Water Hydrogen Bonding Structures and Dynamics Facilitating CO₂ Capture by Amino Acids at the Air-Water Interface

Amino acids (AA) are showing great promise in direct air capture (DAC) of CO₂ at the air-water interface. Water mediates the involved reactions through the solvation of the reactants, intermediates, and products via H-bonding interactions. The local H-bonding structures, their reorganization dynamics during the progress of the reactions, and their reformed structure around the product states are the critical details that set the reaction equilibrium, thermodynamics, and kinetics. In this presentation, we will discuss the utility of reaction rate theory and the semiclassical modeling of the vibrational sum-frequency generation spectroscopy (vSFG) in elucidating the roles of the local solvation structures and reorganization dynamics in the AA-based DAC at the air-water interface. Specifically, the effects of the negative and neutral charge states of the AA and their surface activity on the solvent orientational ordering and coordination number and how these effects are further tailored by the product states of the DAC reactions will be illustrated. In addition, we will provide insight into the solvent rotational dynamics at the interface. Such a molecular-level, detailed understanding of the interfacial structure and dynamics will be critical to enhance the DAC probability.