Fabrication of Thermoresponsive Adsorbents with High Amine Efficiency for Wet CO₂ Capture: Coupling Responsiveness with Adsorption Swing

CO₂ adsorption in humid conditions has wide industrial uses, but the low uptake of adsorbents and the inferior efficiency of amines present a notable challenge for its development. Through the copolymerization of acrylamide (AAm), styrene (ST), and N-(3-(dimethylamino)propyl)methacrylamide (DMAPMA), we developed a thermoresponsive adsorbent with tunable amine sites. In a humid environment, the tertiary amines of the DMAPMA moiety keep an extended state and are exposed to the CO₂ molecules at 20 °C. The optimal adsorption capacity is 3.78 mmol g^-1 with 1 mol of amine reacting with 0.98 mol of CO₂. This amine efficiency in adsorption surpasses that of various typical adsorbents. At 80 °C, the adsorption capacity decreases to 1.10 mmol g^-1, with only 0.34 of the amine efficiency. The elevated temperature makes the AAm moiety form intramolecular H-bonds with the DMAPMA moiety; thus, the amines are shielded in the adsorbent’s particles. This change of amines couples with the feature of adsorption swing, making adsorbents have both the satisfied adsorption capacity and the convenience of desorption.