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Heterogeneous catalysts are commonly used to enhance the rate and the selectivity of chemical reactions. These materials are routinely characterized by analyzing a large amount (up to billions) of catalyst particles at once, thus providing averaged information about their properties. While this approach is widespread in catalysis research, it overlooks intrinsic variability within catalytic materials. Insights into these heterogeneities can be obtained by spatially resolving the properties of individual catalyst particles, enabling a more rational optimization of these materials ultimately. Therefore, several microscopy methodologies have found their way to catalysis research during the past decades, mostly focusing on resolving fine structural details and the elemental composition. Complementary molecular information on the smallest length scales is often less accessible. Stimulated Raman scattering (SRS) microscopy is a promising chemical imaging technique that offers fast, 3D, label-free vibrational imaging with a sub-micrometer resolution. While its power has been showcased in various biomedical studies, the development of this technique in materials and catalysis research is lagging behind. This PhD thesis aims to develop SRS microscopy assays to spatially resolve the fine chemical details of zeolite catalysts at the single-particle level. The impact of synthesis and post-synthetic treatment conditions on the structural and compositional properties of different zeolites were investigated using the Raman signature of molecules located in their porous structure. The results illustrate the capabilities of SRS microscopy as a tool for catalyst characterization in general. Furthermore, the insights gathered by advanced vibrational imaging enable a more rational material optimization.

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The goal of this thesis is to investigate the correlation between missing linker defects and the catalytic activity of Zr- and Hf-based MOF-808 materials. The catalytic activity will be probed in both the selective hydrogenation of 4-nitrostryrene (4-NST) and the transfer hydrogenation of cinnamaldehyde (CA). The effect of loading the Zr- and Hf-based MOF-808 materials with silver on the catalytic activity and selectivity will also be investigated. A solvothemal synthesis method was used to synthesize Zr- and Hf-based MOF-808 with different amounts of missing linker defects. They are characterized by XRD and SEM, and the exact amount of missing linkers is determined via TGA measurements. The MOFs are impregnated with silver and the exact amount of silver deposited into the pores is determined by ICP-OES. The stability of the MOF-808 after the impregnation process is also studied and confirmed. The bare and silver impregnated Zr- and Hf-MOF-808 materials are used as catalysts in the selective hydrogenation of 4-nitrostyrene (4-NST) and in the transfer hydrogenation of cinnamaldehyde (CA). The conversion of these substrates into their products is determined by GC-FID measurements and the stability of the catalyst materials is investigated via XRD and SEM. The Zr- and Hf-based MOF-808 materials with different amount of missing linker defects were successfully synthesized and overall their structure remained unchanged during their impregnation with silver. The amount of missing linker defects is determined by TGA and it showed that the amount of defects can be tuned by varying the linker to metal precursor ratio in the reaction mixture for both the Zr- and Hf-MOF-808. With this increasing amount of missing linker deficiencies an increase in the amount of Lewis acid sites occurs making the material more catalytically active. This increase in missing linker defects also comes with a decrease in stability of the materials. For the selective hydrogenation of 4-NST it is observed that the added silver has a positive effect on the catalytic activity when the impregnated Zr- and Hf-MOF-808 materials are used as the catalyst material. During the transfer hydrogenation of CA the bare Zr- and Hf-MOF-808 materials already showed a high selectivity towards cinnamylalcohol. For this catalytic reaction the bare Zr- and Hf-MOF-808 materials show a higher activity for the reaction than the silver impregnated materials, indicating that the silver has a negative effect om the catalytic activity. The Zr-MOF-808 with 1.52 linkers per secondary building unit (SBU) and Hf-MOF-808 with 1.81 linkers per SBU are also impregnated with different amounts of silver to investigate which amount gives the highest activity towards the transfer hydrogenation reaction of CA. Overall the materials stay stable during the catalytic reaction, only a slight decrease in stability is observed for the MOF-808 materials with a silver loading of 1 %. It can be concluded for the impregnated Zr-MOF-808 with 1.52 linkers per SBU that a silver loading of 0.5 % results in the highest catalytic activity. For the Hf-MOF-808 with 1.81 linkers per SBU no conclusion can be made about which silver loading results in the highest catalytic activity. This because the activity for the 0.1 %, 0.5 % and 5 % silver loading are overall the same. Therefore further investigation with a smaller amount of catalyst material is needed.

