Self-Assembled Oligomers Facilitate Amino Acid-Driven CO2 Capture at the Air-Aqueous Interface.

Abstract

Direct air capture of CO₂ using amino acid absorbents, such as glycine or sarcosine, is constrained by the relatively slow mass transfer of CO₂ through the air-aqueous interface. Our recent study showed a marked improvement in CO₂ capture by introducing CO₂-permeable oligo-dimethylsiloxane (ODMS-MIM⁺) oligomers with cationic (imidazolium, MIM⁺) headgroups. In this work, we have employed all-atom molecular dynamics simulations in combination with subensemble analysis using network theory to provide a detailed molecular picture of the behavior of CO₂ and the glycinate anions (Gly^-) at the ODMS-MIM⁺ decorated air-aqueous interfaces. We show that the cationic head groups of the surfactants enhance the concentration and lifetime of Gly^- in the interfacial region, while ODMS tails promote the physisorption of CO₂ in the interfacial region. Together, these two factors increase the effective region of contact and the probability of interactions between CO₂ and Gly^- compared to that of the pure air-aqueous interface. The fundamental insights gained in this work establish essential foundations for developing hybrid systems with oligomer-decorated interfaces to maximize the overall CO₂ capture rates.