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

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. © 2013 Macmillan Publishers Limited. All rights reserved.I.I. and M.C.S. thank MICINN and ICN for a Ramón y Cajal grant and a research contract, respectively. A.C. thanks the Generalitat de Catalunya for a FI fellowship.Peer Reviewe

Critical Overview of Textural Characterization of Zeolites by Gas Adsorption

Porous materials with pores within molecular size are essential to solve several technological problems taking advantage of their textural properties related to their exposed surface and porosity. Among these materials, zeolites are in the podium, with technological and industrial applications, which are directly related to pore properties (e.g., size, surface chemistry, among others). To obtain their textural properties, there are several techniques, but gas adsorption plays an important role, and it is among the most widely used for this purpose. Despite being a popular technique, with nitrogen at 77 K as the reference probe molecule to obtain adsorption isotherms, the estimation of the textural properties is not a trivial procedure. On the other hand, it is possible to perform adsorption measurements with different gases at different temperatures and pressures, whereby is crucial the choice of adequate analysis conditions because the adsorption-desorption isotherm will be the unique information obtained from the experiment. Once the data are obtained, a careful selection of methods and models to analyze them is mandatory to evaluate textural properties of the samples in a reliable and reproducible manner. Particularly for zeolites, due to their pore sizes and the presence of surface functional groups, the application of this characterization technique is not straightforward, thus needing to pay attention to the previous knowledge that exists about this type of materials, to carry out the experiment as well as to choose the appropriate methodology for data treatment. In this chapter, we introduce an overview of the experimental procedure and data treatment to obtain the more reliable textural properties for zeolites.Fil: Villarroel Rocha, Jhonny. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Barrera, Deicy. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Arroyo Gómez, José Joaquín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; Argentin