Publications by authors named "Hae-Kwon Jeong"

23 Publications

  • Page 1 of 1

Delayed Linker Addition (DLA) Synthesis for Hybrid SOD ZIFs with Unsubstituted Imidazolate Linkers for Propylene/Propane and n-Butane/i-Butane Separations.

Angew Chem Int Ed Engl 2021 Apr 18;60(18):10103-10111. Epub 2021 Mar 18.

Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX, 77843-3122, USA.

We present a novel synthesis strategy termed delayed linker addition (DLA) to synthesize hybrid zeolitic-imidazolate frameworks containing unsubstituted imidazolate linkers (Im) with SOD topology (hereafter termed Im/ZIF-8). Im linker incorporation can create larger voids and apertures, which are important properties for gas storage and separation. To date, there have been only a handful of reports of Im linkers incorporated into ZIF-8 frameworks, typically requiring arduous and complicated post synthesis approaches. DLA, as reported here, is a simple one-step synthesis strategy allowing high incorporation of Im linker into the ZIF-8 framework while still retaining its SOD topology. We fabricated mixed-matrix membranes (MMMs) with 6FDA-DAM polymer and Im/ZIF-8 obtained via DLA as a filler. The Im/ZIF-8-containing MMMs showed excellent performance for both propylene/propane and n-butane/i-butane separation, displaying permeability and ideal selectivity well above the polymer upper bound. Moreover, highly detailed molecular simulations shed light to the aperture size and flexibility response of Im/ZIF-8 and its improved diffusivity as compared to ZIF-8.
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http://dx.doi.org/10.1002/anie.202015635DOI Listing
April 2021

Self-diffusion of pure and mixed gases in mixed-linker zeolitic imidazolate framework-7-8 by high field diffusion NMR.

Microporous Mesoporous Mater 2019 Nov 10;288. Epub 2019 Jul 10.

Department of Chemical Engineering, University of Florida, Gainesville, Florida 32611, USA.

Self-diffusion of pure gases including carbon dioxide, methane, ethylene, ethane, and xenon as well as selected two-component mixtures was studied in hybrid zeolitic imidazolate framework-7-8 (ZIF-7-8) crystals using pulsed field gradient (PFG) NMR. This material was formed by mixing 2-methylimidazolate (ZIF-8 linker) and bulkier benzimidazolate (ZIF-7 linker) in the same framework. The intracrystalline diffusion data measured in mixed-linker ZIF-7-8 was compared with the corresponding data in the parent ZIF-8 material. It was found that under the same or comparable experimental conditions the intracrystalline gas diffusion was always slower in ZIF-7-8 than in ZIF-8. This observation is consistent with the expected lower pore aperture size in ZIF-7-8 than in ZIF-8. At the same time, the ethane/ethylene diffusion selectivity was found to be similar in both ZIFs. It was also observed that for the pure studied gases larger than carbon dioxide the diffusivity ratios in ZIF-8 and ZIF-7-8 do not increase with increasing gas size at all loading pressures used. All these data are attributed to greater framework flexibility effects in ZIF-7-8 than ZIF-8. Such effects manifest themselves in a distortion and/or increase in the aperture size in the presence of large sorbates due to linker flexibility.
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http://dx.doi.org/10.1016/j.micromeso.2019.109603DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7441738PMC
November 2019

Highly Propylene-Selective Mixed-Matrix Membranes by in Situ Metal-Organic Framework Formation Using a Polymer-Modification Strategy.

ACS Appl Mater Interfaces 2019 Jul 11;11(29):25949-25957. Epub 2019 Jul 11.

