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Three linear diquats of different lengths (consisting of two quinuclidinium groups linked by a chain of 8, 6 or 4 methylene groups) have been used as structure directing agents in the synthesis of silica zeolites in the presence of fluoride anions. Phase selectivity changes induced by changes in the concentration of the crystallizing mixture or by the addition of Al have been investigated. For the longest diquat only Beta and ZSM-12 were detected by X ray diffraction in the product, with Beta being favoured at high concentrations, low temperatures and short crystallization times. As the length of the chain decreases other phases, in addition to Beta and ZSM-12, appear: ZSM-5 (for the diquat of intermediate length) and ITQ-8, ITQ-10 and ITQ-14 (for the shortest diquat). ITQ-8 is most likely a layered silicate, while ITQ-10 and ITQ-14 are stable zeolites with intergrown structures related to the zeolite Beta family. Notably, ITQ-14 was found to consist of crystallites with the so far hypothetical “structure C” overgrown on standard zeolite Beta crystals. The phase selectivity effect of introducing Al into the gel is generally similar to the effect of decreasing its water content. However, with the longest diquat a different zeolite, Nu-87, crystallized in the presence of Al in a wide range of Si/Al ratios (25–200) but not for pure silica compositions or for the shortest diquats.

The preparation of macro–micro bifunctional porous materials has been accomplished by a well-controlled, vacuum-assisted technique. Monodisperse polystyrene latex spheres were ordered into close-packed arrays by slow sedimentation, allowing a high flux of water through the interstices between latex spheres. Zeolite LTA, FAU, LTL, BEA, MFI and Si-MFI nanocrystals, synthesized by hydrothermal procedures, permeated the interstices of latex spheres under the driving force of flowing water. After drying and calcination at 500°C, both the latex spheres and zeolite structure-directing molecules were removed, followed by the formation of products consisting of both crystalline micropores and periodic, interconnected networks of submicron macropores. XRD, SEM, TEM, IR, TG/DTA, ICP and N2 adsorption–desorption measurements were performed to monitor the preparation and to characterize the properties of the macro–micro bifunctional porous materials. The materials presented in this paper combine the benefits of both the micropore and macropore regimes. They could potentially improve the efficiency of both separation and catalysis of zeolites.

Silica mesoporous molecular sieves doped with europium were synthesized using Cab-O-Sil M5 silica and europium chloride in the presence of cetyltrimethylammonium bromide surfactant. The materials obtained with lower Eu content (Si∶Eu molar ratio of 100) in the synthesis gel exhibited two-dimensional hexagonally ordered structure of the MCM-41 type, whereas larger Eu contents resulted in lower size of hexagonally ordered porous domains (for Si∶Eu = 33) or in disordered porous structures (for Si∶Eu = 20). The pore size increased from 3.4 to 4.0 nm as the amount of Eu in the synthesis mixture increased. Pore size distributions (PSDs) for Eu-doped silicas were narrower than the PSDs of the pure-silica MCM-41 material synthesized under the same conditions. A decrease in the specific surface area and primary mesopore volume was observed for higher Eu loadings. The volume of secondary (interparticle) pores increased as the content of Eu in the synthesis gel increased, which is consistent with the transmission electron microscopy images that provided an indication of the decrease in the particle size, although the latter was not uniform throughout the materials under study. Energy dispersive X-ray fluorescence (EDX) data indicated that europium is indeed present in the structure of the materials studied, although its content tended to be somewhat lower than that in the synthesis gel and its distribution within the materials appeared to be non-uniform. The synthesis procedure reported herein was used to synthesize silicas doped with other lanthanides, and for given lanthanide loadings, the resultant materials exhibited porous structures similar to those of the Eu-doped samples.

We present a comprehensive analysis for pore structures of cage-type ordered mesoporous carbons (OMCs) using various electron microscopy techniques in addition to conventional nitrogen adsorption i ...

Many research efforts have focused on the synthesis of organic and inorganic hybrid ordered mesoporous silicas (MSs) with functionalization of the exterior and/or interior surfaces aiming for applications in separation, adsorption, catalysis, drug delivery, and nanotechnology. Among the organic groups, the carboxylic group is a particularly useful reactive group for many applications. This article provides a brief overview of the carboxylic group functionalized MSs and the recent progress in synthetic strategies and applications have been reviewed.

Carboxylic group functionalized mesoporous silicas (CFMSs) were successfully synthesized by using cationic surfactants as templates and carboxyethylsilanetriol sodium salt (CES) as a co-structure directing agent (CSDA). Well ordered two-dimensional (2D) p6mm, cubic Fmm, intergrowth of Fmm and P63/mmc, and cubic Fdm with uniform carboxyl group distributions have been synthesized with increasing charge density of carboxylate of CES on the surface of the mesopore, which will provide new families of mesoporous materials with different functionalities and structures.

The formation of anionic surfactant templated mesoporous silica (AMS) is investigated from the perspective of the geometrical molecular design of the surfactant and the co-structure-directing agent (CSDA) toward the rational synthesis of the targeted mesostructure. Increasing the geometrical size of two types of head group of the anionic surfactant in the order (i) sulfonate, sulfate and phosphate, and (ii) carboxylate, N-acylalanate/N-acylglycinate and N-acylglutamate, resulted in the mesophase changing from a disordered or lamellar phase to two-dimensional (2D) hexagonal (p6mm) and three-dimensional (3D) cage-type (hexagonal and a modulated cubic phase) with increasing order of the organic/inorganic interface curvature. A change in the chain length of the surfactant also led to different surfactant packing and mesophase interfacial curvatures, and resulted in a change in mesophase from a modulated cage-type mesophase to cubic Fdm, cubic Pmn and a disordered cage-type mesophase. The geometrical change in the CSDA resulted in an increasing micellar curvature in the order: aminopropyl < N-methylaminopropyl < N,N-dimethylaminopropyl trimethoxysilane, which led to a change of mesophase from bicontinuous cubic Pnm to 2D-hexagonal p6mm. An increase in the CSDA/surfactant ratio in the synthesis gave rise to the mesophase change from a disordered cage-type mesophase to cubic Fmm or from lamellar to 2D-hexagonal p6mm, and elemental analysis results showed that the mesoporous silicas have an increased loading of organic moieties using the CSDA method.

An in-depth study of the synthesis and growth of bicontinuous cubic mesoporous AMS-6 material in the presence of polymeric dispersant P123 is presented, resulting in controlled particle shape attainable over a small range of synthesis conditions. Unlike previous syntheses a remarkable effect on facet formation of the Iad silica particles with cubic morphologies is observed. Trapezoidal icositetrahedra, spherical and elongated morphologies have been prepared with increased faceting on addition of higher concentration of dispersant. Particles are characterised extensively by powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy and nitrogen sorption isotherms. Mesoporous materials produced in this study show textural features suggesting a secondary porous network formed on the external surface of the particle and the origin of this secondary porosity is discussed. Based on the reduced dynamics generated by the presence of the P123 dispersant, we suggest possible growth models for the formation of mainly two different morphologies—the thermodynamically favoured trapezoidal icositetrahedron and elongated particles, the latter not following the expected point group symmetry, mm.