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  1. Article: Hydrocarbon Sorption in Flexible MOFs-Part II: Understanding Adsorption Kinetics.

    Preißler-Kurzhöfer, Hannes / Kolesnikov, Andrei / Lange, Marcus / Möllmer, Jens / Erhart, Oliver / Kobalz, Merten / Hwang, Seungtaik / Chmelik, Christian / Krautscheid, Harald / Gläser, Roger

    Nanomaterials (Basel, Switzerland)

    2023  Volume 13, Issue 3

    Abstract: The rate of sorption ... ...

    Abstract The rate of sorption of
    Language English
    Publishing date 2023-02-02
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 2662255-5
    ISSN 2079-4991
    ISSN 2079-4991
    DOI 10.3390/nano13030601
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Precise control over gas-transporting channels in zeolitic imidazolate framework glasses.

    Smirnova, Oksana / Hwang, Seungtaik / Sajzew, Roman / Ge, Lingcong / Reupert, Aaron / Nozari, Vahid / Savani, Samira / Chmelik, Christian / Reithofer, Michael R / Wondraczek, Lothar / Kärger, Jörg / Knebel, Alexander

    Nature materials

    2023  Volume 23, Issue 2, Page(s) 262–270

    Abstract: Porous metal-organic frameworks have emerged to resolve important challenges of our modern society, such as ... ...

    Abstract Porous metal-organic frameworks have emerged to resolve important challenges of our modern society, such as CO
    Language English
    Publishing date 2023-12-20
    Publishing country England
    Document type Journal Article
    ZDB-ID 2088679-2
    ISSN 1476-4660 ; 1476-1122
    ISSN (online) 1476-4660
    ISSN 1476-1122
    DOI 10.1038/s41563-023-01738-3
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  3. Article ; Online: Hydrocarbon Sorption in Flexible MOFs—Part II

    Hannes Preißler-Kurzhöfer / Andrei Kolesnikov / Marcus Lange / Jens Möllmer / Oliver Erhart / Merten Kobalz / Seungtaik Hwang / Christian Chmelik / Harald Krautscheid / Roger Gläser

    Nanomaterials, Vol 13, Iss 601, p

    Understanding Adsorption Kinetics

    2023  Volume 601

    Abstract: The rate of sorption of n -butane on the structurally flexible metal-organic framework [Cu 2 (H-Me-trz-ia) 2 ], including its complete structural transition between a narrow-pore phase and a large-pore phase, was studied by sorption gravimetry, IR ... ...

    Abstract The rate of sorption of n -butane on the structurally flexible metal-organic framework [Cu 2 (H-Me-trz-ia) 2 ], including its complete structural transition between a narrow-pore phase and a large-pore phase, was studied by sorption gravimetry, IR spectroscopy, and powder X-ray diffraction at close to ambient temperature (283, 298, and 313 K). The uptake curves reveal complex interactions of adsorption on the outer surface of MOF particles, structural transition, of which the overall rate depends on several factors, including pressure step, temperature, as well as particle size, and the subsequent diffusion into newly opened pores. With the aid of a kinetic model based on the linear driving force (LDF) approach, both rates of diffusion and structural transition were studied independently of each other. It is shown that temperature and applied pressure steps have a strong effect on the rate of structural transition and thus, the overall velocity of gas uptake. For pressure steps close to the upper boundary of the gate-opening, the rate of structural transition is drastically reduced. This feature enables a fine-tuning of the overall velocity of sorption, which can even turn into anti-Arrhenius behavior.
    Keywords metal–organic frameworks ; kinetic analysis ; flexible materials ; Chemistry ; QD1-999
    Subject code 660
    Language English
    Publishing date 2023-02-01T00:00:00Z
    Publisher MDPI AG
    Document type Article ; Online
    Database BASE - Bielefeld Academic Search Engine (life sciences selection)

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

    Berens, Samuel / Chmelik, Christian / Hillman, Febrian / Kärger, Jörg / Jeong, Hae-Kwon / Vasenkov, Sergey

    Physical chemistry chemical physics : PCCP

    2018  Volume 20, Issue 37, Page(s) 23967–23975

    Abstract: 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 ... ...

    Abstract 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.
    Language English
    Publishing date 2018-09-13
    Publishing country England
    Document type Journal Article
    ZDB-ID 1476244-4
    ISSN 1463-9084 ; 1463-9076
    ISSN (online) 1463-9084
    ISSN 1463-9076
    DOI 10.1039/c8cp04889d
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: In situ study on molecular diffusion phenomena in nanoporous catalytic solids.

    Chmelik, Christian / Kärger, Jörg

    Chemical Society reviews

    2010  Volume 39, Issue 12, Page(s) 4864–4884

    Abstract: As an omnipresent phenomenon in nature, diffusion is among the rate-determining processes in many technological processes. This is in particular true for catalytic conversion in nanoporous materials. We provide a critical review of the possibilities of ... ...

