Monodisperse metal–organic cages for gas chromatographic separation

Establishing the definitive structure-performance relationship in metal-organic cage (MOC) stationary phases requires isolating intrinsic cavity contributions from dispersion-induced artifacts. However, solvent-dependent dispersion behavior of MOCs often obscures the direct role of molecular cage architecture in chromatographic separation. Here, we constructed a structurally homologous series of Zr-based MOCs with identical V4F4 topology but systematically enlarged cavity and window sizes through ligand elongation, including two newly constructed cages. Systematic investigation of solvent-dependent behavior revealed distinct states ranging from crystalline assemblies to oligomeric aggregates and ultimately to monodisperse cages. When utilized as gas chromatographic (GC) stationary phases, only monodisperse Zr-MOCs translated their discrete cage architectures into efficient separations, establishing dispersion control as a prerequisite for accessing intrinsic structure–property relationships. Under monodisperse conditions, Zr-MOC-BBC with the largest cavity exhibited the highest separation resolution compared to Zr-MOC-BTB and Zr-MOC-BTE. Mechanistic analysis demonstrated that the dispersion state primarily governed diffusion-controlled mass transfer, whereas intrinsic cavity size influenced both mass transfer resistance and thermodynamic host-guest interactions. This work demonstrates that controlling dispersion state is essential for accessing the intrinsic cavity and provides insights into the design of MOC-based separation materials.