The polymeric upper bound for N 2 /NF 3 separation and beyond; ZIF-8 containing mixed matrix membranes

Park, Sung-Hwan; Kang, Woo Ram; Kwon, Hyuk Taek; Kim, Soobin; Seo, Myungeun; Bang, Joona; Lee, Sang Hyup; Jeong, Hae Kwon; Lee, Jong Suk

doi:10.1016/j.memsci.2015.03.030

Cited by 17 publications

(7 citation statements)

References 64 publications

(93 reference statements)

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“…The ligand exchange molar ratio for ZIF-8 powders is 4.5 %. This value is lower than the exchange degree of MIM ligands in ZIF-8 by DMBIM (9.1% ) [36] and ICA (24.1-27.9 %) [45]. Yang and co-workers [36] reported the ligand exchange of bulky DMBIM with MIM in the ZIF-8 structure occurs at the outmost surface of the crystallites.…”

Section: Ligand Exchange Modification On Zif-8 Crystals and Membranesmentioning

confidence: 84%

“…Thus, it can be anticipated that the larger the crystallites are, the lower ligand exchange ratio is in ligand exchange reaction. The ZIF-8 crystal sizes in Ref [36] and Ref [45] are 60 nm and 100 nm, respectively. So, the lower ligand exchange ratio in this work can be attributed to larger size of parent ZIF-8 crystals (4 μm in Fig.1(a) For ZIF-8 membrane, the integrity of membrane is of particular importance as surface modification would impair the tight packing of intergrown grains in the ZIF-8 layer.…”

Section: Ligand Exchange Modification On Zif-8 Crystals and Membranesmentioning

confidence: 99%

“…They found that the outermost MIM ligands in ZIF-8 crystals were substituted by DMBIM, and ZIF-8 was endowed with better hydrophobic properties. This approach was also applied for partial exchange of MIM ligand in ZIF-8 by ICA ,which results in more rigid polymer chains between polyimide matrix and ZIF-8 particles when used as N 2 /NF 3 separation membrane [45].…”

Section: Introductionmentioning

confidence: 99%

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Improving hydrostability of ZIF-8 membranes via surface ligand exchange

Zhang

James

Zhao³

et al. 2017

Journal of Membrane Science

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Zeolitic imidazolate frameworks (ZIFs) are promising materials for gas and liquid separations due to their unique pore structures and tunable surface properties. Recent studies show that ZIF crystalline powders, especially membranes, are not stable in aqueous solutions. The present work shows the improvement of ZIF-8 crystal and membrane stability in water through utilization of a ligand exchange post-modification method which replaces methylimidazole ligands on the outer surface of ZIF-8 crystals or membranes by the more hydrophobic, bulkier 5,6-dimethylbenzimidazole. Ligand exchange modification does not change the crystal structure, morphology or gas permeance as shown ZIF-8 powder and membrane characterization experiments. The modified ZIF-8 powders and membranes retain identical morphologies and crystallinities after static and dynamic water immersion. The modified ZIF-8 membrane exhibits stable water pervaporation flux controlled by the ZIF-8 layer while the unmodified ZIF-8 membrane experiences dissolution of the ZIF-8 layer during water pervaporation. This ligand exchange strategy enables hydrostable ZIF-8 membranes for practical applications involving aqueous solutions.

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Section: Ligand Exchange Modification On Zif-8 Crystals and Membranesmentioning

confidence: 84%

Section: Ligand Exchange Modification On Zif-8 Crystals and Membranesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Improving hydrostability of ZIF-8 membranes via surface ligand exchange

Zhang

James

Zhao³

et al. 2017

Journal of Membrane Science

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“…Although the upperbound concept as originally formulated only applies to homogeneous polymer membranes, comparing permeability and selectivity data on upperbound plots remains a popular way to gauge membrane material performance. In addition to the upper-bound pairs possible from the six gases noted above, upper-bound relationships have been reported for other important gas pairs, such as propylene/propane (36), ethylene/ethane (37), and N 2 /NF 3 (38).…”