    Abstract As an omnipresent phenomenon in nature, diffusion is among the rate-determining processes in many technological processes. This is in particular true for catalytic conversion in nanoporous materials. We provide a critical review of the possibilities of exploring diffusion phenomena over microscopic dimensions in such media by direct experimental observation. By monitoring the probability distribution of molecular displacements as a function of time, the pulsed field gradient technique of NMR (PFG NMR) records the rate of molecular re-distribution. By varying the observation time, PFG NMR is thus able to trace even hierarchies of transport resistances as occurring, e.g., in catalyst particles in the form of binder-compacted assemblages of zeolite crystallites. Alternatively, and complementary to this information, interference microscopy (IFM) and IR microscopy (IRM) are able to follow the evolution of intracrystalline concentration profiles during uptake and release. This allows, in particular, an accurate quantification of the transport resistances on the surface of the individual crystallites and of the probability that reactant molecules from the gas phase, upon colliding with the external surface, are able to penetrate through such "surface barriers" into the crystal bulk phase. Being able to distinguish between different molecular species, IRM is able to record the evolution of intracrystalline concentration profiles even during multi-component adsorption and catalytic reactions (169 references).
    Language English
    Publishing date 2010-12
    Publishing country England
    Document type Journal Article
    ZDB-ID 1472875-8
    ISSN 1460-4744 ; 0306-0012
    ISSN (online) 1460-4744
    ISSN 0306-0012
    DOI 10.1039/c0cs00100g
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article: In situ study on molecular diffusion phenomena in nanoporous catalytic solids

    Chmelik, Christian / Kärger, Jörg

    Chemical Society reviews. 2010 Nov. 16, v. 39, no. 12

    2010  

    Abstract: As an omnipresent phenomenon in nature, diffusion is among the rate-determining processes in many technological processes. This is in particular true for catalytic conversion in nanoporous materials. We provide a critical review of the possibilities of ... ...

    Abstract As an omnipresent phenomenon in nature, diffusion is among the rate-determining processes in many technological processes. This is in particular true for catalytic conversion in nanoporous materials. We provide a critical review of the possibilities of exploring diffusion phenomena over microscopic dimensions in such media by direct experimental observation. By monitoring the probability distribution of molecular displacements as a function of time, the pulsed field gradient technique of NMR (PFG NMR) records the rate of molecular re-distribution. By varying the observation time, PFG NMR is thus able to trace even hierarchies of transport resistances as occurring, e.g., in catalyst particles in the form of binder-compacted assemblages of zeolite crystallites. Alternatively, and complementary to this information, interference microscopy (IFM) and IR microscopy (IRM) are able to follow the evolution of intracrystalline concentration profiles during uptake and release. This allows, in particular, an accurate quantification of the transport resistances on the surface of the individual crystallites and of the probability that reactant molecules from the gas phase, upon colliding with the external surface, are able to penetrate through such “surface barriers” into the crystal bulk phase. Being able to distinguish between different molecular species, IRM is able to record the evolution of intracrystalline concentration profiles even during multi-component adsorption and catalytic reactions (169 references).
    Keywords adsorption ; catalysts ; catalytic activity ; crystallites ; gases ; microscopy ; monitoring ; nanopores ; nuclear magnetic resonance spectroscopy ; probability ; probability distribution ; zeolites
    Language English
    Dates of publication 2010-1116
    Size p. 4864-4884.
    Publishing place The Royal Society of Chemistry
    Document type Article
    ZDB-ID 1472875-8
    ISSN 1460-4744 ; 0306-0012
    ISSN (online) 1460-4744
    ISSN 0306-0012
    DOI 10.1039/c0cs00100g
    Database NAL-Catalogue (AGRICOLA)

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  7. Article ; Online: Anomaly in the Chain Length Dependence of n-Alkane Diffusion in ZIF-4 Metal-Organic Frameworks.

    Hwang, Seungtaik / Gopalan, Arun / Hovestadt, Maximilian / Piepenbreier, Frank / Chmelik, Christian / Hartmann, Martin / Snurr, Randall Q / Kärger, Jörg

    Molecules (Basel, Switzerland)

    2018  Volume 23, Issue 3

    Abstract: Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been ... ...

