Iodine gas sequestration by an imine-functionalised covalent organic polymer via chemisorption process

• A thiophene-based covalent organic polymer ( TPBT-COP ) was synthesized via both mechanochemical and solvothermal methods, ensuring a low-cost and reproducible preparation route. • The material exhibits microporosity with a pore width of 1.15 nm and a high BET surface area of 690.23 m²/g , as confirmed by ¹³C CP-MAS NMR, powder XRD, and FT-IR analyses. • The strategic design of the COP emphasizes strong interactions between iodine and heteroatoms such as sulphur and nitrogen within the polymer framework, which was further validated through DFT and XPS studies. • A monolayer chemisorption mechanism, consistent with the Langmuir model , accounts for the high iodine uptake of 389 wt% in the vapour phase by TPBT-COP. The removal of a radioactive iodine generated from the nuclear reaction waste is generally challenging as it requires expensive materials and sophisticated instrumentation. Recently, porous organic materials have attracted tremendous attention to resolve this issue due to a wide range of porosity and tuneable surface area. Amongst that covalent organic polymer (COP) facilitates high reproducibility in synthesis, low production cost along with stable polymer network for iodine adsorption in both vapour and liquid phase. Henceforth, TPBT-COP , a conjugated thiophene unit was coupled with triamine moiety via Schiff-base condensation reaction by two methods, namely mechanochemical grinding (MG) and solvothermal (ST) process. The obtained material has been confirmed through various characterization techniques like C 13 CP-MAS NMR, p-XRD and FT-IR spectroscopy. From BET analysis, it can be enumerated that the material exhibits a microporosity with a pore width of 1.15nm and a large surface area of about 690.23 m 2 g -1 aiding to adsorb the iodine effectively in both vapour and liquid phase. The adsorption capacity of 389 wt% from vapour phase and around 2.59 g g -1 from the liquid phase were recorded for TPBT-COP material. Additionally, the DFT and XPS analysis reveals that the iodine interacts with imine ‘N’ and thiophene ‘S’, where the iodine captured by TPBT-COP occurs through chemisorption process.