Linking Nitrogen-Rich Organic Cages into Isoreticular Covalent Organic Frameworks for Enhancing Iodine Adsorption Capability

By linking a nitrogen-rich organic cage with linear connectors, three cage-based isoreticular covalent organic frameworks, i.e., Cage-IRCOF-1, Cage-IRCOF-2, Cage-IRCOF3, were successfully designed and synthesized by Schiff-base polycondensation reactions. The structure determination and simulations from powder X-ray diffraction measurements indicated that these COFs have high crystallinity derived from the packing of covalently linked two-dimensional isoreticular layer frameworks. As nitrogen-rich porous materials, iodine capture studies were carried out, proving that they displayed obvious enhancements in iodine uptake as compared with the pristine cage itself. In particular, Cage-IRCOF-1 displayed an iodine adsorption capacity of 262 wt %, which is 12 times higher than the solid packed from the cage itself. Spectral studies revealed that there were strong interactions between the nitrogen rich groups and the adsorbed iodine species. This work demonstrated that linking the discrete organic cages into reticular crystalline frameworks, effective adsorbents can be fabricated for targeted applications.