Confined-based catalyst investigation through the comparative functionalization and defunctionalization of Zr-MOF

A comprehensive study about functionalization and de-functionalization of MOF-808 as a defect-engineered Zr-MOFs for selective catalytic oxidation

In metal-organic frameworks (MOFs), confined space as a chemical nanoreactor is as essential as coordinatively unsaturated metal site catalysis. The properties of MOFs can be adjusted through the incorporation of functional groups and open metal sites in frameworks that can modify the catalytic performance. In this regard, a set of defect-engineered MOFs, Ex-MOF-808(NH2, NO2, H) and Mix-MOF-808(NH2, NO2, H), were synthesized by ultrasonic-assisted linker exchange approach (Ex-MOFs) and solvothermal mixing ligand method (Mix-MOFs), respectively. Further, the relationship between the preparation method, structural properties, and catalytic efficiency of the prepared materials in the selective oxidation of methyl phenyl sulfide (MPS) has been investigated. By analyzing zeta potential, it was found that in the exchange method, the amount of defect and functional groups on the surface of MOFs are more than in the mixing method, which also affects the catalytic activity. In our contribution, mix-MOF-808(NO2) carrying nitro groups at their organic linkers, which has a well-dispersion of nitro groups at the framework exhibits selective conversion of MPS to sulfone (91 %). Furthermore, the performance of stable heterogeneous catalysts was investigated for three cycles, which demonstrated their great potential for advanced catalytic oxidation.

Sensitive determination of 4,6-dinitro-o-cresol based on a glassy carbon electrode modified with Zr-UiO-66 metal-organic framework entrapped FMWCNTs

A DNOC electrochemical sensor has been developed by using a composite of Zr-UiO-66 and FMWCNTs on a glassy carbon electrode (GCE) and using the differential pulse voltammetry technique. The synthesized materials were physico-chemically characterized by BET, PXRD, FTIR, TGA, EDX, and FESEM. Cyclic voltammetry showed that DNOC has three oxidation peaks at 0.03 V (RSD: 0.23%), 0.42 V (RSD: 0.21%), and 1.32 V (RSD: 0.32%) and three reduction peaks at - 0.20 V (RSD: 0.15%), - 0.82 V (RSD: 0.26%), and - 1.14 V (RSD: 0.19%) which follow a diffusion-controlled mechanism. Different parameters were optimized using differential pulse voltammetry and good linear ranges were found for the simultaneous detection of the three reduction peaks. For a specific concentration range of 0.1-50 μM, a limit of detection of 0.119 μM based on 3Sb/m was obtained. The interfering effects of five non-phenolic pesticides and five heavy metals were evaluated to highlight the selectivity of the developed sensor. It is the first report of an electrochemical DNOC sensor in which all three oxidation peaks are prominently visible. Ethion and chloropyriphos were found to inhibit the redox process of DNOC on the developed sensor platform Zr-UiO-66/FMWCNT/GCE. The sensor was successfully applied to DNOC determination in spiked potato samples and the results showed a standard deviation of less than 3%. The proposed method is expected to provide a novel platform for the quantitative determination of DNOC pesticides in vegetables.

Photocatalytic aerobic oxidative functionalization (PAOF) reaction of benzyl alcohols by GO-MIL-100(Fe) composite in glycerol/K2CO3 deep eutectic solvent

An MIL-100 (Fe)/graphene oxide (GO) hybrid, a fairly-known composite, was made through a simple one-step procedure and played a highlighted role in the photo-induced oxidative functionalization of the benzylic C–H bond. To identify the given binary composite, various techniques were applied: FT-IR, P-XRD, SEM, nitrogen absorption–desorption analysis, TGA, TEM, and UV–Visible DRS spectra. Proportions of GO used within the structure of the prepared composite differently ranged from low to high amount, and the most optimized ratio met at 38.5% of GO as the most efficient catalyst. Additionally, the reaction ran in Glycerol/K₂CO₃ (2:1) as the optimal solvent. The elemental roles of O₂^·− and OH⁻ were supposed to be the major ones for running a tandem oxidation-Knoevenagel reaction. The heterogeneity and reusability of the catalyst were also examined and confirmed after five successive runs.