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Exploring Local Disorder within CAU-1 Frameworks Using Hyperpolarized ¹²⁹Xe NMR Spectroscopy

Titelangaben

Kemnitzer, Tobias W. ; Tschense, Carsten ; Wittmann, Thomas ; Rößler, Ernst ; Senker, Jürgen:
Exploring Local Disorder within CAU-1 Frameworks Using Hyperpolarized ¹²⁹Xe NMR Spectroscopy.
In: Langmuir. Bd. 34 (Oktober 2018) Heft 42 . - S. 12538-12548.
ISSN 1520-5827
DOI: https://doi.org/10.1021/acs.langmuir.8b02592

Abstract

The sorption properties of metal-organic frameworks (MOFs) can be influenced by introducing covalently attached functional side chains, which make this subclass of porous materials promising for applications as diverse as gas storage and separation, catalysis, and drug delivery. The incorporation of side groups usually comes along with disorder, as the synthesis procedures rarely allow for one specific position among a larger group of equivalent sites to be selected. For a series of isoreticular CAU-1 frameworks, chosen as model compounds, one out of four positions at every linker is modified with equal probability. Here, we investigate the influence of this disorder on Ar sorption and Xe-129 nuclear magnetic resonance spectroscopy using hyperpolarized Xe-129 gas. Models used for predicting the pore dimensions as well as their distributions were derived from the unfunctionalized framework by replacing one proton at every linker with either an amino, an acetamide, or a methyl urea functionality. The resulting structures were optimized using density functional theory (DFT) calculations. Results from void analyses and Monte Carlo force field simulations suggest that for available Ar nonlocal DFT (NLDFT) kernels, neither the pore dimensions nor the distributions induced by the side-chain disorder are well-reproduced. By contrast, we found the Xe-129 chemical shift analysis for the shift observed at high temperature to be well-suited to develop a detailed fingerprint of the porosity and side-chain disorder within the isoreticular CAU-1 series. After calibrating the Xe-129 limiting shift of the amino-functionalized framework with DFT calculations, the downfield shifts for the other two derivatives are an excellent measure for the reduction of the accessible pore space and reveal a strong preference for the side chains toward the octahedral voids for both cases. We expect that the strategy presented here can be commonly applied to disorder phenomena within MOFs in the future.

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Publikationsform: Artikel in einer Zeitschrift
Begutachteter Beitrag: Ja
Institutionen der Universität: Fakultäten > Fakultät für Mathematik, Physik und Informatik > Physikalisches Institut > Ehemalige Professoren > Professur Experimentalphysik VII - Univ.-Prof. Dr. Ernst Rößler
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Lehrstuhl Anorganische Chemie III
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie > Lehrstuhl Anorganische Chemie III > Lehrstuhl Anorganische Chemie III - Univ.-Prof. Dr. Jürgen Senker
Fakultäten
Fakultäten > Fakultät für Mathematik, Physik und Informatik
Fakultäten > Fakultät für Mathematik, Physik und Informatik > Physikalisches Institut
Fakultäten > Fakultät für Mathematik, Physik und Informatik > Physikalisches Institut > Ehemalige Professoren
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften
Fakultäten > Fakultät für Biologie, Chemie und Geowissenschaften > Fachgruppe Chemie
Titel an der UBT entstanden: Ja
Themengebiete aus DDC: 500 Naturwissenschaften und Mathematik > 540 Chemie
Eingestellt am: 07 Jun 2019 06:39
Letzte Änderung: 30 Okt 2019 09:45
URI: https://eref.uni-bayreuth.de/id/eprint/49290