Core-shell silica particles with dendritic pore channels impregnated with zeolite imidazolate framework-8 for high performance liquid chromatography separation.

Metal-organic frameworks (MOFs) have been emerged as promising stationary phases for separations. However, the irregular shapes and wide size distribution of MOF particles have led to the high column backpressure and low column efficiency. We described here a kinetic controlling method to deposit zeolitic imidazolate framework (ZIF-8) onto the pore surface using core-shell silica spheres as support. By varying the volume ratio of N,N-dimethylformamide and methanol, the formation speed of ZIF-8 crystals were greatly suppressed, resulting in the growth of very thin layer (∼3.4nm) of ZIF-8 nanocrystals on the pore surface of the spheres instead of freedom growth of micron sized crystals in the solution. Thus prepared hybrid particles combined the merits of high selectivity of MOFs and the high separation performance of core-shell silica spheres. As a result, separation performance as high as 210000 plates/m for a mixture of xylene isomers was achieved.