N-rich polymer organic framework for iodine removal from gaseous and aqueous systems

Ever-increasing energy demands and pollution from traditional energy sectors have forced many nations to switch to nuclear energy, which releases radioactive substances, including iodine and iodide species (I 129 & I 131 ) that pose significant environmental and health risks. Hence, efficient capture and immobilization of radioactive iodine is crucial for environmental protection and safe management of nuclear waste. Polymeric organic frameworks (POFs) displaying tunable pore structure, high surface area and tailored chemical functionalities have emerged as an important class of materials for effective removal of iodine. Herein, we present two pyrrole and triazene functionalized POFs (PyPOF-01 and PyPOF-02) for removing iodine from gaseous and aqueous environments. PyPOF-01 and PyPOF-02 are being built from pyrrole and aromatic triazene/benzene rings, which facilitate charge transfer interaction and offer accessible nitrogen-rich binding sites enabling effective iodine adsorption via combined physical and chemical adsorption. PyPOF-01 and PyPOF-02 displayed moderate gas-phase iodine uptake (2.70 and 1.97 g/g), excellent retention (>95%) of iodine species even after 10 days, and high aqueous-phase iodine uptake (1.92 and 1.82 g/g) with exceptional recyclability. In addition, these polymers demonstrate excellent tolerance towards harsh acidic conditions. DFT analysis further reveals the possible binding sites for iodine and iodide species within PyPOFs. It demonstrated that iodine adsorption is not only dependent on the nitrogen content but also governed by methyl groups attached to the benzene ring.