The demand for heating and cooling are increasing due to the growing global population and climate change. There is a growing interest in addressing this demand in an environmentally friendly way, one such method is thermochemical energy storage (TCES). TCES has lower heat losses compared to other methods and can achieve a significantly higher energy storage density. TCES is based on the reversible chemical reactions and/or sorption processes of gases in solids or liquids. Potential adsorbents for heat storage applications, are required to have specific properties, such as high sorption capacity, optimum desorption temperature and released heat temperature. In recent years, the interest in using of metal-organic frameworks (MOFs) and their subgroup zeolite imidazolate frameworks (ZIFs), which have a large specific surface area, various functional groups on the surface of frameworks, different pore sizes and therefore enable selective adsorption of the working fluid into the material, has grown significantly in this field. The majority of ZIF synthesis uses dimethylformamide (DMF) as the solvent, which is not environmentally friendly. Therefore, the aim of this research was to replace DMF with greener solvents, such as water, methanol and ethanol in solvothermal synthesis of ZIF-71 and ZIF-93 materials. Both materials were synthesised by using mechanochemical method as well. Initially, the samples were synthesised using methods from literature, these methods were then optimised by changing various parameters (including the amount of solvent, type of solvent, the amount of acid/base added, type of zinc precursor and duration of the reaction). The characterization of the samples was performed using powder X-ray diffraction, thermogravimetric analysis, nitrogen physisorption and scanning electron microscope. Aditionally thermogravimetric method was also used to determine the % ethanol and % water uptake of the optimised ZIF samples. While the synthesis time for ZIF-93 was reduced from 18 hours down to 4 hours with similar properties, the initial synthesised ZIF-93 sample from literature showed the best uptake. Furthermore, ZIF-93 was synthesised from zinc nitrate hexahydrate in just 5 hours, with no activation required. Solvothermal synthesis of ZIF-71 was not optimised, as the product with the best characteristics among the synthesized samples has a slightly lower ethanol sorption capacity than the initial sample, synthesized according to the procedure described in the literature. Currently there are no published procedures for mechanochemical synthesis of the two ZIFs. Therefore, they were synthesized by using different ratios of reactants and type of solvents. Additionally, the best synthesis procedure was optimised and the influence of various reaction parameters, such as the time and frequency of milling, the influence of the addition of different amounts of acid/base... on the crystallinity and phase composition of the product were analysed. The mechanochemically synthesised ZIF-93 sample has comparable properties to the product of solvothermal synthesis at room temperature. ZIF-71 was synthesised by using the named method as well. However, it is not useful for heat storage applications as it was converted into poorly porous ZIF-72 during the water and ethanol sorption studies.
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