Mesoporous Zeolitic Imidazolate Framework-67 Nanocrystals on Siliceous Mesocellular Foams for Capturing Radioactive Iodine

Effective disposal of radioactive iodine has been a persistent challenge in nuclear fuel recycling. Herein, we synthesized a series of micro-/mesoporous hierarchical adsorbents by the zeolitic imidazolate framework-67 (ZIF-67) nanocrystal growth onto siliceous mesocellular foams (MCFs) with functional amino groups. The combination of both benefits of microporous ZIF-67 and mesoporous MCF allows for obtaining a series of nanoscale ZIF-67@MCF hybrid materials, featuring enhanced porosity, good crystallinity, and excellent thermal stabilities. The abundant imidazole rings and amino groups not only function as organic linkers but also serve as active adsorption sites for the potential application of I2 remediation. The maximum liquid adsorption amount of ZIF-67@MCF toward I2 can reach up to 1630 mg·g–1 with an amination time of 10 h. The iodine adsorption kinetics were well fitted with pseudo-second-order kinetics, and isotherms were fitted by Langmuir models, respectively, implying a monolayer chemisorption process. The vapor I2 adsorption capacities of 1602–1779 mg·g–1 also indicated these ZIF-67@MCF nanomaterials are promising for the application in both vapor- and liquid-phase iodine removal. The electron transfers from the N atom to I atom can be confirmed by X-ray photoelectron spectroscopy and are responsible for the strong affinity for iodine adsorption. Compared to conventional materials, this study proves these talented nanoporous adsorbents for the application in iodine capture.