ETD

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Tesi etd-06222022-175500


Tipo di tesi
Tesi di laurea magistrale
Autore
ALBANO, VITTORIO
URN
etd-06222022-175500
Titolo
Aliovalent doping in Zr-based MOF UiO-66 with Y3+ cations
Dipartimento
CHIMICA E CHIMICA INDUSTRIALE
Corso di studi
CHIMICA
Relatori
relatore Dott. Taddei, Marco
Parole chiave
  • Y3+
  • Aliovalent
  • Zr-based MOF
Data inizio appello
11/07/2022
Consultabilità
Non consultabile
Data di rilascio
11/07/2025
Riassunto
UiO-66(Zr), a MOF based on Zr(IV) and terephthalic acid (BDC), has achieved resounding success due to its cheap and easy synthesis, high thermal and hydrolytical stability, high porosity and high chemical versatility. The inorganic unit of UiO-66 is a metal oxo-hydroxo cluster with the same local Zr-O connectivity found in cubic zirconia, a metastable form of zirconia at room temperature. Doping ZrO2 with Y(III), alias aliovalent doping, leads to the stabilization of cubic topology at room temperature yielding yttria-stabilised-zirconia (YSZ), with general formula YxZr1-xO2-x/2. The charge imbalance caused by the introduction of a lower valent cation in the structure leads to the formation of oxygen vacancies, as a result of charge compensation in the material, giving anionic conductivity of O2- ions.
Based on this premise, it can be expected that doping of UiO-66(Zr) with Y(III) might alter the material's chemical-physical properties. We explored doping by direct synthesis, screening a wide range of synthetic parameters, such as different Zr and Y precursors and Zr/Y ratio, with and without the addition of crystallization modulators. The highest Y loading (xx%) was achieved using ZrCl4 and YCl3·6H2O as metal precursors, in N,N-dimethylformamide as the solvent and in the presence of 2-fluorobenzoic acid and 2,6-difluorobenzoic acid as modulators. Because of the large difference in ionic radii between Y3+ (1.02 Å) and Zr4+ (0.84 Å), we believe that Y causes an excessive strain in the structure, leading to a low incorporation of Y in the MOF and the formation of a second crystalline phase at higher amount of dopant
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