The effect of solvent polarity on the properties of activated cyclodextrin based metal organic framework crystals (CD-MOFs) -

Abstract

Cyclodextrin based metal organic framework crystals (CD-MOFs) were prepared by methanol vapor diffusion into an aqueous solution of potassium hydroxide and γ-cyclodextrin. The trapped water during the formation of the CD-MOF crystals was then evacuated using various solvents with different polarities. Consequently, the morphology and stability of the crystals were evaluated using thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and colorimeter. In addition to the specific surface area, pore size and total pore volume were determined using the nitrogen adsorption technique. According to the XRD and SEM results, the crystalline structure of CD-MOFs remained intact upon activation regardless of the polarity of the organic solvent used during activation. Moreover, the findings from FTIR and TGA indicated that water has been evacuated from the pores. Furthermore, the various solvents with polarities ranging from 0 (hexane) to 5.1 (methanol and acetone) used for activation didn’t reveal any significant impact on the surface area and total pore volume of the crystals. CD-MOF activated with hexane showed a surface area of 1063 m2-g and a total pore volume of 0.42 cc-g whilst crystals activated using methanol showed a surface area of 1036 m2-g and total pore volume of 0.40cc-g. These results show that polarity has no effect on surface area, pore volume, crystallinity, and thermal stability of CD-MOFs.