    Abstract Molecular diffusion is commonly found to slow down with increasing molecular size. Deviations from this pattern occur in some host materials with pore sizes approaching the diameters of the guest molecules. A variety of theoretical models have been suggested to explain deviations from this pattern, but robust experimental data are scarcely available. Here, we present such data, obtained by monitoring the chain length dependence of the uptake of
    MeSH term(s) Alkanes/chemistry ; Metal-Organic Frameworks/chemistry ; Molecular Structure ; Monte Carlo Method ; Zeolites/chemistry
    Chemical Substances Alkanes ; Metal-Organic Frameworks ; Zeolites (1318-02-1)
    Language English
    Publishing date 2018-03-15
    Publishing country Switzerland
    Document type Journal Article
    ZDB-ID 1413402-0
    ISSN 1420-3049 ; 1431-5165 ; 1420-3049
    ISSN (online) 1420-3049
    ISSN 1431-5165 ; 1420-3049
    DOI 10.3390/molecules23030668
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    In stock of ZB MED Cologne/Königswinter

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  8. Article ; Online: Metal-Organic Framework Co-MOF-74-Based Host-Guest Composites for Resistive Gas Sensing.

    Strauss, Ina / Mundstock, Alexander / Treger, Marvin / Lange, Karsten / Hwang, Seungtaik / Chmelik, Christian / Rusch, Pascal / Bigall, Nadja C / Pichler, Thomas / Shiozawa, Hidetsugu / Caro, Jürgen

    ACS applied materials & interfaces

    2019  Volume 11, Issue 15, Page(s) 14175–14181

    Abstract: Increasing demands in the field of sensing, especially for gas detection applications, require new approaches to chemical sensors. Metal-organic frameworks (MOFs) can play a decisive role owing to their outstanding performances regarding gas selectivity ... ...

    Abstract Increasing demands in the field of sensing, especially for gas detection applications, require new approaches to chemical sensors. Metal-organic frameworks (MOFs) can play a decisive role owing to their outstanding performances regarding gas selectivity and sensitivity. The tetrathiafulvalene (TTF)-infiltrated MOF, Co-MOF-74, has been prepared following the host-guest concept and evaluated in resistive gas sensing. The Co-MOF-74-TTF crystal morphology has been characterized via X-ray diffraction and scanning electron microscopy, while the successful incorporation of TTF into the MOF has been validated via X-ray photoemission spectroscopy, thermogravimetric analysis, UV/vis, infrared (IR), and Raman investigations. We demonstrate a reduced yet ample uptake of CO
    Language English
    Publishing date 2019-04-01
    Publishing country United States
    Document type Journal Article
    ISSN 1944-8252
    ISSN (online) 1944-8252
    DOI 10.1021/acsami.8b22002
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  9. Article: Microimaging of transient guest profiles to monitor mass transfer in nanoporous materials.

    Kärger, Jörg / Binder, Tomas / Chmelik, Christian / Hibbe, Florian / Krautscheid, Harald / Krishna, Rajamani / Weitkamp, Jens

    Nature materials

    2014  Volume 13, Issue 4, Page(s) 333–343

    Abstract: The intense interactions of guest molecules with the pore walls of nanoporous materials is the subject of continued fundamental research. Stimulated by their thermal energy, the guest molecules in these materials are subject to a continuous, irregular ... ...

    Abstract The intense interactions of guest molecules with the pore walls of nanoporous materials is the subject of continued fundamental research. Stimulated by their thermal energy, the guest molecules in these materials are subject to a continuous, irregular motion, referred to as diffusion. Diffusion, which is omnipresent in nature, influences the efficacy of nanoporous materials in reaction and separation processes. The recently introduced techniques of microimaging by interference and infrared microscopy provide us with a wealth of information on diffusion, hitherto inaccessible from commonly used techniques. Examples include the determination of surface barriers and the sticking coefficient's analogue, namely the probability that, on colliding with the particle surface, a molecule may continue its diffusion path into the interior. Microimaging is further seen to open new vistas in multicomponent guest diffusion (including the detection of a reversal in the preferred diffusion pathways), in guest-induced phase transitions in nanoporous materials and in matching the results of diffusion studies under equilibrium and non-equilibrium conditions.
    Language English
    Publishing date 2014-03-20
    Publishing country England
    Document type Journal Article
    ZDB-ID 2088679-2
    ISSN 1476-4660 ; 1476-1122
    ISSN (online) 1476-4660
    ISSN 1476-1122
    DOI 10.1038/nmat3917
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  10. Article ; Online: Revealing the Transient Concentration of CO

    Hwang, Seungtaik / Semino, Rocio / Seoane, Beatriz / Zahan, Marufa / Chmelik, Christian / Valiullin, Rustem / Bertmer, Marko / Haase, Jürgen / Kapteijn, Freek / Gascon, Jorge / Maurin, Guillaume / Kärger, Jörg

    Angewandte Chemie (International ed. in English)

    2018  Volume 57, Issue 18, Page(s) 5156–5160

    Abstract: Through IR microimaging the spatially and temporally resolved development of the ... ...

    Abstract Through IR microimaging the spatially and temporally resolved development of the CO
    Language English
    Publishing date 2018-03-25
    Publishing country Germany
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2011836-3
    ISSN 1521-3773 ; 1433-7851
    ISSN (online) 1521-3773
    ISSN 1433-7851
    DOI 10.1002/anie.201713160
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