Despite the potential of CH/CH separation, there have been no industrial applications of zeolitic-imidazole framework-8 (ZIF-8) mixed-matrix membranes (MMMs) because of the moderate separation performances and several challenging processing issues. Herein, we present a new paradigm of MMM fabrication, named polymer-modification-enabled in situ metal-organic framework formation (PMMOF), enabling in situ formation of ZIF-8 fillers inside the 4,4-(hexafluoroisopropylidene)diphthalic anhydride 2,4,6-trimethyl-1,3-phenylenediamine polymer. PMMOF consists of four steps including hydrolysis of a polymer, ion-exchange, ligand treatment, and imidization. Each step was thoroughly analyzed and important processing parameters were identified, enabling the structural control of MMMs by PMMOF. The binary CH/CH separation performance of the MMMs showed much higher separation factors than conventionally prepared MMMs at similar filler loadings, satisfying the commercial CH/CH separation performance criteria. PMMOF was successfully applied for other MOFs, demonstrating that the process could be general. Finally, as a proof of concept, asymmetric mixed-matrix hollow fiber membranes (i.d. of 0.45 mm and o.d. of 0.63 mm) with ultrathin selective skin layers were prepared by PMMOF, showing CH permeance of 2.17 GPU and CH/CH separation factor of ∼20.
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http://dx.doi.org/10.1021/acsami.9b07106DOI Listing
July 2019

Linker-Doped Zeolitic Imidazolate Frameworks (ZIFs) and Their Ultrathin Membranes for Tunable Gas Separations.

ACS Appl Mater Interfaces 2019 May 13;11(20):18377-18385. Epub 2019 May 13.

Zeolitic imidazolate frameworks (ZIFs) have gained much interest due to their potentials in gas separations. A hybrid approach by mixing metals and/or linkers has been recently investigated to fine-tune the ZIF framework porosity and surface properties and potentially extending their separation applications for many important gas mixtures. In general, the hybrid approach requires mixing of isostructural ZIFs to maintain their topology, thus limiting the options of linkers and metal centers to obtain hybrid ZIFs. Linker-doping, as reported here, can be a strategy to expand the option of imidazolate linkers to obtain mixed-linker hybrid ZIFs. Two linkers are investigated to be doped into the ZIF-8 framework: 2-ethylimidazole (eIm) and 2-phenylimidazole (phIm). The linker-doping strategy is shown to tune the "stiffness" of Zn-N bonding as characterized by FT-IR, thereby the linker flip-flopping motion of ZIF-8, which is analyzed through gas adsorption isotherms. Furthermore, well-intergrown ultrathin eIm-doped ZIF-8 membranes are grown on α-AlO substrates, in which the incorporation of eIm affects the morphology and thickness of the polycrystalline membranes, improving the permeance of propylene and propane molecules.
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http://dx.doi.org/10.1021/acsami.9b02114DOI Listing
May 2019

Nano-gate opening pressures for the adsorption of isobutane, n-butane, propane, and propylene gases on bimetallic Co-Zn based zeolitic imidazolate frameworks.

Dalton Trans 2019 Apr;48(14):4685-4695

Department of Chemical Engineering, Qatar University, P.O. Box 2713, Doha, Qatar.

In this article, zeolitic-imidazolate framework-8 (ZIF-8) and its mixed metal CoZn-ZIF-8 were synthesized via a rapid microwave method. The products were characterized by Raman spectroscopy, XPS, XRD, EDX, TEM, NanoSEM, TGA, and DSC. The gas adsorption properties of samples were determined using C3 and C4 hydrocarbons, including propane, propylene, isobutane and n-butane at a temperature of 25 °C. The adsorption equilibrium and kinetics of these gases on various ZIFs were studied. It was noted that ZIF-8 and mixed metal CoZn-ZIF-8 samples start to adsorb these gases after certain pressures which are believed to result in the opening of their nano-gates (i.e., 6-membered rings) to allow the entry of gas molecules. The nanogate opening pressure value (p0) for each ZIF towards different gases was determined by fitting adsorption equilibrium data against a modified form of the Langmuir adsorption isotherm model. It was observed that the value of p0 differs significantly for each gas and to various extents for various ZIFs. Therefore, it is possible that the distinct values of p0 afford a unique technique to separate and purify these gases at the industrial scale. The overall mass transfer coefficient values of the adsorption process were also investigated.
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http://dx.doi.org/10.1039/c9dt00222gDOI Listing
April 2019

On the Efficient Separation of Gas Mixtures with the Mixed-Linker Zeolitic-Imidazolate Framework-7-8.

ACS Appl Mater Interfaces 2018 Nov 12;10(46):39631-39644. Epub 2018 Nov 12.

