Synthesis of electron-rich benzbisimidazole-containing amorphous poly(Schiff-base) networks for efficient iodine capture

In this work, two benzbisimidazole-containing amorphous poly(Schiff-base) networks (namely ATA-BA and ATA-BZ) are synthesized by reacting benzbisimidazole-containing aromatic tetra-aldehyde building block (ATA) with benzene-1,4-diamine and benzidine, respectively, under solvothermal conditions. The resultant ATA-BA and ATA-BZ networks possess the specific surface areas of 113 and 87 m2/g, respectively. Owing to the presence of abundant imine bond, alkyl-substituted imidazole ring, and extended π-conjugated system, ATA-BA network can effectively capture iodine in both vapor and solution phases with the capture capacities up to 5.29 g g−1 and 2343 mg g−1, respectively, although its specific surface area is not high. The exceptional iodine capture performance of ATA-BA network can be attributed to the strong charge-transfer interactions between imine bond/imidazole ring/π-conjugated system and iodine molecules, as demonstrated by spectroscopic analysis and density functional theory (DFT) calculations. In addition, the iodine capture by ATA-BA network in cyclohexane solution is systematically investigated. The experimental results indicate that the iodine adsorption kinetics and capture behavior obey pseudo-second-order model and Freundlich isotherm model, respectively.