| Summary: | <p>This thesis introduces characterising porous crystalline materials implanted with single metal sites or controlled metal clusters for catalysis, where several successful cases are provided to correlate the material microstructure with catalytic performance.</p>
<p>Compared with conventional catalyst supports, porous crystalline materials have many unique characteristics of topology, porosity, ionic charge distribution and surface chemical functionality, etc. Among the rich families of porous crystalline materials, zeolites are one that has been widely applied in petrochemistry. They have been designed with specific shapes, sizes and functions for many catalytic applications. Especially, the characteristic of encapsulating metal particles of various species and configurations endows porous crystalline materials with exceptional catalytic activity.</p>
<p>One key question regarding the catalytic activity of zeolites is the location of Brønsted acid site (BAS) within its framework. Therefore, this thesis conducted many advanced characterisation methods to determine the localisation of metal probes. It was directly observed that the position of silver (Ag) within the ZSM-5 framework exhibited the periodic distribution of aluminium on a 10-membered ring (10MR) adjacent to the different tetrahedral sites, T6, T8 and T12 rather than random occupancy using scanning transmission electron microscopy (STEM) and synchrotron radiation techniques. The Ag/ZSM-5 structural model was obtained through Rietveld refinement of the synchrotron powder X-ray diffraction (SXRD) data, the corresponding simulated results were consistent with the high-angle annular dark-field incoherent contrast. This evidence verified the atomic arrangement and the presence of Al and BAS in the metal-doped zeolite framework. This study plays a crucial role in understanding the highly active and selective catalytic pathways for hydrocarbon reactions.</p>
<p>Then, a strategy modular assembly for synthesising multinuclear copper clusters into the ZSM-5 framework is presented. STEM and SXRD combined with Rietveld refinement allow for the visualisation of non-noble metal clusters anchored by the ZSM-5 framework. The computational method of density functional theory (DFT) and the multislice algorithm of STEM contrast confirmed that Cu3 cluster exhibited a lower energy methanol absorption configuration, promoting more efficient methanol activation for hydrogen formation. If a noble metal single atom was doped within the USY zeolitic framework as a catalyst, it is crucial to investigate the position of Rhenium (Re) probe bonding with specific BAS of extra-framework Al (EFAl) in synergistic catalytic olefin metathesis reaction. Re-site is found to be the active site isolated within ReOx/USY zeolite. This thesis also demonstrated the use of low-dose 4D-STEM ptychography to verify the complex structure of beam-sensitive zeolites.</p>
<p>The detailed structure characterisation by complementarity between high-throughput synchrotron radiation technique, and STEM quantification, combining imaging simulation and DFT provides a comprehensive understanding of the potential correlation of atomic structures with catalytic activity. This detailed and systematic description serves as a crucial foundation for materials design as complex catalyst with enhanced performance.</p>
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