Zeolitic Imidazolate Frameworks: thin film syntheses, post-synthetic cation exchange in bulk material and its catalytic applications
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In this thesis, multiple approaches for the use of Zeolitic Imidazolate Frameworks (ZIFs) are reported and described in three chapters: Chapter 1 – Surface Mounted Imidazolate Frameworks An attempt was made to gain control over the growth of ZIFs on gold surfaces functionalized with specific thiols. With the use of carboxylic acid-, imidazole- and methyl-terminated SAMs, no homogeneous growth was observed. This result was ascribed to a bad quality of gold coated silicon wafers. Characterization of the products was performed with AFM, grazing Angle IR and contact angle measurements. Chapter 2 – Post-synthetic Cation Exchange (PScE) A method to exchange zinc ions in the framework with manganese ions from solution was reproduced from Fei et al. With atomic absorption spectrometry (AAS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX), exchange yields were observed to be 2-20% after an exchange period of 1 day; this was increased to a maximum of 35% after 3 days. Although it was proven that the particles did not leach zinc or manganese ions, no evidence was found with X-ray diffraction (XRD), XPS and N2-physisorption that manganese was truly incorporated into the framework. Chapter 3 – Catalytic Testing of ZIF-8 [Zn1-xMnx] Exchanged ZIF-8 crystals were used as a catalyst in the oxidation reaction of veratryl alcohol to veratraldehyde and in the epoxidation of olefins. An increase in the conversion of veratryl alcohol was measured with Gas Chromatography (GC). Additionally, no leaching of metal ions was observed with ICP-OES and after hot-filtration. The ZIF-8 [Zn1-xMnx] material exhibited no catalytic activity in the epoxidation of olefins.