From simple molecules to highly functionalised lamellar materials

Abstract

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)_nSi(OR)₃) and diethylphosphonatoalkyltriethoxysilane ((EtO)₂(O)P-(CH₂)_nSi(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 ¹³C and ²⁹Si NMR spectroscopies. The accessibility and adsorption capacity of these groups towards lanthanide ions were investigated.