Highly CO₂ perm-selective metal-organic framework membranes through CO₂ annealing post-treatment

Gas separation by metal-organic framework (MOF) membranes are still unsatisfactory due partly to unsatisfied separation characteristics caused by the trade-off between selectivity and permeability. Herein, we provide a facile post CO₂ annealing method to remarkably improve both the permeance and separation factor of IRMOF-1 membranes for CO₂ separation from CO₂/H₂ mixture. Post-treatment of the IRMOF-1 membrane by annealing at 100 °C under a high pressure CO₂ stream deceases H₂ permeance while increasing CO₂ permeance, leading to simultaneous enhancement in both CO₂/H₂ separation factor from 721 up to 5781 and CO₂ permeance from 5.67 × 10⁻⁷ up to 9.38 × 10⁻⁷ mol m⁻² s⁻¹ Pa⁻¹ at CO₂ molar fraction of 98%, feed pressure of 5 atm and 298 K. The unusual separation behavior is related to the enhanced CO₂ adsorption selectivity over H₂ and reduced CO₂ affinity of the membrane due to the formation of surface carbonate anions caused by the CO₂ treatment. The proposed gas atmosphere post-treatment strategy opens a window for designing next generation MOF-related gas separation membranes.