The chemisorption process with amines is the major separation and recovery method of CO2 because of its high processing capacity and simplicity. However, large energy consumption for the desorption of CO2 is also associated with the process. To develop a separation and recovery process that is capable of desorbing CO2 at low temperatures and with minimal energy consumption, polymer hydrogels with a lower critical solution temperature (LCST) polymer network and amine groups immobilized in the polymer network of the hydrogels were exploited. Thermo-responsive amine gels with a series of hydrophobicity of polymer networks were systematically synthesized, and the influence of the hydrophobicity of the gels on the CO2 desorption temperature and cycle capacity (CO2 amount that can be separated and recovered by 1 cycle of temperature swing operation) was investigated using slurries with the series of gels. A significant decrease in the CO2 desorption temperature and increase in the cycle capacity occurred simultaneously by lowering the LCST of the gels via hydrophobisation of the polymer network. Based on an equilibrium adsorption model representing the CO2 separation and a recovery system with the gel slurries, an analysis of the system dynamics was performed in order to understand the recovery mechanism in the process.

Temperature‐responsive change in pKa of tertiary amines that are immobilized in the cross‐linked LCST polymer chains (temperature‐responsive amine gels) is applied to the separation and recovery of CO2 gas. Adsorption and desorption behaviors of CO2 gas on the temperature‐responsive amine gels are experimentally investigated using a temperature‐controlled gas‐liquid contact reactor with the slurries of the gels. Based on the control of the swelling volume of the temperature‐responsive gels via temperature swing, pKa of the amines in the gels was controlled. Influences of monomer composition in the gels and solvent composition in the slurry on the performance of CO2 recovery were investigated.