Electrospun Cellulosic Membranes toward Efficient Chiral Resolutions via Enantioselective Permeation

Abstract

Cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC), known as one of the most versatile chiral selectors packed in columns for chiral chromatography, is electrospun for the first time. The electrospun nanofibers with a mean diameter of 329 nm form a self-standing nonwoven textile with a specific surface area of 5.6 m²/g. The textile is sandwiched between commercially available polytetrafluoroethylene membrane filters as a support material to fabricate a CDMPC membrane system for the chiral resolution of a racemic mixture, (<i>R</i>,<i>S</i>)-1-(1-naphthyl)ethanol. A vacuum filtration of the racemic mixture through the membrane system using a mixed solvent of <i>n</i>-hexane/2-propanol = 9/1 (v/v) enriches the <i>S</i>-enantiomer in the filtrate due to an enantioselective sorption of the <i>R</i>-enantiomer. The sorption capacity can be regenerated repeatedly via extractions of the adsorbed enantiomers from the membrane system after the filtrations. By repeating the vacuum filtration-extraction process for 15 cycles, the enantiomeric excess (<i>e.e.</i>) of the <i>S</i>-isomer in the filtrate increases up to 32.9%.