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Charge Transport In Metal-Organic Frameworks

  • Author(s): Wiers, Brian Michael
  • Advisor(s): Long, Jeffrey R.
  • et al.
Abstract

This dissertation documents efforts to synthesize and measure ionically and electronically conductive porous, three-dimensional metal-organic frameworks. Chapter 1 introduces concepts of conductivity, mixed-valency, measurement techniques and gives a survey of charge-transport in metal-organic and covalent-organic frameworks. Concepts that directed the work detailed in this thesis is given, as is a perspective on possible future avenues to generate conductive metal-organic frameworks and possible applications. Chapter 2 details the attainment of a solid lithium fast-ion conductor by post-synthetic grafting of lithium alkoxides to a metal-organic framework with open metal-sites, Mg2(DOBDC). Chapter 3 shows the synthesis of a novel metal-organic framework Fe2(BDP)3, and its chemical reduction to obtain the compositional series KxFe2(BDP)3 that displays porosity and tunable charge transport as demonstrated by contactless microwave measurements. Chapter 4 investigates this system further and shows the first 4-point and field effect transistor measurements of a metal-organic framework. FET measurements show the effects of sequential reduction on a single crystal device and high electron mobilities. Mössbauer spectroscopy and solid state cyclic voltammetry confirm the high degree of electronic delocalization in the partially reduced material. Chapter 5 shows a new chalcogen-based metal organic framework Fe2(DSBDC)(N,N-DMF)2, isostructural with the known and heavily investigated series of metal-organic frameworks, M2(DOBDC)(SOLVENT)2. Contactless microwave measurements reveal high charge mobilities and pressed pellet measurements indicate intrinsic conductivity, that increases upon oxidation, indicative of p-type conduction. Appendix A shows five novel dipyrazole ligands and five novel dipyrazolate metal-organic frameworks.

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