Silica SOS@HKUST-1 composite microspheres as easily packed stationary phases for fast separation

Abstract

Metal-organic frameworks (MOFs) have been investigated for separations including chromatography.Typically, MOF particles are directly packed into columns for the separations. The irregular shapes and wide size distributions of MOF particles have led to difficulty in column packing and low column efficiency or high back pressure. We describe here the preparation of MOF-silica microspheres as packing materials for fast and efficient liquid chromatography. Spheres-on-sphere (SOS) silica particles are prepared, modified with -COOH and -NH 2 groups, and then used as support to grow HKUST-1.HKUST-1 nanocrystals and films are formed and attached firmly onto the SOS particles with adjustable porosity. The composite microspheres, showing core-shell properties, are directly packed into columns to offer separation capability of MOFs and efficient packing and support of silica microspheres. These columns show separation of toluene/ethylbenzene/styrene and toluene/o-xylene/thiophene within 1.5 minutes. Although HKUST-1 is not good for separating xylene isomers, the separation can be achieved in 5 minutes using the composite microspheres after conditioning the column with dichloromethane or toluene. Remarkably, it is observed that conditioning with DCM can change retention time and selectivity (elution order) of xylene isomers. It is also possible to produce other types of MOFs (e.g., ZIF-8) on the SOS particles, indicating the potential of this method for wider applications.

Cu-BTC and Fe-BTC metal-organic frameworks: Role of the materials structural features on their performance for volatile hydrocarbons separation

“…Activated carbons, zeolites, silica and alumina have been evaluated, with well performance only for some cation-free zeolites [7][8][9][10][11][12]. More recently, the preparation and characterization of metal-organic frameworks (MOFs) have opened new opportunities in the search of highly efficient materials for adsorptive separation of light hydrocarbons [3,[13][14][15][16][17]. Practically infinite combinations of metal ions and organic ligands (or building blocks) are available to form porous frameworks with pore topology and surface functionality with potentiality for light hydrocarbons adsorption-based separation.…”

A facile strategy to fabricate carboxyl-rich carbon spheres with copper-based MOFs through coordination bond

“…This phenomenon indicates that the interaction of the carboxyl groups on the CCSs with Cu 2? in HKUST-1 [10].…”

“…However, the low mechanical strength and block nature of the MOF products greatly prevent their application in these certain areas. To overcome this issue, great efforts have been made on designed synthesis of novel-type composites of MOFs with polymers or nanocarbons in recent years [8][9][10]. For instance, Schwab et al [11] reported the in situ immobilisation of a MOF (HKUST-1) into a hydrophilized macroporous polyHIPE monolith, and revealed that the resulting HKUST-1@polyHIPE composites effectively combines the macroporosity of the polyHIPE with the microporosity of the crystalline MOF of HKUST-1, which is an attractive combination for applications where diffusion processes are limiting.…”

Application of metal and metal oxide nanoparticles@MOFs

“…Silica is the most common stationary phase used in normal phase chromatography and therefore, a natural step forward is to combine silica and MOFs to achieve better performances. Bradshaw's group [8] introduced a sphere-on-sphere (SOS) technique to immobilize small engineered 200 nm silica nanospheres on 5.5 µm silica microspheres. The SOS system with carboxylic groups acted as scaffold for the subsequent growth of HKUST-1 crystals, and the obtained SOS-COOH@HKUST-1 composite ( Fig.…”

“…These unique features have led researchers to explore combining MOFs with other functional materials to form novel composites with advanced properties [6]. Indeed, ceramics, metal nanoparticles, polymers and biomolecules have been combined with MOFs to afford new materials that have demonstrated unprecedented performance in the areas of catalysis [7], molecular separations [8], sensing [9], plasmonics [10], gas storage [11], controlled guest release [12,13], and protection of biomacromolecules [14]. The most widely studied of these composite systems are based on integrating metal and metal oxide nanoparticles with MOFs.…”