The Development of Hybrid Liquids and Glasses
Abstract: The Development of Hybrid Liquids and Glasses Louis Michael David Longley Metal-organic framework (MOF) glasses are amorphous materials formed by heating a crystalline MOF into the liquid phase and then cooling to form an amorphous solid material. The hybrid nature, defined here as materials containing both inorganic and organic bonding, of MOF glasses makes them distinct from previous glass families which have inorganic, organic, or metallic bonding. Most of the work on MOF glasses reported in the literature has focused on a sub-set of MOFs known as Zeolitic Imidazolate Frameworks (ZIFs). This work begins with a discussion of the structure of MOF glasses, particularly focusing on structure occurring beyond the first metal-metal correlation, also termed mid-range order. The observed midrange order in MOF glasses, measured by X-ray total-scattering, is interpreted using existing theory for inorganic glasses. The number of MOFs which form liquids on heating is small relative to the total number of known crystalline MOF structures due to decomposition of the framework occurring before melting in most cases. This work therefore takes an alternative approach to expanding the MOF glass domain through exploitation of the reactivity of the liquid phase as a route to the synthesis of new glass structures. ‘Complex’ glasses formed from two parent MOF crystals heated into the liquid phase were synthesised, and their structures investigated by a variety of techniques, including x-ray total-scattering, differential scanning calorimetry, and electron microscopy. Following this work the scope of MOF glasses was further expanded through the production of composite materials of MOF and inorganic phosphate glasses. The structures and properties of these materials were also investigated thoroughly with attention being given to the interaction occurring at the interface between the two highly dissimilar components. Finally, as an extension of this, the interaction between a phosphate glass and a crystalline ZIF was investigated to probe the potential for inorganic glass crystalline MOF composite formation.
Metal-organic Frameworks, Zeolitic Imidazolate Frameworks, MOFs, ZIFs, Glass Science
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