Chiral supramolecular organic nanotube used as a stationary phase for capillary gas chromatographic separations

Supramolecular organic nanotubes (SONTs) constructed by organic synthetic strategies have garnered widespread attention in recent years owing to their unique properties. Supramolecular imine nanotubes (SINTs) are a family of SONTs that have shown promising application prospects in many fields due to their characteristics of facile synthesis, tubular structures, ordered transport channels, excellent solubility, and confined cavities. In this work, a homochiral SINT, TCC3-R, was fabricated via the condensation reaction between 1,4-bis(3,5-diformylphenyl)phenylethynylbenzene and (1R, 2R)-1,2-cyclohexanediamine, and further exploited as a stationary phase for gas chromatography (GC). The TCC3-R coated capillary GC column was fabricated by the static coating method, and its chromatographic separation performance was systematically evaluated. The findings indicate the column achieves excellent separation efficiency for various achiral compounds and racemates. High-resolution separations of three types of organic mixtures (n-alkanes, aromatic hydrocarbons, and n-alcohols) and twenty organic isomers (disubstituted benzene positional isomers, structural isomers, and cis-/trans-isomers) were achieved on this column. Sixteen racemates can be well separated on the column, and ten of which attained baseline separation. Relative to the commercially available β-DEX 120 column and our previously reported TCC1-R column, the proposed TCC3-R column exhibits good enantioseparation complementarity, successfully separating several racemates that were unresolved or poorly separated on these two reference columns. Half of the tested racemates (8 out of 16) and nearly one-third (5 out of 16) failed to be resolved on the reference TCC1-R column and β-DEX 120 column, respectively, whereas all of them achieved satisfactory enantioseparation on the proposed TCC3-R column. Furthermore, the TCC3-R column possesses satisfactory repeatability and stability. Its separation performance remains almost consistent with the initial state after 400 injections and heating treatment at 200 °C for a certain period. The relative standard deviations (RSDs) (n = 3) for retention time and resolution value were less than 1.62% and 2.83% after hundreds of injections, and less than 2.08% and 3.06% after high-temperature treatments, respectively. The results demonstrate that the homochiral SINT TCC3-R column greatly expands the enantioseparation scope of previously reported SINT TCC1-R column with promising application prospects. The synergistic combination of these SINT-based columns could address the enantioseparation challenges for more chiral analytes. This study also facilitates the development of chiral SINTs as a novel class of GC stationary phases.