Abstract
Mixed matrix membranes (MMMs) based on three distinctively different MOFs (MIL-53(Al) (breathing MOF), ZIF-8 (flexible MOF) and Cu3BTC2 (rigid MOF)) dispersed in Matrimid®-PI have been investigated. MOF loading was varied between 0 wt% and 30 wt%. The fabricated MOF-MMMs were characterized for pure and binary gas mixture separations at low and high pressures and their performance in terms of CO2 permeability and CO2/CH4 selectivity was evaluated. The use of a less volatile co-solvent, optimized priming protocol to prepare the MMMs and thermal annealing resulted in a good dispersion of MOF particles in the Matrimid®-PI matrix. Incorporation of MOFs resulted in increased density, Tg and improved degradation behavior of the membranes confirming a good compatibility between the polymer and the MOFs. Low pressure gas separation showed moderate enhancement in CO2 permeability and CO2/CH4 selectivity of MOF-MMMs compared to native polymer membranes, but the improvement becomes pronounced at high pressures. At high pressures, the native Matrimid®-PI membrane showed typical plasticization behavior, while in MMMs, MOF particles limit the mobility of polymer chains thus suppressing CO2 induced plasticization and maintain large separation factors over a wide pressure range investigated. The respective increase in performance of MMMs is very much dependent on MOF crystal structure and its interactions with CO2 gas molecules. Among the three MOF-MMMs, membranes based on Cu3BTC2 showed highest selectivity while ZIF-8 based membranes showed highest permeability. In general it can be concluded that the high CO2 permeability and CO2/CH4 selectivity of MMMs is the combined effect of an increased sorption and diffusion selectivity and reduced plasticization. Overall, this work reveals that MOF-MMMs delay CO2 induced plasticization and show good separation performance even at high pressures, showing their potential to a wide range of newly emerging high pressure energy applications.
Original language | English |
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Pages (from-to) | 166-177 |
Number of pages | 12 |
Journal | Journal of Membrane Science |
Volume | 470 |
Early online date | 23 Jul 2014 |
DOIs | |
Publication status | Published - 15 Nov 2014 |
Keywords
- MOF-mixed matrix membranes
- MOF
- CO2 plasticization
- High pressure gas separation
- Matrimid