Artie McFerrin Department of Chemical Engineering , Texas A&M University , College Station , Texas 77843-3122 , United States.

A recently reported modification of the zeolitic-imidazolate framework-8 (ZIF-8) with partial replacement of the 2-methylimidazolate (mIm) linker with benzimidazolate (bIm), namely ZIF-7-8, is investigated with molecular simulations using a first-time reported force field. The size of the ZIF-7-8 aperture, which governs the gas-separation efficiency of this material and which has not been estimated before for this modification, is smaller than that of the original ZIF-8. The diffusivities of CO, N, and CH estimated through transition state theory calculations result in remarkably high diffusion selectivities for CO/CH and CO/N mixtures. This performance enhancement is investigated in terms of structural flexibility in the form of the aperture motion through extensive estimation of the effective diameter, the total effective area, and the motion of the aperture linkers, of both ZIF-8 and ZIF-7-8. Both apertures exhibit an oscillation through the rotation of the linkers, which are adjusted according to the size of the penetrant molecules the moment they pass through it. Finally, a subsequent analysis reveals that there is strong dependency of the separation performance on the bIm-to-mIm ratio: below 33% bIm incorporation, the appearance of ZIF-8-alike wide apertures decreases dramatically the size-based selectivity of the mixtures in ZIF-7-8.
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http://dx.doi.org/10.1021/acsami.8b12605DOI Listing
November 2018

Ethane diffusion in mixed linker zeolitic imidazolate framework-7-8 by pulsed field gradient NMR in combination with single crystal IR microscopy.

Phys Chem Chem Phys 2018 Oct 13;20(37):23967-23975. Epub 2018 Sep 13.

Department of Chemical Engineering, University of Florida, Gainesville, FL 32611, USA.

Pulsed field gradient (PFG) NMR was used in combination with single crystal IR microscopy (IRM) to study diffusion of ethane inside crystals of a mixed linker zeolitic imidazolate framework (ZIF) of the type ZIF-7-8 under comparable experimental conditions. These crystals contain 2-methylimidazolate (ZIF-8 linker) and benzimidazolate (ZIF-7 linker). It was observed that the PFG NMR attenuation curves measured for ethane in ZIF-7-8 exhibit deviations from the monoexponential behaviour, thereby indicating that the ethane self-diffusivity in different crystals of a crystal bed can be different. Measurements of the ethane uptake curves performed by IRM under the same conditions in different ZIF-7-8 crystals of the bed yield different transport diffusivities thus confirming that the rate of ethane diffusion is different in different ZIF-7-8 crystals. The IRM observation that the fractions of ZIF-8 and ZIF-7 linkers are different in different ZIF-7-8 crystals allowed attributing the observed heterogeneity in diffusivities to the heterogeneity in the linker fraction. The quantitative comparison of the average ethane self-diffusivities measured by PFG NMR in ZIF-7-8 with the corresponding data on corrected diffusivities from IRM measurements revealed a good agreement between the results obtained by the two techniques. In agreement with the expectation of smaller aperture sizes in ZIF-7-8 than in ZIF-8, the average ethane self-diffusivities in ZIF-7-8 were found to be significantly lower than the corresponding self-diffusivities in ZIF-8.
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http://dx.doi.org/10.1039/c8cp04889dDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6190695PMC
October 2018

Computational Design of Functional Amyloid Materials with Cesium Binding, Deposition, and Capture Properties.

J Phys Chem B 2018 08 20;122(30):7555-7568. Epub 2018 Jul 20.

Department of Materials Science and Technology , University of Crete , Heraklion 700 13 , Crete , Greece.

