(706b) Insights into the Performance and Stability of Contrasting Iron- and Zirconium-Based MOFs for Aqueous Pollutant Oxidation | AIChE

(706b) Insights into the Performance and Stability of Contrasting Iron- and Zirconium-Based MOFs for Aqueous Pollutant Oxidation

Authors 

Sarazen, M., Princeton University
Ritchie, A. L., Princeton University
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.

References

  1. https://doi.org/10.1021/acsami.7b02563
  2. https://doi.org/10.1002/aic.18205