Chiral permselectivity in nanoporous opal films surface-modified with chiral selector moieties

The chiral permselectivity in thin opal films modified on the silica surface with chiral selector moieties was studied as a function of opal film geometry, supporting electrolyte concentration, solvent polarity, and chiral selector and linker structure. While opal film thickness, supporting electrolyte concentration and linker length and structure did not have a significant influence on the chiral permselectivity, the nanopore size, solvent polarity and selector structure had a pronounced effect. These observations are in agreement with the chiral selectivity mechanism in the opal films in which the permeating enantiomers are transported with different rates through the surface utilizing non-covalent interactions between the chiral permeant molecules and surface-bound chiral selectors. The chiral selectivity (transport rate ratio for S and R enantiomers) achieved in the present study was 4.5, which is one of the highest reported for chiral membranes.