Water-promoting effect of amine resins in capturing CO₂ in humid air

Two commercial amine-functionalized resins, A110DR （Resin-1） and D6768DR （Resin-2）, were investigated for direct air capture （DAC） of CO₂. Thermogravimetric analysis, Fourier transform infrared spectroscopy, N₂ adsorption-desorption, CO₂ adsorption, and dynamic breakthrough experiments were conducted to evaluate their adsorption performance and the effect of water. Both resins exhibited good thermal stability and abundant amine active sites. After activation at 100 ℃, the CO₂ adsorption capacities of Resin-1 and Resin-2 reached 25 and 28 cm³·g⁻¹, respectively, at 400 µL·L⁻¹ CO₂. Under 75% relative humidity, the CO₂ breakthrough time increased by 56.7% for Resin-1 and 14.0% for Resin-2 compared with those under dry conditions. Water promoted proton transfer and the formation of favorable chemisorbed species, leading to higher amine utilization and enhanced CO₂ capture. The results show that both resins possess comparable low-concentration CO₂ capture performance, good cyclic stability, and significant humidity responsiveness, demonstrating their potential for DAC applications.