Directed Hydrogen Bond Placement: Low Viscosity Amine Solvents for CO₂ Capture

Capture of CO₂ from power generation is required for its conversion or sequestration. Toward this goal, numerous CO₂ capture processes have been developed, with the most widely deployed technology utilizing aqueous solutions of amines. Our group has focused on the design of several classes of water-lean solvents in order to identify molecular-level descriptors to control materials properties such as viscosity and regeneration energy. Density functional theory calculations and classical molecular dynamic simulations have shown that strategic placement of hydrogen bonding and tuning of the acid/base equilibria are critical for controlling viscosity at CO₂-rich loadings. Here, we extend these principles to a new class of pyridine-based molecules with a secondary amine functionality for binding CO₂. The result is a class of water-lean amines that retains high gravimetric capacity (20%) while exhibiting the lowest CO₂-rich viscosities (<150 cP, 40 °C) of any 100% concentrated amine currently known. Additionally, these newly identified solvents exhibit regeneration temperatures as low as 60 °C when applying a polarity swing assisted regeneration, resulting in a solvent that can conceptually absorb and desorb CO₂ with only a 20 °C temperature swing.