The Fluoride Route to Zeolites

From that time, the synthesis of zeolites by the so-called fluoride route has developed to a large extent, with great contributions by Guth et It has been successfully appHed to pure-silica, alumi- 

Beta and ITQ-3 (ITE)] fluoride hopping. Both situations can be characterised by Si NMR spectroscopy, which reveals either a broad resonance in the —120/—140 ppm region or sharper lines around —140/ —150 ppm, respectively. Fluoride motion was frozen at low temperature (—143 to —133 °C). The number of pure silica zeolites that have been 

We have to stress, however, that with regard to Si-F interactions in zeolites, in addition to the ( dynamic or fixed ) pentacoordinated [Si04/2F] units described above, there is another very common third situation, characterised by the lack of direct Si-F bonding that could be evidenced by experimental techniques, even at low temperature. As far as we know this only occurs when fluoride anions are occluded inside [4 ] silica cages, which is the case in octadecasil, ITQ-7 (ISV), ITQ-12 (ITW),f ° and in one of the two types of occluded fluoride in ITQ-13 and IM-7 We speculate that the available space 

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