Mesoporous Zirconium Phenylenesiliconate-phosphonate Hybrids with Ordered Lamellar Nanostructures

Novel ordered lamellar mesostructure pZrPS-2 was hydrothermally prepared by using zirconium propoxide and 4-(EtO)2OPC6H4Si(OEt)3 (pPPS-E), which was hydrolyzed to organic building units substituted with both siliconate and phosphonate groups, in the presence of CnTAB and TMAOH. The pZrPS-2 materials were obtained at a Zr/PPS ratio of 2 or higher and the basal spacing was increased by using a longer-chain surfactant (n=12–18). Removal of the occluded surfactants at 300 °C resulted in retention of the lamellar structure with negligible shrinkage of the interlayer distance. Nitrogen adsorption studies revealed the ordered mesoporous nature of pZrPS-2 with a pore diameter of approximately 2 to 3 nm. The lamellar structure is assumed to be composed of layers that include zirconia-based crystalline nanodomains and interlayer pillars mainly based on PPS units. Although lamellar structures with the same crystalline phase also formed when no surfactant was added or when the meta isomer of PPS was used, no mesoporous materials were obtained except pZrPS-2. A possible schematic model to elucidate these results is also proposed.