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Title: Multinuclear solid-state NMR for the characterisation of inorganic materials
Author: Seymour, Valerie Ruth
ISNI:       0000 0004 2738 1261
Awarding Body: University of St Andrews
Current Institution: University of St Andrews
Date of Award: 2013
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In this work, multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy is used to investigate a range of inorganic materials, often in combination with DFT (density functional theory) studies. Solid-state NMR is particularly suited to the study of aluminophosphates (AlPOs), as the basic components of their frameworks have NMR active isotopes (²⁷Al, ³¹P, ¹⁷O), as do many of the atoms that comprise the structure directing agent (¹³C, ¹H, ¹⁵N), and the charge-balancing anions (OH⁻, F⁻). A study of the AlPO STA-15 (St Andrews microporous solid-15) provides an introduction to using solid-state NMR spectroscopy to investigate AlPOs. More in-depth studies of AlPO STA-2 (St Andrews microporous solid-2) and MgAPO STA-2 (magnesium-substituted AlPO) examine charge-balancing mechanisms in AlPO-based materials. A range of scandium carboxylate metal-organic frameworks (MOFs), with rigid and flexible frameworks, have been characterised by multinuclear solid-state NMR spectroscopy (⁴⁵Sc, ¹³C and ¹H). The materials studied contain a variety of metal units and organic linkers. ¹³C and ¹H magic-angle spinning (MAS) NMR were used to study the organic linker molecules and ⁴⁵Sc MAS NMR was used to study the scandium environment in the MOFs Sc₂BDC₃ (BDC = 1,4-benzenedicarboxylate), MIL-53(Sc), MIL-88(Sc), MIL-100(Sc) and Sc-ABTC (ABTC = 3,3`,5,5`-azobenzenetetracarboxylate). Functionalised derivatives of Sc₂BDC₃ and MIL-53(Sc) were also studied. The ⁴⁵Sc MAS NMR spectra are found to be strongly dependant on the Sc³⁺ coordination environment. ²⁷Al and ²⁵Mg MAS NMR have been used to study Ti-bearing hibonite samples (of general formula Ca(Al, Ti, Mg)₁₂O₁₉), and results compared to a recent complementary neutron powder diffraction study, in order to investigate the substitution sites for Ti³⁺/⁴⁺ and Mg²⁺. A DFT investigation was also carried out on the aluminium end member, CaAl₁₂O₁₉, due to debate in the literature on the ²⁷Al NMR parameters for the trigonal-bipyramidal site. The substitution of Mg onto the tetrahedral site (M3) and Ti primarily onto one of the octahedral sites (M4) is supported.
Supervisor: Ashbrook, Sharon E. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Solid-state NMR ; Aluminophosphate ; Metal-organic framework ; Hibonite ; DFT