DEFECT ENGINEERING: ADVANCING THE STRUCTURAL PROPERTIES OF UIO-66 VIA MODULATION APPROACH

Date

2024-6-26

Author

Baltacı, Öykü

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Among the porous material classes, Metal-Organic Frameworks (MOFs) draw attention with their structural and chemical diversity, pore size distribution spectrum and chemical functionality. These diversity and unique structures give MOFs incredible potential in many fields such as adsorption and catalysis. Zirconium-based MOFs stand out with their high thermal, chemical and mechanical stability. UiO-66, a Zirconium-based MOFs, is one of the most researched metal-organic frameworks in literature. Defect engineering approach, is used to improve the porosity and functionality of UiO-66, thereby increasing its performance. Defect engineering manipulates the structural defects in MOFs by controlled and synthetic means. This approach has proven effectiveness on UiO-66, which retains its stability while tolerating high density of defects. Due to these positive properties of UiO-66, many studies have been carried out in the literature on controlling the defects in the UiO66 framework. MOFs synthesized through modulation approach tend to have higher porosity, surface area, and hydrophilicity than ideal (defect-free) frameworks, and therefore improved adsorption performance, thanks to the missing linker/cluster defects in their structures. In this way, control over structural defects in the UiO-66 vi MOF can be achieved. Defective metal-organic frameworks can be used in many applications in the fields of adsorption, catalysis and purification. In this study, firstly, the reference Zirconium-based UiO-66 has been synthesized as the base material, and then defective UiO-66 has been synthesized through temperature, time modulation, and in the presence of modulating agents. Thus, the effects of changing modulator amount, reaction temperature and reaction time on the physical and chemical properties of UiO-66 has been determined by various analyses. The results revealed that the surface area, porosity, total pore volume and the water uptake capacity of UiO-66 tend to increase with increasing modulator concentration and modulator acidity. Moreover, the lower reaction temperature and the lower synthesis time led to a more defective UiO-66 framework. The results also exhibited that the morphology, surface area, defectivity and the water uptake capacity of UiO-66 can be tailored by the modulation approach via de-novo synthesis of MOFs. The results obtained in this study can lead to the improvement of performance in water harvesting applications of MOFs synthesized in the presence of modulator with a defect engineering approach.

Subject Keywords

Metal-Organic Frameworks, UiO-66, MOF, Defect Engineering

URI

https://hdl.handle.net/11511/110376

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Graduate School of Natural and Applied Sciences, Thesis