A spray-drying strategy for synthesis of nanoscale metal–organic frameworks and their assembly into hollow superstructures

Abstract

Metal-organic frameworks (MOFs) are among the most attractive porous materials known today. Their miniaturization to the nanoscale--into nanoMOFs--is expected to serve myriad applications from drug delivery to membranes, to open up novel avenues to more traditional storage and catalysis applications, and to enable the creation of sophisticated superstructures. Here, we report the use of spray-drying as a versatile methodology to assemble nanoMOFs, yielding spherical hollow superstructures with diameters smaller than 5 µm. This strategy conceptually mimics the emulsions used by chemists to confine the synthesis of materials, but does not require secondary immiscible solvents or surfactants. We demonstrate that the resulting spherical, hollow superstructures can be processed into stable colloids, whose disassembly by sonication affords discrete, homogeneous nanoMOFs. This spray-drying strategy enables the construction of multicomponent MOF superstructures, and the encapsulation of guest species within these superstructures. We anticipate that this will provide new routes to capsules, reactors and composite materials.

Lanthanide–Organic Framework Nanothermometers Prepared by Spray‐Drying

“…[ 22 ] The synthesis of MOF nanoparticles is still a challenging task, despite many attempts and several proposed strategies including coordination modulation, ultrasonic-, microwave-, interfacial-, and ionic liquid/microemulsionsynthesis. [ 23 ] Maspoch and co-workers [ 24 ] and Marquez et al [ 25 ] reported approaches capable of affording a wide range of nanosized MOFs based on the spray-drying method: the reaction medium is atomized into droplets and MOF nanoparticles form during the drying process and self-assemble into superstructures within the droplets, which act as individual reactors confi ning the growth of the crystals. This method is attractive because it emulates the microemulsion synthesis, restraining the reagents to the droplets, without using a secondary immiscible solvent.…”

PdO/ZnO@mSiO2 Hybrid Nanocatalyst for Reduction of Nitroarenes

“…The size distribution in Figure 1c clearly shows that the PS spheres had an average size of around 315 nm. The PS spheres were copolymerized with acrylic acid, resulting in the functionalization of the surface with carboxylic groups to facilitate coordination with metal ions and metal particles [25,26]. The presence of the carboxyl group on the PS surface was confirmed by FT-IR spectroscopy (Figure 1d).…”

“…Firstly, carboxylate-terminated polystyrene spheres (PS spheres) were prepared according to a previously described method [25,26]. Figure 1a,b show the scanning electron microscopy (SEM) images of the PS spheres, illustrating the spherical shape with a smooth surface and monodisperse size distribution.…”

“…The polystyrene nanoparticles were synthesized according to a previously reported method [25,38]. Polymerization was carried out in a 250 mL Schlenk flask with 21 mL of styrene, 0.92 mL of acrylic acid, 1.1 mL of methyl 2-methylpropenoate, and 0.49 g ammonium bicarbonate in 100 mL of deionized under magnetic stirring at 70 °C.…”

Synthesis and Characterization of Nontoxic Hollow Iron Oxide (α-Fe2O

“…Template methods are most effective in the formation of hollow structures in accordance with the uniformity [10]. These procedures are expensive and include many steps for the synthesis as well as for the removal of templates that often lead to the breakage of hollow sphere while template is removed [2,11,12]. So there is a need of simple, straight forward, and cost effective solution based approaches for the synthesis of hollow iron oxide NPs although there have been many reports on solution based 2 Journal of Nanomaterials synthesis of uniform hollow nanostructures [13].…”