Cryptand-Based Nonporous Polymer Adsorbent for Ultrafast Iodine Adsorption from Vapor and Water

A urea-functionalized octaaminocryptand-based cross-linked polymer (CPT-HDI) was designed and synthesized through a simple one-step reaction between octaaminocryptand (CPT) and hexamethylene diisocyanate (HDI). The resulting nitrogen-rich, nonporous polymer is decorated with octaaminocryptand with an interior cavity and urea functionality, enabling strong supramolecular interactions with iodine via N···I and hydrogen-bonding interactions. Despite a modest surface area of 8.56 m2 g–1, CPT-HDI exhibits exceptional iodine adsorption capacities of 3.52 g g–1 (352 wt %) from the vapor phase and 662 mg g–1 from aqueous solution. Surprisingly, the octaaminocryptand demonstrated an exceptional iodine vapor adsorption capacity of 7.44 g g–1. Thermogravimetric analysis confirms reversible adsorption behavior, while kinetic and isotherm studies reveal pseudo-second-order and Langmuir-type adsorption, indicative of chemisorption on homogeneous sites. The polymer demonstrates recyclability over multiple cycles and efficient dynamic flow-through performance, validating its potential for scalable nuclear wastewater remediation and radioactive iodine vapor capture applications.