Doctor of Philosophy
Metal-organic frameworks (MOFs) are a class of microporous materials constructed from virtually endless combinations of metal centres and organic linkers. MOFs have attracted intense research interest in recent decades, since MOFs have outstanding properties such as extremely high surface area, tuneable pore topology, good stability, and many others. MOFs are also promising candidates for gas storage. In this work, solid-state NMR (SSNMR) spectroscopy has been investigated to study MOFs and their guest molecules, since SSNMR can provide information on the short-range environment about target nuclei and can also reveal the dynamics of guest molecules.
An introduction to MOFs and SSNMR is given in Chapter 1. In Chapter 2 and Chapter 3, CO2 dynamics within the MIL-53 series MOFs as well as H2 dynamics within UIO-66, MOF-74 series MOFs and α-Mg3(COOH)6 are described, as obtained using variable temperature (VT) static 13C and 2H SSNMR experiments with isotopically-labeled 13CO2 and 2H2. CO2 adsorption sites within MIL-53 MOFs also have been experimentally confirmed using 1H-13C cross polarization (CP) SSNMR experiments. Along with dynamic information, the CO2 and H2 binding strength of MOFs can be investigated using SSNMR experiments. In Chapter 4, complementary techniques including single crystal X-ray diffraction (SCXRD), DFT calculations, and 2H SSNMR experiments have been used to study methane adsorption within four MOFs: α-Mg3(COOH)6, α-Zn3(COOH)6, SIFSIX-3-Zn and MOF-74. This study revealed the methane adsorption sites, methane adsorption behaviour, and the presence of the nuclei independent chemical shift (NICS) effect within these MOF systems. Chapter 5 describes the synthesis and characterization of novel Ga- and In-fumarate MOFs. Powder X-ray diffraction (pXRD) refinement and 69/71Ga SSNMR experiments at 21.1 T have been employed to determine the structure of Ga-fumarate. CO2 adsorption within the Al-, Ga-, and In-fumarate MOFs also has been comprehensively studied in this Chapter. Chapter 6 consists of a SSNMR study of different phases of the flexible Ga-MIL-53 MOF. 69/71Ga SSNMR spectra are very sensitive to distortions in the octahedral GaO6 secondary building units within Ga-MIL-53; by extension, 69/71Ga NMR parameters are indicative of the particular crystallographic phase of Ga-MIL-53.
Zhang, Yue, "Studying Metal-Organic Frameworks via Solid-State NMR: Gas Dynamics, Structure Determination, and Phase Transition" (2017). Electronic Thesis and Dissertation Repository. 5162.