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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 CO 2 preferentially bind. 13C NMR of 13CO 2 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 CO 2 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 CO 2 NMR frequency on the angle (θ) with respect to the CO 2 axis and the channel of the MOF, reflected in the Legendre polynomial, P 2. In the fast motion limit, the NMR spectra reveal the time-averaged value of P 2, where θ is the angle between the instantaneous CO 2 axis and the channel axis. DFT calculations were used to determine a weighted average of P 2 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 13CO 2 binding in Mg-MOF-74 loaded at two levels (~0.88 and 1.08 molecules of CO 2 per metal), revealing temperature-dependent lineshapes. We have investigated the effect of partial substitutionmore » of Cd for Mg in Mg-MOF-74 on the 13CO 2 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 CO 2.« less

Authors:
ORCiD logo [1];  [2];  [2];  [3]; ORCiD logo [2]; ORCiD logo [2]; ORCiD logo [1]
  1. Washington Univ., St. Louis, MO (United States). Dept. of Chemistry
  2. Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemical and Biomolecular Engineering
  3. Washington Univ., St. Louis, MO (United States). Dept. of Chemistry; Washington Univ., St. Louis, MO (United States). Dept. of Physics; ABQMR, Inc., Albuquerque, NM (United States)
Publication Date:
Research Org.:
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:
Journal Article: Published Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
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.. CO2 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.. CO2 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.. Fri . "CO2 Dynamics in Pure and Mixed-Metal MOFs with Open Metal Sites". United States. doi:10.1021/acs.jpcc.7b07179.
@article{osti_1396742,
title = {CO2 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 = {Fri Sep 22 00:00:00 EDT 2017},
month = {Fri Sep 22 00:00:00 EDT 2017}
}

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

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Cited by: 6 works
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