Structural Dynamics by NMR in the Solid State: II. The MOMD Perspective of the Dynamic Structure of Metal-Organic Frameworks Comprising Several Mobile Components

Eva Meirovitch, Zhichun Liang, Robert W. Schurko, Stephen J. Loeb, Jack H. Freed

Research output: Contribution to journalArticlepeer-review

Abstract

We describe the application of the microscopic-order-macroscopic-disorder (MOMD) approach, developed for the analysis of dynamic 2H NMR lineshapes in the solid state, to unravel interactions among the constituents of metal-organic frameworks (MOFs) that comprise mobile components. MOMD was applied recently to University of Windsor Dynamic Material (UWDM) MOFs with one mobile crown ether per cavity. In this work, we study UWDM-9-d4, which comprises a mobile 2H-labeled phenyl-ring residue along with an isotopically unlabeled 24C8 crown ether. We also study UiO-68-d4, which is structurally similar to UWDM-9-d4 but lacks the crown ether. The physical picture consists of the NMR probe-the C-D bonds of the phenyl-d4 rotor-diffusing locally (diffusion tensor R) in the presence of a local ordering potential, u. For UiO-68-d4, we find it sufficient to expand u in terms of four real Wigner functions, D0|K|L, overall 2-3 kT in magnitude, with R relatively fast, and Rin the (2.8-5.0) × 102 s-1 range. For UWDM-9-d4, u requires only two terms 2-3 kT in magnitude and slower rate constants R and R. In the more crowded macrocycle-containing UWDM-9-d4 cavity, phenyl-d4 dynamics is more isotropic and is described by a simpler ordering potential. This is ascribed to cooperative phenyl-ring/macrocycle motion, which yields a dynamic structure more uniform in character. The experimental 2H spectra used here were analyzed previously with a multi-simple-mode (MSM) approach where several independent simple motional modes are combined. Where possible, similar features have been identified and used to compare the two approaches.

Original languageEnglish
Pages (from-to)2452-2465
Number of pages14
JournalJournal of Physical Chemistry B
Volume126
Issue number13
DOIs
StatePublished - 7 Apr 2022

Bibliographical note

Funding Information:
This work was supported by the Israel–U.S.A. Binational Science Foundation (Grant No. 2016097 to E.M. and J.H.F.) and the Israel Science Foundation (Grant No. 288/20 to E.M.). This work was also supported by NIH/NIGMS grant P41GM103521 to J.H.F. R.W.S. is grateful for the research support from The Florida State University and the National High Magnetic Field Laboratory (NHMFL), which is funded by the National Science Foundation Cooperative Agreement (DMR-1644779) and by the State of Florida, as well as the support of the National Science Foundation Chemical Measurement and Imaging Program, with partial co-funding from the Solid State and Materials Chemistry Program (NSF-2003854). S.J.L. acknowledges the Natural Sciences and Engineering Research Council of Canada for support of a Discovery Grant (RGPIN-2018_101694) and a Canada Research Chair.

Publisher Copyright:
© 2022 American Chemical Society.

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