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The Role of Defects in the semiconducting-metallic discrepancy in Metal-Organic Graphene Analogues
Journal article   Open access

The Role of Defects in the semiconducting-metallic discrepancy in Metal-Organic Graphene Analogues

Mark D. Allendorf, Michael E. Foster, Karl Sohlberg, Vitalie Stavila, Yuping He, Monica C. So and A. Alec Talin
Meeting abstracts (Electrochemical Society), v MA2018-02(40), pp 1322-1322
23 Jul 2018
DOI: https://doi.org/10.1149/MA2018-02/40/1322
url
https://doi.org/10.1057/s41599-021-00794-xView
Published, Version of Record (VoR)CC BY V4.0,  Open

Abstract

The Metal-Organic Framework Ni 3 (2,3,6,7,10,11-hexaiminotriphenylene) 2 , also known as a “Metal-Organic Graphene Analogue,” or MOG, is a two-dimensional layered structure with a topology and extended π-conjugation analogous to graphene. Recent experimental results indicate that this material is semiconducting, as indicated by a non-zero band gap and conductivity that increases with temperature. Intriguingly however, several theoretical studies predict that the bulk material should be metallic. Characterization data suggest that the morphology of the MOG films used for conductivity measurements could play a role in the charge transport properties. In particular, samples used for electrical measurements, both films and pressed pellets, had complex nanocrystalline microstructures. We hypothesized that the tendency for internal interfaces to introduce transport barriers could be the source of the theory-experiment discrepancy. Here, we discuss DFT calculations we performed to probe the influence of internal interface defects on the electronic structure of bulk Ni 3 (HITP) 2 . The results show that interface defects can introduce a transport barrier by breaking the π-conjugation, and/or by decreasing the dispersion of the electronic bands near the Fermi level. Both defect types cause a small band gap to form (in the range of 15-200 meV), which is consistent with the experimentally inferred hopping barrier. These results provide strong evidence supporting the ongoing speculation that the charge transport properties of MOFs are strongly influenced by defects, in much the same way as conventional inorganic and organic conducting materials.

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