Subscriber access provided by University of Colorado Boulder
Letter
Continuous Flow Processing of ZIF-8 Membranes on Polymeric Porous Hollow Fiber Supports for CO2 Capture Anne M. Marti, Wasala Wickramanayake, Ganpat Dahe, Ali Sekizkardes, Tracy L. Bank, David P. Hopkinson, and Surendar R. Venna ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b16297 • Publication Date (Web): 08 Feb 2017 Downloaded from http://pubs.acs.org on February 9, 2017
Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.
ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.
Continuous Flow Processing of ZIF-8 Membranes on Polymeric Porous Hollow Fiber Supports for CO2 Capture Anne M. Marti*,a,b, Wasala Wickramanayakea,c, Ganpat Dahea,b, Ali Sekizkardesa,b, Tracy L. Banka,c, David P. Hopkinsona, and Surendar R. Venna*,a,c a
DOE National Energy and Technology Laboratory (NETL), Pittsburgh, PA 15236, USA
b
Oak Ridge Institute for Science and Education, Pittsburgh, PA 15236, USA
c
AECOM Pittsburgh, PA 15236, USA
KEYWORDS Inorganic membranes, Gas separation, ZIF-8 continuous film, porous hollow fiber support, environmental friendly synthesis
ABSTRACT
We have utilized an environmentally friendly synthesis approach for the accelerated growth of a selective inorganic membrane on a polymeric hollow fiber support for post combustion carbon capture. Specifically, continuous defect-free ZIF-8 thin films were grown and anchored using continuous flow synthesis on the outer surface of porous supports using water as solvent. These membranes demonstrated CO2 permeance of 22 GPU and the highest reported CO2/N2 selectivity of 52 for a continuous flow synthesized ZIF-8 membrane.
1
CO2 emissions produced from the combustion of fossil fuels is one of the most significant factors contributing to global climate change.1 The National Energy Technology Laboratory (NETL), an affiliate of the U.S. Department of Energy (DOE), is developing advanced technologies to improve CO2 capture materials and processes to enable the reduction of energy production related greenhouse gas emissions.2 Processes currently under investigation by the DOE include post-combustion, precombustion and oxy-fuel combustion CO2 capture. Post-combustion carbon capture from coal derived flue gas involves the separation of CO2 (~10-16 %) from N2, H2O, and other contaminants including SOx and NOx. Amine chemistry is commonly used for post-combustion CO2 capture due to its strong affinity for CO2 even at low concentrations, however this is paired with a high regeneration energy penalty, equipment corrosion, and degradation.3,4 Therefore alternative carbon capture technologies are under investigation. Membrane separation is potentially a more energy efficient and cost effective alternative that has been gaining momentum within the scientific community.4 One advantage of membranes is the passive nature of gas separation with no heat regeneration of the capture media and the potential to be retrofitted to an existing power plant as a true bolt-on technology. Polymer membranes have the additional benefits of being inexpensive and easy to manufacture. However, polymer membranes have well documented performance limitations, including a tradeoff between the gas permeability and selectivity.5 Therefore, researchers have modified polymeric membranes with the addition of filler particles forming continuous dense films known as mixed matrix membranes (MMMs). Such membranes improve both CO2 permeability and selectivity while taking advantage of the processability of a polymer with the high gas separation performance of the fillers such as zeolites,6 or metal organic frameworks (MOFs).7 They can be fabricated via direct mixing,8-10 or using in-situ growth methods.11-13 These processes involves several time consuming and labor intensive steps which are difficult to scale up, causing implementation of MMMs in industry to remain a challenge. MOFs, first introduced to the scientific community by 2
Omar Yaghi,14 are promising filler materials, as they can possess high surface areas, controllable pore sizes, permanent porosity, and exceptional gas affinities. The fabrication of pure MOF membranes is typically done on ceramic porous supports, which are also processed via direct growth,15 secondary growth using seeds,16 and using in-situ growth methods.17 But the processing of these pure MOF membranes requires aggressive synthetic conditions (high pressure and temperature) and the ceramic supports are expensive and mechanically weak, making them difficult to assemble into large, multimembrane modules. From these drawbacks it is challenging to implement them as CO2 separation materials, as cost and reliability dictate