Temperature‐Responsive Microgel Films as Reversible Carbon Dioxide Absorbents in Wet Environment

Hydrogel films composed of temperature‐responsive microgel particles (GPs) containing amine groups work as stimuli‐responsive carbon dioxide absorbent with a high capacity of approximately 1.7 mmol g^?1. Although the dried films did not show significant absorption, the reversible absorption capacity dramatically increased by adding a small amount of water (1 mL g^?1). The absorption capacity was independent of the amount of added water beyond 1 mL g^?1, demonstrating that the GP films can readily be used under wet conditions. The amount of CO₂ absorbed by the GP films was proportional to their thickness up to 200–300 μm (maximum capacity of about 2 L m^?2). Furthermore, the films consisting of GPs showed faster and greater absorption and desorption of CO₂ than that of monolithic hydrogel films. These results indicated the importance of a fast stimulus response rate of the films that are composed of GPs in order to achieve long‐range and fast diffusion of bicarbonate ions. Our study revealed the potential of stimuli‐responsive GP films as energy‐efficient absorbents to sequester CO₂ from high‐humidity exhaust gases.