Facile separation of enantiomers via covalent organic framework bonded stationary phase

Covalent organic frameworks (COFs), a type of crystalline polymers, have attracted increasing interest because of their controllability of geometry and functionality. Featuring infinitely extended networks and tremendous interaction sites, COFs emerge as a potential platform for separation science. Here, a novel chiral COF (beta-CD COFBPDA) constructed by the imine condensation of 4,4 '-biphenyldicarboxaldehyde and heptakis(6-amino-6-deoxy)-beta-cyclodextrin was introduced into an electrochromatographic system via a photopolymerization method and applied to the separation of enantiomers. The structure and properties of as-synthesized beta-CD COFBPDA were investigated by powder X-ray diffraction (PXRD) patterns, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), and N(2)adsorption-desorption isotherms. It was proved that beta-CD COFBPDA was provided with larger pore size and BET surface area. The beta-CD COFBPDA coating endowed the chiral stationary phase with superior three-dimensional orientation, and realized satisfactory separation with improved selectivity and column efficiency for a dozen racemic drugs. Under the optimized conditions, homatropine, ondansetron, metoprolol, terbutaline, tulobuterol, and promethazine were all baseline separated with resolution values of 2.24, 2.03, 1.65, 1.62, 1.60, and 1.58, respectively. The results indicate the high perspective of COF modified stationary in enantioseparation.

Automated summary

COFs, a type of crystalline polymers with controllable geometry and functionality, have attracted increasing interest. A novel chiral COF, β-CD COFBPDA, constructed through specific imine condensation, shows potential in separation science. Under optimized conditions, the COF-modified stationary phase demonstrates superior separation performance for racemic drugs.