Enhancing the CO2 adsorption performance on 13× zeolite by optimising K+ ion-exchange degree

Alkali ion (such as potassium, K + ) exchanged zeolite is considered a s promising carbon dioxide (CO 2 ) sorbent. However, the effect of ion-exchange degree on CO 2 adsorption remains unclear. In this study, a series of K + ion-exchanged 13× zeolite materials (P13X-K) were synthesised to investigate the effect of K + ion exchange degree on the CO 2 adsorption capacity and the material structural properties. The CO 2 adsorption capacity exhibited a volcano-shaped trend as the degree of K + exchange increasing. In situ characterisations indicates that linear physisorption on extra framework alkali cations is the predominant adsorption configuration in 13× before and after K + ion exchanged. Specifically, K + form K + (CO 2 ) 2 complexes, while the Na + forms only Na + (CO 2 ), resulting in a higher CO 2 adsorption capacity for K + . This accounts for the initial enhancement of CO 2 update with increasing K + exchange. However, excessive K + exchange induces a gating effect in 13× channels, hindering CO 2 diffusion and thus reducing the adsorption capacity. These findings highlight the importance of balancing the number of adsorption sites and CO 2 internal diffusion efficiency to optimise the CO 2 adsorption capacity, providing new insight for rational design of solid CO 2 sorbent. • CO 2 capture capacity on 13× shows a volcano trend with K + ion exchange degree. • In situ DRIFTS and XAS reveal K + forms geminal K + (CO 2 ) 2 , unlike Na + only form Na + (CO 2 ), giving higher CO 2 uptake. • Excessive K + ion exchange causing gating effect, hindering CO 2 diffusion in 13×.