Exploring Photocatalytic Degradation of Aqueous Pollutants Using Iron-Doped UiO Metal-Organic Frameworks

Abstract

Metal-organic frameworks (MOFs) are porous crystalline materials that consist of networks of metal or metal-oxo nodes coordinatively bound to organic linkers. MOFs are rapidly growing in popularity and importance due to their highly modular nature—granting them potential for applications in environmental remediation, specifically the degradation of organic pollutants in wastewater treatment. Zirconium-based UiO-67 MOFs, though widely studied in various catalytic applications, represent a void in the pollutant degradation literature even though they have several attractive structural and chemical properties. Previous studies have indicated that integrating iron into the MOF structure and exposing it to light can enhance its catalytic capabilities through photo-Fenton reactions. While MOF light activation experiments typically utilize UV light, visible light conditions are also studied as a renewable energy alternative. In this thesis, multiple iron-loaded UiO-67 MOFs are synthesized, characterized, and photocatalytically tested under both visible and UV light conditions for their effectiveness to degrade methylene blue (MB)—which serves as a model dye and medication pollutant. Tethering iron chloride (F eCl3) to the linker site of a UiO-67 derivative proves to be an unsuccessful post-synthetic doping mechanism, whereas iron-loading of UiO-67 to form iron oxide nanoparticles through an incipient wetness impregnation method achieves desirable material stability and enhanced photo-degradative capabilities under UV light conditions resultant from its reduction in material band gap energy relative to the parent MOF. Recharging supernatent fluid recovered after solid catalyst with MB results in no significant degradation, indicating no leached species active for the chemistry are present in solution. Additionally, the material retains long-range order after recovery from reaction and washing with organic solvents. Coupled together, this thesis provides strong evidence that the catalysts are stable under the aqueous conditions employed, highlighting the potential of iron-doped UiO-67 materials for photocatalytic pollutant oxidation.