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

Area of Science:

• Materials Science
• Polymer Chemistry
• Green Chemistry

Background:

• Developing efficient CO2 capture materials is critical for environmental sustainability.
• Polymeric ionic liquids (PILs) offer tunable properties for various applications.
• Novel synthetic pathways for PILs are needed to enhance their performance and accessibility.

Purpose of the Study:

• To present a methanol-assisted pathway for synthesizing polymeric ionic liquids (PILs) via direct CO2 fixation.
• To transform the synthesized PIL into a cross-linked ionic polymer (CL-IP).
• To investigate the role of methanol in mediating the CO2 capture and polymerization process.

Main Methods:

• Hydroxyl-containing amidine reacted with CO2 in the presence of methanol.
• Spectroscopic analyses (FTIR, NMR) to characterize intermediates and products.
• Viscosity and mass measurements to monitor polymerization.
• Density Functional Theory (DFT) calculations to understand reaction mechanisms.
• Cross-linking of PIL with glutaraldehyde to form CL-IP.
• Material characterization using FTIR, XPS, SEM, and TGA.

Main Results:

• Methanol facilitates CO2 capture by amidine through hydrogen bonding, activating the molecule.
• Formation of amidinium and alkyl-carbonate groups observed, indicating successful CO2 fixation and PIL formation.
• Progressive polymerization confirmed by viscosity and mass measurements during CO2 absorption.
• DFT calculations support methanol's stabilizing effect and reduced HOMO-LUMO gap, promoting PIL synthesis.
• Successful synthesis of a 3D cross-linked ionic polymer (CL-IP) network via condensation.
• Characterization confirmed the structure and properties of the CL-IP.

Conclusions:

• A straightforward and sustainable methanol-assisted pathway for synthesizing ionic polymers from CO2 was established.
• The developed ionic polymers exhibit tunable CO2 capture capabilities.
• The strategy offers potential applications in environmentally compatible materials and advanced carbon capture technologies.