Leveraging Low-Pressure-Induced Structural Distortions in Unsubstituted Imidazole-Incorporated Zeolitic Imidazolate Framework-8 Nanostructures for Permanent Trapping of Iodine Gas

The permanent confinement of guest molecules within porous nanomaterials is of paramount importance, particularly for toxic gases, such as radioactive iodine (I 2 ). This study aims to develop and evaluate an advanced nanoporous framework capable of achieving irreversible I 2 trapping. For this purpose, we systematically investigated the I 2 capture and irreversible trapping capacities of both prototypical zeolitic imidazolate framework-8 (ZIF-8) and unsubstituted imidazole (Im)-incorporated ZIF-8. The latter was synthesized via a rationally optimized method, termed delayed linker addition (DLA)-solvent-assisted linker exchange (SALE) integrated approach (DSIA), which enables one-pot synthesis at low temperature, and eliminates the complexity of conventional postsynthetic modifications. Using this method, we achieved a maximum Im loading of 58 mol %, which is the highest for a low-temperature linker exchange strategy. Significantly, Im incorporation did not disrupt the sodalite topology or thermal stability of ZIF-8; instead, it reduced the framework’s flexibility, as confirmed by N 2 gas adsorption measurements. The Im-incorporated ZIF-8 loaded with I 2 was partially amorphized by pressure treatment for permanent I 2 trapping. Thermogravimetric measurements confirmed that the I 2 release step was absent for the partially amorphized Im-incorporated ZIF-8, indicating its permanent trapping. Positron annihilation lifetime spectroscopy was used to study the pressure-induced changes in the pore architecture of the frameworks. It revealed that Im-incorporated ZIF-8 exhibits an easily distortable pore network compared with the prototypical form. It is proposed that pressure-induced amorphization triggers permanent distortion of the central cavity and a significant loss in pore interconnectivity, resulting in the permanent trapping of I 2 . Remarkably, this study introduces a versatile and straightforward synthesis strategy that enables secondary linker incorporation into ZIF-8 under ambient conditions. It eliminates the need for complex postsynthetic modifications and provides a promising nanoporous material for the permanent confinement of toxic guest molecules within the pore network.