Homochiral Porous Organic Imine Supramolecular Nanotube as a Stationary Phase for Highly Efficient Separation of Isomers and Racemates in Gas Chromatography

Porous organic imine supramolecular nanotubes (ISNTs), as a subclass of synthetic organic molecular nanotubes with nanotubular structures, permanent and confined cavities, and defined transport channels, have recently attracted considerable interest in diverse applications. In this study, a homochiral porous organic ISNT, TCC1-R, was synthesized by condensing 5,5'-(ethyne-1,2-diyl)diisophthalaldehyde with (1<i>R</i>, 2<i>R</i>)-1,2-diaminocyclohexane and used as a stationary phase for gas chromatographic (GC) separations. The statically coated TCC1-R capillary column exhibited outstanding separation performance not only for diverse organic isomers but also for a broad range of racemic compounds. High-resolution separation of 20 organic isomers was achieved on the column, including positional isomers of disubstituted benzenes, structural isomers, and <i>cis</i>-/<i>trans</i>-isomers. The separation of these achiral isomers on the TCC1-R column was compared with that on a commercial HP-35 column and showed some advantages. Of greater importance, 74 racemates were effectively enantioseparated on the column, including the challenging chiral hydrocarbons, nitriles, sulfoxides, ketones, amides, lactones, halohydrocarbons, epoxides, alcohols, amines, aldehydes, esters, and ethers. Moreover, the resolution of all possible enantiomers of some challenging chiral compounds with two chiral centers can also be achieved on this column. Compared with the widely used commercial β-DEX 120 column and our previously proposed porous organic cage-based CC3-R column, the TCC1-R column exhibited superior enantioselectivity for separating these studied racemates. In addition, the column also showed good stability and reproducibility on separation. This study demonstrates that chiral porous organic ISNTs are a highly promising class of stationary phases with promising application prospects in chromatographic separations.