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The rational improvement of solid catalysts requires a thorough understanding of the structure-activity relationship down to the smallest possible length scales. Recently developed approaches that correlate fluorescence microscopy (FM) and scanning electron microscopy (SEM) allow such insights by direct linking of nanoscale catalytic activity maps, as recorded using fluorescence, to the local structural context. The goal of this PhD was to investigate structure-activity relationships at the nanoscale, by developing an integrated light and electron microscope (ILEM) that combines the power of single molecule sensitive FM to resolve reactivity at the nanoscale with a high-end SEM. Initially, the ILEM was applied to visualize silver nanoparticle photodeposition from an aqueous silver(I) solution on individual ZnO crystals, in real time. This was enabled by the ability to simultaneously perform local UV irradiation using the integrated light microscope and SEM imaging at the same region of interest (ROI) while the sample was contained inside a specialized liquid cell. This research revealed that silver nanoparticle formation predominantly occurs at crystal edges. However, the contribution of the electron beam during silver nanoparticle deposition was found to be non-negligible. Follow-up research was performed by applying the ILEM in a correlative fashion; i.e., by performing structural imaging before and after, and not during, UV induced silver photodeposition. As such, the facet dependent photocatalytic reactivity could be explored at the single particle level and, at the sub-particle level, variations were related to crystallographic structural features and defects. The first correlative super-resolution fluorescence and electron microscopic investigation of zeolite catalysts was made possible after resolving several technical challenges encountered during the ZnO research and by further optimizing the fluorescence microscope to enable the detection of individual catalytic fluorogenic conversions. This improved setup made it possible to directly observe the effect of intercrystalline intergrowths on the overall catalytic performance of acid mordenite zeolites. By determining the orientation of the individual reaction products compared to the underlying zeolitic framework, it was found that shape-selectivity was maintained at the defect-rich intergrowth boundary. Hence, the intergrowth was identified as a void space that facilitates mass transport into these pores. Acid leaching did not dramatically change this, as activity increased on previously active regions while the molecular orientation was maintained. A second correlative zeolite structure-activity investigation targeted individual ZSM-22 catalyst particles. The typical needle-shaped morphology of these particles results from a lateral fusion of elementary nanorods and indirect experimentation already suggested that during this lateral fusion, external, catalytically inactive, aluminum is converted into catalytically active internal aluminum. This was confirmed by the visualization of catalyst activity and shape-selectivity at the sub-particle level on the ILEM. In summary, over the course of this PhD, a performant ILEM was developed that combined super-resolution fluorescence microscopy based on the localization of individual fluorescent molecules with high-end field emission SEM. Also the necessary experimental routines and software tools were developed, enabling the determination of the structure-activity relationship of heterogeneous catalysts at the nanoscale. This powerful research tool allows a direct correlation of catalyst structure and activity beyond the single particle level. It is anticipated that the further application and development of this ILEM will ultimately lead to a more rationalized catalyst optimization.

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Mordenites are important solid acid catalysts for the isomerisation of alkanes and aromatics. The most important features responsible for their applicability are that they are heterogeneous and that they are very selective towards a certain reaction. This selectivity is caused by the specific dimensions of the porous network. In order to optimize their properties as solid acid catalysts for a certain reaction process there are some post-synthesis treatments available. One of the most important of these treatments is dealumination. Aluminium is removed from the framework structure, causing a change in the strength of the acid sites and the accessibility. An increased accessibility causes an increased lifetime of the catalyst particles. In this thesis most of the research is performed by means of fluorescence microscopy. A fluorescent molecule is excited at a certain wavelength and emits at a longer wavelength. This separation in excitation and emission wavelength makes it possible to obtain a high signal to noise ratio and even to observe single emitters. In this thesis the acid catalysed oligomerization of furfuryl alcohol is used to locate the acid sites by means of fluorescence. The reaction products exhibit fluorescence and hence every single emitter represents a single catalytic turnover. By applying a localization algorithm to the obtained image it is possible to determine the exact position of the catalytically active sites. The result is thus a map of the active sites in high resolution. Our research is performed on a series of mordenites with different grades of dealumination to study the influences of this process on the different aspects of mordenite crystals.To get a full understanding of the sample we start with a scanning electron microscopy study. This allowed us to obtain first insights in the influence of dealumination on the bulk scale. By measuring a size distribution, identifying the different structures and measuring the average crystal size, ...