their usefulness in the field. Here our goal is to process a thin continuous inorganic membrane within or on top of a less-costly polymeric support in a single step while showing the improved gas separation performance compared to MMMs and ceramic-supported MOF membranes. Here we demonstrated an improved process for forming a selective membrane that is simple, inexpensive, and environmentally benign. Most importantly, we have achieved the highest reported selectivity for CO2/N2 in a ZIF-8 membrane that was fabricated by this method, demonstrating the practical viability of this synthetic technique. Continuous flow synthesis is a method to fabricate membranes while minimizing the number of preparation steps, and thereby reducing costs.18 For example, Aguado et al.19 demonstrated the successful growth of NaA zeolite using continuous flow along the inner side of alumina tubular supports. Kong et al.20 then grew ZIF-8 on the inner side of an alumina tubular support using continuous flow; by flowing both reagents through the alumina tube, direct MOF growth occurred and was tested for H2/N2 and H2/CH4 separation. Ceramic supports, however, are high cost and difficult to scale up. On the other hand, the fabrication of such membranes on polymeric hollow fibers (HFs) have many advantages such as high surface area to volume ratio and very good mechanical properties. Brown et al.21 fabricated ZIF-8 films (~8.8 µm thickness) on a polymeric HF support at the interface of two immiscible solvents. They were able to control the position of the selective layer within the support by 3
adjusting the precursor concentration and solvent locations. They tested these membranes with ZIF-8 on the inner surface of the polymeric support for H2/C3H8 and C3H6/C3H8. Eum et al.22 later refined the flow synthesis technique described by Brown et al.21 and obtained higher performance for H2/C3H8 and C3H6/C3H8 with thinner ZIF-8 films (~5 µm thickness). In addition, different continuous flow fabrication routes have been applied for other MOF/polymeric support systems.23-25 As described in these reports, minimal synthetic steps were needed for the fabrication of such membranes, making this a promising technique for industrial production. In this work, using a modified continuous flow synthesis technique we report the growth of ZIF-8 on the outer surface of a HF and its gas separation evaluated for post combustion carbon capture. Most importantly, here we used an environmentally friendly solvent (water) for the fabrication of ZIF-8 membranes. Torlon®, a polyimide-amide polymer, was used as the porous HF support (Figure S1). Torlon® support is chemically resistant to many solvents and does not dissolve in solvents like chloroform, THF, Toluene, MEEK etc. Torlon® hollow fiber support is a very mechanically strong support which can withstand high pressures without plasticization (~ 30 bar). These Torlon® HF supports have an outer diameter of ~400 µm, and a wall thickness of ~ 100 µm; they are highly permeable to CO2 and N2 with Knudsen selectivity. ZIF-8 was grown on Torlon® using continuous flow, where aqueous zinc nitrate solution was flowed on the shell side of HF, and an aqueous 2methylimidazole solution, MeIm, was flowed through the bore at a flow rate of 0.25 and 0.13 ml/min respectively as shown in Figure 1A. The detailed synthesis procedure can be found in the supporting information. The MOF growth was controlled by three parameters; 1) ZIF-8 reagent locations, 2) solvent medium, and 3) flow rate. First, the reagent locations for MOF film growth were chosen based on results from Brown et al.21 They determined that the membrane location is dictated by the Zn2+ reagent location. To confirm this, we flowed Zn2+ along the shell side (0.25 ml/min) of the HF and the linker through the bore (0.13 4
ml/min), upon which we observed the formation of ZIF-8 on the outer surface of HF. As a control, we switched the locations of Zn2+ and MeIm solutions while keeping the same flow rates, which resulted in ZIF-8 being formed on the inner surface of HF. Therefore for our study we chose to flow Zn2+ along the shell side of the HF and MeIm through the bore in order to form ZIF-8 on the outer surface (Figure 1). Forming the selective layer on the outside surface has several advantages compared to the inner surface such as higher surface area and minimal pressure drop in a module with feed gas on the shell side, which is typical in industrial applications. Membranes on the outer surface of porous support can also withstand higher pressures without delamination under a shell side feed, as opposed to membranes formed on the inner surface which tend to collapse inwards.
