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Porous pure and doped silicas with pore sizes at two length scales (meso/macroporous) have been prepared and shaped both as powders and monoliths through a one-pot surfactant assisted procedure by using a simple template agent and starting from atrane complexes as inorganic precursors.High surface porous materials showing tailor-made pore sizes and shapes are especially interesting in a variety of applications where molecular recognition is needed. 1 The discovery of the M41S family of mesoporous silicas was a breakthrough finding in this field by opening a new way towards ordered uniform mesoporous systems, which in turn implied an opportunity for expanding the available pore sizes typical of zeolites. 2 Once the preparation of MCM-41 related solids began to be controlled, a new key objective was to achieve the incorporation of different elements to the silica materials to modulate their catalytic properties. 3 Among the many problems associated to this goal, those related with accessibility to the active sites have meant, in some cases, non-attainment of the catalytic performances which could be a priori expected on the basis of the intimate nature of a given material. Several strategies have been developed to overcome such a limitation. Thus, the site accessibility (and, therefore, the catalytic response) can be enhanced through insertion of active elements in mesoporous solids having relatively small particle sizes (HMS solids) 4 or displaying interconnected 3-D channel systems (MCM-48). 5 In some cases, this goal can be simply achieved by expansion of the pore sizes. 6 Recently, it has been reported on the preparation of bimodal (meso-macro or micro-macro) porous materials having enhanced site accessibility. 7 In this last case, the synthesis strategy includes the use of additional templates (besides the proper surfactant), such as latex spheres and microemulsions. This is a polished successful approach.However, besides its apparent singularity, it necessarily implies previous somewhat cumbersome processes of preparation and stabilisation of the large-scale template.We report here on a new direct and reproducible one-pot surfactant-assisted procedure that has allowed us to prepare silica-based materials, both as powders and monoliths (denoted UVM-7 and M-UVM-7), having bimodal pore systems (mesolarge mesoporous or meso-macroporous) and containing a diversity of dopant elements (M = Al, Ti, V, Zr). 8 Modulation of pore sizes depends on both the surfactant (small pores) and the procedural (synthesis and ageing) conditions (large pores).The procedure is based on the use of a simple structural directing agent (CTABr = cetyltrimethylammonium bromide) and a complexing polyalcohol (2,2A,2B-nitrilotriethanol, TEAH3) able to adequately regulate the rates of the hydrolysis and condensation processes involving the different inorganic components (or heteroelements) of the final material. 9 In fact, TEAH3 derivatives have been also used as hydrolytic precursors in the synthesis of mesoporous silicas through nonsurfactan...

Nanoparticulated bimodal porous silicas (NBSs) with pore systems structured at two length scales (meso- and large-meso-/macropores) have been prepared through a one-pot surfactant-assisted procedure by using a simple template agent and starting from silicon atrane complexes as hydrolytic inorganic precursors. The final bulk materials are constructed by an aggregation of pseudospherical mesoporous primary nanoparticles process, over the course of which the interparticle (textural) large pore system is generated. A fine-tuning of the procedural variables allows not only an adjustment of the processes of nucleation and growth of the primary nanoparticles but also a modulation of their subsequent aggregation. In this way, we achieve good control of the porosity of both the intra- and interparticle pore systems by managing independent variables. We analyze in particular the regulating role played by two physicochemical variables: the critical micelar concentration (cmc) of the surfactant and the dielectric constant of the reaction medium.

Silica-based nanoparticulated bimodal mesoporous materials with high Zr content (43 Ն Si/Zr Ն 4) have been synthesized by a one-pot surfactant-assisted procedure from a hydroalcoholic medium using a cationic surfactant (CTMABr = cetyltrimethylammonium bromide) as structure-directing agent, and starting from molecular atrane complexes of Zr and Si as hydrolytic inorganic precursors. This preparative technique allows optimization of the dispersion of the Zr guest species in the silica walls. The bimodal mesoporous nature of the final high surface area nano-sized materials is confirmed by XRD, TEM, and N 2 adsorption-desorption isotherms. The small intraparticle mesopore system (with pore sizes around 2-3 nm) is due to the supramolecular templating effect of the surfactant, while the large mesopores (around 12-24 nm) have their

Nanosized Ti-UVM-7 materials with a hierarchical system of pores at two different length scales have been prepared through a one-pot procedure by using a simple template agent; the catalytic activity and selectivity of the resulting materials in bulky olefin epoxidation by organic peroxides are the highest reported to date.

We report a new development of the so-called MSU route, the first route to use nonionic surfactants and block-copolymers, for the synthesis of silica with bimodal porosity in the micromesoporous range. Among the different synthesis strategies that have been explored until now, the "two-step" process led to the formation of stable hybrid micelles before silica condensation. This mechanism provided a large freedom in the adjustment of the reaction parameters and consequently of the final material structure. We report here that these hybrid micelles are stable enough to allow them to be concentrated through a new three-step method that involves (i) hybrid micelle assembly, (ii) hybrid micelle concentration (HMC), and (iii) silica condensation that leads to monolithic bodies instead of the usual powder. The silica: surfactant ratio is critical to achieving a well-ordered structure that exhibits a final pore size in between zeolites and mesoporous materials with a bimodal distribution centered at 0.6 and 2.0 nm. This method allowed us to homogeneously insert metal salts that remain trapped between the hybrid micelles after the second step without any disturbance of the silica framework. This is illustrated in this report by the addition of aluminum with different rates. Aluminum was inserted homogeneously up to a Si:Al (respectively, Al:Si %) atomic ratio of 2.6 (respectively, 38%). The Al-MSU obtained by this method exhibits strong acidity with a homogeneous broad range of acidity strength that varies linearly with the aluminum content, as demonstrated by NH 3 TPD ranging from 100 to more than 600 °C and preliminary catalytic tests.

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Ordered mesoporous TiO 2 -NiTiO 3 thin films, with nickel content x o 0.5, were prepared by dip-coating an acidic solution of hydrolysed transition metal chlorides in controlled humidity, followed by a very careful annealing treatment. These latter treatments were studied by in situ SAXS-WAXS experiments involving synchrotron radiation and TEM analysis. They revealed that the walls can be composed of amorphous, single crystalline or multi crystalline nanoparticles depending on x and the conditions applied during the thermal treatment.