Vapor-phase adsorption of the C8 alkylaromatic components p-xylene (p-x), m-xylene (m-x), o-xylene (o-x), and ethylbenzene (eb) on the three-dimensional microporous metal−organic framework (MOF) Zn(BDC)(Dabco)0.5 (BDC = 1,4-benzenedicarboxylate, Dabco = 1,4-diazabicyclo[2.2.2]octane) was investigated. Single- and multicomponent fixed-bed experiments were carried out at temperatures ranging from 125 to 175 °C and total hydrocarbon pressures up to 0.10 bar. At high pressure, the adsorption capacity for all the components varies from 35 to 26 g/100 gads at 125 and 175 °C. Henry’s constants are slightly different for all C8 alkylaromatics, except for o-xylene, which is significantly higher. The adsorption enthalpies at zero coverage for the different isomers ranges from 77.40 (eb) to 79.84 kJ/mol (o-x), indicating that the C8 alkylaromatics have comparable interactions with the framework at the low coverage. On the basis of binary and quaternary breakthrough experiments performed at different hydrocarbon pressures and temperatures, MOF Zn(BDC)(Dabco)0.5 was realized for the efficient and feasible separation of o-xylene from other C8 alkylaromatic components with the selectivity up to 1.88 because of the stronger interactions between o-xylene molecules and the framework and their differential pore-filling and molecular-packing effects confined within nanopores of MOFs.

a b s t r a c tSingle and multicomponent adsorption equilibria of xylene isomers: o-xylene (o-x), m-xylene (m-x), pxylene (p-x) and ethylbenzene (eb) was investigated on the three dimensional microporous metal-organic framework Zn(BDC)(Dabco) 0.5 (BDC = 1,4-benzenedicarboxylate, Dabco = 1,4-diazabicyclo[2.2.2]-octane), MOF 1, in the range of temperatures between 398 and 448 K and partial pressures up to 0.1 bar. The equilibrium data show that a significant amount (around 34 g/100g ads at 398 K) of xylene isomers can be adsorbed in MOF 1. The affinity to the adsorbent measured by the Henry's constants to decreases in the order o-x > m-x > eb > p-x for all temperatures. The zero coverage adsorption enthalpies are all similar and range from 77.4 (eb) to 79.8 kJ/mol (o-x). The Dual-Site Langmuir model (DSL) was used for the interpretation and correlation of the experimental data. The parameters obtained from the pure component isotherms fitting were also used to predict the multicomponent equilibrium data by an extended DSL model. A good agreement was obtained between the predictions and the experimental data. It was also demonstrated that the DSL model is also capable to explain the increase in the isosteric heat of sorption with increasing coverage.