Insights into the separation performance of MOFs by high-performance liquid chromatography and in-depth modelling

Carboxyl functionalized magnetic cores coated homogeneously with UiO-67 metal-organic frameworks (MOFs) through a liquid phase epitaxy (LPE) process are introduced. Using the as-synthesized core-shell microparticles as stationary phase in HPLC runs with different phenol derivatives, good separation efficiencies can be achieved when applying an acetonitrile/water mobile phase. To understand the advantages and limitations of such MOF based stationary phases in more detail, the experimental elution profiles are compared with simulations from a powerful chromatography modeling software (ChromX) newly developed at the KIT. The simulation results reveal that the affinities of UiO-67 to the tested phenol derivatives strongly differ (2,6-dimethylphenol < benzene-1,3-diol < 2,6-dichlorophenol), while its maximum capacity remains identical for each derivative with 0.14 mol L−1. The uptake kinetics are dominated by intraparticle diffusion while axial dispersion and film diffusion play only minor roles. The pore diffusivities of the phenol derivatives are found to be around 1.3 ⋅ 10−13 m2 s−1. Based on single component data, the successful simulation of multicomponent isocratic pulse experiments is demonstrated. In summary, HPLC runs combined with in-depth modeling are a powerful tool to investigate the interactions between solute molecules and thin MOF films, and to reveal data about affinities, capacities and uptake kinetics.