Improved CO₂ separation performance and interfacial affinity of mixed matrix membrane by incorporating UiO-66-PEI@[bmim][Tf₂N] particles

This study demonstrated a new method for simultaneously improving the interfacial morphology and gas separation properties of mixed matrix membrane by designing a new type of nanocomposite filler (UiO-66-PEI@[bmim][Tf₂N]). Nano-sized UiO-66 particle was post-synthetically modified with branched polyethyleneimine (PEI) and then was decorated with ionic liquid. The abundant amino groups in UiO-66-PEI improve the gas separation properties of the MMM due to the affinity between PEI and CO₂. The ionic liquid acts as a lubricant agent, which is coated on the crystal surface improves the interface morphology of the MMM. Compared to pristine 6FO and MOF/6FO membrane, MOF@IL/6FO membrane has higher gas separation performance. Characterization and gas separation results indicated the UiO-66-PEI@ILs particles were homogeneous dispersed in 6FDA-ODA and promoted CO₂ transport by reversible reaction with amine groups. Consequently, the membrane sample containing 15 wt% loading of the UiO-66-PEI@[bmim][Tf₂N] filler displayed an optimum CO₂/CH₄ selectivity of 59.99 for CO₂ and CH₄ mixture gas.