Chelation-assisted ion exchange of MOR zeolite for enhancing CO2 capture under humid condition

Capturing CO 2 from humid flue gas remains a major challenge due to the severe competitive adsorption between CO 2 and H 2 O on zeolites. In this study, a novel chelation-assisted K + ion exchange strategy was proposed to simultaneously enhance both the CO 2 adsorption capacity and moisture resistance of mordenite (MOR) zeolites. Compared to the conventional ion exchange, this approach induced the mild surface dealumination, effectively removed the hydrophilic extra-framework Al(VI), and increased the K + exchange content. Structural refinement revealed that in the resulting MOR-EDTA-2K sample, K + ions were distributed in both the 12-membered ring (12MR) channels and the 8MR side pockets, which favored CO 2 adsorption. MOR-EDTA-2K achieved comparable uptake of 15 vol% CO 2 (46 mg/g) but with lower H 2 O uptake than conventional ion-exchange derived MOR sample, resulting in an improved CO 2 /H 2 O selectivity. Furthermore, DRIFTS analysis confirmed a mechanistic shift in CO 2 adsorption status from the HCO 3 − to CO 3 2− species, attributed to the inhibited water adsorption on MOR-EDTA-2K. For practical application, monolithic adsorbents prepared with MOR-EDTA-2K demonstrated prolonged CO 2 breakthrough time, excellent cyclic stability, and well regeneration at 75 °C. This facile and scalable method, with the advantage of low-temperature regeneration, renders the prepared zeolite a highly promising candidate for industrial CO 2 capture under humid conditions.