Modified polyethyleneimine with abundant N/O/S-heteroatoms and aromatic segments: Convenient synthesis via sulfur-isocyanide-amine multicomponent reaction and application in high-performance iodine capture

With the continuous development of nuclear industry, the discharge of radioactive iodine (129I and 131I) become a potential danger to ecological environment. The development of high-performance iodine capture materials has important practical significance to reduce the harm of radioactive iodine. With the aim to construct new iodineadsorbing polymer under the "bottom -up" structural designing guidance, using sulfur (S), branched polyethyleneimine (PEI) and 4,4'-oxybis(isocyanobenzene) (OBI) as starting substrates, a thiourea -modified PEI derivative (PEI-SIA) with abundant N/S/O-heteroatoms and aromatic molecular fragments was successfully prepared here via efficient sulfur-isocyanide-amine multicomponent polymerization (SIA-MCP). Characterization of PEI-SIA's fundamental properties indicated that it is a new type of covalent organic polymer (COP). The iodine adsorption performance of PEI-SIA was systematically investigated. Experimental results showed that PEI-SIA can effectively adsorb iodine in steam (75 degrees C), cyclohexane, and aqueous phases, with the equilibrium adsorption capacities up to 6.48, 2.63, and 3.01 g g-1, respectively. The iodine adsorption mechanism of PEI-SIA was characterized by experimental investigation and Density Functional Theory (DFT) calculation. The results revealed that PEI-SIA's high iodine adsorption performance can be attributed to the synergistic effect brought by N/S/O-containing segments and the electron rich aromatic skeletons in PEI-SIA.