Particle Size Regulation of Single-Crystalline Covalent Organic Frameworks for High Performance of Gas Chromatography

Although polycrystalline covalentorganic frameworks (PCOFs) havealready shown great potential as stationary phases for chromatography,irregular shape and size distribution of PCOFs make regulation ofparticle size of PCOFs for high separation performance impossible,which is accessible by the application of single-crystalline COFs(SCOFs). Herein, we showed preparation of three-dimensional SCOF (SCOF-303)bonded capillaries (SCOF-303-capillary) with different particle sizes(about 0.4-1.6 mu m) and further investigated gas chromatographicseparation ability of these SCOF-303-capillaries for isomers of xylene,dichlorobenzene, and pinene. It was found resolution and column efficiencyof SCOF-303-capillaries for isomers decreased with the increase inparticle size, mainly resulting from the weaker size-exclusion effectand higher mass transfer resistance of the larger particle size offlexible SCOF-303. The obtained SCOF-303-capillary (particle sizeof similar to 0.4 mu m) offered baseline separation of xylene isomerswith the high resolution of 2.26-3.52, great efficiency of7879 plates m(-1) for p-xylene, betterthan PCOF-303-capillary, and commercial DB-5 and HP-FFAP capillarycolumns as well as many reported capillaries. This work not only showsthe great potential of SCOFs for gas chromatography but also providesthe theoretical direction for the design of the efficient COF basedstationary phase by adjusting the particle sizes.