The synthesis and precise structural characterization of highly ordered three-dimensional close-packed cage-type mesoporous silica is reported. The siliceous mesoporous material is proven to be commensurate with the face-centered-cubic Fm3m symmetry in high purity by a combination of experimental and simulated powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) analyses. The cage-type calcined samples were additionally characterized by nitrogen physisorption. The aqueous synthesis method to prepare large cage mesoporous silica with cubic Fm3m structure is based on the use of EO106PO70EO106 triblock copolymer (F127) at low HCl concentrations, with no additional salts or organic additives. Here, emphasis is put on the low HCl concentration regime, allowing the facile thermodynamic control of the silica−triblock copolymer mesophase self-assembly. Further, simple application of hydrothermal treatments at various temperatures ranging from 45 to 150 °C enables the tailoring of the mesopore diameters and apertures. The combination of experimental and simulated XRD patterns and TEM images is confirmed to be a very powerful means for the accurate elucidation of the structure of new mesoporous materials.

In this work, the X-ray diffraction structure modeling was employed for analysis of hexagonally ordered large-pore silicas, SBA-15, to determine their pore width independently of adsorption measurements. Nitrogen adsorption isotherms were used to evaluate the relative pressure of capillary condensation in cylindrical mesopores of these materials. This approach allowed us to extend the original Kruk-Jaroniec-Sayari (KJS) relation (Langmuir 1997, 13, 6267) between the pore width and capillary condensation pressure up to 10 nm instead of previously established range from 2 to 6.5 nm for a series of MCM-41 and to improve the KJS pore size analysis of large pore silicas.

In this paper, we bring forward an effective strategy, solvothermal postsynthesis, to prepare ordered mesoporous silica materials with highly branched channels. Structural characterizations indicate that the titled mesoporous materials basically have the cubic double gyroidal (space group Ia-3d) structure with small fraction of distortions. The mesopore sizes and surface areas can be up to 8.8 nm and 540 m2/g, respectively, when microwave digestion is employed to remove the organic templates. A phase transition model is proposed, and possible explanations for the successful phase transition are elucidated. The results show that the flexible inorganic framework, high content of organic matrix, and nonpenetration of poly(ethylene oxide) segments may facilitate the structural evolution. This new synthetic strategy can also be extended to the preparation of other double gyroidal silica-based mesoporous materials, such as metal and nonmetal ions doped silica and organo-functionalized silica materials. The prepared 3D mesoporous silica can be further utilized to fabricate various ordered crystalline gyroidal metal oxide "negatives". The mesorelief "negatives" (Co3O4 and In2O3 are detailed here) prepared by impregnation and thermolysis procedures exhibit undisplaced, displaced, and uncoupled enantiomeric gyroidal subframeworks. It has been found that the amount of metal oxide precursors (hydrated metal nitrates) greatly influence the (sub)framework structure and single crystallinity of the mesorelief metal oxide particles. The single crystalline gyroidal metal oxides are ordered both at mesoscale and atomic scale. However, these orders are not commensurate with each other.

Exceptional control of the phase behavior of highly ordered large pore mesostructured silica (with the choice of Fm3m, Im3m or p6mm symmetry) is achieved using a triblock copolymer (EO(106)PO(70)EO(106)) and butanol at low acid concentrations.

SBA‐15 (2D hexagonal structure) and KIT‐6 (3D cubic structure) silica materials are used as templates for the synthesis of two different crystalline mesoporous WO3 replicas usable as NO2 gas sensors. High‐resolution transmission electron microscopy (HRTEM) studies reveal that single‐crystal hexagonal rings set up the atomic morphology of the WO3 KIT‐6 replica, whereas the SBA‐15 replica is composed of randomly oriented nanoparticles. A model capable of explaining the KIT‐6 replica mesostructure is described. A small amount of chromium is added to the WO3 matrix in order to enhance sensor response. It is demonstrated that chromium does not form clusters, but well‐distributed centers. Pure WO3 KIT‐6 replica displays a higher response rate as well as a lower response time to NO2 gas than the SBA‐15 replica. This behavior is explained by taking into account that the KIT‐6 replica has a higher surface area as demonstrated by Brunauer–Emmett–Teller analyses and its mesostructure is fully maintained after the screen‐printing step involved in sensors preparation. The presence of chromium in the material results in a shorter response time and improved sensor response to the lowest NO2 concentrations tested. Electrical differences related to mesostructure are reduced as a result of additive introduction.

