Carbon Dioxide Capture and Release by Anions with Solvent-Dependent Behaviour: A Theoretical Study

Area of Science:

• Computational Chemistry
• Materials Science
• Environmental Chemistry

Background:

• The cyanoformate anion exhibits polarity-switchable stability, enabling reversible CO2 capture.
• Understanding anion behavior in different solvent polarities is key for developing new CO2 capture technologies.

Purpose of the Study:

• To investigate the CO2 capture potential of 26 different anions.
• To explore the influence of solvent dielectric constant on anion-CO2 adduct stability.
• To identify anions with promising reversible CO2 capture capabilities.

Main Methods:

• Density functional theory calculations (M06-2X, B3LYP-D3) with aug-cc-pVTZ basis set.
• Polarizable Continuum Model (PCM) used to simulate gas phase and three solvents (water, THF, toluene).
• Analysis of relative free energies for anion-CO2 adduct formation.

Main Results:

• Identified alkoxylate and thiolate anions as particularly promising for reversible CO2 capture.
• Demonstrated that substituent nature critically influences anion-CO2 adduct stability and reversibility.
• Confirmed that moderate binding energy (~10 kcal/mol) and significant solvent dielectric effect are crucial for switchable behavior.

Conclusions:

• The design of anions for on-demand CO2 complex formation and destruction via solvent switching is feasible.
• Tailoring anion structure and selecting appropriate solvents can lead to efficient and reversible CO2 capture systems.
• This study provides a computational framework for designing novel materials for carbon capture and utilization.