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Title: Charge Delocalization and Bulk Electronic Conductivity in the Mixed-Valence Metal–Organic Framework Fe(1,2,3-triazolate) 2(BF 4) x

Abstract

Metal–organic frameworks are of interest for use in a variety of electrochemical and electronic applications, although a detailed understanding of their charge transport behavior, which is of critical importance for enhancing electronic conductivities, remains limited. Herein, we report isolation of the mixed-valence framework materials, Fe(tri) 2(BF 4) x (tri = 1,2,3-triazolate; x = 0.09, 0.22, and 0.33), obtained from the stoichiometric chemical oxidation of the poorly-conductive iron(II) framework Fe(tri) 2, and find that the conductivity increases dramatically with iron oxidation level. Notably, the most oxidized variant, Fe(tri) 2(BF 4) 0.33, displays a room-temperature conductivity of 0.3(1) S/cm, which represents an increase of eight orders of magnitude from that of the parent material and is one of the highest conductivity values reported among three-dimensional metal–organic frameworks. Detailed characterization of Fe(tri) 2 and the Fe(tri) 2(BF 4) x materials via powder X-ray diffraction, Mössbauer spectroscopy, and IR and UV-vis-NIR diffuse reflectance spectroscopies reveals that the high conductivity arises from intervalence charge transfer between mixed-valence low-spin Fe II/III centers. Further, Mössbauer spectroscopy indicates the presence of a valence-delocalized Fe II/III species in Fe(tri) 2(BF 4) x at 290 K, one of the first such observations for a metal–organic framework. The electronic structure ofmore » valence-pure Fe(tri) 2 and the charge transport mechanism and electronic structure of mixed-valence Fe(tri) 2(BF 4) x frameworks are discussed in detail.« less

Authors:
ORCiD logo [1];  [1];  [1]; ORCiD logo [1];  [1];  [2]; ORCiD logo [2]; ORCiD logo [3]
  1. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry
  2. Missouri Univ. of Science and Technology, Rolla, MO (United States). Dept. of Chemistry
  3. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry, and Dept. of Chemical and Biomolecular Engineering; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Sciences Division
Publication Date:
Research Org.:
Univ. of Minnesota, Minneapolis, MN (United States). Nanoporous Materials Genome Center
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
Contributing Org.:
Beamline 17-BM at the Advanced Photon Source
OSTI Identifier:
1495016
Grant/Contract Number:  
SC0008688; FG02-17ER16362
Resource Type:
Accepted Manuscript
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 140; Journal Issue: 27; Journal ID: ISSN 0002-7863
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Park, Jesse G., Aubrey, Michael L., Oktawiec, Julia, Chakarawet, Khetpakorn, Darago, Lucy E., Grandjean, Fernande, Long, Gary J., and Long, Jeffrey R. Charge Delocalization and Bulk Electronic Conductivity in the Mixed-Valence Metal–Organic Framework Fe(1,2,3-triazolate)2(BF4)x. United States: N. p., 2018. Web. doi:10.1021/jacs.8b03696.
Park, Jesse G., Aubrey, Michael L., Oktawiec, Julia, Chakarawet, Khetpakorn, Darago, Lucy E., Grandjean, Fernande, Long, Gary J., & Long, Jeffrey R. Charge Delocalization and Bulk Electronic Conductivity in the Mixed-Valence Metal–Organic Framework Fe(1,2,3-triazolate)2(BF4)x. United States. doi:10.1021/jacs.8b03696.
Park, Jesse G., Aubrey, Michael L., Oktawiec, Julia, Chakarawet, Khetpakorn, Darago, Lucy E., Grandjean, Fernande, Long, Gary J., and Long, Jeffrey R. Tue . "Charge Delocalization and Bulk Electronic Conductivity in the Mixed-Valence Metal–Organic Framework Fe(1,2,3-triazolate)2(BF4)x". United States. doi:10.1021/jacs.8b03696. https://www.osti.gov/servlets/purl/1495016.
@article{osti_1495016,
title = {Charge Delocalization and Bulk Electronic Conductivity in the Mixed-Valence Metal–Organic Framework Fe(1,2,3-triazolate)2(BF4)x},
author = {Park, Jesse G. and Aubrey, Michael L. and Oktawiec, Julia and Chakarawet, Khetpakorn and Darago, Lucy E. and Grandjean, Fernande and Long, Gary J. and Long, Jeffrey R.},
abstractNote = {Metal–organic frameworks are of interest for use in a variety of electrochemical and electronic applications, although a detailed understanding of their charge transport behavior, which is of critical importance for enhancing electronic conductivities, remains limited. Herein, we report isolation of the mixed-valence framework materials, Fe(tri)2(BF4)x (tri–= 1,2,3-triazolate; x = 0.09, 0.22, and 0.33), obtained from the stoichiometric chemical oxidation of the poorly-conductive iron(II) framework Fe(tri)2, and find that the conductivity increases dramatically with iron oxidation level. Notably, the most oxidized variant, Fe(tri)2(BF4)0.33, displays a room-temperature conductivity of 0.3(1) S/cm, which represents an increase of eight orders of magnitude from that of the parent material and is one of the highest conductivity values reported among three-dimensional metal–organic frameworks. Detailed characterization of Fe(tri)2 and the Fe(tri)2(BF4)x materials via powder X-ray diffraction, Mössbauer spectroscopy, and IR and UV-vis-NIR diffuse reflectance spectroscopies reveals that the high conductivity arises from intervalence charge transfer between mixed-valence low-spin FeII/III centers. Further, Mössbauer spectroscopy indicates the presence of a valence-delocalized FeII/III species in Fe(tri)2(BF4)x at 290 K, one of the first such observations for a metal–organic framework. The electronic structure of valence-pure Fe(tri)2 and the charge transport mechanism and electronic structure of mixed-valence Fe(tri)2(BF4)x frameworks are discussed in detail.},
doi = {10.1021/jacs.8b03696},
journal = {Journal of the American Chemical Society},
number = 27,
volume = 140,
place = {United States},
year = {2018},
month = {6}
}

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Works referencing / citing this record:

CCDC 1835203: Experimental Crystal Structure Determination: UFOBAV : catena-[hexakis(μ-1,2,3-triazolato)-tri-iron(ii)]
dataset, April 2018


CCDC 1835204: Experimental Crystal Structure Determination: UFOBEZ : catena-[hexakis(μ-1,2,3-triazolato)-tri-iron tetrafluoroborate]
dataset, April 2018


CCDC 1835205: Experimental Crystal Structure Determination: UFOBEZ01 : catena-[hexakis(μ-1,2,3-triazolato)-tri-iron tetrafluoroborate]
dataset, April 2018