Pore Space Partitioning MIL-88(Co): Developing Robust Adsorbents for CO₂/CH₄ Separation Featured with High CO₂...

Metal-organic frameworks (MOFs) have attracted significant attention as sorbents for gas separation and purification. Ideally, an industrially potential adsorbent should combine exceptional gas uptake, excellent stability, and a lower regeneration energy; however, it remains a great challenge. Here, by utilizing the pore space partition (PSP) strategy, we develop three isostructural MOF materials (Co-BDC-TPB, Co-DCBDC-TPB, and Co-DOBDC-TPB) based on pristine MIL-88(Co). The three pore-space-partitioned crystalline microporous MOFs have triangular bipyramid cages and segmented one-dimensional channels, and among them, Co-DOBDC-TPB exhibits the highest CO₂ uptake capacity (4.35 mmol g^-1) and good CO₂/N₂ (29.7) and CO₂/CH₄ (6.2) selectivity. The selectivity-capacity synergy endows it with excellent CO₂/N₂ and CO₂/CH₄ separation performance. Moreover, Co-DOBDC-TPB can complete desorption within 10 min. The satisfactory CO₂ adsorption ability can be attributed to both microporous aperture arising from PSP and modification of the pore surface by the polar hydroxy group, which enhances the interaction between Co-DOBDC-TPB and CO₂ molecules significantly. The exceptional regeneration property may be due to its lower CO₂ isosteric heat of adsorption (23.6 kJ/mol). The developed pore-space-partitioned MIL-88(Co) material Co-DOBDC-TPB may have potential application to flue gas and natural gas purification.