Dual amino-functionalised phosphonium ionic liquids for CO2 capture.

Area of Science:

• Materials Science
• Chemical Engineering
• Green Chemistry

Background:

• Ionic liquids (ILs) are versatile materials with tunable properties for various applications.
• Developing efficient and recyclable CO2 capture agents is crucial for mitigating climate change.
• Amino-functionalized phosphonium ILs offer potential for enhanced CO2 solubility and chemical interaction.

Purpose of the Study:

• To synthesize and characterize a series of 20 dual amino-functionalized phosphonium ionic liquids ([aP(4443)][AA]).
• To investigate the physicochemical properties of these novel ionic liquids, including thermal stability and conductivity.
• To evaluate the CO2 absorption capacity and recyclability of selected [aP(4443)][AA] ionic liquids.

Main Methods:

• Synthesis of 20 (3-aminopropyl)tributylphosphonium amino acid salts ([aP(4443)][AA]).
• Determination of physicochemical properties: density, viscosity, glass transition temperature, decomposition temperature, and conductivity.
• Investigation of CO2 absorption using selected ILs ([aP(4443)][Gly], [aP(4443)][Ala], [aP(4443)][Val], [aP(4443)][Leu]) and assessment of recyclability.

Main Results:

• The synthesized [aP(4443)][AA] ionic liquids possess low glass transition temperatures (-69.7 to -29.6 °C) and high decomposition temperatures (>200 °C).
• CO2 absorption equilibrium was reached within 80 minutes for the tested ILs.
• Chemical CO2 absorption approached 1 mol CO2 per mol IL, with successful repeated recycling demonstrated.

Conclusions:

• The structure of the amino acid anion significantly influences the physicochemical properties of the phosphonium ionic liquids.
• The [aP(4443)][AA] ionic liquids demonstrate high CO2 absorption capacity and excellent recyclability.
• These novel ionic liquids show significant promise as effective materials for carbon capture technologies.