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Metal Organic and Covalent Triazine Frameworks as Templates for the Synthesis of Metallic Nanostructures and Doped Carbons

  • Author(s): Volosskiy, Boris
  • Advisor(s): Duan, Xiangfeng
  • et al.
Abstract

Metal Organic Frameworks (MOFs) are highly porous, crystalline frameworks composed of an organic linker and a metal oxide cluster. Covalent Triazine Frameworks (CTFs) are a subclass of MOFs and similarly are highly porous crystalline frameworks, but unlike MOFs, are composed of purely organic building units. Since the initial reports of a successful synthesis and characterization of MOF-5 in 1995, the interest in these frameworks has exploded. The ability to design the MOF properties and functionality by simply selecting the starting precursors make MOFs optimal materials for a multitude of fields. However, even with all of the research being conducted, there are many MOF applications yet to be discovered. In the first part of this thesis we explore the application of MOFs as templates for the synthesis of metallic nanostructures based on the size and the shape of the MOF pores. The limitless number of MOF structures with different pore shapes and sizes allow for the synthesis of nanostructures with any desired shape or size. It is shown that by using MOF-545 with one dimensional pores, well aligned, ultra-thin gold and platinum nanowires are grown. The nanowires inside the MOF pores are confirmed by imaging the focus-ion beam cross-section of the metal loaded MOF-545 using a transmission electron microscope. In the second part of this thesis, the use of MOFs as a precursor to fabricate nitrogen and metal co-doped carbons is discussed. MOF-545 is an excellent precursor for one-pot synthesis of metal and nitrogen co-doped carbon wires. Two different annealing methods are studied, either under pure argon or argon mixed with air impurities, and the resulting carbon wires are tested as an electro-catalyst for oxygen reduction reaction (ORR). Surprisingly, the air treated carbon wires show much higher ORR activity, comparable to that of platinum in basic electrolyte. Finally, the last part of this thesis will discuss controlling the surface area and porosity of carbon frameworks fabricated from CTFs. By using three different precursors, 12 carbon networks are synthesized and analyzed for porosity, surface area and capacitance. By varying the precursor composition and ratio, as well as the temperature, we are able to control the average pore size distribution between 1-17 nm, while the samples treated at 900�C show the best capacitance of 130 F/g.

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