Controllable Fabrication of Nitrogen-Containing Hyper-Cross-Linked Polymers with Pyrazine–Aromatics Dual Building Blocks for Effective Iodine Capture

Introducing high-affinity heteroatoms as binding sites to improve iodine uptake is a promising strategy for developing porous materials that exhibit efficient iodine capture. Herein, we report the design and synthesis of a series of pyrazine-functionalized hyper-cross-linked polymers (HCPs) for high-performance iodine vapor capture. These materials were constructed via a straightforward Friedel–Crafts reaction using a nitrogen-rich cross-linker, 2,5-dibromomethylpyrazine (2,5-DBMP), with aromatic monomers of varying sizes (biphenyl, p -terphenyl, and 1,3,5-triphenylbenzene). The strategic use of 2,5-DBMP not only facilitates the formation of a robust porous network but also incorporates abundant electron-deficient pyrazine rings, serving as potent chemisorption sites. The resulting HCPs possess high specific surface areas and a nitrogen-enriched, π-conjugated framework. Iodine adsorption experiments demonstrate that these materials exhibit excellent capture capacities. Further investigations into the adsorption mechanism reveal a synergistic effect of physisorption within the porous structure and chemisorption via charge-transfer interactions with the pyrazine nitrogen atoms. The adsorbents also show controlled iodine release in ethanol and promising reusability, maintaining over 80% iodine removal efficiency after four adsorption–desorption cycles. This work highlights the effectiveness of heteroatom-incorporated cross-linkers in developing advanced HCPs for efficient radioactive iodine capture.