The metal-organic framework Zn2(BDC)2(TED) (1) has been reported to be water-stable and highly selective toward the adsorption of water and alcohols, suggesting the application of this material as a separation membrane for the production of bioethanol. We have studied the adsorption mechanism of water, methanol, ethanol, and dimethylether in this framework by means of density-functional theory with corrections for London dispersion. We show that the combination of the hydrogen bond between the hydroxyl group in ethanol with the oxy group in 1 and the van der Waals interaction between the ethanol alkyl chain with the phenyl ring in 1 is responsible for the preferential adsorption of ethanol over water in the framework. The calculated enthalpy of adsorption for the four compounds in 1 is in excellent agreement with experimental results. We further note that the computational approach has to be chosen with care: It is essential to account for London dispersion interactions, as well as the use of large models, preferably the full periodic structure, to obtain correct adsorption geometries and energies.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films