Chiral-induced synthesis of chiral covalent organic frameworks core-shell microspheres for HPLC enantioseparation

Two chiral covalent organic frameworks (CCOFs) core-shell microspheres based on achiral organic precursors by chiral-induced synthesis strategy for HPLC enantioseparation are reported for the first time. Using n-hexane/isopropanol as mobile phase, various kinds of racemates were selected as analytes and separated on the CCOF-TpPa-1@SiO₂ and CCOF-TpBD@SiO₂-packed columns with a low column backpressure (3 ~ 9 bar). The fabricated two CCOFs@SiO₂ chiral columns exhibited good separation performance towards various racemates with high column efficiency (e.g., 19,500 plates m⁻¹ for (4-fluorophenyl)ethanol and 18,900 plates m⁻¹ for 1-(4-chlorophenyl)ethanol) and good reproducibility. Some effects have been investigated such as the analyte mass and column temperature on the HPLC enantioseparation. Moreover, the chiral separation results of the CCOF-TpPa-1@SiO₂ chiral column and the commercialized Chiralpak AD-H column show a good complementarity. This study demonstrates that the usage of chiral-induced synthesis strategy for preparing CCOFs core-shell microspheres as a novel stationary phase has a good application potential in HPLC.