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|Title: ||Structural Evolution of Metal-Organic Frameworks - From Primary Crystals to Spherical Agglomerates|
|Keywords: ||動力學;金屬有機結構材料;球晶;Kinetics;Metal-Organic Frameworks;Spherical Agglomeration|
|Issue Date: ||2014-10-15 14:37:21 (UTC+8)|
;The aim of this thesis was to show the structural evolution of [In(OH)bdc]n crystals from molecular synthesis to primary crystals, which then aggregated into spherical agglomerates. The synthesis of [In(OH)bdc]n crystals were conducted at three different temperatures 60o, 80o and 100oC. The crystal growth curves can be deduced by UV/vis spectroscopy. The crystallite structure, chemical bonding, agglomerate size distribution, pore size, adsorptive capability, and sensing characteristics were illustrated and compared among the products synthesized at three different temperatures. From the crystal growth curves, the secondary crystallization of MOFs was discovered which had not been reported before. The [In(OH)bdc]n crystals synthesized at 80oC were the best based on their superior adsorption surface areas and crystallinity. It was because the diffusion control taking place during the initial period of nucleation had removed the amorphous molecules and led to the best crystallinity. Only [In(OH)bdc]n crystals synthesized at 60oC showed clear hysteresis indicating the existence of both micro- and mesopores. The micropores and high crystallinity led to the highest adsorption surface area of [In(OH)bdc]n crystals synthesized at 80oC. The PL sensing characteristics were consistent between the three products synthesized at 60o, 80o and 100oC individually. The process-history independence of PL allowed [In(OH)bdc]n crystals to be synthesized in various conditions. The crystal growth curve can be served as a relationship between the synthetic parameters and the final product properties. Combined with the in situ monitoring instruments, we could control the conditions during synthesis and attained products with the desired properties.
On the other hand, the spherical agglomeration of [In(OH)bdc]n crystals was carried out in a n-heptane/ethanol/PEG system. Different amounts of MOF crystals (i.e. 1g and 5g) were used to compare the effect of sample loading. After the agglomeration process, the structure of MOF crystals remained integrity. But the lower desolvation temperature at 150oC could not eliminate the trapped n-heptane entirely, which led to the reduction in the amount of N2 adsorbed. The micropores were covered by PEG which worsened the situation and the adsorption volume decreased to 3.5 cm3/g. Although the spherical agglomerates lost the gas storage capability, the PL sensing characteristics were still remained. The improvement of flowability was indicated from the reduction in the Carr’s index which would benefit the powder handling for sensor fabrication.
|Appears in Collections:||[化學工程與材料工程研究所] 博碩士論文|
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