A nitrogen-rich halogen-bonded organic framework (XOF) for efficient iodine capture and security printing

The escalating utilization of nuclear energy and nuclear medicine raises concerns about the environmental impact of radioactive iodine, necessitating the development of effective iodine adsorbents, especially under a real-world scenario with extremely low iodine concentration and elevated temperature. Herein, we have presented the construction of a nitrogen-abundant two-dimensional (2D) halogen-bonded organic framework, XOF-TNP, characterized by exceptional crystallinity, thermal stability, and nitrogen-rich structures. XOF-TNP exhibits strong binding to iodine, thanks to the fact that iodine can be pre-enriched into the framework through N⋯I interactions. The nitrogen-rich framework and I⁺ synergistically have extremely high binding force to iodine, enabling the rapid and efficient capture of iodine in both vapor and solution phases, with significant recyclability. Further flow-through adsorption experiments using an XOF-TNP-packed column achieve 99% iodine removal from hexane and aqueous solutions, surpassing traditional activated carbon. This highlights its potential for environmental remediation. XOF-TNP enables the development of a novel rewritable security paper, utilizing its iodine adsorption properties to encrypt and decrypt QR codes. This research expands the application scope of halogen-bonded organic frameworks, providing insights into the design of materials for environmental remediation and security applications.