Thermal modulation of reaction equilibria controls mass transfer in CO2-binding organic liquids

Abstract

CO₂-Binding organic liquids (CO₂BOLs) are non-aqueous solvents which may reduce the parasitic energy of carbon capture processes. These solvents exhibit surprising mass transfer behavior: at fixed pressure driving force, the flux of CO₂ into CO₂BOLs decreases exponentially with increased temperature, a phenomenon not observed in aqueous amines. Here, we demonstrate that this phenomenon is primarily driven by a shift in reaction equilibrium, which reduces the degree to which chemical reactions enhance the CO₂ flux. First-principles surface renewal models quantitatively reproduce mass transfer data for CO₂ absorption into 2-EEMPA, IPADM-2-BOL and DBU:Hexanol across a range of temperatures. Density functional theory calculations are used to identify structural modifications likely to improve the CO₂ flux. These findings reveal a fundamental trade-off between CO₂ flux and the energy required for solvent regeneration, and provide a theoretical foundation for rational solvent design and the development of physics-informed mass transfer models.