Effect of Modifications Applied to the Synthesis Steps of MOF-UiO-66

Abstract

Structured metal-organic materials (MOFs) are stable crystalline structures with great applicability as catalysts. Among the large number of known MOFs, the UiO-66 MOF stands out, mainly due to its good stability at high temperatures and high specific surface area, giving it potential for use in separation, catalysis, adsorption, etc. processes. In the present work, the influence of replacing Dimethylformamide (DMF) with acetone in the washing step of the UiO-66 MOF and the effect of replacing magnetic stirring with ultrasonic stirring at 60°C are studied.  The synthesis is carried out by the solvothermal method at 120 ºC for 24 h, the zirconium chloride (metallic source) and the terephthalic acid (organic ligand) are brought into contact by magnetic or ultrasonic stirring, as appropriate, in a molar ratio 1:1, using DMF as solvent. In the wash, the DMF is replaced by acetone in 50, 70 and 80% by volume, obtaining the materials M1, M2 and M3. In the synthesis with ultrasonic stirring at 60°C, a wash was carried out with 80% acetone, obtaining the material called MU. The physicochemical properties were evaluated by X-ray Diffraction (XRD), Fourier Transform Infrared Spectrometry (FTIR), Scanning Electron Microscopy (SEM) and surface area (BET). Through the analysis of the XRD results, the presence of the characteristic signals corresponding to the crystallographic planes (1 1 1), (2 0 0) and (6 0 0) of the MOF structure is observed, determining that the use of ultrasound in the stirring stage and the Increase in acetone during washing does not generate changes in the crystallinity of the material. The FTIR results show the signals corresponding to the organic binder and the inorganic cluster in all materials. By SEM and FTIR, a decrease in the presence of ZrO2 crystals is observed, and by BET, an increase in the area from 816 m2g-1 (M1) to 924 m2g-1 (M3) as the DMF is replaced in the washing by acetone from 50 to 80% in volume, and an increase from 924 m2g-1 (M3) to 1099 m2g-1 (MU) when ultrasound is used in the stirring stage.