Figure 1. (A) Processing of supported ZIF-8 hollow fiber membrane. (B) Cross section diagram showing the hollow core, porous Torlon® structure, and ZIF-8 on the surface of the support. The second parameter controlling MOF growth was the choice of solvent for the metal salt and linker reagents. Brown et al.21 and Eum et al.22 used two immiscible solvents for flow synthesis; here the MOF film is fabricated at the interface of the two solutions.26 However, we require a selective film that is 5
strongly bound to the flexible HF support on the outer surface. Typically to achieve this, intermediate steps such as reactive seeding would be implemented to ensure anchoring of the selective film to the support.27 Intermediate synthetic steps can result in increased costs and lengthy fabrication schemes, which are not ideal for our desired process. Also, using organic solvents for the reagents may swell and damage the polymer support. Here, we showed that ZIF-8 can be prepared on a polymeric hollow fiber support by using aqueous solvents. The resulting ZIF-8 selective layer had two different regions along the outer edge of the porous HF support (Figure 2). ZIF-8 grew within the microstructure of porous support as well as a dense film with crystal like characteristics on the outer surface as shown in the energy dispersive X-ray (EDX) mapping. As demonstrated in Figure S2 (green box) there is a high carbon and low zinc content (weight %) for ZIF-8 that grew in the porous support micro-structure. By comparison, at the outer surface of the HF, we observe a decrease in the carbon content by ~20 % and an increase in the amount of zinc by ~25 % (Table S1). From these composition breakdowns, we estimate that the microstructure of the HF contains carbon from both Torlon® and ZIF-8; whereas the HF outer surface is mostly ZIF-8 due to the higher zinc content. This structure is beneficial for our application, as we hypothesize that the ZIF-8 within the microstructure acts as an anchor for ZIF-8 film on the outer surface of the support thus counteracting delamination of the ZIF-8 layer. The third parameter for flow synthesis, the reagent flow rate, influences where the ZIF-8 selective layer forms along the fiber wall. We determined that by varying the aqueous reagent flow rate, the morphology and film thickness can be refined. Three different flow rates were tested for the flow synthesis of ZIF-8: 0.1/0.1, 0.25/0.13, and 0.5/0.5 ml/min of Zn2+/MeIm linker (Table S2). Using a flow rate of 0.1/0.1 ml/min, no dense ZIF-8 film was observed on the outer HF surface (Figure S3). The morphology resembled ZIF-8 powder, and it was difficult to define the thickness of the film as the ZIF8 appeared to be present throughout the entire cross section of the HF. Next the flow rate was increased to Zn2+ to 0.25/0.13 ml/min (Figure 2). The ZIF-8 film was grown within the microstructure of the 6
Torlon® HF and has a dense film on the outer surface. The overall thickness of the ZIF-8 film was determined by taking multiple SEM measurements from 3 different membranes to be ~8.5 ± 0.5 µm. The ZIF-8 film within the microstructure had a thickness of 2.5 µm, while the dense film on the outer surface of the HF was 6 µm. Following this, the flow rate was increased to 0.5/0.5 ml/min to determine if there is an upper flow rate limit for the formation of such membranes. We observed only a dense ZIF8 film on the outer surface of the HF using the higher flow rate; no ZIF-8 was observed within the
polymer microstructure. Such films were also extremely brittle and fractured easily (Figure S4). We believe that the brittle nature of ZIF-8 film under these conditions is due to the absence of ZIF-8 within the HF microstructure (i.e. the film anchor). As such, we expect membranes produced using the higher flow rates will yield poor gas separation properties due to selective layer defects that are likely to form during handling. As the flow rate of the bore solution increases, pressure drop in the small HF bore (~200 µm) increases and pushes the reaction interface between MeIm and Zn2+ solution toward the outside of HF. Therefore, in order to obtain the membrane at a desired cross-section of HF, it is necessary
to
maintain
an
optimum
pressure
drop
in
HF
bore.
Figure 2. Supported ZIF-8 HF membranes fabricated using a flow rate of 0.25/0.13 ml/min. SEM images shown on left, EDX mapping shown on right; purple-carbon map, green- zinc map. Porous supported ZIF-8 HF membranes were analyzed using inductively-coupled plasma – Optical Emission spectroscopy (ICP-OES) to determine the amount of ZIF-8 present within the membranes.
