UiO-66 metal-organic frameworks for water treatment
Creators: name: Ahmadijokani, Farhad
Publisher: name: University of British Columbia
Year: 2023

description: Metal-organic frameworks (MOFs), specifically Zr-based UiO-66, have gained attention for removing toxic pollutants due to their unique attributes. These include a large surface area, high porosity, active adsorption sites, tunable chemistry, pore control, and robust host-guest interactions. However, the practical use of pure MOF powders in water treatment faces limitations such as insolubility, processability, brittleness, safety concerns, and separation challenges. One of the significant concerns when using MOFs for water treatment is how well they maintain stability when exposed to aqueous environments. Therefore, this thesis demonstrates the stability of UiO-66 MOF over one year in water and chloroform, with minor changes observed in structure when exposed to dimethylformamide (DMF). The results from the stability studies contribute to a better understanding of UiO-66's stability in aqueous media. UiO-66 exhibits effective removal of organic pollutants, including methyl red (MR), methyl orange (MO), malachite green (MG), and methylene blue (MB), which possess different charges. The stable UiO-66 polycrystalline MOFs still grapple with the challenge of effective separation from the treated water. This thesis pursued a magnetic approach for the magnetization of UiO-66, coupled with subsequent post-modification. This strategy aimed to facilitate the efficient separation of UiO-66 from treated water using an external magnet. A two-step post-modification procedure, utilizing 2,4,6-trichloro-1,3,5-triazine (TCT) and 5-phenyl-1H-tetrazole (PTZ) agents, was introduced to enhance the adsorption performance of the magnetic nanocomposite. Despite a reduction in porosity and specific surface area compared to the pristine UiO-66-NH2, the resulting magnetic post-modified UiO-66 exhibited significantly improved adsorption capacity. Notably, magnetic UiO-66-TCT demonstrated a high adsorption capacity of approximately 298 mg/g for methyl orange (MO), offering facile MOF separation via an external magnet. The research further underscores the significance of post-modifying UiO-66 with novel functional groups to create effective adsorbents for the removal of organic contaminants. Combining MOFs with electrospun nanofibers offers efficient water treatment, addressing challenges linked to polycrystalline MOFs and their separation from treated water. This thesis employed a hybrid approach by integrating UiO-66 with thermally oxidized nanodiamond (TOND) to enhance its affinity for removing targeted organic contaminants. These hybrid UiO-66 particles were then incorporated into chitosan/ polyvinyl alcohol (PVA) nanofibers. The resulting nanofiber composite, containing 1.5 wt% hybrid UiO-66, exhibited a twofold increase in the maximum adsorption capacity for anionic Congo red dye (1429 mg/g) compared to the unfilled nanofiber (769 mg/g). Further advancements in UiO-66 nanofiber composite development were achieved by functionalizing UiO-66-NH2 with TCT and PTZ, followed by their incorporation into chitosan/PVA nanofibers. The optimal composite, consisting of 7 wt% functionalized MOF, exhibited a remarkable maximum adsorption capacity for MO (619 mg/g), surpassing most previously reported adsorbents such as activated carbon.