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Title: CO 2 Dynamics in Pure and Mixed-Metal MOFs with Open Metal Sites

Abstract

Metal–organic frameworks (MOFs), such as MOF-74, can have open metal sites to which adsorbates such as CO2 preferentially bind. 13C NMR of 13CO2 is highly informative about the binding sites present in Mg-MOF-74. We used this technique to investigate loadings between ~0.88 and 1.15 molecules of CO2 per metal in Mg-MOF-74 at 295 K. 13C lineshapes recorded as a function of loading can be understood in terms of the dependence of the CO2 NMR frequency on the angle (θ) with respect to the CO2 axis and the channel of the MOF, reflected in the Legendre polynomial, P2. In the fast motion limit, the NMR spectra reveal the time-averaged value of P2, where θ is the angle between the instantaneous CO2 axis and the channel axis. DFT calculations were used to determine a weighted average of P2 in this regime and are in good agreement with experimental data. Static variable temperature 13C NMR from cryogenic temperatures to room temperature was used to investigate 13CO2 binding in Mg-MOF-74 loaded at two levels (~0.88 and 1.08 molecules of CO2 per metal), revealing temperature-dependent lineshapes. We have investigated the effect of partial substitution of Cd for Mg in Mg-MOF-74 on the 13CO2 variable temperaturemore » NMR spectra. The chemical shift anisotropy (CSA) that leads to characteristic lineshapes of 13C indicates that incorporation of Cd leads to weaker binding energies for adsorbed CO2.« less

Authors:
ORCiD logo [1];  [2];  [2];  [3]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [1]
  1. Department of Chemistry, Washington University, One Brookings Drive, Saint Louis, Missouri 63130, United States
  2. School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, 311 Ferst Drive NW, Atlanta, Georgia 30332, United States
  3. Department of Chemistry, Washington University, One Brookings Drive, Saint Louis, Missouri 63130, United States, Department of Physics, Washington University, One Brookings Drive, Saint Louis, Missouri 63130, United States, ABQMR, 2301 Yale Boulevard SE, Albuquerque, New Mexico 87106, United States
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Understanding and Control of Acid Gas-induced Evolution of Materials for Energy (UNCAGE-ME); Georgia Tech Research Corporation, Atlanta, GA (United States); Energy Frontier Research Center (EFRC). Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
OSTI Identifier:
1396742
Alternate Identifier(s):
OSTI ID: 1413259
Grant/Contract Number:  
SC0012577
Resource Type:
Published Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Name: Journal of Physical Chemistry. C Journal Volume: 121 Journal Issue: 46; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Marti, Robert M., Howe, Joshua D., Morelock, Cody R., Conradi, Mark S., Walton, Krista S., Sholl, David S., and Hayes, Sophia E. CO 2 Dynamics in Pure and Mixed-Metal MOFs with Open Metal Sites. United States: N. p., 2017. Web. doi:10.1021/acs.jpcc.7b07179.
Marti, Robert M., Howe, Joshua D., Morelock, Cody R., Conradi, Mark S., Walton, Krista S., Sholl, David S., & Hayes, Sophia E. CO 2 Dynamics in Pure and Mixed-Metal MOFs with Open Metal Sites. United States. doi:10.1021/acs.jpcc.7b07179.
Marti, Robert M., Howe, Joshua D., Morelock, Cody R., Conradi, Mark S., Walton, Krista S., Sholl, David S., and Hayes, Sophia E. Wed . "CO 2 Dynamics in Pure and Mixed-Metal MOFs with Open Metal Sites". United States. doi:10.1021/acs.jpcc.7b07179.
@article{osti_1396742,
title = {CO 2 Dynamics in Pure and Mixed-Metal MOFs with Open Metal Sites},
author = {Marti, Robert M. and Howe, Joshua D. and Morelock, Cody R. and Conradi, Mark S. and Walton, Krista S. and Sholl, David S. and Hayes, Sophia E.},
abstractNote = {Metal–organic frameworks (MOFs), such as MOF-74, can have open metal sites to which adsorbates such as CO2 preferentially bind. 13C NMR of 13CO2 is highly informative about the binding sites present in Mg-MOF-74. We used this technique to investigate loadings between ~0.88 and 1.15 molecules of CO2 per metal in Mg-MOF-74 at 295 K. 13C lineshapes recorded as a function of loading can be understood in terms of the dependence of the CO2 NMR frequency on the angle (θ) with respect to the CO2 axis and the channel of the MOF, reflected in the Legendre polynomial, P2. In the fast motion limit, the NMR spectra reveal the time-averaged value of P2, where θ is the angle between the instantaneous CO2 axis and the channel axis. DFT calculations were used to determine a weighted average of P2 in this regime and are in good agreement with experimental data. Static variable temperature 13C NMR from cryogenic temperatures to room temperature was used to investigate 13CO2 binding in Mg-MOF-74 loaded at two levels (~0.88 and 1.08 molecules of CO2 per metal), revealing temperature-dependent lineshapes. We have investigated the effect of partial substitution of Cd for Mg in Mg-MOF-74 on the 13CO2 variable temperature NMR spectra. The chemical shift anisotropy (CSA) that leads to characteristic lineshapes of 13C indicates that incorporation of Cd leads to weaker binding energies for adsorbed CO2.},
doi = {10.1021/acs.jpcc.7b07179},
journal = {Journal of Physical Chemistry. C},
number = 46,
volume = 121,
place = {United States},
year = {2017},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1021/acs.jpcc.7b07179

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Cited by: 14 works
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