Multi-molar CO₂ capture beyond the direct Lewis acid-base interaction mechanism

Area of Science:

• Physical Chemistry
• Materials Science
• Chemical Engineering

Background:

• Singly charged ionic liquids (ILs) show high CO2 absorption capacity.
• Conventional models inadequately explain strong CO2 binding in ILs.
• A cation-channel mechanism involving proton transfer explains high CO2 uptake in some ILs.

Purpose of the Study:

• To extend the proton transfer mechanism to imidazole- and ammonium-based ILs.
• To investigate the role of IL structure and interactions in CO2 absorption.
• To understand the factors governing high CO2 uptake in functionalized ILs.

Main Methods:

• Density functional theory (DFT) calculations were employed.
• Proton transfer mechanisms in various ILs were modeled.
• Interactions between ILs and CO2 molecules were analyzed.

Main Results:

• Proton transfer mechanism successfully applied to imidazole- and ammonium-based ILs.
• Carbene formation in imidazole-ILs enhances CO2 reactivity.
• CO2-assisted proton transfer is key for ammonium-based ILs.
• Multi-ion pair models better capture intermolecular hydrogen bonding and CO2 absorption.

Conclusions:

• Proton transfer mechanism is a viable pathway for high CO2 uptake in diverse ILs.
• IL cation/anion acidity and basicity are critical for CO2 capture functionality.
• Advanced modeling considering multiple ion pairs improves understanding of CO2-IL interactions.