- Titel
- High Pressure In Situ ¹²⁹Xe NMR Spectroscopy:
- Untertitel
- Insights into Switching Mechanisms of Flexible Metal-Organic Frameworks Isoreticular to DUT-49
- Zitierfähige Url:
- https://nbn-resolving.org/urn:nbn:de:bsz:14-qucosa2-724659
- Quellenangabe
- Chemistry of materials / American Chemical Society Erscheinungsort: Washington, DC
Verlag: American Chemical Society
Erscheinungsjahr: 2019
Jahrgang: 31
Heft: 16
Seiten: 6193-6201
E-ISSN: 1520-5002 - Erstveröffentlichung
- 2019
- Abstract (EN)
- Flexible metal-organic frameworks (MOFs) are capable of changing their crystal structure as a function of external stimuli such as pressure, temperature, and type of adsorbed guest species. DUT-49 is the first MOF exhibiting structural transitions accompanied by the counterintuitive phenomenon of negative gas adsorption (NGA). Here, we present high pressure in situ ¹²⁹Xe NMR spectroscopic studies of a novel isoreticular MOF family based on DUT-49. These po-rous materials differ only in the length of their organic linkers causing changes in pore size and elasticity. The series encompasses both, purely microporous materials as well as materials with both, micropores and small mesopores. The chemical shift of adsorbed xenon depends on xenon-wall interactions and thus, on the pore size of the material. The xenon adsorption behavior of the different MOFs can be observed over the whole range of relative pressure. Chemical shift adsorption/desorption isotherms closely resembling the conventional, uptake-measurement based isotherms were obtained at 237 K where all materials are rigid. The comparable chemical environment for adsorbed xenon in these isoreticular MOFs allows establishing a correlation between the chemical shift at a relative pressure of p/p₀ = 1.0 and the mean pore diameter. Furthermore, the xenon adsorption behavior of the MOFs is studied also at 200 K. Here, struc-tural flexibility is found for DUT 50, a material with an even longer linker than the previously known DUT-49. Its structural transitions are monitored by ¹²⁹Xe NMR spectroscopy. This compound is the second known MOF showing the phenomenon of negative gas adsorption. Further increase in the linker length results in DUT-151, a material with interpenetrated network topology. In situ ¹²⁹Xe NMR spectroscopy proves that this material exhibits another type of flexibility compared to DUT-49 and DUT-50. Further surprising observations are made for DUT-46. Volumetric xenon adsorption measurements show that this non-flexible microporous material does not exhibit any hysteresis. In contrast, in situ ¹²⁹Xe NMR spectroscopically detected xenon chemical shift isotherms exhibit a hysteresis even after longer equilibration times than in the volumetric experiments. This indicates kinetically hindered re-distribution processes and long-lived metastable states of adsorbed xenon within the MOF persisting at the time scale of hours or longer.
- Andere Ausgabe
- Link zum Artikel der zuerst in der Zeitschrift 'Chemisty of materials' erschienen ist
DOI: 10.1021/acs.chemmater.9b02003 - Freie Schlagwörter (DE)
- MOF, ¹²⁹Xe NMR, in situ, DUT-49, Flexibilität
- Freie Schlagwörter (EN)
- MOF, ¹²⁹Xe NMR, in situ, DUT-49, flexibility
- Klassifikation (DDC)
- 540
- Verlag
- American Chemical Society, Washington, DC
- Förder- / Projektangaben
- Deutsche Forschungsgemeinschaft Schaltbare metallorganische Gerüstverbindungen (MOF switches)
(FOR2433)
ID: 279409724 - European Commission H2020
Understanding negative gas adsorption in highly porous networks for the design of pressure amplifying materials
(AMPLIPORE)
ID: 742743 - Bundesministerium für Bildung und Forschung ID: 05K16OD1
- Deutsche Forschungsgemeinschaft; Agence Nationale de la Recherche FUN
- Version / Begutachtungsstatus
- angenommene Version / Postprint / Autorenversion
- URN Qucosa
- urn:nbn:de:bsz:14-qucosa2-724659
- Veröffentlichungsdatum Qucosa
- 23.10.2020
- Dokumenttyp
- Artikel
- Sprache des Dokumentes
- Englisch
- Lizenz / Rechtehinweis
