From simple molecules to highly functionalised lamellar materials

We describe here a new method permitting the one-step synthesis of ordered (lamellar phase) organosilicas highly functionalised with carboxylic acid or phosphonic acid groups. These materials were obtained by hydrolysis and polycondensation of monosilylated precursors cyanoalkyltrialkoxysilane (NC-(CH2)(n)Si(OR)(3)) and diethylphosphonatoalkyltriethoxysilane ((EtO)(2)(O) P-(CH2)(n)Si(OEt)(3)) in acidic media without any structure-directing agent. The hydrolysis of-CN and-P(O)(OEt)(2) groups into-COOH and-P(O)(OH) 2 involves the in situ formation of dimers by strong hydrogen bonds, which is the crucial step to obtain a solid. The involvement of hydrophobic interactions between alkylene chains was also evidenced. All materials were characterised by X-ray diffraction measurements, elemental analyses and solid-state C-13 and Si-29 NMR spectroscopies. The accessibility and adsorption capacity of these groups towards lanthanide ions were investigated.