This paper deals with the use of the fluoride route in the synthesis of silica-based zeolites and metallophosphates (mainly gallophosphates) microporous materials, with a special emphasis on the work of the Mulhouse's group during the last recent years. The first part of this account relates to silica-based zeolites and is divided into three sections. The first section is mainly devoted to pure silica and variously substituted MFI-type zeolite (T = Al, Ga, B, Ti....), whereas the second section concerns the synthesis of pure silica or (Si, Al) zeolites with other framework topologies. Among the numerous structure-types so far obtained in fluoride medium, some of them are new and display the small F --containing double four-ring unit (D4R-F). The formation of this type of unit was first observed in the case of the clathrasil octadecasil (AST-structure-type), and is only possible due to the templating and stabilizing effect of the fluoride anion. Besides, the fluoride route leads to pure silica zeolite samples with very few or no connectivity defects. The resulting hydrophobic character allowed us to develop a new application in the field of energetics, where the systems zeolite-water can be used as molecular springs or bumpers. The third section concerns specifically the recently discovered silicogermanate zeolites with new framework topologies. Germanium acts indeed as a real structuredirecting agent, favoring in particular the formation of structures displaying the small D4R or D4R-F unit. The example of IM-10 (IM standing for Institut Français du Pétrole: Mulhouse), with UOZ structure-type, prepared in our laboratory in fluoride medium and from germanium-rich mixtures in the presence of hexamethonium cations, is described. Two other new materials called IM-9 and IM-12, both characterized by the presence of the same D4R-F or D4R unit in their structures, and prepared, respectively, from fluoride-containing or fluoride-free systems in the presence of the (6R,10S)-6,10-dimethyl-5-azoniaspiro [4,5] organic agent, are also presented. The second part concerns the phosphate-based microporous materials prepared in fluoride media and mainly the gallophosphates. As for silica-based zeolites, besides its mineralizing role, Fcan play a templating role, being found inside the small D4R units. Thus many fluorogallophosphates of the Mu-n family, with 0-D, 1-D, 2-D or 3-D frameworks (Mu standing for Mulhouse), showing such a building unit were obtained. Specific experiments are reported about the hydrothermal transformation of the fluorogallophosphate Mu-3 (1-D framework) into the fluorogallophosphate Mu-2 (3-D framework), both containing D4R-F units, and a possible mechanism of reaction is suggested. Several examples are also given where fluorine is part of the framework as terminal groups (Ga-F) or bridging species (Ga-F-Ga). Finally the observed variety

Stable zeolites that have larger pore apertures and a three-dimensional pore topology are of interest because they could be used to adsorb larger molecules, particularly for application in oil refining. Several large-pore zeolitic materials with channels formed by openings of more than 12 rings are known, but all of them have a one-dimensional channel system that limits their use in catalysis. We report the synthesis and some characterizations of IM-12, a thermally stable germanium-containing zeolite that contains the first two-dimensional channel system with extra-large pores formed by 14- and 12-ring channels.

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Water intrusion-extrusion isotherms performed at room temperature on hydrophobic pure silica chabazite show that the water-Si-CHA system displays real spring behavior. However, differences in pressure-volume diagrams are observed between the first and the other intrusion-extrusion cycles, indicating that some water molecules interact with the inorganic framework after the first intrusion. (29)Si and especially (1)H solid-state NMR showed the creation of new defect sites upon the intrusion-extrusion of water and the existence of two kinds of water molecules trapped in the supercage of Si-CHA: a first layer of water strongly hydrogen bonded with the silanols of the framework and a subsequent layer of liquidlike physisorbed water molecules undergoing interaction with the first layer. This hydrogen bonding scheme is also supported by X-ray powder diffraction.

To study the energetic performance of the 1D 12-membred-ring pure silica ITQ-4 zeolite (IFR topology), a high-pressure water intrusion-extrusion isotherm at room temperature was performed. The pressure-volume diagram indicates an irreversible phenomenon, water molecules remaining confined in ITQ-4 micropores. Therefore, the "water-ITQ-4" system appears to behave as a bumper. The water intrusion pressure and intruded volume are of 42 MPa and 0.136 mL/g, respectively. Investigations on the ITQ-4 samples by 29 Si and 1 H solid-state NMR spectroscopy and powder X-ray diffraction have confirmed the existence of a small amount of silanol defects in the nonintruded sample and an increase of these defects after the water intrusion-extrusion experiment. It appears clearly that one of the crystallographic silicon sites of the porous framework is particularly affected after such a treatment, leading to the creation of Si-OH groups by the breaking of siloxane bonds, these silanols being strongly hydrogen bonded with water molecules.

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Metal−organic framework-type Al-, Ga-, and Ga(OH,F)-MIL-53 have been characterized by solid-state NMR and powder X-ray diffraction (PXRD). 1H 2D double-quantum–single-quantum (DQ–SQ) magic angle spinning (MAS) NMR experiments unambiguously evidence two inequivalent water molecules in Al-MIL-53_np_H2O. A careful reinvestigation of the XRD structure of hydrated Al-MIL-53 proves, for the first time, the doubling of the unit cell supporting the presence of two inequivalent water molecules. One type of water molecule is located in the type A channel, interacting with the aromatic protons of framework organic moieties, whereas the other type of water molecule is in the type B channel far away from aromatic protons. Assignment of the corresponding 1H resonances to each water molecule was possible. 1H 1D MAS NMR leads to the same conclusion (i.e., two inequivalent water molecules) for the isostructural gallium-based material thanks to the positioning of the hydrogen atoms by Rietveld refinement. Moreover, when Ga-MIL-53 is prepared with fluorine in the synthesis medium (giving Ga(OH,F)-MIL-53_np_H2O), the situation is different. 2D 1H–13C heteronuclear correlation MAS NMR, high-field 1H DQ–SQ, and radio-frequency-driven recoupling MAS NMR indicate that only one type of water molecule is found in this material, in agreement with the structure.

IM-20 is a novel microporous germanosilicate with an interesting zeolitic structure. It has been prepared via the fluoride route with 3-butyl-1-methyl-3H-imidazol-1-ium as the organic structure-directing agent and its structure solved from synchrotron powder X-ray diffraction data. The chemical formula per unit cell is Si(42.2)Ge(17.8)O(120) under its calcined form. IM-20 possesses a new framework topology, the 3D channel system being formed by straight intersecting 12- and 10-membered rings. Two types of d4r composite building units are present in IM-20, their average Si/Ge molar ratio being about 8.52 or 0.56. Surprisingly, the pure silica or silica-rich units are fluoride-free in the as-synthesized material.