Zirconium Metal–Organic Framework UiO-66: Stability in an Aqueous Environment and Its Relevance for Organophosphate Degradation

Abstract

Zirconium-based metal–organic frameworks were recently investigated as catalysts for degradation of organophosphate toxic compounds, such as pesticides or chemical warfare agents. The most utilized UiO-66 is considered as a stable material for these applications in an aqueous environment. However, the presented results indicate that the properties of UiO-66 are changing considerably in aqueous media under common conditions used for organophosphate degradations, and therefore its catalytic activity is not related to the number of structural defects created during the material synthesis. We delineate the stability of UiO-66 in water of various pHs, the in situ formation of new catalytic sites, and the correlation of these two parameters with the degradation rate of a model organophosphate pollutant, dimethyl-4-nitrophenyl phosphate (methyl-paraoxon). The stability was quantified using high-performance liquid chromatography (HPLC) by measuring the amounts of leached terephthalic acid, the linker of UiO-66, and monocarboxylic acids, the modulators bound at UiO-66 defects. We demonstrate that the HPLC analysis is a more suitable method for metal–organic frameworks stability assessment than commonly used methods, e.g., powder X-ray diffraction, adsorption isotherms, or electron microscopy.

Synthesis and Functionalization of Porous Zr-Diaminostilbenedicarboxylate Metal–Organic Framework for Storage and Stable Delivery of Ibuprofen

“…Finally, the possible destruction of Zr-DASDCA (especially at pH 7.4) after several days in PBS solution cannot be ruled out since, recently, it has been reported that Zr-MOFs such as UiO-66 are not very stable even in the condition of pH 7. 70 Further work is required to understand the possible contribution of destruction of Zr-DASDCAs in the delivery of IBU.…”

Metal–organic frameworks vs. buffers: case study of UiO-66 stability

“…18,[33][34][35][36][37][38][39] Recently, our own group demonstrated that these methods are not able to conclusively assess structural changes induced in MOFs by exposure to aqueous media having various pH values. 40 Indeed, even though the UiO-66 structure is quite stable in pure water, leaching of the terephthalate linkers has been shown to occur after adjustment to a pH of 6.0 while, at higher pH values, the UiO-66 framework is completely degraded.…”

Novel Approaches Utilizing Metal-Organic Framework Composites for the Extraction of Organic Compounds and Metal Traces from Fish and Seafood

“…As revealed from the TEM micrographs (Figure 9), the Fe 3 O 4 nanoparticles were successfully coated with a 10 nm in thickness silica layer. The XRD pattern of the Fe3O4@SiO2@UiO-66 core-shell microspheres revealed to match perfectly with UiO-66 [107,108]. As revealed from the TEM micrographs (Figure 9), the Fe3O4 nanoparticles were successfully coated with a 10 nm in thickness silica layer.…”

“…Under optimum conditions, extraction recovery ranged between 93.1-107.3%, however no potential sorbent reusability was reported [106]. The XRD pattern of the Fe 3 O 4 @SiO 2 @UiO-66 core-shell microspheres revealed to match perfectly with UiO-66 [107,108]. As revealed from the TEM micrographs (Figure 9), the Fe 3 O 4 nanoparticles were successfully coated with a 10 nm in thickness silica layer.…”