(363f) Examining Reactivity and Contextualizing Stability of Earth-Abundant Metal-Organic Frameworks for Aqueous Pollutant Degradation

Increasing water consumption and pollution motivate interest in enhancing the efficacy of wastewater treatment methods. Exploration of advanced oxidation processes (AOPs) that apply solid catalysts in lieu of traditional metal salts has gained attention for the degradation of recalcitrant organic pollutants. Metal-organic frameworks (MOFs), consisting of networks of organic ligands coordinated to metal-containing nodes, are one such material type of interest, particularly when constructed from earth-abundant metals.[1] Herein, the dye and medication methylene blue (MB) is used to probe the performance of contrasting iron(Fe) and zirconium(Zr) MOFs toward aromatic pollutant oxidation using excess hydrogen peroxide (H₂O₂). While MIL-101(Fe) and MOF-235 are constructed from the same Fe and linker source materials, they feature alternate crystal morphologies (MTN zeotype vs. acs) and differences in metal node coordination. This manifests in MIL-101(Fe) exhibiting a lumped, metal-normalized first order rate constant over 3x that of MOF-235 under excess oxidant loading. However, loss in crystallinity, alongside metal leaching, is evident.[2] In contrast, MIL-100(Fe), featuring the same bulk crystallographic arrangement as MIL-101(Fe) but constructed with an alternate linker, shows similar levels of reactivity to MIL-101(Fe) when pre-activated under heated vacuum, with reduced leachate reactivity. Meanwhile, Zr-based UiO-67 retains its long-range order after MB reaction, but photocatalytic activation by UV is necessary to induce degradation. Lowering the energy intensity of its oxidation is considered through reduction of the MOF band gap energy via both incipient wetness impregnation of Fe (Fe-UiO-67) and extension of the coordinating linker length (UiO-68).[3] Each strategy is shown to enhance apparent dye degradation compared to UiO-67 (by ~3x and ~2x under 340 nm light on a mass-normalized rate constant basis), but Fe-UiO-67 demonstrates lower effective H₂O₂ utilization and apparent Fe-leaching. Together, this work clarifies the performance and stability of several Fe- and Zr-MOFs for MB degradation and AOPs more broadly.

Research Interests

My graduate research career focused on MOF synthesis and use in dye degradation, alongside a project on incorporating noble metals onto MOF scaffolds for small molecule transformations relevant for pharmaceutical production. Through this work, I have extensively honed my capabilities in kinetic analysis and reaction engineering in catalytic systems, as well as in material characterization. Going forward, I aim to leverage these skills and my prior experience in process engineering in the food and beverage industry to solve problems relating to cleaner energy production, environmental protection and remediation, and health.

References

1. https://doi.org/10.1021/acsami.7b02563
2. https://doi.org/10.1002/aic.18205
3. https://doi.org/10.1039/d4re00172a