Azide‐based Cross‐Linking of Polymers of Intrinsic Microporosity (PIMs) for Condensable Gas Separation

Abstract

Cross‐linked polymers of intrinsic microporosity (PIM)s for gas separation membranes, were prepared by a nitrene reaction from a representative PIM in the presence of two different diazide cross‐linkers. The reaction temperature was optimized using TGA. The homogenous membranes were cast from THF solutions of different ratios of PIM to azides. The resulting cross‐linked structures of the PIMs membranes were formed at 175 °C after 7.5 h and confirmed by TGA, XPS, FT‐IR spectroscopy and gel content analysis. These resulting cross‐linked polymeric membranes showed excellent gas separation performance and can be used for O2/N2 and CO2/N2 gas pairs, as well as for condensable gases, such as CO2/CH4, propylene/propane separation. Most importantly, and differently from typical gas separation membranes derived from glassy polymers, the crosslinked PIMs showed no obvious CO2 plasticization up to 20 atm pressure of pure CO2 and CO2/CH4 mixtures. magnified image

Polymers of Intrinsic Microporosity

“…It is possible that cross-linking may help to solve this problem and produce membranes that can function reliably over their expected lifetime (3-5 years). Cross-linking of PIM-1 has been achieved by thermal processing [131], UV treatment [132], and the reaction of azides [133]. In addition to enhancing mechanical robustness and reducing ageing, cross-linking [131,132] has been shown to provide gas permeabilities that lie above the Robeson upper bound (although formally the Robeson plot is only for solution processable polymers).…”

Enhanced propylene/propane separation by thermal annealing of an intrinsically microporous hydroxyl-functionalized polyimide membrane

“…KAUST-PI-1 exhibited a C 3 H 6 /C 3 H 8 selectivity of 16 with the highest C 3 H 6 permeability of any polyimide reported to date of 817 Barrer, positioning it well above the experimentally observed upper bound. The only other reported works using PIMs for C 3 H 6 /C 3 H 8 separation were conducted with pristine, aged, annealed, and covalently cross-linked variations of ladder-type PIM-1 showing permeabilitydriven performance, with low to moderate selectivities in the range of 2.5 to 9 [30] [31].…”

Pure- and mixed-gas propylene/propane permeation properties of spiro- and triptycene-based microporous polyimides

“…Only a few studies on PIMs, specifically the prototypical ladder-type PIM-1, have revealed outstanding vapor/gas separation properties [26,27]. Additionally, two studies investigated the C 3 H 6 /C 3 H 8 separation properties of PIM-1 in its pristine, annealed, and covalently crosslinked states and demonstrated permeability-driven performance enhancements (ranging from 18 to ~8,000 Barrer) at the expense of selectivity (ranging from 2.5 to 9) [28,29]. However, the latter studies reported only pure-gas data measured at 1-2 bar.…”