A study of metal-organic frameworks for the storage and release of medical gases

Abstract

This thesis presents a study of the interaction of medical gases nitric oxide, carbon monoxide and hydrogen sulfide with metal-organic framework materials. Most analysis is performed via single-crystal X-ray diffraction and Rietveld and pair distribution function analysis of powder X-ray diffraction data. A background to the field and the experimental methods used are described in Chapters 1 and 3. The use of a specially designed static environmental gas cell to assess the role of coordinatively unsaturated metal sites in nitric oxide storage in Co-CPO-27 via in situ single-crystal structure determination is described in Chapter 4. Nitric oxide was shown to bind to the Co-centre of the material in a bent geometry in an approximately 1:1 Co:NO ratio. A multi-technique study was conducted on the framework Cu-SIP-3 in Chapters 5 and 6, utilising both single-crystal X-ray diffraction and pair distribution function analysis to obtain complementary information about atomic movements during a thermally active single-crystal to single-crystal transition. These techniques were further applied during in situ gas-loading experiments on the same framework. Application of the pair distribution function technique to metal-organic frameworks is described in Chapter 7, where refinements of both known and unknown metal-organic framework structures are presented. Partial PDFs are used to determine the secondary building block of a new metal-organic framework and verify the structural solution determined from powder X-ray diffraction data. Chapter 8 presents the study of the M-CPO-27 isostructural series for the adsorption and release of hydrogen sulfide and carbon monoxide. Gas adsorption isotherms and release measurements are correlated with the structure of the Ni-CPO-27 hydrogen sulfide-adduct determined by both powder X-ray diffraction and differential pair distribution function methods which reveal the open-metal site as the primary adsorption interaction in the material. The hydrogen sulfide released from Zn-CPO-27 is determined to be biologically active through vasodilatation experiments.