Amyloid materials are gaining increasing attention as promising materials for applications in numerous fields. Computational methods have been successfully implemented to investigate the structures of short amyloid-forming peptides, yet their application in the design of functional amyloid materials is still elusive. Here, we developed a computational protocol for the design of functional amyloid materials capable of binding to an ion of interest. We applied the protocol in a test case involving the design of amyloid materials with cesium ion deposition and capture properties. As part of the protocol, we used an optimization-based design model to introduce mutations at non-β-sheet residue positions of an amyloid designable scaffold. The designed amino acids introduced to the scaffold mimic how amino acids bind to cesium ions according to experimentally resolved structures and also aim at energetically stabilizing the bound conformation of the pockets. The optimum designs were computationally validated using a series of simulations and structural analysis to select the top designed peptides, which are predicted to form fibrils with cesium ion binding properties for experimental testing. Experiments verified the amyloid-forming properties of the selected top designed peptides, as well as the cesium ion deposition and capture properties by the amyloid materials formed. This study demonstrates the first, to the best of our knowledge, computational design protocol to functionalize amyloid materials for ion binding properties and suggests that its further advancement can lead to novel, highly promising functional amyloid materials of the future.
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http://dx.doi.org/10.1021/acs.jpcb.8b04103DOI Listing
August 2018

Rapid One-Pot Microwave Synthesis of Mixed-Linker Hybrid Zeolitic-Imidazolate Framework Membranes for Tunable Gas Separations.

ACS Appl Mater Interfaces 2018 Feb 31;10(6):5586-5593. Epub 2018 Jan 31.

Artie McFerrin Department of Chemical Engineering and ‡Department of Materials Science and Engineering, Texas A&M University , 3122 TAMU, College Station, Texas 77843-3122, United States.

The relatively slow and complex fabrication processes of polycrystalline metal-organic framework (MOF) membranes often times restrict their way to commercialization, despite their potential for molecular separation applications. Herein, we report a rapid one-pot microwave synthesis of mixed-linker hybrid zeolitic-imidazolate framework (ZIF) membranes consisting of 2-methylimidazolate (ZIF-8 linker) and benzimidazolate (ZIF-7 linker) linkers, termed ZIF-7-8 membranes. The fast-volumetric microwave heating in conjunction with a unique counter diffusion of metal and linker solutions enabled unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes in ∼90 s, the fastest MOF membrane preparation up to date. Furthermore, we were able to tune the molecular sieving properties of the ZIF-7-8 membranes by varying the benzimidazole-to-2-methylimidazole (bIm-to-mIm) linker ratio in the hybrid frameworks. The tuning of their molecular sieving properties led to the systematic change in the permeance and selectivity of various small gases. The unprecedented rapid synthesis of well-intergrown ZIF-7-8 membranes with tunable molecular sieving properties is an important step forward for the commercial gas separation applications of ZIF membranes.
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http://dx.doi.org/10.1021/acsami.7b18506DOI Listing
February 2018

High-Flux Zeolitic Imidazolate Framework Membranes for Propylene/Propane Separation by Postsynthetic Linker Exchange.

Angew Chem Int Ed Engl 2018 01 5;57(1):156-161. Epub 2017 Dec 5.

Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, 77843-3122, USA.

While zeolitic imidazolate framework, ZIF-8, membranes show impressive propylene/propane separation, their throughput needs to be greatly improved for practical applications. A method is described that drastically reduces the effective thickness of ZIF-8 membranes, thereby substantially improving their propylene permeance (that is, flux). The new strategy is based on a controlled single-crystal to single-crystal linker exchange of 2-methylimidazole in ZIF-8 membrane grains with 2-imidazolecarboxaldehyde (ZIF-90 linker), thereby enlarging the effective aperture size of ZIF-8. The linker-exchanged ZIF-8 membranes showed a drastic increase in propylene permeance by about four times, with a negligible loss in propylene/propane separation factor when compared to as-prepared membranes. The linker-exchange effect depends on the membrane synthesis method.
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http://dx.doi.org/10.1002/anie.201708924DOI Listing
January 2018

Defect-induced ripening of zeolitic-imidazolate framework ZIF-8 and its implication to vapor-phase membrane synthesis.

Chem Commun (Camb) 2016 Sep;52(78):11669-11672

Department of Chemical & Biological Engineering, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul 02841, Republic of Korea and Green School, Korea University, 145 Anam-Ro, Seongbuk-Gu, Seoul 02841, Republic of Korea.

