4. Conclusion
In conclusion, an ultrathin mixed
matrix composite membrane (MMCM) with NH2-ZIF-8 nanocrystals protruding
structure was successfully fabricated. Through engineering the
polyimide/MOF interfacial hydrogen or covalent bonds, the thickness of
the selective layer can be reduced to 280 or 140 nm.
The protruding MOF filler can
considerably reduce the transport resistance and promote the
CO2 permeation. As a result, the MMCMs
exhibit
a high CO2 permeance of 778 GPU and a
CO2/CH4 selectivity of 34, surpassing
most of the reported MOF-based MMMs and polyimide composite membranes
towards CO2/CH4 separation. Moreover,
due
to the robustness of the interfacial interactions between MOFs and the
polymer chains in the thin films, the MMCMs show a significantly
enhanced plasticization-resistant and aging-resistant performance at a
high CO2 partial pressure up to 20 bar and exhibit a
long-term stability for nearly one month. Overall, this work
demonstrates an efficient and general strategy to fabricate advanced
ultrathin mixed matrix composite membranes with both high separation
performance and excellent stabilities under high pressure, which hold
great potential to address many critical separation issues in chemical
industry.