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. Carbon dioxide capture: Hydrogel films composed of temperature-responsive microgel particles (GP) containing amine groups reversibly absorbed carbon dioxide with a high capacity in response to the thermal stimuli (30-75 °C; see picture). A fast stimulus response rate of the GP films enabled the long-range and fast diffusion of bicarbonate ions into the films.