Difference for SO2 and CO2 in TGML ionic liquids: a theoretical investigation

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Ionic liquids (ILs) are promising solvents for gas capture.
• Understanding gas-molecule interactions within ILs is crucial for designing efficient absorbents.
• 1,1,3,3-tetramethylguanidium (TMG) lactate (LAC) ionic liquid (TMGL) shows potential for gas solubility.

Purpose of the Study:

• To investigate the interaction mechanisms between sulfur dioxide (SO(2)) and carbon dioxide (CO(2)) with the TMGL ionic liquid.
• To elucidate the factors governing the differential solubility of SO(2) and CO(2) in TMGL.
• To provide a deeper understanding of SO(2) absorption in ILs using quantum chemical methods.

Main Methods:

• Quantum chemical calculations (QM) were employed.
• Analysis of predicted molecular geometries and binding energies.
• Investigation of interaction sites and strengths between gas molecules and IL components.

Main Results:

• SO(2) exhibits strong interactions with the TMGL ionic liquid, especially with the lactate (LAC) anion.
• CO(2) shows weaker interactions with TMGL compared to SO(2).
• The oxygen atoms of the LAC anion are identified as primary active sites for SO(2) absorption.

Conclusions:

• The strong SO(2)-LAC interaction explains the high solubility of SO(2) in TMGL.
• The differential binding energies account for the observed differences in SO(2) and CO(2) solubility.
• QM calculations provide valuable insights into the molecular-level mechanisms of gas absorption in ionic liquids.