Preparation of COF-based membranes via chiral induction for efficient enantioselective resolution

Abstract

Efficient chiral resolution is highly important in the food, pharmaceutical and agriculture industries because of the distinctive biological or pharmaceutical properties of enantiomers. Membrane-assisted chiral separation, which has the potential advantages of low cost and high yield, has attracted significant research attention, but the fabrication of high-quality chiral membranes displaying both high selectivity and high flux of enantiomers is still a challenge. Covalent organic frameworks (COFs), a class of porous materials with high porosity and diverse functionalities, are promising for the development of high-performance chiral separation membranes; however, these materials have yet to be developed. In this work, we demonstrated the in situ growth of a chiral TpPa-1 (cTpPa-1) membrane on polymer substrates via chiral induction. The resulting cTpPa-1@PAN membrane displayed a maximum enantioselectivity of 99.3 ​% ee for resolving limonene racemates with a flux of 5.5 ​mmol ​m⁻² ​h⁻¹. Furthermore, the effects of feed solvent polarity on membrane performance, the versatility of cTpPa-1 for making chiral composite membranes, and the mechanisms associated with cTpPa-1-based membranes were studied and are discussed.