Section: Origin Of the Permeability-selectivity Trade-offmentioning

confidence: 87%

Maximizing the right stuff: The trade-off between membrane permeability and selectivity

Park

Kamcev

Robeson

et al. 2017

Science

2,184

1,530

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Increasing demands for energy-efficient separations in applications ranging from water purification to petroleum refining, chemicals production, and carbon capture have stimulated a vigorous search for novel, high-performance separation membranes. Synthetic membranes suffer a ubiquitous, pernicious trade-off: highly permeable membranes lack selectivity and vice versa. However, materials with both high permeability and high selectivity are beginning to emerge. For example, design features from biological membranes have been applied to break the permeability-selectivity trade-off. We review the basis for the permeability-selectivity trade-off, state-of-the-art approaches to membrane materials design to overcome the trade-off, and factors other than permeability and selectivity that govern membrane performance and, in turn, influence membrane design.

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“…Neat polymeric membranes were fabricated by using a knife-casting method on the flat and clean glass plate and then immediately dried at 180 o C under vacuum for 12 h. The formed thin films were peeled off from the glass plate and further dried at the same conditions for 12 h. Molecular sievecontaining polymer solutions were prepared by the "priming" method, which can be found elsewhere [19]. Each particle was dispersed in 70 wt % of the total NMP by water bath sonicator (MUJIGAE, South Korea) with a power of 100 W for 1 h. It should be noted that the interaction between nanoparticles and solvent plays a role in uniformly dispersing nanoparticles in solvent [20]. Our previous work exhibited that commercial ZIF-8 particles were well-dispersed in NMP while they were agglomerated in both chloroform (CHCl3) and tetrahydrofuran (THF) [20].…”

Section: Fabrication Of Dense Filmsmentioning

confidence: 99%

A new superior competitor for exceptional propylene/propane separations: ZIF-67 containing mixed matrix membranes

Park

Kwon

et al. 2017

Journal of Membrane Science

Self Cite

102

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Recently, the ZIF-67 molecular sieve has emerged as an excellent substitute for the ZIF-8 counterpart due to its potentially high C3H6/C3H8 separation performance. Here, for the first time, we investigated the effect of ZIF-67 in mixed matrix membranes (MMMs) for C3H6/C3H8 separations by integrating them into 6FDA-DAM polymeric matrix. The 6FDA-DAM/ZIF-67 (80/20 wt/wt) MMMs achieved an ideal selectivity of 29.9 and a separation factor of 19 under single and equimolar mixed gas conditions, respectively, at 35 °C. The intrinsic C3H6/C3H8 separation performance of ZIF-67 was estimated from our experimental transport results based on the Maxwell model. The calculation demonstrated its superior C3H6/C3H8 selectivity of 251, which is twice of that of ZIF-8, supporting the high molecular sieving capacity of ZIF-67 containing MMMs. Moreover, a thorough investigation on the temperature-dependent gas transports elucidated that the energetic selectivity is a major contributor for the high C3H6/C3H8 diffusivity selectivity in ZIF-67 containing MMMs, although the minimum aperture size of 4.5 Å of ZIF-67 substantially sacrificed the C3H6/C3H8 entropic selectivity. Lastly, the defect-free incorporation of ZIF-67 nanoparticles into 6FDA-DAM polymer matrix effectively retarded physical aging process, maintaining the excellent separation performance of the associated MMMs for 75 days.

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The polymeric upper bound for N 2 /NF 3 separation and beyond; ZIF-8 containing mixed matrix membranes

Cited by 17 publications

References 64 publications

Improving hydrostability of ZIF-8 membranes via surface ligand exchange

Improving hydrostability of ZIF-8 membranes via surface ligand exchange

Maximizing the right stuff: The trade-off between membrane permeability and selectivity

A new superior competitor for exceptional propylene/propane separations: ZIF-67 containing mixed matrix membranes

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