Performance of chiral zeolites for enantiomeric separation revealed by molecular simulation

We used molecular simulations to test the adsorption selectivity for enantiomers in the chiral zeolites SOF, STW, and ITQ-37. This work is the first simulation study which demonstrates the chirality of SOF, STW, and ITQ-37. We obtain information at the molecular level that explains the nature of the chiral selectivity. We selected CHBrClF and 4-ethyl-4-methyloctane as the probe molecules for the study. We calculated pure component and racemic mixture adsorption isotherms, Henry coefficients, adsorption enthalpies, and radial distribution functions. While STW is enantioselective for the probe molecules studied, ITQ-37 is likely to be enantioselective for other chiral molecules, and SOF is not a candidate for chiral separation. Appropriate pore geometry, resulting in differences in the adsorption behavior between the two isomers, is required for observing chiral selectivity. We provide insight that could be used for the synthesis and characterization of new chiral structures aimed to separate specific isomers. Using the methodology described here, it could be possible to easily determine if a new zeolite structure would show adsorption selectivity for a given chiral molecule.