Advanced Electron Diffraction Techniques for Structural Elucidation of Microporous Materials
- Autores: Juan Ignacio Tirado Castaño
- Directores de la Tesis: Partha Pratim Das (dir. tes.), José Luis Jordá (dir. tes.), Sara Iborra Chornet (tut. tes.)
- Lectura: En la Universitat Politècnica de València ( España ) en 2025
- Idioma: español
- Tribunal Calificador de la Tesis: Enrico Mugnaioli (presid.), M. Jose Diaz Cabañas (secret.), Mónica Giménez Marqués (voc.)
- Programa de doctorado: Programa de Doctorado en Química Sostenible por la Universidad de Castilla-La Mancha; la Universidad de Extremadura; la Universidad Jaume I de Castellón; la Universitat de València (Estudi General) y la Universitat Politècnica de València
- Materias:
- Enlaces
- Tesis en acceso abierto en: RiuNet
- Resumen
Microporous materials such as zeolites have been highlighted due to their broad impact on catalytic processes and industry. The knowledge of their crystalline structure and the study of their properties and applications are intrinsically related. Therefore, conventional diffraction techniques such as single-crystal and powder X-ray diffraction (SCXRD and PXRD) have been the usual methods to retrieve structural information. However, the limitation in growing crystals large enough for SCXRD and the strong peak overlapping in PXRD patterns frequently hamper the structure determination of these materials, with complex structures and large unit cell parameters. Therefore, studying state-of-the-art diffraction techniques for structural characterization in new microporous materials, such as zeolites, is paramount. The incentive of this work is to investigate Electron Diffraction Tomography (EDT), also known as Three-Dimensional Electron Diffraction (3DED). These methods can be an exceptional technique for structural analysis of microporous materials using conventional and already available Transmission Electron Microscopes (TEM). These techniques generate single-nanocrystal diffraction patterns with enhanced scattering intensities using electron beams. These patterns are acquired as the nanocrystal rotates within the TEM's goniometer, resulting in electron diffraction (ED) patterns from single small crystals of nanometer-scale dimensions. These methods require developing and optimizing all experimental parameters, often demanding TEM expertise operators. Additionally, strong multiple diffractions ("dynamical effects") can hinder the collection of accurate intensities. Moreover, many materials suffer structural damage by the interaction with the electron beam. To address this issue, the combination of the precession electron diffraction tomography (PEDT) technique, which applies a precession of the beam, together with a fast 3DED procedure will minimize these effects, leading to a successful data collection, processing, and structure determination.
This methodology has been applied to solve the structure new microporous materials, named ITQ-70 and ITQ-35, in as-made form containing organic guest molecules, and one already known as-made zeolites structure with two different guest organic molecules, ITQ-52. This approach will lead to the complete atomic localization of the hybrid inorganic and organic zeolitic materials through the approachability of 3DED techniques combined with X-ray diffraction refinements. This will offer a promising general protocol for developing a novel characterization tool for an accurate structure determination from small crystal materials.
