Anionization of 2-Amino-2-methylpropanol for Efficient Low-Partial-Pressure Carbon Dioxide Capture

Currently, achieving higher carbon dioxide (CO2) removal efficiencies in industry means greater regeneration and energy consumption. The high regeneration energy of most absorbents hinders the commercial capture of CO2 from industrial flue gas. Although sterically hindered amine 2-amino-2-methylpropanol (AMP) has a low desorption energy consumption, its absorption performance hardly meets the requirements for industrial flue gas decarbonization, especially at low CO2 pressure. In this work, a novel sterically hindered ionic liquid [N1111+][AMPA–] (tetramethylammonium aminoisobutyrate) was synthesized to address the regeneration energy challenge through a simple AMP anionization strategy. Compared with AMP, [N1111+][AMPA–] demonstrated a 30% increase in equilibrium CO2 loadings at 40 °C and 1.5 kPa. Meanwhile, the anionized product still showed favorable regeneration performance. Quantum chemical calculations revealed that anionization enhances the electron density of active site N atoms, thereby facilitating the nucleophilic CO2 absorption reaction. In addition, the steric hindrance effect ensured that the product predominantly exists in the form of bicarbonate without requiring a high regeneration energy. In this work, an anionization strategy is proposed to balance the conflict between absorption performance and regeneration energy by artificially modulating the intermolecular forces between CO2 and amine.