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Since its emergence, microfluidics has proven to be a powerful tool in chemistry and the life sciences. Microfluidic devices, consisting of networks of micron-scale flow channels, leverage high surface-area-to-volume ratios and precision fluid control to provide advantages over conventional methods in chemistry and biology. In chemistry, reactions with greater speed, selectivity, and safety can be achieved thanks to fast mixing and efficient heat transfer. In biology, greater control over mechanical and biochemical microenvironments allow cell culture studies with greater relevance to living organisms.The progression of microfluidics over the past three decades, however, has not lived up to the high expectations that were held at its beginnings. While numerous factors can be identified as bottlenecks in the continued development of microfluidics, one critical element is the need for new microfluidic materials. Microfluidic devices, or "chips," can be fabricated from a variety of different materials, such as silicon, glass, and polymers, with each one possessing its intrinsic advantages and drawbacks, as discussed in Chapter 1. A material must possess suitable material properties for the microfluidic application at hand, but one must also evaluate its fabrication and cost as factors key to its accessibility and transferability across manufacturing scales. The most common microfluidic material, an elastomer called polydimethylsiloxane (PDMS), possesses numerous drawbacks in its material properties that make it unideal for many biology applications and unusable for many chemistry applications. Moreover, the techniques used for its fabrication are low-throughput, limiting the possibility of large-scale implementation (i.e., a transfer from academic research to industry). A group of materials called soft thermoplastic elastomers (sTPE) have been recently developed for microfluidics, with preliminary reports in literature demonstrating their favorable material properties and transferable fabrication methodologies. This PhD, conducted between academia and industry, focuses on two distinct sTPE materials, Flexdym™ and Fluoroflex, and their use for cell culture and flow chemistry applications, respectively. It aims to evaluate the properties of these novel sTPE materials and capitalize on them by providing sTPE device demonstrations that give scope for broader and more widespread microfluidic applications in these fields.Chapter 2 describes the development of a composite microfluidic platform for membrane-based cell culture, consisting of two micropatterned Flexdym™ layers separated by a commercially available porous polycarbonate membrane. Membrane-based cell culture can be used to simulate tissue-tissue interface, valuable for drug development and disease modeling, and provides the basis for cutting-edge organ-on-chip technology. The thermoplastic platform leverages the rapid hot embossing and self-sealing property of Flexdym™, as well as the simplicity of the off-the-shelf polycarbonate membrane, to improve upon the fabrication time and complexity of similar microfluidic geometries made in PDMS. The pressure capacity of the bond formed between Flexdym™ and polycarbonate was characterized and found to be sufficient for cell culture applications (> 500 mbar). To validate the device's utility for membrane-based cell culture, cell culture trials were performed, showing cell adhesion and proliferation inside the device.Chapter 3 reports the extensive material characterization of Fluoroflex and the development of a modular microfluidic platform using the material. Fluoroflex was found to exhibit good chemical resistance in comparison to PDMS and other polymers, allowing its use with common organic solvents, such as toluene, dichloromethane, and hexane. Key optical, mechanical, and surface properties of Fluoroflex were also characterized, and showed the material's appropriateness for use as a microfluidic device. A 30 s hot embossing protocol was developed, allowing for the rapid micropatterning of Fluoroflex. Like Flexdym™, Fluoroflex possesses an intrinsic adhesive property, allowing spontaneous bonding with itself to occur after the formation of conformal contact. This self-sealing was evaluated through burst testing and found to withstand a pressure of 1.4 bar after only five minutes of conformal contact between two Fluoroflex surfaces. This fast, reversible bonding was used to create a modular microfluidic platform, with which microfluidic droplet generation (water in toluene) of variable size was demonstrated.Chapter 4 expands on the microfluidic applications of Fluoroflex by presenting the preliminary work toward a microfluidic packed bed photoreactor consisting of a Fluoroflex microchannel and PDMS microbeads. PDMS microbeads were synthesized and subsequently injected into a Fluoroflex microchannel and trapped by a micropillar array. An on-chip functionalization protocol was used to create an aminosilane surface layer on the microbeads, to which fluorescein was then coupled. Separately, a derivative of perixanthenoxanthene (PXX), a photoactive molecule, was coupled to PDMS microbeads (off-chip) in a similar manner, and subsequently shown to retain its photocatalytic properties through a debromination reaction. These results provide a proof-of-concept and clear next steps toward the implementation of microbead-supported heterogeneous photocatalysis in a Fluoroflex device.Finally, Chapter 5 consists of a market evaluation of flow chemistry microreactors, aimed at providing industrial context to the Fluoroflex characterization and microfluidic development work. A competitive landscape analysis summarizes commercially available microreactors. Interviews of flow chemistry researchers were conducted to understand the needs of microreactor end-users and any technological difficulties they face. Lastly, a market size assessment is conducted, in which publication metrics are used to estimate the size, value, and growth trends of the flow chemistry research market for a Fluoroflex microreactor offering.