Methanol-Assisted CO2 Fixation by Hydroxyl-Containing Amidine Leading to Polymeric Ionic Liquid and Cross-Linked Network Formation.

This study presents a methanol-assisted pathway that converts hydroxyl-containing amidine into a polymeric ionic liquid (PIL) through direct CO2 fixation, followed by its transformation into a cross-linked ionic polymer (CL-IP). Methanol plays a crucial role in this process, acting as both a structural and electronic mediator. Its strong hydrogen-bonding interactions with amidine activate the molecule toward CO2 capture and promote the formation of ionic intermediates. Spectroscopic analyses (FTIR, 1H and 13C NMR) revealed the emergence of amidinium and alkyl-carbonate groups, while viscosity and mass measurements indicated progressive polymerization during CO2 absorption. Density functional theory calculations confirmed the stabilizing effect of methanol and the reduced HOMO-LUMO gap, which facilitates PIL formation. The subsequent condensation of the PIL with glutaraldehyde produced a dense three-dimensional cross-linked network (CL-IP), as verified by FTIR, XPS, SEM, and TGA analyses. These results highlight a straightforward and sustainable strategy for constructing hydrogen-bond-mediated ionic polymers capable of tunable CO2 capture and potential application in environmentally compatible materials.