METAL-ORGANIC FRAMEWORKS (MOFs): SYNTHESIS, CHARACTERIZATION, AND POTENTIAL APPLICATIONS

2022-8-22
KHAN, SAEED AHMAD
Metal-organic frameworks (MOFs) are an emerging class of crystalline porous materials that consist of metal clusters (nodes) connected by organic linkers (struts) to form a three-dimensional molecular framework. MOFs have attracted considerable attention in recent years owing to their exceptional properties. Due to their remarkable design flexibility, ultra-high porosity, large specific surface area, and tunable chemistry, MOFs are indispensable for potential applications in clean energy, gas adsorption, and catalysis. In this study, three types of MOFs were synthesized by the solvothermal method i.e. UiO-66 a zirconium-based MOF (Zr-MOF), MIL-125 a titanium-based MOF (Ti-MOF), and MIL-47 a vanadium-based MOF (V-MOF). The three MOFs synthesized in this study have different molecular framework structures and topologies. MOFs were synthesized by varying synthesis temperatures, precursor concentrations, reaction time, and using modulators. UiO-66 MOF was synthesized at different synthesis temperatures (80oC, 100oC, and 120oC) and precursor (ZrCl4 and H2bdc) concentrations i.e. ZrCl4 8.6-19.1 mM and H2bdc 8.6-36.1 mM. It was shown that the synthesis temperature and concentration of precursors have affected the synthesis (reaction) time for UiO-66 as well as thesize and morphology of the UiO-66 crystals. The use of modulators like HCl, acetic acid, and triethylamine changed the morphology and the size of the crystals. Moreover, the synthesis time was also affected by the introduction of modulators in the synthesis solution of UiO-66. The water adsorption capacity of UiO-66 MOF was also tested for relative humidity (%Rh) values of 25-80% at 30oC. MIL-125 synthesis was achieved under different experimental conditions without the use of a glove box. MIL-125 was synthesized from 100oC, 130oC, 150oC, and 160oC, and it was observed that the synthesis temperature affected the morphology of MIL-125 crystals. The synthesis time (2 days and 3 days) changed the morphology of the synthesized MIL-125 crystals. The reactant concentrations (H2bdc and titanium isopropoxide) and the impurities formed during the synthesis affected the MIL-125 MOF product. Furthermore, some variation in the MIL-125 crystal shape was observed from batch to batch even when synthesized at the same experimental conditions and precursor concentrations. MIL-47 was synthesized at different synthesis temperatures (160oC and 220oC), reaction times (1 day, 3 days, and 5 days), and precursors (H2bdc and VOSO4.nH2O) concentrations. The synthesis temperature affected the shape of the MIL-47 crystals as well as the synthesis (reaction) time. Different crystal morphologies were obtained for MIL-47 MOF at different experimental conditions.

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Citation Formats
S. A. KHAN, “METAL-ORGANIC FRAMEWORKS (MOFs): SYNTHESIS, CHARACTERIZATION, AND POTENTIAL APPLICATIONS,” M.S. - Master of Science, Middle East Technical University, 2022.