Communications of the ACM
Researchers Describe New Method to Boost Electron Mobility, Conductivity
Structure of the iron-based metal-organic framework that enhances conductivity.
Credit: Nature Materials
Two chemistry researchers from Missouri University of Science and Technology are part of an international team that has designed a new metal-organic framework that exhibits dramatic improvements in electron mobility, which could lead to new applications for fuels cells, batteries, and other technologies. The team describes its research in "Electron Delocalization and Charge Mobility as a Function of Reduction in a Metal-Organic Framework," published in Nature Materials.
Gary J. Long, professor of chemistry, and Fernande Grandjean, adjunct professor of chemistry, are among the paper's 16 authors. Lead author Jeffrey R. Long, professor of chemistry at the University of California, Berkeley, is Gary Long's son.
In the Nature Materials paper, the researchers describe how an iron-based metal-organic framework, or MOF, could be altered to greatly enhance its electric conductivity. Designed at the atomic level, MOFs are crystalline materials made up of metal sites connected by organic linkers. Their open framework makes them useful as porous materials and for use in gas storage, purification, and separation.
The strong bonds between the metal and organic linkers are not conducive to electron flow, however. Combining both porosity and electric conductivity is "a worthy challenge" that makes these materials attractive for possible use as conductor devices for fuel cells, batteries, and supercapacitors, Gary Long says.
Using a variety of testing methods—from spectroscopy and computational techniques to single-microcrystal field-effect transistor measurements—the researchers found that altering the iron-based MOF they studied resulted in "a nearly 10,000-fold enhancement in conductivity along a single crystallographic axis." The alteration consisted of a partial reduction of iron(III) to iron(II) in a series of MOFs.
S&T researchers Long and Grandjean played a significant role in this research through their analysis of the Mössbauer spectral properties of the partially reduced compounds.
The team also includes Michael L. Aubrey, Brian M. Wiers, Sean C. Andrews, Samia M. Hamed, Chung-Jui Yu, Lucy E. Darago, Jarad A. Mason, Jeffrey B. Neaton, and Peidong Yang from UC Berkeley, Tsuneaki Sakurai and Shu Seki from Kyoto University in Japan, Sebastian E. Reyes-Lillo from UC Berkeley and Universidad Andres Bello in Santiago, Chile, and Jin-Ook Baeg of the Korea Research Institute of Chemical Technology in Daejeon, South Korea.
"If as is shown in our paper, reduction can increase the electron mobility in such compounds, they become attractive for use in various electronic applications," Gary Long says. "This dramatic increase upon reduction has been nicely demonstrated by studying a single crystal of the compound in the form of a field-effect transistor," as illustrated in the paper.
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