Kinetics and theoretical investigations on CO2 conversion and iodine vapor adsorption by polyethyleneimine-functionalized ionic polymers.

Developing efficient ionic polymers for catalysis and adsorption, such as the fixation of CO2 into high-value-added chemicals and iodine adsorption, represents a promising yet challenging avenue of research. In this study, a series of ionic organic polymers, designated as CPEIs (CPEI-1, CPEI-2, CPEI-3, CPEI-4, and CPEI-5) were assembled from the Zincke reaction involving branched polyethyleneimine and Zincke salt. These polymers were thoroughly characterized, and subsequently implemented to CO2 immobilization reactions, iodine vapor, and methyl iodide adsorption. Owing to their abundant nitrogen content and basic amino groups, these CPEIs not only exhibited excellent catalytic performance on CO2 cycloaddition reaction, but also possess good adsorption capacities on iodine vapor. The CPEI-3 demonstrated exceptional efficiency, achieving a 96.2% yield in the cycloaddition of CO2 with epichlorohydrin (ECH) without the need for co-catalyst or solvents under mild conditions. Furthermore, it displayed excellent recyclability over five consecutive cycles without an obvious decline in conversion. Additionally, the iodine adsorption performance of CPEIs was further examined, with adsorption capacities reaching 4.18 g g-1, 4.14 g g-1, 4.17 g g-1, 4.12 g g-1, and 4.24 g g-1, respectively. Furthermore, CPEIs demonstrated a measurable adsorption capacity for methyl iodide, with adsorption capacities recorded at 0.26, 0.21, 0.17, 0.28, and 0.23 g g-1, respectively. Experimental results indicate that the capture mechanism of CPEIs for iodine vapor primarily involves physical adsorption. The potential reaction mechanism was proposed in accordance with kinetics and density functional theory (DFT) calculations.