7
By this analysis ZIF-8 HF membranes contain 1.1 % zinc. Using SEM, the thickness of the ZIF-8 films was ~8.5 µm while the Torlon® HF wall thickness is ~100 µm. However, as ZIF-8 is 23% Zn2+ (Cambridge Crystallographic Data Center (CCDC) 602542)28 that estimates that our membranes contain ~1.9 % Zn2+ via scanning electron microscopy (SEM). From this comparison, we approximate that the ZIF-8 thickness measured via SEM is within reasonable error. Our ZIF-8 HF membranes were also examined using XRD (Figure 3). X-ray diffraction (XRD) results confirm that ZIF-8 was indeed grown on the support as the experimental reflections correspond to reported ZIF-8 powder reflections of highest intensity.28 The peak intensity of the ZIF-8 membranes on the porous support were weak compared to peak intensity of the ZIF-8 powder. The similar decrease in peak intensity was observed by several literature reports.20,21,23 N2 adsorption measurements were completed at 77K (Figures S5 and S6) in order to determine if any changes occurred to the surface area and porosity of the HF support upon ZIF-8 growth and are described in detail in supporting information. We observed a decrease in the surface area of Torlon ® HFs upon ZIF-8 growth by 30 %. The decrease in surface area suggests that the ZIF layer is forming on the surface of the support, since the monolayer capacity is reduced. The pore size distribution was also calculated using the Density Functional Theory (DFT) models and Horvath-Kawazoe (HK) method. No substantial changes were observed upon ZIF-8 growth using DFT methods (Figure S7), however the HK particle size distribution method (Figure S8) shows the generation of microporosity within Torlon® support upon ZIF-8 growth (Figure S8).
8
Figure 3. XRD patterns of ZIF-8, CCDC 602542 (black), as synthesized ZIF-8 (blue), and ZIF-8 HF membrane (red). The * represents the by-product, zinc hydroxide nitrate hydrate. Our goal for these ZIF-8 membranes is to capture CO2 from post-combustion flue gas which contains mostly N2. Therefore, the gas separation properties of thin hollow fiber ZIF-8 membranes were evaluated with an equimolar mixture of CO2 and N2 (20 mol% CO2, 20 mol% N2, balance Ar) using an isobaric permeation system at room temperature. The pressure drop across the membrane was 4 psi with an upstream pressure of 22.7 psia and downstream pressure of 18.7 psia. The detailed testing procedure was described in the supporting information. Torlon®, the polymer support material, is highly permeable compared to the membrane and has negligible resistance to gas flux. Torlon® HFs had a CO2 permeance of 81,300 GPU with an ideal selectivity for CO2/N2 of 0.83. The supported ZIF-8 HF membranes showed a CO2 permeance of 22 GPU with an ideal selectivity for CO2/N2 of 52, a notably high selectivity for CO2/N2 (Table S3). In comparison, ZIF-8 was grown on the inside of a porous polymeric support by Cacho-Bailo et al.23 These membranes showed CO2 permeance of 4.8 GPU and a selectivity for CO2/N2 of 7.1. Kong et al.20 synthesized ZIF-8
9
membranes (thickness ~2.5µm) on porous alumina supports using the flow synthesis method which showed a CO2 permeance of ~4x10-7 mol/m2.s.pa, which is equal to 1200 GPU (1 GPU = 3.35 x 1010
mol/m2.s.pa) , but the CO2/N2 selectivity was only ~ 2.7. Also, this study proved that continuous
flow synthesis of supported MOF membranes yielded higher performance than traditional seeding/solvo-thermal growth methods to achieve the same. For example, Brown et al.29 used dip coating technique to fabricate ZIF-90 seeds on a Torlon® support followed by solvo-thermal growth of ZIF-90 membranes on a porous support and observed a low CO2/N2 selectivity of 3.5 with CO2 permeance of ~300 GPU. Brown et al were also prepared ZIF-8 membrane on polymer support and used for propylene/propane separation.21 In this work, we have successfully fabricated, characterized, and tested a supported MOF HF membrane that demonstrated potential to be used as for CO2/N2 separation in post-combustion carbon capture. The continuous flow process is a unique alternative method to traditional membrane fabrication (solvo-thermal processes) that is simple, scalable, reduces manufacturing costs, and is environmentally friendly. Most importantly, the high selectivity that was achieved suggests that it may be the first time that this method has been used to produce a defect-free selective layer. We have started implementing this approach with other materials as well, and anticipate testing the results using a slipstream of actual flue gas at the National Carbon Capture Center in Wilsonville, Alabama.
Supporting Information The Supporting Information is available free of charge on the ACS Publications website. The document contains materials list, experimental and characterization description along with figures.
