Enhancing CO2/N2 separation performances by turning membrane affinity for CO2

Membrane technology holds great promise for efficient gas separation, but effectively manipulating the affinity between the target gas and the membrane remains a challenge. This study presents an innovative strategy to optimize the separation performance by precisely tuning the basicity of ionic liquid (IL) guests within the metal-organic framework-808 (MOF-808) fillers of mixed matrix membranes (MMMs). By exploiting the sensitivity of the CO2 binding affinity with the hosted ILs, the transmembrane behavior of CO2 differs from N2 under varied feed pressures, resulting in enhanced separation performance. Under a transmembrane pressure of 4 bar, the optimized CO2/N2 selectivity reaches an impressive 43.6, accompanied by a CO2 permeability of 10,106 Barrer, surpassing the latest upper bound. This study showcases the significant potential of gas and membrane affinity modification to achieve remarkable permeability and selectivity in gas separation applications.