Chiral-induced covalent organic framework as novel chiral stationary phase for chiral separation using open-tubular capillary electrochromatography.

As a novel class of chiral stationary phase (CPS) material, chiral covalent organic frameworks (CCOFs) have already shown great promise in open-tubular capillary electrochromatography (OT-CEC) for chiral separation. The synthesis methods of CCOFs used in OT-CEC mainly include bottom-up, post modification and chiral induction. The CCOFs synthesized by bottom-up and post modification strategies already have lots of applications in capillary electrochromatography, however, the chiral-induced synthesized via an asymmetric catalytic strategy has not yet been reported for using as the chiral stationary phase (CPS) in OT-CEC or even in chromatographic separation. Herein, the chiral-induced COF (Λ)-TpPa-1 was synthesized by asymmetric catalytic synthesis and coated on the inner surface of a capillary by an in-situ growth strategy as the CPS for chiral drug separation. The baseline separation of six enantiomers was achieved within 14 min, with a high-resolution (Rs) range from 1.85 to 6.75. Moreover, the resolution and migration time of the capillary keep stable within 160 runs, showing its superior stability and repeatability. This research provides a new idea for the development and application of novel CPS materials in the field of capillary electrochromatography separation, also shows the new application of chiral induced COFs. Furthermore, the chiral-induced CCOFs can be easily applied to other chromatographic separation fields, exhibiting its extensive application value in chiral analysis separation.

Synthesis of spherical three-dimensional covalent organic frameworks and in-situ preparation of capillaries coated with them for capillary electrochromatographic separation.

Covalent organic frameworks (COFs) are divided into two-dimensional (2D) and three-dimensional (3D) structures according to the connection dimension of covalent bonds. 3D COFs have smaller pore size and larger surface area, which would facilitate the separation of small organic molecules with similar structures and properties in capillary electrochromatographic (CEC) separation. However, the application of 3D COFs in CEC is still in its early stages. Thus, 3D COFs (3D-IL-COF-1 and 3D-IL-COF-2) were synthesis by a new synthesis method in this work. The related characterization results confirmed that spherical 3D-IL-COFs formed by the accumulation of small polyhedral particles were successfully synthesized. Then, 3D-IL-COFs were introduced into the inner wall of capillary by in-situ growth method to prepare the 3D COFs coated capillaries for the first time. The electrochromatographic separation performance of the 3D-IL-COFs coated capillaries was investigated using the 3D-IL-COF-1 coated capillary as the model. The results indicate that the 3D-IL-COF-1 coated capillary with uniform coating exhibits a broad-spectrum separation capacity not only for acidic, basic and neutral analytes but also for neutral isomers, which shows that 3D-IL-COFs becomes an attractive potential stationary phase for electrochromatographic separation.