Efficient gaseous iodine capture enhanced by charge-induced effect of covalent organic frameworks with dense tertiary-amine nodes

Based on the outstanding application advantages of nitrogen-rich materials with regular porous frameworks in the capture of gaseous radioactive iodine, a series of covalent organic frameworks (COFs) with dual channels and abundant tertiary-amine active sites were constructed herein via a unique multi-nitrogen node design. The high density of up-to-six nitrogen adsorption sites in a single structural unit of the products effectively improved the adsorption capacities of the materials for iodine. Moreover, the adsorption affinity of the active sites can be further regulated by charge-induced effect of different electron-donating groups introduced into the COFs. Adsorption experiments combined with DFT theoretical calculations confirmed that the introduction of electron-donating groups can effectively increase the electron density around the active sites and enhance the binding energy between the materials and iodine, and thus improve the iodine adsorption capacity to 5.54 g/g. The construction strategy of multi-nitrogen node and charge-induced effect proposed in this study provides an important guidance for the study of the structure-activity relationship of functional materials and the design and preparation of high-performance iodine adsorption materials.