Direct imaging of the pores and cages of three-dimensional mesoporous materials

Abstract

Mesostructured composite materials, with features ranging from 20 to 500 A in size, are obtained by the kinetically controlled competitive assembly of organic and inorganic species into nanostructured domains. Short-range order is limited, and long-range order is determined by weak forces such as van der Waals or hydrogen-bonding. Three-dimensional mesoporous materials obtained by removing the organic phase are of particular interest for applications such as catalysis and chemical sensing or separation, for which structural features such as cavity shape, connectivity and ordered bimodal porosity are critical. But atomic-scale structural characterization by the usual diffraction techniques is challenging for these partially ordered materials because of the difficulty in obtaining large (> 10 microm) single crystals, and because large repeat spacings cause diffraction intensities to fall off rapidly with scattering angle so that only limited small-angle data are available. Here we present a general approach for the direct determination of three-dimensional mesoporous structures by electron microscopy. The structure solutions are obtained uniquely without pre-assumed models or parametrization. We report high-resolution details of cage and pore structures of periodically ordered mesoporous materials, which reveal a highly ordered dual micro- and mesoscale pore structure.

A Re-Evaluation of the Morphology of a Bicontinuous Block Copolymer−Ceramic Material

“…The double gyroid, 24 double diamond, 7 and I-WP 25 structures have all previously been observed in bicontinuous silica-type materials. Table 2 reports structure factors for double gyroid (G), double diamond (D), plumber's nightmare (P), and I-WP structures calculated using the parametric equations of Garstecki and Holyst.…”

Maximizing Entropy by Minimizing Area: Towards a New Principle of Self-Organization

“…The relevance of these universal guidelines is as broad as the use of colloids themselves, ranging from photonic bandgap crystals 55,56 to micro-or mesoporous materials used for chemical microreactors and molecular sieves. 57,58 To meet the demands of a particular application, these designer materials must be characterized by a given lattice constant, symmetry, and mechanical properties, and, in the case of porous structures, void size and connectivity. All these parameters can be controlled by tuning the structure and size of the (template) colloidal particles and the interaction between them, and our model establishes a semiquantitative relationship between particle geometry and bulk material properties.…”

Facile preparation of 3D ordered mesoporous CuOx–CeO2 with notably enhanced efficiency for the low temperature oxidation of heteroatom-containing volatile organic compounds

“…35,37,38 Among these, SBA-16 has three-dimensional (3D) channels and a cubic Im3m (bodycentered cubic arrangement of cages with 8 apertures to the nearest neighbors) structure, which could be more favorable for mass and thermal transfer than a unidirectional pore system. 39 In order to introduce the maximum quantity of metal precursors, as many silanol groups as possible must be retained during the preparation of the silica template. In our previous work, we found that the mesochannels of SBA-15 and KIT-6 were far from completely filled by metal precursors due to a large loss of Si-OH groups during the organic template removal process that involved a thermal calcination, 40,41 and this phenomenon has also been reported by other groups.…”