Surface Cross-Linking of ZIF-8/Polyimide Mixed Matrix Membranes (MMMs) for Gas Separation

Abstract

The demand for cost-efficient separations requires membranes with high gas flux and high selectivity which opens the path for further improvements. Mixed matrix membranes (MMMs) made from 33.3 wt % ZIF-8 in 6FDA-durene were tested at 35 °C and 3.5 atm. At 33.3 wt % loading of ZIF-8, H 2 , N 2 , O 2 , and CH 4 gas permeabilities increased approximately 400%. Cross-linking the surface of this MMM, by reacting with ethylenediamine vapor, yielded a 10-fold increase in H 2 /CO 2 , H 2 /N 2 , and H 2 /CH 4 selectivities with respect to 6FDA-durene, preserving 55% of the H 2 permeability of 6FDA-durene. The permselective properties of the cross-linked skin of the MMM fall above the most recent permeability−selectivity trade-off lines (2008 Robeson upper bounds) for H 2 /CO 2 , H 2 /N 2 , and H 2 /CH 4 separations. To the best of our knowledge, this is the first example of a cross-linked ZIF/polymer MMM for gas separation.

High performance mixed matrix membranes (MMMs) composed of ZIF-94 filler and 6FDA-DAM polymer

“…Therefore, the region of optimal membrane properties for the separation of CO 2 from flue gas identified by Merkel et al [69] can be amply reached with any of the MMMs prepared in this work (10-40 wt% ZIF-94 loading). [36], (d) PMDA-ODA/HKUST-1 [64], (e) 6FDA-DAM:DABA 4:1 /ZIF-8 [22], (f) Pebax®/ZIF-8 [26], (g) 6FDA-durene/ZIF-8 [24], (h) PDMS/CPO-27(Mg) [36], (i) 6FDA-durene/ZIF-8 [23], (j) PDMS/HKUST-1 [65], (k) 6FDA-4MPD/[Zn 2 (bdc) 2 (dabco)]·4DMF·0.5H 2 O [66], (l) PDMS/[Zn 2 (bdc) 2 (dabco)]· 4DMF·0.5H 2 O [66], (m) 6FDA-durene/ZIF-71 [25] and (n) PIM-1/ZIF-8 [67]. Separation performance of 6FDA-DAM MMMs reported in literature is represented by △ [59] and □ [36].…”

“…At 20 wt% loading, the membrane permeability increased by 2.5 times over the neat polymer membrane, with only a modest 9.4% loss in CO 2 /N 2 selectivity. ZIF-8 was also used as filler by Nafisi et al [23] and Wijenayake et al [24] for the preparation of 6FDA-durene MMMs. In both cases an increase on CO 2 permeability was observed due to polymer chain interruption and increase in fractional free volume caused by the filler, 1.5 times higher CO 2 permeability for 30 wt% ZIF-8 loaded membrane and 3.3 times higher for 33.3 wt% loaded respectively.…”

Monitoring iodine adsorption onto zeolitic-imidazolate framework-8 film using a separated-electrode piezoelectric sensor

“…With the frequency of the blank quartz resonator as the reference, the frequency decrease of SEPS with ZIF-8 film was measured to estimate the mass of film grown. The thickness of the film was calculated from the mass per area by using the density of 0.95 g/cm 3 [17]. The adsorption was started by adding 20 mg I 2 (in 1 g NaCl powder) in the box.…”

Surface-etched halloysite nanotubes in mixed matrix membranes for efficient gas separation

“…Also, introducing a cross-linkable polymer (e.g. copolyimides) and solidifying it after the cast of MMMs [35,36] or surface cross-linking the MMMs with a cross-linking agent provides more flexibility to facilitate the filler dispersion and adhesion [37]. One-pot synthesis can also be effective in dispersing nano-fillers and restraining agglomeration [38].…”