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-IRCOF-3, 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.