10
AUTHOR INFORMATION Corresponding Author *
[email protected],
[email protected], Phone: 412-386-4909 Funding Sources This work was supported as part of the Center for Gas Separations Relevant to Clean Energy Technologies, an Energy Frontier Re-search Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0001015 (membrane fabrication), U.S. Department of Energy’s National Energy Technology Laboratory under the contract DEFE0004000 (characterization of membranes). Acknowledgment We thank Michael Gipple of Smart Data Solutions (NETL,) for his assistance with the table of contents graphic.
REFERENCES (1) Monastersky, R. Global Carbon Dioxide Levels near Worrisome Milestone. Nature 2013, 497, 13-14. (2) Orr, F. M. Addressing Climate Change with Clean Energy Technology. ACS Energy Lett. 2016, 113-114. (3) Zhao, S.; Feron, P. H. M.; Deng, L.; Favre, E.; Chabanon, E.; Yan, S.; Hou, J.; Chen, V.; Qi, H. Status and Progress of Membrane Contactors in Post-combustion Carbon Capture: A State-of-theArt Review of New Developments. J. Membr. Sci. 2016, 511, 180-206.
11
(4) Merkel, T. C.; Lin, H.; Wei, X.; Baker, R. Power Plant Post-combustion Carbon Dioxide Capture: An Opportunity for Membranes. J. Membr. Sci. 2010, 359, 126-139. (5) Robeson, L. M. The Upper Bound Revisited. J. Membr. Sci. 2008, 320, 390-400. (6) Zhao, L.; Chen, Y.; Wang, B.; Sun, C.; Chakraborty, S.; Ramasubramanian, K.; Dutta, P. K.; Ho, W. S. W. Multilayer Polymer/zeolite Y Composite Membrane Structure for CO2 Capture from Flue Gas. J. Membr. Sci. 2016, 498, 1-13. (7) Li, W.; Zhang, Y.; Li, Q.; Zhang, G. Metal-organic Framework Composite Membranes: Synthesis and Separation Applications. Chem. Eng. Sci. 2015, 135, 232-257. (8) Venna, S. R.; Lartey, M.; Li, T.; Spore, A.; Kumar, S.; Nulwala, H. B.; Luebke, D. R.; Rosi, N. L.; Albenze, E. Fabrication of MMMs with Improved Gas Separation Properties using ExternallyFunctionalized MOF Particles. J. Mater. Chem. A 2015, 3, 5014-5022. (9) Su, N. C.; Sun, D. T.; Beavers, C. M.; Britt, D. K.; Queen, W. L.; Urban, J. J. Enhanced Permeation Arising from Dual Transport Pathways in Hybrid Polymer-MOF Membranes. Energy Environ Sci 2016, 9, 922-931. (10) Denny, M. S.; Cohen, S. M. In Situ Modification of Metal–Organic Frameworks in MixedMatrix Membranes. Angew. Chem., Int. Ed. 2015, 54, 9029-9032. (11) Shahid, S.; Nijmeijer, K.; Nehache, S.; Vankelecom, I.; Deratani, A.; Quemener, D. MOFMixed Matrix Membranes: Precise Dispersion of MOF Particles with Better Compatibility via a Particle Fusion Approach for Enhanced Gas Separation Properties. J. Membr. Sci. 2015, 492, 21-31.
12
(12) Rodenas, T.; Luz, I.; Prieto, G.; Seoane, B.; Miro, H.; Corma, A.; Kapteijn, F.; Llabrés i Xamena, F. X.; Gascon, J. Metal–Organic Framework Nanosheets in Polymer Composite Materials for Gas Separation. Nat. Mater. 2015, 14, 48-55. (13) Campbell, J.; Szekely, G.; Davies, R. P.; Braddock, D. C.; Livingston, A. G. Fabrication of Hybrid Polymer/Metal Organic Framework Membranes: Mixed Matrix Membranes versus in situ Growth. J. Mater. Chem. A 2014, 2, 9260-9271. (14) Li, H. L.; Eddaoudi, M.; O'Keefe, M.; Yaghi, O. M. Design and Synthesis of an Exceptionally Stable and Highly Porous Metal-Organic Framework. Nature 1999, 402, 276-279. (15) Li, W.; Yang, Z.; Zhang, G.; Fan, Z.; Meng, Q.; Shen, C.; Gao, C. Stiff Metal-Organic Framework-Polyacrylonitrile Hollow Fiber Composite Membranes with High Gas Permeability. J. Mater. Chem. A 2014, 2, 2110-2118. (16) Hu, Y.; Dong, X.; Nan, J.; Jin, W.; Ren, X.; Xu, N.; Lee, Y. M. Metal-Organic Framework Membranes Fabricated via Reactive Seeding. Chem. Commun. 2011, 47, 737-739. (17) Shah, M. N.; Gonzalez, M. A.; McCarthy, M. C.; Jeong, H.-K. An Unconventional Rapid Synthesis of High Performance Metal–Organic Framework Membranes. Langmuir 2013, 29, 78967902. (18) Batten, M. P.; Rubio-Martinez, M.; Hadley, T.; Carey, K.-C.; Lim, K.-S.; Polyzos, A.; Hill, M. R. Continuous Flow Production of Metal-Organic Frameworks. Curr. Opin. Chem. Eng. 2015, 8, 5559. (19) Aguado, S.; Gascón, J.; Jansen, J. C.; Kapteijn, F. Continuous Synthesis of NaA Zeolite Membranes. Microporous Mesoporous Mater. 2009, 120, 170-176.
