Polymer Layer-Accelerated CO₂ Absorption in Aqueous Amino Acid Solutions

Direct air capture (DAC) of CO2 via solvent-based absorption is considered a promising negative-emission technology. However, the low concentration of CO2 in the air and slow transport into the solvent make DAC notoriously challenging to implement without costly investments. In this study, we explore the fundamental role that the bulk and surface properties of CO2-permeable polymer membranes play in enhancing the efficiency of the solution sorption process in passive DAC of CO2. This work leverages various spectroscopic and computational studies to demonstrate that a hybrid system, comprising a reusable CO2-permeable polymer layer placed atop an aqueous amino acid (AA) solution, can outperform a pure aqueous AA system by 2-fold. We show how the enhanced solubility of CO2 in the polymer layer can improve the transport of CO2 into the aqueous phase, while the chemistry of the polymer can control the interfacial barrier for CO2 permeation and the interfacial concentration of reactive AAs. The derived knowledge of the material properties achieved here can aid in the design of DAC systems with improved performance.