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The increasing awareness of the need to create green and sustainable production processes in all fields of chemistry has stimulated materials scientists to search for innovative catalysts supports. These new catalytic supports should allow the heterogenization of most catalytic processes, increasing the efficiency and selectivity of the synthesis and reducing waste and byproducts. Following the development of several micellar templated structures, such as M41S 1 , FSM-16, 2,3 HMS, 4,5 MSU-x, 6 and SBA-x, 7,8 it is a crucial next step to create support materials, consisting of a composite matrix with combined micro-and mesoporosities and a sufficient stability to withstand most industrial treatments. We describe in this paper the very first development of a hexagonal material with large pore diameters and thick walls (4 nm), containing internal microporous silica nanocapsules. These plugged hexagonal templated silicas (PHTS) have two types of micropores (originating from the walls and the nanocapsules respectively) and a tunable amount of both open and encapsulated mesopores. The micropore volumes have a high value (up to 0.3 cm 3 /g) and the total pore volume exceeds 1 cm 3 /g. The obtained materials are much more stable than the conventional micellar templated structures known so far, and can easily withstand severe hydrothermal treatments and mechanical pressures.

The thermal, hydrothermal, and mechanical stabilities of a wide range of ordered mesoporous materials, in particular, the molecular sieves MCM-41, MCM-48, HMS, FSM-16, KIT-1, PCH, and SBA-15, have been studied in detail using X-ray diffraction (XRD) and nitrogen sorption. The thermal stability was found to be strongly related to the wall thickness and the silica precursor used during synthesis, and the following stability trend was observed: MCM-41 (fumed silica), MCM-48 (fumed silica), KIT-1 (colloid silica) > SBA-15 (TEOS) > FSM-16 (layered silicate), PCH (layered silicate) > MCM-41 (TEOS), MCM-48 (TEOS), HMS (TEOS). The hydrothermal stability is influenced by the wall thickness and the polymerization degree and decreases according to the following trend: KIT-1 > SBA-15 > MCM-48 (fumed silica and TEOS), PCH > FSM-16, MCM-41 (fumed silica and TEOS), HMS. The mechanical stability is little influenced by the nature of the mesoporous molecular sieves. All materials collapsed at a maximum pelletizing pressure of 450 MPa.

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