Readily accessible metal-hybrid organic linker gels for high-efficient recyclable iodine capture

Efficient capture of iodine concerns nuclear waste management. Crystalline metal–organic frameworks (MOF) have been demonstrated to be useful in iodine adsorption, but remain a great challenge due to their complex synthesis conditions and poor processibility. In this study, we synthesized a novel metal-hybrid organic linker gel composed of Zr-carboxylate-tannate networks via competitive coordination-driven gelation. By virtue of supramolecular nuclei aggregation, the gels exhibited a hierarchical micro-mesoporous structure to accommodate iodine molecules. Moreover, the abundant phenolic OH groups of the tannate linker provided adsorption sites for iodine, imparting gels high binding energy with iodine. The gels demonstrated an exceptional iodine vapor adsorption capacity (311 wt%), surpassing many crystalline MOFs. The gels manifested impressively recyclable adsorption performances. The iodine capacity was retained over 95% during three consecutive adsorption–desorption cycles. Interestingly, the metal-hybrid linker coordination and gelation enabled the in-situ formation of monolithic structures, which displayed satisfactory iodine capacity. There is nearly no capacity loss compared to the powder form, indicating that gelation offers a promising in-situ adsorbent shaping manner. This study unlocks the great potential of non-crystalline, easily accessible metal–organic gels as high-performance adsorbents for radionuclide sequestration.