We report for the first time that ZIF-8 crystals undergo an Ostwald-ripening-like process without degradation in the presence of a ligand vapor. The ripening process is dependent on the defect density of the crystals: the more defective the more amenable to the ripening. The process was adapted to synthesize ultra-thin ZIF-8 membranes by vapor-phase secondary growth.
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http://dx.doi.org/10.1039/c6cc05433aDOI Listing
September 2016

Heteroepitaxially grown zeolitic imidazolate framework membranes with unprecedented propylene/propane separation performances.

J Am Chem Soc 2015 Sep 18;137(38):12304-11. Epub 2015 Sep 18.

Center for Environment, Health and Welfare Research, Korea Institute of Science and Technology , Hwarang-ro 14-gil, Seongbuk-gu, Seoul 136-791, Republic of Korea.

Propylene/propane separation is one of the most challenging separations, currently achieved by energy-intensive cryogenic distillation. Despite the great potential for energy-efficient membrane-based separations, no commercial membranes are currently available due to the limitations of current polymeric materials. Zeolitic imidazolate framework, ZIF-8, with the effective aperture size of ∼4.0 Å, has been shown to be very promising for propylene/propane separation. Despite the extensive research on ZIF-8 membranes, only a few reported ZIF-8 membranes have displayed good propylene/propane separation performances presumably due to the challenges of controlling the microstructures of polycrystalline membranes. Here we report the first well-intergrown membranes of ZIF-67 (Co-substituted ZIF-8) by heteroepitaxially growing ZIF-67 on ZIF-8 seed layers. The ZIF-67 membranes exhibited impressively high propylene/propane separation capabilities. Furthermore, when a tertiary growth of ZIF-8 layers was applied to heteroepitaxially grown ZIF-67 membranes, the membranes exhibited unprecedentedly high propylene/propane separation factors of ∼200 possibly due to enhanced grain boundary structure.
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http://dx.doi.org/10.1021/jacs.5b06730DOI Listing
September 2015

Hot Electrons Generated from Doped Quantum Dots via Upconversion of Excitons to Hot Charge Carriers for Enhanced Photocatalysis.

J Am Chem Soc 2015 Apr 21;137(16):5549-54. Epub 2015 Apr 21.

We show that hot electrons exhibiting the enhanced photocatalytic activity in H2 production reaction can be efficiently generated in Mn-doped quantum dots via the "upconversion" of the energy of two excitons into the hot charge carriers. The sequential two-photon-induced process with the long-lived Mn excited state serving as the intermediate state is considered as the pathway generating hot electrons. H2 production rate from doped quantum dots is significantly higher than that from undoped quantum dots and also exhibited the quadratic increase with the light intensity, demonstrating the effectiveness of the hot electrons produced in doped quantum dots in photocatalytic reaction. Due to the very long lifetime of Mn excited state (∼6 ms) in the doped quantum dots, the sequential two-photon excitation requires relatively low excitation rates readily achievable with a moderately concentrated solar radiation, demonstrating their potential as an efficient source of hot electrons operating at low excitation intensities.
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http://dx.doi.org/10.1021/jacs.5b02026DOI Listing
April 2015

In situ synthesis of thin zeolitic-imidazolate framework ZIF-8 membranes exhibiting exceptionally high propylene/propane separation.

J Am Chem Soc 2013 Jul 9;135(29):10763-8. Epub 2013 Jul 9.

Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX-77843, USA.

Metal-organic frameworks (MOFs) are a class of hybrid porous crystalline materials comprising of metal centers coordinated to organic linkers. Owing to their well-defined pores and cavities in the scale of molecules combined with abundant surface chemistry, MOFs offer unprecedented opportunities for a wide range of applications including membrane-based gas separations. It is not straightforward (often requiring multiple steps) to prepare membranes of MOFs due to the fact that the heterogeneous nucleation and growth of MOF crystals on porous supports are not generally favored. Furthermore, the performance of polycrystalline MOF membranes strongly depends on the membrane microstructure, in particular, the grain boundary structure. Here we report a simple one step in situ method based on a counter-diffusion concept to prepare well-intergrown ZIF-8 membranes with significantly enhanced microstructure, resulting in exceptionally high separation performance toward propylene over propane.
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http://dx.doi.org/10.1021/ja403849cDOI Listing
July 2013

An unconventional rapid synthesis of high performance metal-organic framework membranes.

