Doctor of Philosophy
Microporous materials have attracted tremendous attention since 18th century due to their industrial importance. It is essential to understand the relationships between the properties of microporous materials and their structures. However, the structures of many microporous materials are determined from the more limited powder X-ray diffraction (XRD) data due to the lack of suitable single-crystals for XRD. In such cases, an unambiguous structure solution of microporous materials requires additional information from other techniques such as solid-state NMR (SSNMR) spectroscopy. This thesis is focused on the study of two types of microporous materials, metal–organic frameworks (MOFs) and titanosilicates, by multinuclear SSNMR spectroscopy in combination with quantum chemical calculations for computational modeling.
Multinuclear SSNMR investigations of two prototypical MOFs with potential industrial applications, CPO-27-M (M = Mg, Zn, Co, Ni), and a-Mg3(HCOO)6, are carried out. The results demonstrate that SSNMR spectroscopy is very suitable for the characterization of MOFs: The local Mg environments and the rehydration/adsorption processes of CPO-27-Mg were examined by natural abundance 25Mg SSNMR at an ultrahigh magnetic field of 21.1 T. The dynamics of several guest molecules inside of CPO-27-M were monitored by variable-temperature 2H SSNMR. The structures of a-Mg3(HCOO)6, before and after guest adsorption, were also thoroughly investigated by 1H, 2H, 13C, 17O, and 25Mg SSNMR.
A comprehensive study of titanosilicates by 29Si, 23Na, 39K, and 47/49Ti SSNMR was also performed. This work is highlighted by the acquisition of natural abundance SSNMR spectra for three unreceptive quadrupolar nuclei, 47/49Ti and 39K, at 21.1 T. 47/49Ti SSNMR provides insights into the coordination environments of Ti inside the framework, whereas 39K SSNMR allows one to directly probe the local environment of extra-framework counter cations in titanosilicates.
Xu, Jun, "Multinuclear Solid-State Nuclear Magnetic Resonance Spectroscopy of Microporous Materials" (2013). Electronic Thesis and Dissertation Repository. 1752.