Ethene/ethane separation by the MOF membrane ZIF-8: Molecular correlation of permeation, adsorption, diffusion

The newly developed MOF membrane ZIF-8 separates an equimolar ethene/ethane mixture at room temperature for 1 and 6 bar feed pressure, respectively, with a selectivity of 2.8 and 2.4. Independent sorption uptake studies of an ethene/ethane mixture on a big ZIF-8 single crystal by IR microscopy detection show in combination with grand canonical Monte Carlo simulations that this moderate ethene selectivity of the ZIF-8 membrane can be explained by the interplay of a preferential ethane adsorption selectivity competing with a preferential ethene diffusion selectivity. This means, that ethane adsorbs stronger than ethene, but ethene diffuses faster and overcompensates the adsorption preference of ethane, resulting in a membrane permeation selectivity for ethene.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (190 K)Download as PowerPoint slideResearch highlights▶ ZIF-8 membrane can separate ethene/ethane mixtures with selectivities between 2 and 3. ▶ From mixture adsorption and diffusion data, the membrane selectivity can be predicted. ▶ Both IR microscopy and grand canonical Monte Carlo simulation can give the mixture data.