Intermolecular Interactions in Direct Air Capture Materials: Insights from Charge Density Analysis

Area of Science:

• Materials Science
• Chemistry
• Environmental Science

Background:

• Direct air capture (DAC) is crucial for atmospheric CO2 removal.
• Understanding intermolecular interactions in DAC materials is key to improving efficiency.
• Methylglyoxal-bis(iminoguanidine) (MGBIG) is a promising DAC material.

Purpose of the Study:

• To experimentally investigate the electron density of MGBIG.
• To correlate intermolecular interactions with CO2 sorption and release behavior.
• To provide a framework for rational design of improved DAC materials.

Main Methods:

• High-resolution X-ray and neutron diffraction.
• Quantum crystallographic analysis including multipolar refinement.
• Electrostatic potential and multipole moment calculations.
• Topological analysis of electron density and energetic analyses.

Main Results:

• Identified distinct hydrogen-bonding environments in two MGBIG carbonate phases (P1 and P3).
• Quantified electron density distributions and mapped hydrogen bonds crucial for CO2 capture.
• Revealed a cooperative hydrogen-bonding network in the stable P3 phase, enhancing lattice stability.
• Energetic analyses confirmed superior stability of P3 due to stronger hydrogen bonding.

Conclusions:

• Established a direct experimental link between electron density and intermolecular interactions in DAC materials.
• Demonstrated that stronger hydrogen bonding networks enhance MGBIG stability and CO2 capture.
• Provided a rational design strategy for optimizing DAC sorbents for efficiency and reduced energy demand.