Constructing Thin and Cross-Linked Polyimide Membranes by Interfacial Reaction for Efficient CO2 Separation

At present, the glassy polymeric membrane technology for CO2 separation is still confronted with a predicament that it is still difficult to fabricate membranes with both high CO2 permeance and high gas selectivity. Fortunately, newly developed thin film composite membranes (TFC) (∼100 nm) can facilitate high CO2 permeation by minimizing gas trans-membrane resistance and macrovoid defects. Herein, a novel TFC membrane containing a thin polyimide (PI) selective layer on a PDMS-modified PSf substrate was successfully constructed in situ by an interfacial cross-linking reaction between the amine-end-capped PI oligomer and the trimesoyl chloride (TMC) in a mild solvent system. The thickness of the thin PI selective layer is in the range of 103–485 nm and can be optimized by adjusting the interfacial polymerization parameters such as the TMC concentration. The resultant TFC membrane comprising a polyimide selective layer exhibits an optimum CO2 permeance of 330 GPU with the CO2/N2 and CO2/CH4 ideal selectivities of 30 and 32, respectively. It is an obvious improvement in CO2 separation performance compared with conventional PI flat membrane. In addition, these membranes also show an excellent plasticizing resistance and long-term stability attributed to the cross-linking structure and thin nature. It is expected that this TFC membrane structure combined with its facile fabricating process can facilitate the development of thin glassy polymeric membranes for CO2 separation.