Synthesis, characterization and applications of 2:1 phyllosilicates and organophyllosilicates: Contribution of fluoride to study the octahedral sheet

The synthesis and characterization of 2:1 phyllosilicates and organophyllosilicates belonging to the smectite group are reported. The fluorine medium was used both as mineralizing agent and as a local probe to determine directly the coordination of structural fluorine. This latter was found to be sensitive to the chemical nature of the octahedral elements and therefore to the type of the octahedral sequences. Fluorine atoms substituted part of hydroxyl groups in the layer creating defects in the lattice and therefore increased the thermal stability. Compared to the pure hydroxyl medium, the reaction time was decreased from 7 to 2 days. A hydrothermal treatment at 220 °C was necessary for the crystallization of 2:1 phyllosilicates, whereas room temperature was sufficient for the preparation of organophyllosilicates. In theses structures, organic groups are covalently bonded to each silicon atom. Organosilane are used as silica sources. A formation mechanism based on the different characterization results was proposed for both phyllosilicates and organophyllosilicates.