Construction of MOFs@COFs composite material as stationary phase for efficient separation of diverse organic...

The development of efficent chromatographic stationary phases (SP) with mixed-mode or multiple interactions in high-performance liquid chromatography (HPLC) for the separation of complex samples is a challenging task. Metal organic frameworks (MOFs)-based SP can provide desired multiple interactions and enable the separation of a diverse range of solutes, but have limitations of low column efficiency and poor stability.

Herein, the hybrid MOFs@Covalent organic frameworks (COFs) materials were used as SP in HPLC due to their synergistic structural features. The SiO₂@NH₂-UiO-66@CTF SP was synthesized by integration of NH₂-UiO-66 and covalent triazine framework (CTF) onto silica surface. Due to the unique structure of SiO₂@NH₂-UiO-66@CTF with hierarchical-pores, this column showed higher column efficiency (up to 49,369 plates m^-1 for alkylbenzenes) than the reported columns packed with MOFs-based SP. Owing to the Zr⁴⁺-N coordination bonding between CTF and NH₂-UiO-66, the structural stability of SiO₂@NH₂-UiO-66@CTF can be improved. Furthermore, this new column exhibited remarkable column stability with relative standard deviation of retention time of <0.40% after 400 injections. With the combined advantages of multifunctional properties, high column efficiency, and good stability, SiO₂@NH₂-UiO-66@CTF SP showed excellent selectivity for the separation of a variety of hydrophobic, aromatic, heteroatomic, and hydrophilic analytes.

This work not only offers a promising SP with multiple retention mechanisms for HPLC, but also provides an efficient strategy for development of high column efficiency MOFs-based SP with good stability. Moreover, the MOFs@COFs hybrid materials were expanded in application area through this study, and the research results can also afford the foundation for further explore its structural characteristics.