title: Superexchange Charge Transport in Loaded Metal Organic Frameworks.
abstract: In the past, nanoporous metal-organic frameworks (MOFs) have been mostly studied for their huge potential with regard to gas storage and separation. More recently, the discovery that the electrical conductivity of a widely studied, highly insulating MOF, HKUST-1, improves dramatically when loaded with guest molecules has triggered a huge interest in the charge carrier transport properties of MOFs. The observed high conductivity, however, is difficult to reconcile with conventional transport mechanisms: neither simple hopping nor band transport models are consistent with the available experimental data. Here, we combine theoretical results and new experimental data to demonstrate that the observed conductivity can be explained by an extended hopping transport model including virtual hops through localized MOF states or molecular superexchange. Predictions of this model agree well with precise conductivity measurements, where experimental artifacts and the influence of defects are largely avoided by using well-defined samples and the Hg-drop junction approach.
authors.forename: Tobias
authors.initials: T
authors.lastname: Neumann
authors.forename: Jianxi
authors.initials: J
authors.lastname: Liu
authors.affiliation: Applied Physical Chemistry, Heidelberg University , 69120 Heidelberg, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Wächter
authors.forename: Pascal
authors.initials: P
authors.lastname: Friederich
authors.forename: Franz
authors.initials: F
authors.lastname: Symalla
authors.forename: Alexander
authors.initials: A
authors.lastname: Welle
authors.forename: Veronica
authors.initials: V
authors.lastname: Mugnaini
authors.forename: Velimir
authors.initials: V
authors.lastname: Meded
authors.affiliation: Applied Physical Chemistry, Heidelberg University , 69120 Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Zharnikov
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wenzel
keywords: TCNQ; electric transport properties; guest loading; mercury-based tunneling junctions; metal−organic frameworks; thin films