The structure of ordered mesoporous carbons (OMC) synthesized with sucrose, furfuryl alcohol or acenaphthene using the SBA-16 mesoporous silica template with cubic Im3 ¯m structure has been investigated with X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N 2 adsorption. This work shows that, in contrast to carbons prepared from sucrose by using SBA-15 silica as template, the impregnation of SBA-16 with sucrose failed to produce OMC with cubic Im3 ¯m structure. However, when furfuryl alcohol and acenaphthene were used as carbon precursors, the cubic Im3 ¯m structure was retained in the products. Thus, the latter carbon precursors were more suitable than sucrose for the formation of rigidly interconnected carbon bridges through narrow apertures of the cage-like siliceous SBA-16 mesostructure. In particular, the use of furfuryl alcohol as carbon precursor allowed us to control the degree of mesopore filling in SBA-16 and consequently, to synthesize hollow or fully filled cage-like silica-carbon mesostructures as was done in the case of channel-like SBA-15. In the case of acenaphthene only fully filled mesostructures were formed but with a much higher degree of graphitization. In the present work, we took advantage of the recent developments in the synthesis of SBA-16 with tailored diameter and entrance size of mesopores and made a step forward in the fabrication of OMC by using cage-like mesoporous silicas with narrow interconnections as templates.{ Electronic supplementary information (ESI) available: Fig. 1S, 4S, and 5S showing N 2 adsorption-desorption isotherms for the SBA-16/ carbon composites, the recovered SBA-16 samples obtained from the composites, and the carbon samples, respectively; Fig. 2S and 3S showing XRD patterns for the C FA1 -t carbons and the recovered SBA-16 samples obtained from the composites. See

A new method of full-pro®le re®nement is developed on the basis of the minimization of the derivatives of the pro®le difference curve. The use of the derivatives instead of the absolute difference between the observed and calculated pro®le intensities allows re®nement independently of the background. The procedure is tested on various powder diffraction data sets and is shown to be fully functional. Besides having the capability of powder diffraction structure analysis without modelling the background curve, the method is shown to allow the derivation of structure parameters of even higher quality than those obtained by Rietveld re®nement in the presence of systematic errors in the model background function. The derivative difference minimization principles may be used in many different areas of powder diffraction and beyond.

A detailed characterization of large-pore cagelike mesoporous SBA-16 silica materials with tailored pore dimensions is reported. The materials were synthesized in a EO106PO70EO106 (F127)−butanol−H2O system under mildly acidic conditions, and the pore diameters were tailored by varying the hydrothermal treatment temperature. Structural information was acquired by full-profile analysis of powder X-ray diffraction (XRD) patterns. High-resolution diffraction data were obtained for all the materials using synchrotron radiation as the X-ray source, enabling a comprehensive XRD modeling supplemented with the generation of electron density distribution maps. The structural parameters derived from the XRD modeling were compared with data obtained from nitrogen and argon physisorption experiments performed at −196 °C. An excellent agreement was found between the XRD modeling results and those obtained by a new nonlocal density functional theory (NLDFT) kernel developed for pore size analysis based on gas adsorption in spherical pores, while NLDFT analysis based on a cylindrical pore model was shown to systematically underestimate the pore dimensions by about 30% which exceeds previous expectations. Furthermore, the Barrett−Joyner−Halenda model was shown to give errors up to about 45% in the pore size range above 4 nm. The structure of the surfactant−silica hybrid materials was also analyzed by XRD, which shed more light on the structural changes accompanying the thermal surfactant removal process. The present study is expected to provide a reference source for the accurate characterization of large cagelike mesoporous silica materials, on the basis of a direct comparison of suitable data collected independently by gas physisorption and comprehensive XRD modeling.