Facile method for enhancing the CO₂ adsorption capacity of zeolites through vacuum-assisted alkaline treatment

Zeolites are considered as promising CO₂ adsorbents due to their affordability, exceptional stability, and porous characteristics, yet they are still facing the challenges of low adsorption capacity and selectivity. In this study, we present a straightforward method to significantly improve the CO₂ adsorption performance of zeolites through vacuum-assisted alkaline treatment. Under alkaline conditions, the pore structure and surface functionality can be modulated through desilication, dealumination, and ion exchange. Additionally, vacuum conditions aid in releasing gas molecules trapped in the pores, facilitating the solution entry. Three typical zeolites, including SSZ-13 (CHA), T (ERI/OFF) and NaA (LTA) zeolites, are utilized through the vacuum-assisted alkaline treatment. At an optimized pH of 12, their CO₂ adsorption capacities increase by 7.67% to 16.99%. The significant enhancement in the CO₂ adsorption capacity is attributed to the modified pore size and pore volume. Thus, we suggest that the vacuum-assisted alkaline treatment is an effective approach for improving gas adsorption performance.