Reversible Multi‐Complexation of CO₂ to Alkaline Earth Metal Ion‐Pair at 400 ppm and 298 K

The efficient capture of low‐pressure CO 2 remains a significant challenge due to the lack of established multi‐complexation of CO 2 to active sites in microporous materials. In this study, we introduce a novel concept of reversible multi‐complexation of CO 2 to alkaline earth metal (AEM) ion pairs, utilizing a host site in ferrierite‐type zeolite (FER). This unique site constrains two AEM ions in proximity, thereby enhancing and isotopically spreading their electrostatic potentials within the zeolite cavity. This electrostatic potential‐engineered micropore can trap up to four CO 2 molecules, forming M 2+ −(CO 2 ) n −M 2+ ( n =0–4, M=Ca, Sr, Ba) complexes, where each CO 2 molecule is stabilized by interactions between terminal oxygen (O t ) in CO 2 and the AEM ions. Notably, the Ba 2+ pair site exhibits higher thermodynamic stability for multiple adsorptions due to the optimal binding mode of Ba 2+ −O t −Ba 2+ . Through high‐accuracy energy calculations, we have established the relationship among structure, CO 2 uptake, and operating temperature/pressure, demonstrating that the Ba 2+ pair site can capture four CO 2 molecules even at concentrations as low as 400 ppm and at 298 K. Three of the four molecules of CO 2 trapped were removable at room temperature and under vacuum. The findings in the present study provide a new direction for developing efficient CO 2 adsorbents.