Heterogeneity of Adsorption Sites and Adsorption Kinetics of n-Hexane on Metal-Organic Framework MIL-101(Cr)

The heterogeneity of adsorption sites and adsorption kinetics of n-hexane on a chromium terephthalate-based metal-organic framework MIL-101(Cr) were studied by gravimetric method and temperature-programmed desorption (TPD) experiments. The MIL-101 crystals were synthesized by microwave irradiation method. The adsorption isotherms and kinetic curves of n-hexane on the MIL-101 were measured. Desorption activation energies of n-hexane from the MIL-101 were estimated by TPD experiments. The results showed that equilibrium amount of n-hexane adsorbed on the MIL-101 was up to 5.62 mmol.g(-1) at 298 K and 1.6 x 10(4) Pa, much higher than that of some activated carbons, zeolites and so on. The isotherms of n-hexane on the MIL-101 could be well fitted with Langmuir-Freundlich model. TPD spectra exhibit two types of adsorption sites on the MIL-101 with desorption activation energies of 39.41 and 86.69 kJ.mol(-1). It reflects the surface energy heterogeneity on the MIL-101 frameworks for n-hexane adsorption. The diffusion coefficients of n-hexane are in the range of (1.35-2.35) x 10(-10) cm(2).s(-1) with adsorption activation energy of 16.33 kJ.mol(-1). (c) 2014 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.