Characterization of synthetic Cs-Li cancrinite grown in a butanediol-watersystem: An NMR spectroscopic and Rietveld refinement study

A Cs-Li-analogue of cancrinite has been synthesized from tetraethoxysilane and Al sec-butoxide in a mixture of 1,3-butanediol and water. Ca and Li wer e introduced as hydroxides. Synthesis was done at autogeneous pressure and T = 473 K for 100 h. The synthesis product was characterized by powder X-ra y diffraction, IR-spectroscopy, thermogravimetry, H-1, Li-6, Li-7,Cs-133, A l-27, Si-29 MAS, and {H-1} C-13 CPMAS NMR and Rietveld structure refinement . Si-29 MAS NMR and Al-27 MAS NMR spectroscopy show a framework with strong alternating order of the SiO4 and AlO4 tetrahedra and an Si/Al ratio of on e. Li-6 MAS NMR suggests the existence of two different signals that cannot be resolved in the Li-7 MAS NMR spectrum. Cs-133 MAS NMR shows only a sing le resonance. The thermogravimetric analysis reveals a continuous weight lo ss in several steps, indicating the evaporation of water of hydration. IR s pectroscopy shows evidence for hydroxyl anions and water included in the ca ncrinite framework. The Rietveld structure refinement is consistent with a completely ordered alumosilicate framework with an Si/Al ratio of one and t he presence of both molecular water and hydroxyl groups in the hexagonal ch annel, a result different from the previously published structure. Cs is ex clusively located in the epsilon -cages; Li ions are located in the channel s and are coordinated by water molecules.