Novel Zn-based MOFs stationary phase with large pores for capillary electrochromatography

Metal-organic frameworks (MOFs) are attractive stationary phases in the field of separation sciences for their unique properties such as large specific surface areas, high porosity, and diverse structures. However, there are few MOFs, which have ultrahigh porosities and gas uptake capacities. In this work, MOF-180 with exceptional porosity, a cage size of 15 x 23 angstrom, was grown on inner wall of capillary as a novel stationary phase for open-tubular CEC. It has been demonstrated that the MOF-180-modified capillary column exhibited good performance for separation of acidic, basic, and neutral analytes. As compared with MOF-199-modified column, MOF-180-modified column exhibited specific recognition and size selectivity to the tested compounds. The characteristics observed by SEM and FTIR indicated that MOF-180 was successfully grafted on the inner wall of the capillary. The precisions (RSDs) of retention time, peak area, and W1/2 for methylbenzene, ethylbenzene, n-propylbenzene, chlorobenzene, o-dichlorobenzene, and 1,2,4-trichlorobenzene were 0.50-0.54%, 3.31-4.13%, 0.35-1.61%, 1.73-4.22%, 2.67-4.37%, and 1.60-3.38%, respectively. Besides, the run-to-run, day-to-day, and column-to-column RSDs of EOF were 0.6%, 4.19%, and 4.31%, respectively.