Solvation Shell Structures of Ammonia in Reline and Ethaline Deep Eutectic Solvents

Area of Science:

• * Environmental Chemistry
• * Computational Chemistry
• * Materials Science

Background:

• * Rising atmospheric anthropogenic ammonia (NH3) emissions necessitate novel capture technologies.
• * Deep eutectic solvents (DESs) are emerging as effective media for NH3 mitigation.
• * Understanding solute-solvent interactions within DESs is crucial for optimizing NH3 capture.

Purpose of the Study:

• * To investigate the solvation shell structures of ammonia (NH3) in two distinct DESs: reline and ethaline.
• * To elucidate the fundamental interactions stabilizing NH3 within these DESs at a molecular level.
• * To analyze the structural arrangement of DES components around the NH3 solute.

Main Methods:

• * Employed *ab initio* molecular dynamics (AIMD) simulations.
• * Analyzed the solvation shell structures of NH3 in reline (choline chloride:urea) and ethaline (choline chloride:ethylene glycol).
• * Focused on identifying specific solute-solvent interactions and structural arrangements.

Main Results:

• * In reline, NH3 hydrogens interact with chloride anions and urea carbonyl oxygens; NH3 nitrogen bonds with choline hydroxyl hydrogens.
• * In ethaline, NH3 strongly hydrogen bonds with ethylene glycol hydroxyl hydrogens and choline cations.
• * Ethylene glycol plays a key role in NH3 solvation in ethaline, while chloride anions are less involved in the first solvation shell.

Conclusions:

• * Both reline and ethaline demonstrate potential for NH3 capture via specific hydrogen bonding and charge transfer interactions.
• * Ethaline exhibits slightly stronger solute-solvent interactions compared to reline.
• * The study provides molecular-level insights into NH3 stabilization in DESs, guiding future solvent design for emission control.