Fabrication of isoreticular metal-organic framework coated capillary columns for high-resolution gas chromatographic separation of persistent organic pollutants.

The unusual properties of metal-organic frameworks (MOFs), such as permanent nanoscale porosity, high surface area, uniformly structured cavities, and the availability of in-pore functionality and outer-surface modification, are advantageous for diverse applications. However, most existing methods for the synthesis of nanosized MOFs require an activation procedure or auxiliary stabilizing agents. Here we report a 1-min, room-temperature approach for the synthesis of nanosized isoreticular MOFs (IRMOFs) to fabricate IRMOF coated capillary columns for the high-resolution gas chromatographic separation of persistent organic pollutants (POPs), including polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), polybrominated diphenylethers (PBDEs), and hexachlorocyclohexanes (HCHs). The developed method allows the synthesis of well-shaped nanosized IRMOFs within 1 min at room temperature without the need for any activation procedure or auxiliary stabilizing agents. The IRMOF coated capillary columns offer good separation efficiency that is generally comparable to that of a commercial HP-5MS column for POPs. The IRMOF-1 and IRMOF-3 coated capillary columns gave the theoretical plate values of 2293 and 2063 plates m(-1) for naphthalene, respectively, which are slightly smaller than those with a HP-5MS column (2845 plates m(-1)). The IRMOF-1 coated capillary column offered good resolution for the separation of several intractable PAH isomer pairs, such as anthracene/phenanthrene, benzo[a]anthracene/chrysene, and benzo[b]fluoranthene/benzo[k]fluoranthene, with resolutions of 3.0, 1.1, and 4.1, respectively, which were difficult to be baseline separated on a HP-5MS column with a resolution of 1.0. In addition, the IRMOF-1 and IRMOF-3 coated capillary columns offered a clear group separation of the PCB isomers and a linear range covering three orders of magnitude. The relative standard deviations for the five replicate separations of PAHs were 0.23-0.26% and 2.1-4.5% for retention time and peak area, respectively. The fabricated IRMOF coated capillary columns have been shown to be very promising for the separation of POPs with good reproducibility, high resolution, great selectivity, and a wide linear range.