Stable nitrogen-containing covalent organic framework as porous adsorbent for effective iodine capture from water

Enrichment of radioiodine accompanied by nuclear fission threatens the health of humans, and efficient capture of iodine has attracted wide public attention in recent years. Here we report a crystalline mesoporous nitrogen-containing covalent organic framework (TAPB-BPDA COF) as a highly efficient iodine adsorbent, which is synthesized by imine condensation reaction between 1,3,5-tris(4-aminophenyl)benzene and 4,4′-biphenyldicarboxaldehyde. The TAPB-BPDA COF possesses permanent porous structure, high BET surface area of 1082 m2/g, excellent chemical and thermal stability and plenty of nitrogen in the skeleton as effective sorption sites. It displays remarkable adsorption of iodine in aqueous solution up to 988.17 mg/g at room temperature. The adsorption kinetics of iodine onto TAPB-BPDA COF is followed the pseudo-second-order kinetic model, and the adsorption isotherm fits well with the Langmuir model. The TAPB-BPDA COF adsorbs iodine through the weak interaction between the benzene ring on its backbone and iodine, and the electron transfer between nitrogen atoms and iodine promotes the adsorption process. Moreover, TAPB-BPDA COF still maintains efficient adsorption performance after five cycles. These results suggest the great potential of TAPB-BPDA COF as a designable porous to address the problem of nuclear fission waste contamination that threatens human health.