Metal-organic framework MIL-101(Cr) for high-performance liquid chromatographic separation of substituted aromatics

The diverse structures and pore topologies, accessible cages and tunnels, and high surface areas make metal-organic frameworks attractive as novel media in separation sciences. Here we report the slurry-packed MIL-101(Cr) column for high-performance liquid chromatographic separation of substituted aromatics. The MIL-101(Cr) packed column (5 cm long × 4.6 mm i.d.) offered high-resolution separation of ethylbenzene (EB) and xylene, dichlorobenzene and chlorotoluene isomers, and EB and styrene. The typical impurities of toluene and o-xylene in EB and styrene mixtures were also efficiently separated on the MIL-101(Cr) packed column. The column efficiencies for EB, m-dichlorobenzene, and m-chlorotoluene are 20000, 13000, and 10000 plates m(-1), respectively. The relative standard deviation for five replicate separations of the substituted aromatics was 0.2-0.7%, 0.9-2.9%, 0.5-2.1%, and 0.6-2.7% for the retention time, peak area, peak height, and half peak width, respectively. The MIL-101(Cr) offered high affinity for the ortho-isomer, allowing fast and selective separation of the ortho-isomer from the other isomers within 3 min using dichloromethane as the mobile phase. The effects of the mobile phase composition, injected sample mass, and temperature were investigated. The separation of xylene, dichlorobenzene, and chlorotoluene on MIL-101(Cr) was controlled by entropy change, while the separation of EB and styrene on MIL-101(Cr) was governed by enthalpy change.