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Title: Hyperpolarized 129Xe Nuclear Magnetic Resonance Studies of Isoreticular Metal-Organic Frameworks

Abstract

The pore environments of a series of isoreticular metal-organic frameworks (IRMOF) have been studied using hyperpolarized (HP) 129Xe nuclear magnetic resonance (NMR) spectroscopy. Xenon gas behaved as an efficient probe molecule for interrogating the variability of adsorption sites in functionalized IRMOF materials through variations in the NMR chemical shift of the adsorbed xenon. The xenon adsorption enthalpies extracted from variable temperature HP 129Xe NMR were found to be lower than published values for the physisorption of xenon. The low heats of adsorption were corroborated by xenon adsorption measurements that revealed two atoms per pore under one atmosphere of pressure at 19ºC. Average pore diameters estimated from the empirical chemical shift and pore size correlations based on a geometrical model were compared with x-ray crystallography data. The exchange processes of xenon in IRMOFs also were explored using 2D EXSY 129Xe NMR. It was found the exchange of xenon from adsorption sites within the IRMOF to the free gas space is much slower than that between the adsorption sites within the lattice. Cross-polarization experiments showed that the preferred adsorption sites were spatially removed from the phenylene rings of the network. This agrees with previous spectroscopic, structural and computational studies of gas adsorptionmore » (H2, N2, Ar) in IRMOFs that indicate the preferred binding sites reside near the carboxylate groups of the inorganic clusters.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
912505
Report Number(s):
PNNL-SA-51427
Journal ID: ISSN 0022-3654; JPCHAX; KC0201050; TRN: US200801%%903
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry, 11(16):6060 -6067; Journal Volume: 11; Journal Issue: 16
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ADSORPTION HEAT; CHEMICAL SHIFT; CRYSTALLOGRAPHY; NUCLEAR MAGNETIC RESONANCE; XENON 129; ORGANOMETALLIC COMPOUNDS; PORE STRUCTURE; MOLECULAR STRUCTURE

Citation Formats

Pawsey, Shane, Moudrakovski, I. L., Ripmeester, J. A., Wang, Li Q., Exarhos, Gregory J., Rowsell, Jesse L., and Yaghi, Omar M. Hyperpolarized 129Xe Nuclear Magnetic Resonance Studies of Isoreticular Metal-Organic Frameworks. United States: N. p., 2007. Web. doi:10.1021/jp0668246.
Pawsey, Shane, Moudrakovski, I. L., Ripmeester, J. A., Wang, Li Q., Exarhos, Gregory J., Rowsell, Jesse L., & Yaghi, Omar M. Hyperpolarized 129Xe Nuclear Magnetic Resonance Studies of Isoreticular Metal-Organic Frameworks. United States. doi:10.1021/jp0668246.
Pawsey, Shane, Moudrakovski, I. L., Ripmeester, J. A., Wang, Li Q., Exarhos, Gregory J., Rowsell, Jesse L., and Yaghi, Omar M. Tue . "Hyperpolarized 129Xe Nuclear Magnetic Resonance Studies of Isoreticular Metal-Organic Frameworks". United States. doi:10.1021/jp0668246.
@article{osti_912505,
title = {Hyperpolarized 129Xe Nuclear Magnetic Resonance Studies of Isoreticular Metal-Organic Frameworks},
author = {Pawsey, Shane and Moudrakovski, I. L. and Ripmeester, J. A. and Wang, Li Q. and Exarhos, Gregory J. and Rowsell, Jesse L. and Yaghi, Omar M.},
abstractNote = {The pore environments of a series of isoreticular metal-organic frameworks (IRMOF) have been studied using hyperpolarized (HP) 129Xe nuclear magnetic resonance (NMR) spectroscopy. Xenon gas behaved as an efficient probe molecule for interrogating the variability of adsorption sites in functionalized IRMOF materials through variations in the NMR chemical shift of the adsorbed xenon. The xenon adsorption enthalpies extracted from variable temperature HP 129Xe NMR were found to be lower than published values for the physisorption of xenon. The low heats of adsorption were corroborated by xenon adsorption measurements that revealed two atoms per pore under one atmosphere of pressure at 19ºC. Average pore diameters estimated from the empirical chemical shift and pore size correlations based on a geometrical model were compared with x-ray crystallography data. The exchange processes of xenon in IRMOFs also were explored using 2D EXSY 129Xe NMR. It was found the exchange of xenon from adsorption sites within the IRMOF to the free gas space is much slower than that between the adsorption sites within the lattice. Cross-polarization experiments showed that the preferred adsorption sites were spatially removed from the phenylene rings of the network. This agrees with previous spectroscopic, structural and computational studies of gas adsorption (H2, N2, Ar) in IRMOFs that indicate the preferred binding sites reside near the carboxylate groups of the inorganic clusters.},
doi = {10.1021/jp0668246},
journal = {Journal of Physical Chemistry, 11(16):6060 -6067},
number = 16,
volume = 11,
place = {United States},
year = {Tue Apr 03 00:00:00 EDT 2007},
month = {Tue Apr 03 00:00:00 EDT 2007}
}