13
(20) Kong, L.; Zhang, X.; Liu, Y.; Li, S.; Liu, H.; Qiu, J.; Yeung, K. L. In situ Fabrication of HighPermeance ZIF-8 Tubular Membranes in a Continuous Flow System. Mater. Chem. Phys. 2014, 148, 10-16. (21) Brown, A. J.; Brunelli, N. A.; Eum, K.; Rashidi, F.; Johnson, J. R.; Koros, W. J.; Jones, C. W.; Nair, S. Interfacial Microfluidic Processing of Metal-Organic Framework Hollow Fiber Membranes. Science 2014, 345, 72-75. (22) Eum, K.; Rownaghi, A.; Choi, D.; Bhave, R. R.; Jones, C. W.; Nair, S. Fluidic Processing of High-Performance ZIF-8 Membranes on Polymeric Hollow Fibers: Mechanistic Insights and Microstructure Control. Adv. Funct. Mater. 2016, 26, 5011-5018. (23) Cacho-Bailo, F.; Catalán-Aguirre, S.; Etxeberría-Benavides, M.; Karvan, O.; Sebastian, V.; Téllez, C.; Coronas, J. Metal-Organic Framework Membranes on the Inner-Side of a Polymeric Hollow Fiber by Microfluidic Synthesis. J. Membr. Sci. 2015, 476, 277-285. (24) Cacho-Bailo, F.; Caro, G.; Etxeberria-Benavides, M.; Karvan, O.; Tellez, C.; Coronas, J. High Selectivity ZIF-93 Hollow Fiber Membranes for Gas Separation. Chem. Commun. 2015, 51, 1128311285. (25) Cacho-Bailo, F.; Caro, G.; Etxeberria-Benavides, M.; Karvan, O.; Tellez, C.; Coronas, J. MOFPolymer Enhanced Compatibility: Post-annealed Zeolite Imidazolate Framework Membranes Inside Polyimide Hollow Fibers. RSC Advances 2016, 6, 5881-5889. (26) Huang, K.; Li, Q.; Liu, G.; Shen, J.; Guan, K.; Jin, W. A ZIF-71 Hollow Fiber Membrane Fabricated by Contra-Diffusion. ACS Appl. Mater. Interfaces 2015, 7, 16157-16160.
14
(27) Hou, J.; Sutrisna, P. D.; Zhang, Y.; Chen, V. Formation of Ultrathin, Continuous Metal-Organic Framework Membranes on Flexible Polymer Substrates. Angew. Chem., Int. Ed. 2016, 55, 39473951. (28) Park, K. S.; Ni, Z.; Côté, A. P.; Choi, J. Y.; Huang, R.; Uribe-Romo, F. J.; Chae, H. K.; O'Keeffe, M.; Yaghi, O. M. Exceptional Chemical and Thermal Stability of Zeolitic Imidazolate Frameworks. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 10186-10191. (29) Brown, A. J.; Johnson, J. R.; Lydon, M. E.; Koros, W. J.; Jones, C. W.; Nair, S. Continuous Polycrystalline Zeolitic Imidazolate Framework-90 Membranes on Polymeric Hollow Fibers. Angew. Chem., Int. Ed. 2012, 51, 10615-10618.
Table of Content Graphic:
15
16
