The synthesis and characterization of mixed ligand AlF(bdc) Metal-Organic Framework

Abstract

Mixed ligand aluminum fluoride 1, 4-benzeneducarboxylate (AlF(bdc)) and aluminum fluoride 2-amino-1, 4-benzeneducarboxylate (AlF(bdc-NH₂)) has been successfully synthesized via solvothermal route. Several techniques such as powder X-ray diffraction, Fourier-transform infrared spectroscopy, field emission scanning electron microscopy and thermogravimetric analysis have been employed to characterize the as-made materials. Mixed ligand AlF(bdc) includes AlF(75%bdc)(25%bdc-NH₂), AlF(50%bdc)(50%bdc-NH₂) and AlF(25%bdc)(75%bdc-NH₂) and complete ligand substitution of bdc by bdc-NH₂ yields AlF(bdc-NH₂). All of them are isostructural to AlF(bdc) but poorer in crystallinity. The crystal morphology of each synthesized materials was observed and found to be similar. AlF(bdc) crystal has a shape of prism with random diameter. Substitution of bdc-NH₂ into the AlF(bdc) framework promotes needle like crystals which become the majority of crystal form when the amount of bdc-NH₂ is increased. AlF(bdc-NH₂) crystal is similar in shape with AlF(bdc) except that the crystals are shorter in length and present together with random shaped aggregates. Decomposition temperatures of each as-made materials were observed. They show a variation of weight loss profile. However, it is evident that the incorporation of bdc-NH₂ deprives the thermal stability of the structure. Increasing amount of bdc-NH₂ lowers the decomposition temperature of the materials and the complete substitution of bdc-NH₂ leads to a hundred temperature degree lower of decomposition temperature when compared to that of AlF(bdc).