Polybenzimidazole Based Porous Organic Polymers with Dipyridine Units for Iodine Capture

Clean energy nuclear power generation is always accompanied by the release of harmful radioactive iodine. Therefore, developing efficient adsorbents has become a universal strategy to deal with this problem. Two distinct porous organic polymers (BTM-POP and DAB-POP) containing dipyridine units and benzimidazole structure were synthesized by 5,5'-([2,2'-bipyridine]-5,5'-diyl) diisophthalaldehyde with 1,2,4,5-benzenetetramine (BTM) or 3,3'-diaminobenzidine (DAB), respectively. The structures and morphologies of BTM-POP and DAB-POP were confirmed through Fourier transform infrared (FT-IR) spectroscopy, N₂ sorption isotherm measurement and scanning electron microscopy (SEM). Furthermore, iodine vapor capture of BTM-POP and DAB-POP reach 3.26 g g^-1 and 3.58 g g^-1, respectively. Mechanism study reveals that the adsorbed iodine in the material mainly exists in the form of I₃ ^- and I₅ ^- and the adsorption sites are mainly bipyridine and benzimidazole units. The results show that two POPs exhibit good thermal/chemical stability, high pore properties, and offer more adsorption sites. In combination with rich N atom content, large conjugated structure, synergistically influences the iodine vapor capture capacity of POPs.