Multi-component strategy for the preparation of covalent organic frameworks-based stationary phase for high resolution separation of isomers.

Functionalization of covalent organic frameworks (COFs) is a critical means to prepare COF-based gas chromatography stationary phases for high-resolution separation. Here, we report a simple and controllable multi-component strategy for the functionalization of COF stationary phases. As a proof of concept, a COF fabricated from 1,3,5-tris(4-aminophenyl) benzene (Tab) and 2,5-dihydroxy-1,4-benzenedicarboxaldehyde (DHTA), Tab-DHTA, was chosen as a model. 2,5-Dimethoxyterephthalaldehyde (DMTA) containing methoxy groups as a third monomer was incorporated into Tab-DHTA to prepare three-component COFs, Tab-DHTA-(DMTA)x%. The incorporated amount of DMTA was adjusted to balance hydrogen bonding and van der Waals interactions. The prepared Tab-DHTA-(DMTA)50% demonstrated high-resolution separation of ethyl valerate isomers (R > 1.5, 23021-29796 plates m-1), which was impossible on Tab-DHTA. Moreover, it not only kept the separation ability of Tab-DHTA for dichlorobenzene, chlorotoluene, pinene, 1,3-dichloropropene and propylbenzene isomers (R > 1.5, 7243-27328 plates m-1), but also gave faster separation than Tab-DHTA. The better chromatography capability of Tab-DHTA-(DMTA)50% than Tab-DHTA resulted from the alteration in separation thermodynamics by introducing DMTA to balance hydrogen bonding and van der Waals interactions. This work provides a new avenue for designing COF stationary phases with high separation performance.