Enantioselective Adsorption in Achiral Zeolites

摘要

The separation of mixtures of chiral compounds into their left- and right-handed forms is of vital importance for the pharmaceutical and agrochemical industries. For decades, extensive research has been devoted to the development of chiral separation processes. Zeolites contain channels and cages of molecular dimensions and therefore are ideally suited for molecular separation. However, chiral zeolites are scarce. Here, we demonstrate, by means of computer simulations, the enantioselective adsorption of 4-ethyl-4-methyloctane in aluminosilicate MFI zeolites containing positively charged ions. Our results are remarkable, as the fixed crystallographic zeolite framework is perfectly mirror symmetric. This overthrows the general belief that enantioselective adsorption requires a chiral adsorbent. The nonlocal enantioselective correlations characteristic of this system are induced by packing into hydrocarbon-cation pairs at the channel intersections and by long-range repulsions between cations. Our findings have important technological consequences, as they open perspectives for a whole new approach to enantioseparation.