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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

Synthesis, Characterization, and Crystal Structure of the New Clathrasil Phase Octadecasil.-A new clathrasil (silica-only porous tectosilicate) named octadecasil is prepared hydrothermally (170 • C, autoclave, 10-15 d) from aqueous silica (or aluminosilica) gels at near neutral pH in the presence of quinuclidine (Q) or Me4N+ cations as a template and F-ion as a mobilizing agent. The structure of octadecasil is closely related to that of the natural mineral zunyite and AlPO4-16. Among clathrasils, octadecasil is an exception, insofar as the all-silica framework consists of 4-and 6-membered rings only. The truncated rhombododecahedral (46612) cages and the hexahedral (46) cages are occupied by Q+ and F-ions, resp. (single crystal XRD, DTA, TG, 29Si, 13C, 19F MAS NMR data). -(CAULLET, P.; GUTH, J. L.; HAZM, J.; LAMBLIN, J. M.; GIES, H.; Eur. J. Solid State Inorg. Chem. 28 (1991) 2, 345-361; Lab. Mater. Miner., CNRS, Ec. Natl. Super. Chim. Mulhouse, Univ. Haute-Alsace, 68093 Mulhouse, Fr.; EN)

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.

A two-dimensional aluminosilicate microporous compound, synthesized from fluoride-containing aqueous media at 170 "C in the presence of 4-amino-2,2,6,6-tetramethylpiperidine as the template, transforms upon calcination above 500 "C into a FER-type zeolite.

Fluorination of a precipitated silica (supplied by Rhodia) by aqueous solutions of NH 4 F (0.1-2 mol L -1 ) is performed at room temperature (RT), the resulting fluorinated samples recovered after drying (RT or 70 °C) being possibly calcined (110-600 °C, for 5 or 24 h). The fluorinated silica samples are analyzed by TEM, nitrogen adsorption manometry, 19 F (Hahn echo sequence), 29 Si and 1 H MAS NMR, and 1 H-29 Si and 19 F-29 Si CPMAS NMR spectroscopy. The 19 F NMR allows both a qualitative and quantitative determination of the various detected fluoride-containing (in particular, fluosilicate) species, whereas the 1 H MAS NMR leads to a complete speciation of the proton-containing species. The whole of the experimental data confirms clearly the existence of two kinds of fluorination mechanisms. For low fluoride concentrations, a nucleophilic substitution of OH groups by Fions occurs, whereas, for higher fluoride concentrations, this substitution reaction is accompanied by a second mechanism implying the fluorinative opening of siloxane bonds, leading in particular to the formation of octahedral (hydroxy)fluosilicate species. The effect of the calcination, involving a secondary fluorination processsthrough the decomposition of the octahedral fluosilicate speciessis also demonstrated. Finally, four kinds of fluosilicate species are determined, corresponding to isolated O 3/2 SiF groups (δ 19 F ) -156 ppm/CFCl 3 ; δ 29 Si ) -105 ppm/TMS), pentacoordinated O 4/2 SiF groups (δ 19 F ) -153 ppm; δ 29 Si ) -119 ppm), O 3/2 SiF species close to other groups of the same type (δ 19 F ) -147 ppm; δ 29 Si ) -105 ppm), and octahedral SiF 6 2or Si(OH) 1-2 F 5-4 2ions (δ 19 F ) -127 or -129 ppm, respectively; δ 29 Si ) -188 ppm).

Speciation of the various proton species present in precipitated silica samples by 1H high-spinning frequency magic-angle spinning (MAS) NMR (25 kHz) is achieved. External standards are used for the calibration of the absolute amount of protons, the relevance of the proton spin counting being checked by comparison with the data deduced from classical thermogravimetric (TG) and 29Si MAS NMR experiments. The method also allows to follow postsynthesis modifications of silica, corresponding for instance to fluorination or deuteration treatments. In particular, a 1H resonance occurring at 1.1 ppm/TMS and corresponding to a constant proton amount whatever the applied treatment is tentatively assigned for the first time to inaccessible isolated silanol groups.

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