Produção, caracterização estrutural e morfológica de filmes baseados em redes metalorgânicas

Abstract

There is a constant search for new functional materials to meet society's demands in various fields to reduce the environmental impacts caused by humans and the sustainability of processes. In this context, Metal-Organic Frameworks (MOFs) have sparked great interest in the scientific community due to their number of applications like greenhouse effect gas absorption and adsorption. MOFs are constructed from metal ions or clusters linked through organic ligands, forming rigid and stable porous structures. This work focuses on films' production, structural characterization, and morphological analysis based on Metal-Organic Frameworks known as MOF-74, which exhibit infinite 1D honeycomb-shaped pores. MOF-74 is a highly versatile material with applications in greenhouse gas sensing, selective gas storage, drug delivery, and catalysis due to its uniform porosity, flexibility in choosing metals and ligands, pore size, and chemical functionalization possibilities. We synthesized polycrystalline films of Me-MOF-74 where Me = (Zn, Co, Ni, Mg), using the solvothermal method, on a fluorine-doped tin oxide-coated glass substrate (FTO, SnO2:F) and confirmed their formation using conventional θ-2θ X-ray diffraction (XRD) techniques, by observing the characteristic peaks of these materials in the X-ray diffractograms. The crystallographic parameters obtained for the films are.a = b ≈ 26Å, c ≈ 6.8Å, α = β = 90°, and γ = 120° (R3 ̅ symmetry), which are consistent with the literature. The Ni-MOF-74 film on FTO, produced using a mixed solution of DMF: H2O: EtOH (1:1:1 vol) containing (0.29 mmol) of 2,5-dihydroxyterephthalic acid and (1.2 mmol) of nickel hexahydrate nitrate, in an autoclave kept at 120°C for 20 hours, exhibited the best substrate adhesion, uniformity, and particle growth connectivity and was selected for further investigation by varying parameters such as temperature, reagent concentration, and synthesis time. Films of Ni-MOF-74 on FTO were produced at different temperatures, reagent concentrations, and synthesis times. The crystallographic parameters of all these Ni-MOF-74 films were determined using grazing-incidence X-ray diffraction (GIXRD) experiments, and their morphology was investigated using scanning electron microscopy (SEM). In general, we observed structural parameters similar to the literature. Nevertheless, we observed a significant particle shape and size variation depending on the chosen synthesis parameters.