Langmuir 2013 Jun 11;29(25):7896-902. Epub 2013 Jun 11.

Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX, USA.

Metal-organic frameworks (MOFs) are attractive for gas separation membrane applications due to their microporous channels with tunable pore shape, size, and functionality. Conventional MOF membrane fabrication techniques, namely in situ and secondary growth, pose challenges for their wider commercial applications. These challenges include reproducility, scalability, and high manufacturing cost. Recognizing that the coordination chemistry of MOFs is fundamentally different from the covalent chemistry of zeolites, we developed a radically different strategy for MOF membrane synthesis. Using this new technique, we were able to produce continuous well-intergrown membranes of prototypical MOFs, HKUST-1 and ZIF-8, in a relatively short period of time (tens of min). With a minimal consumption of precursors and a greatly simplified synthesis protocol, our new technique provides potential for a continuous, scalable, reproducible, and easily commercializable route for the rapid synthesis of MOF membranes. RTD-prepared MOF membranes show greatly improved gas separation performances as compared to those prepared by conventional solvothermal methods, indicating improved membrane microstructure.
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http://dx.doi.org/10.1021/la4014637DOI Listing
June 2013

Highly propylene-selective supported zeolite-imidazolate framework (ZIF-8) membranes synthesized by rapid microwave-assisted seeding and secondary growth.

Chem Commun (Camb) 2013 May;49(37):3854-6

Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX, USA.

Here we report a rapid and simple microwave-assisted seeding technique for the synthesis of high-quality ZIF-8 membranes with an average propylene-propane selectivity of about 40. The new seeding method was found to be applicable to other ZIFs including ZIF-7 and SIM-1.
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http://dx.doi.org/10.1039/c3cc41039kDOI Listing
May 2013

Isoreticular metal-organic frameworks and their membranes with enhanced crack resistance and moisture stability by surfactant-assisted drying.

Langmuir 2011 Mar 7;27(6):2652-7. Epub 2011 Feb 7.

Artie McFerrin Department of Chemical Engineering and ‡Materials Science and Engineering Program, Texas A&M University , College Station, Texas 77843-3122, United States.

Here we report a new strategy that can not only prevent the formation of cracks and fractures in the crystals and films of metal-organic frameworks (MOFs) but also substantially enhance their stability with respect to moisture. It involves the addition of surfactants during a drying process. Surfactants reduce interfacial tension, thereby repressing the formation of fractures and cracks during the final drying process. It was found that, once dried, surfactants adsorbed on the crystal surface render the surface hydrophobic, leading to the enhancement in the stability toward moisture. Using this new strategy, the first crack-free IRMOF-3 membrane was successfully prepared, and its gas permeation performance was tested. IRMOF-3 membranes are found to favor CO2 over C3H8 mainly due to the affinity of CO2 to the amine groups in the structure. In addition, crack-free IRMOF-3 membranes were postsynthetically modified with heptanoic anhydride, thereby changing the effective pore size and surface property of the MOF. Once modified with the anhydride, the membranes favor C3H8 over CO2 due to the increased solubility of C3H8 in the presence of the hydrocarbon moiety.
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http://dx.doi.org/10.1021/la104775dDOI Listing
March 2011

Synthesis of zeolitic imidazolate framework films and membranes with controlled microstructures.

Langmuir 2010 Sep;26(18):14636-41

Artie McFerrin Department of Chemical Engineering, 3122 TAMU, Texas A&M University, College Station, Texas 77843, USA.

Zeolitic imidazolate frameworks (ZIFs) are hybrid organic-inorganic microporous materials that exhibit zeolite-like structures and can be synthesized with a wide range of pore sizes and chemical functionality. ZIFs as thin films and membranes are of interest for their applications in sensors and gas separation. Here, we report a method for ZIF film and membrane fabrication, based on support surface modification and in situ solvothermal growth, which has potential for general application to other ZIF membranes. Our simple surface modification method results in strong covalent bonds between α-Al(2)O(3) supports and imidazolate ligands, which promote the heterogeneous nucleation and growth of ZIF crystals. The microstructure of ZIF-8 films can be controlled by controlling the pH of the growth solution. ZIF-7 films were fabricated to demonstrate the potential for general applicability of our method. Finally, the separation performance of several ZIF-8 membranes was evaluated, revealing molecular sieving behavior with an ideal selectivity for H(2)/CH(4) of 13.
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http://dx.doi.org/10.1021/la102409eDOI Listing
September 2010

Grain boundary defect elimination in a zeolite membrane by rapid thermal processing.

