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Five‐Coordinate Silicon in Zeolites: Probing SiO 4/2 F − Sites in Nonasil and ZSM‐5 with 29 Si Solid‐State NMR Spectroscopy

1997; Wiley; Volume: 36; Issue: 24 Linguagem: Inglês

10.1002/anie.199728231

1521-3773

Hubert Koller, A. Wölker, Hellmut Eckert, Christian Panz, Peter Behrens,

Chemical Synthesis and Characterization

With fluoride as a mineralizing agent, the high-silica zeolites nonasil and ZSM-5 were obtained by hydrothermal syntheses. 29Si NMR spectroscopy showed that five-coordinate silicon exists in the form of SiO4/2F− in the zeolite frameworks (see the 29Si{19F} CPMAS NMR spectrum of nonasil on the right). In ZSM-5 at room temperature the fluoride ion undergoes a dynamic exchange between different silicon atoms, which is frozen out at 140 K.