Ambient-temperature assembly of multi-site ionic hydrogen-bonded organic framework@silica composites for high-efficiency chromatographic separation

Conventional stationary phases, which rely on a limited repertoire of interaction mechanisms, exhibit restricted selectivity for complex samples. Hydrogen-bonded organic frameworks (HOFs) are promising separation media owing to their well-defined structures and mild synthesis, yet their poor stability has impeded practical chromatographic applications. The integration of charged components into the hydrogen-bonded network yields ionic HOFs (iHOFs) with substantially improved structural stability over conventional HOFs, accompanied by the introduction of electrostatic interaction sites. iHOF-45 features a unique crystal structure that integrates sulfonate, amino, and pyrene functional units within a single framework, providing multiple interaction mechanisms ideal for chromatographic separation.

Herein, we report the first application of iHOF-45 as an effective liquid chromatographic stationary phase. The iHOF-45@SiO₂ composite was fabricated via a room-temperature ionic self-assembly strategy, which can avoid high temperature and high pressure, offering a more energy-efficient synthetic route. The separation ability of iHOF-45@SiO₂ was systematically evaluated using diverse analytes, including nucleosides/bases, sulfonamides, vitamins, organic pollutants and ionic species. Mechanistic studies revealed that retention behavior was governed by the synergistic cooperation of hydrophilic, hydrophobic, π-π, hydrogen-bonding, and electrostatic interactions. The iHOF-45@SiO₂ exhibited favorable intra-/inter-day repeatability, long-term stability, acid/base stability, and batch-to-batch reproducibility, along with strong resistance to matrix interference, which was successfully applied to real sample analysis of water sample and vitamin B complex tablets. Furthermore, comparative studies against commercial columns and other porous framework-based stationary phases distinctly underscore the unique advantages of the iHOF-45@SiO₂.

This work reports the first iHOF-based versatile liquid chromatographic stationary phase via room-temperature ionic self-assembly, which features a synergistically stabilized framework through hydrogen bonding and ionic interactions. The iHOF-45@SiO₂ uniquely integrates multimode separation capability, mild fabrication and promising practical applicability, establishing iHOF as a robust platform for developing multifunctional chromatographic separation material toward complex sample analysis.