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

Title data

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. Vol. 34 (October 2018) Issue 42 . - pp. 12538-12548.
ISSN 1520-5827
DOI: https://doi.org/10.1021/acs.langmuir.8b02592

Abstract in another language

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.

Further data

Item Type: Article in a journal
Refereed: Yes
Institutions of the University: Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Former Professors > Professorship Experimental Physics VII - Univ.-Prof. Dr. Ernst Rößler
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry III
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry > Chair Anorganic Chemistry III > Chair Anorganic Chemistry III - Univ.-Prof. Dr. Jürgen Senker
Faculties
Faculties > Faculty of Mathematics, Physics und Computer Science
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics
Faculties > Faculty of Mathematics, Physics und Computer Science > Department of Physics > Former Professors
Faculties > Faculty of Biology, Chemistry and Earth Sciences
Faculties > Faculty of Biology, Chemistry and Earth Sciences > Department of Chemistry
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 540 Chemistry
Date Deposited: 07 Jun 2019 06:39
Last Modified: 30 Oct 2019 09:45
URI: https://eref.uni-bayreuth.de/id/eprint/49290