(706b) Insights into the Performance and Stability of Contrasting Iron- and Zirconium-Based MOFs for Aqueous Pollutant Oxidation
AIChE Annual Meeting
2024
2024 AIChE Annual Meeting
Catalysis and Reaction Engineering Division
Microporous and Mesoporous Materials III: Sites
Thursday, October 31, 2024 - 3:48pm to 4:06pm
Rising water consumption and pollution motivate continued efforts to improve the efficacy of wastewater treatment technologies. Metal-organic frameworks (MOFs), consisting of highly tunable networks of organic linkers coordinated to metal-containing nodes, hold potential for use in adsorptive and (photo)catalytic removal of aqueous pollutants. MOFs made from earth-abundant metals, such as zirconium (Zr) and iron (Fe), are attractive given their low metal cost and previous demonstration of aqueous pollutant abatement.[1] This work focuses on oxidation of methylene blue (MB), a medication and dye, by hydrogen peroxide to elucidate connections between structure and function of Zr- and Fe-based MOFs in the (photo)catalytic removal of pollutants pertinent to industrial effluent, with a particular emphasis on contextualizing MB degradation with framework topology and stability. MIL-100(Fe) demonstrates improved MB degradation upon thermal vacuum activation, as indicated by the rise in its lumped, metal-normalized first order rate constant, driven by removal of moieties coordinated to its metal trimers in synthesis. While observed reactivity rivals that for isostructural MIL-101(Fe) (made from a different linker but the same secondary building units), MIL-100(Fe) shows minimal leaching of active species in comparison, suggesting its potential for longer catalyst lifetime.[2] These MOFs, amongst others such as the thermochemically stable UiO-series based on Zr, possess semiconductor-like characteristics, making photocatalysis another promising route toward pollutant degradation via light at or above the framework band gap energy (BGE). This study shows that addition of Fe-oxide nanoparticles and dispersed Fe moieties to UiO-67 via incipient wetness impregnation or pore size modulation through synthesis of UiO-68 (longer linker) decrease MOF BGE, allowing for enhanced photocatalytic degradation of MB at lower energy wavelengths, with contrasting oxidant utilization efficiencies. Continued development of hybrid structures using earth-abundant metal source MOFs demonstrates a promising route forward in refining their structure and use in wastewater treatment.
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