Metal-Ion-Mediated Morphology and Pore-Environment Engineering in Isostructural MOFs for Isomer Separation.

Metal-organic frameworks (MOFs) provide an ideal platform for regulating pore environments, yet the role of metal-node substitution in chromatographic separation remains insufficiently understood. Here, a series of isoreticular frl-topology MOFs Al-TBAPy, Sc-TBAPy, and Y-TBAPy (TBAPy = 1,3,6,8-tetrakis(4-carboxyphenyl)pyrene) were constructed to achieve systematically tuned pore structures, crystallization, and morphology. Structural characterization revealed that Al-TBAPy exhibited a slightly larger pore aperture and nanosheet morphology, whereas Sc-TBAPy and Y-TBAPy possessed slightly smaller pores and nanoflower-like structures. Inverse gas chromatography showed that adsorption affinity toward xylene isomers increased from Al-TBAPy to Y-TBAPy, while diffusion coefficients followed the opposite trend. Al-TBAPy achieved the highest separation performance for aromatic isomers among the three materials due to balanced adsorption and mass transfer, whereas Sc-TBAPy and Y-TBAPy exhibited high separation resolutions for alkane isomers owing to enhanced confinement effects. These results demonstrate that rational metal-node substitution can provide a strategy for designing high-performance MOF-based GC stationary phases.