights into coordination mechanism were obtained by in-depth X-ray photoelectron spectroscopy (XPS) analysis and density functional theory (DFT) calculation, suggesting a dominant role of the oxime ligands forming a 1:1 metal ions/ligands (M/L) coordination model with uranyl ions while demonstrating the synergistic engagement of the amino functionalities via direct binding to uranium center and hydrogen-bonding involved secondary-sphere interaction. This work sheds light on the underlying principles of ortho-substituted functionalities directed synergistic effect to promote the coordination of amidoxime with uranyl ions. And the synthetic strategy established here would enable the task-specific development of more novel CMP-based functional materials for broadened applications.