Composite particles containing the Zr-based metal–organic framework (MOF) UiO-66 were prepared using microwave-assisted solvothermal synthesis. Scanning electron microscopy, infrared spectroscopy, powder X-ray diffraction and nitrogen physisorption studies confirmed the deposition of 100–300 nm microporous particles with the UiO-66 topology on the surface of mesoporous 5 μm and non-porous 2.1 μm silica particles. The core–shell particles exhibited a unique flow-dependent separation selectivity (FDSS) effect which allows changes in both the retention and separation selectivity of small molecules by simple variation of the mobile phase flow rate under isocratic conditions. The impact of the loading of UiO-66 as well as the porosity of the underlying silica core (mesoporous and non-porous) on the FDSS effect was evaluated. The prepared adsorbents were also tested for the normal-phase (NP) and reversed-phase (RP) separation of xylene isomers, substituted benzenes and polyaromatic hydrocarbons (PAHs). Efficiencies of up to 32 400 plates per m (styrene, k 1.59) and 37 200 plates per m (anisole, k 2.90) were achieved under NP and RP modes, respectively. The results demonstrate the potential of novel MOF-based stationary phases for the separation of closely related compounds (e.g. positional isomers).

Within recent years there has been an increase in research focused on the design and application of organic polymer monoliths in all areas of separation science. This is largely driven by the theoretical and practical benefits that these materials should be able to provide, particularly in terms of improved biocompatibility and high permeability. This review summarises recent new developments in this field with a focus on new approaches to the design and synthesis of polymeric monolithic materials for analytical separation science. This includes the use of alternative synthetic methodologies such as the development of hyper-crosslinked monoliths, preparation of hybrid materials and incorporation of nanostructures in the polymeric scaffold. New and developing approaches for the structural characterisation of monolithic columns are also included. Finally, we critically discuss the current chromatographic performances achieved with this column technology as well as where future developments in this field may be directed.