Building ternary mixed matrix membranes with ionic liquid-functional COF fillers for efficient CO2 separation

Developing novel mixed matrix membranes (MMMs) with high CO₂ permeability and selectivity, while overcoming the limitations of traditional MMMs, presents a significant challenge. Herein, we reported a simple and straightforward method to develop ternary mixed matrix membranes (TMMMs) featuring excellent matrix-filler compatibility for CO₂ separation through the modification of the covalent organic framework (COF) using ionic liquid (IL) additives. A novel IL ([Bmim][Tf₂N]) encapsulated COF filler (IL@TpTta-COF) was facilely prepared, and incorporated into the PIM-1 matrix to develop a series of TMMMs.The incorporation of ILs with high affinity towards CO₂ within the TpTta-COF improves the molecular sieving effect of the functional filler, and helps to enhance polymer-filler interfacial compatibility, and mitigates particle agglomeration during the preparation of TMMMs. Notably, the resultant TMMMs demonstrate remarkable stability, and achieve an impressive CO₂ permeability of 10,035 Barrer and an excellent selectivity of 30.2 for CO₂/N₂ mixtures, exceeding the Robeson upper bound in 2019. This research underscores the potential of integrating functional additives to produce novel COF-based MMMs with enhanced CO₂ separation efficiency for industrial applications.