Robust hydrogels with hierarchical porosities from the controlled assembly of metal–organic polyhedra for rapid removal of low-concentration aqueous iodine

Abstract

The removal of radioactive aqueous iodine is critical to the minimization of environmental impacts from nuclear energy production; however, its rapid and efficient removal at low-concentration level is still challenging. Herein, 2 nm metal–organic polyhedra (MOP) with a high binding affinity towards iodine are supramolecularly complexed with hydrophilic telechelic polymers and robust hybrid hydrogels with controlled hierarchical porosities can be obtained. The topologies of macromolecular ligands and the polymer/MOP concentrations are varied to elucidate the phase diagrams for hydrogel formation. The gels' meso-channel sizes and the distribution of hierarchical pores can be effectively regulated by varying the polymers' end groups and topologies. The meso-channels with optimized sizes favor the rapid diffusion of iodine while the homogenous distribution of MOP units maximizes the accessible area of MOP micropores, which cooperatively contributes to the high iodine capture efficiency. The MOP hydrogel demonstrated high absorption rate (2.336 g g⁻¹ h⁻¹) towards iodine molecules, surpassing most of the as-reported adsorbents. The work not only provides solutions for the robust formation of MOP-based hydrogels, but also paves new avenues for the effective treatment of low dose aqueous radioactive iodine.