[Recent advances in porous materials based silica stationary phases for liquid chromatography]

Recent years have seen significant progress in nanoscience and materials chemistry， driving the development of novel porous materials such as metal organic frameworks （MOFs）， covalent organic frameworks （COFs）， and porous organic cages （POCs）. MOFs form through coordination bonds between metal ions and organic bridging ligands， COFs result from strong covalent linkages connecting predesigned organic building blocks into extended crystalline networks， and POCs are three-dimensional cage-like organic molecules with well-defined intrinsic cavities. Nowadays， the use of porous materials as stationary phases in high-performance liquid chromatography （HPLC） continues to draw sustained research interest. By precisely designing the building blocks of porous materials， researchers can flexibly modulate separation selectivity in terms of pore size， pore morphology， and interlayer stacking patterns， thus enabling the efficient separation of complex samples， particularly for positional isomers and chiral compounds. Despite their considerable promise for chromatographic applications， the direct use of porous materials as stationary phases is constrained by inherent limitations. A primary challenge lies in synthesizing pure porous materials with both regular morphology and uniform particle size. Irregular particle shapes combined with broad size distributions typically result in high column pressure and low column efficiency， which severely restricts the practical application of porous materials in HPLC. To overcome these limitations， combining porous materials with silica gel （SiO₂） supports has become a widely adopted strategy. As the most mature stationary phase support in HPLC， SiO₂ offers excellent mechanical strength， chemical stability， and a readily functionalizable surface， thereby providing a robust structural platform for porous materials. By immobilizing porous materials onto the silica surfaces， their mechanical robustness and packing uniformity can be significantly improved while retaining their selective adsorption capability， thus promoting their reliable use in chromatographic applications. Furthermore， in order to further enhance separation efficiency and selectivity， researchers have proposed the co-modification of silica gel with porous materials and other functional components such as ionic liquids， hydrogels， and carbon dots， aiming to construct multifunctional composite stationary phases. The key advantage of this strategy lies in the synergistic integration of multiple separation mechanisms， including hydrophobic effects， hydrogen bonding， π-π interactions， and chiral recognition， through material hybridization， thereby achieving higher performance and selectivity in separating complex systems. Moreover， this composite approach effectively mitigates the limitations of single-component materials， for example， by improving the aqueous stability of MOFs or extending the applicability of COFs in the analysis of polar compounds， thereby significantly broadening the application scope of stationary phases. This review systematically summarizes the research progress in silica-based composites incorporating advanced porous materials for HPLC in the last five years， and offers a comprehensive overview of prevalent synthetic methodologies used to fabricate these composite stationary phases. Furthermore， the review addresses the major challenges currently facing the field and provides perspectives on future developments.