Science 2009 Jul;325(5940):590-3

Department of Chemical Engineering and Materials Science, University of Minnesota, 151 Amundson Hall, 421 Washington Avenue SE, Minneapolis, MN 55455, USA.

Microporous molecular sieve catalysts and adsorbents discriminate molecules on the basis of size and shape. Interest in molecular sieve films stems from their potential for energy-efficient membrane separations. However, grain boundary defects, formed in response to stresses induced by heat treatment, compromise their selectivity by creating nonselective transport pathways for permeating molecules. We show that rapid thermal processing can improve the separation performance of thick columnar films of a certain zeolite (silicalite-1) by eliminating grain boundary defects, possibly by strengthening grain bonding at the grain boundaries. This methodology enables the preparation of silicalite-1 membranes with high separation performance for aromatic and linear versus branched hydrocarbon isomers and holds promise for realizing high-throughput and scalable production of these zeolite membranes with improved energy efficiency.
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http://dx.doi.org/10.1126/science.1176095DOI Listing
July 2009

Rapid fabrication of metal organic framework thin films using microwave-induced thermal deposition.

Chem Commun (Camb) 2008 Jun 23(21):2441-3. Epub 2008 Apr 23.

Artie McFerrin Department of Chemical Engineering, Texas A&M University, 3122 TAMU, College Station, TX, USA.

We have demonstrated a novel method to rapidly fabricate nanoporous MOF thin films and patterns on porous alumina substrates under microwave irradiation.
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http://dx.doi.org/10.1039/b800061aDOI Listing
June 2008

A highly crystalline layered silicate with three-dimensionally microporous layers.

Nat Mater 2003 Jan;2(1):53-8

Department of Chemical Engineering, 159 Goessmann Laboratory, University of Massachusetts, Amherst, Massachusetts 01003-9303, USA.

Layered silicates with three-dimensional microporosity within the layers have the potential to enable new applications in catalysis, adsorption and ion-exchange. Until now no such materials have been reported. However, here we present the synthesis and structure of AMH-3, a silicate with three-dimensionally microporous layers, obtained in high purity and crystallinity. AMH-3 is composed of silicate layers containing eight-membered rings in all three principal crystal directions, and spaced by strontium cations, sodium cations and water molecules. Because of its three-dimensional pore structure, acid and thermal stability, this layered material could find applications in polymer-silicate composites for membrane applications, for synthesis of combined microporous-mesoporous materials, and for the formation of new zeolites and microporous films. Its existence also opens new possibilities for the synthesis of other layered silicates with multidimensional microporous framework layers.
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http://dx.doi.org/10.1038/nmat795DOI Listing
January 2003

Synthesis of a new open framework cerium silicate and its structure determination by single crystal X-ray diffraction.

Chem Commun (Camb) 2002 Oct(20):2398-9

Department of Chemical Engineering, Goessmann Laboratory, University of Massachusetts, Amherst, MA 01003, USA.

Hydrothermal synthesis of a new open framework cerium silicate and its structure determination by single crystal X-ray diffraction are reported.
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http://dx.doi.org/10.1039/b206738mDOI Listing
October 2002

Oriented molecular sieve membranes by heteroepitaxial growth.

J Am Chem Soc 2002 Nov;124(44):12966-8

Department of Chemical Engineering, University of Massachusetts, Amherst Massachusetts 01003, USA.

Heteroepitaxial growth of titanosilicates (ETS-10 and ETS-4) is reported. Using this heteroepitaxial growth, oriented ETS-10/-4 membranes have been fabricated, demonstrating a novel way to achieve preferred orientation of molecular sieve films.
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http://dx.doi.org/10.1021/ja020947wDOI Listing
November 2002