Highly Efficient and Reversible Iodine Capture in\nHexaphenylbenzene-Based Conjugated Microporous Polymers

Abstract

The effective and safe capture and\nstorage of radioactive iodine (¹²⁹I or ¹³¹I)\nis of significant importance during nuclear waste storage and nuclear\nenergy generation. Here we present detailed evidence of highly efficient\nand reversible iodine capture in hexaphenyl­benzene-based conjugated\nmicroporous polymers (HCMPs), synthesized via Buchwald–Hartwig\n(BH) cross-coupling of a hexakis­(4-bromo­phenyl)­benzene (HBB)\ncore and aryl diamine linkers. The HCMPs present moderate surface\nareas up to 430 m² g^–1, with narrow pore\nsize distribution and uniform ultramicropore sizes of less than 1\nnm. Porous properties are controlled by the strut lengths and rigidities\nof linkers, while porosity and uptake properties can be tuned by changing\nthe oxidation state of the HCMPs. The presence of a high number of\namine functional groups combined with microporosity provides the HCMPs\nwith extremely high iodine affinity with uptake capacities up to 336\nwt %, which is to the best of our knowledge the highest reported to\ndate. Two ways to release the adsorbed iodine were explored: either\nslow release into ethanol or quick release upon heating (with a high\ndegree of control). Spectral studies indicate that the combination\nof microporosity, amine functionality, and abundant π-electrons\nensured well-defined host–guest interactions and controlled\nuptake of iodine. In addition, the HCMPs could be recycled while maintaining\n90% iodine uptake capacity (up to 295%). We envisage wider application\nof these materials in the facile uptake and removal of unwanted oxidants\nfrom the environment.