Synthesis of Highly Ordered Thermally Stable Cubic Mesostructured Zirconium Oxophosphate Templated by Tri-Headgroup Quaternary Ammonium Surfactants

Abstract

Highly ordered cubic mesostructured zirconium oxophosphate with Pm3n symmetry analogous to SBA-1 silica is first obtained by using tri-headgroup quaternary ammonium surfactant CH3(CH2)16CH2N(CH3)2CH2CH2N(CH3)2CH2CH2CH2N(CH3)3Br3 (C18-2-3-1) as a structure-directing agent and zirconium sulfate as an inorganic precursor under hydrothermal condition. X-ray diffraction (XRD), transmission electron microscopy (TEM), and 31P magic angle spinning nuclear magnetic resonance (MAS NMR) have been used to characterize these mesostructured zirconium-based composites. The cubic mesostructured zirconium oxophosphates are thermally stable up to 500 °C. In addition, a phase transition from Pm3n through mixed mesophase to p6m symmetry is observed through finely tuning the spacer methylene chain length among the hydrophilic headgroups in the multi-charged amphiphile (from C18-2-3-1 through C18-3-3-1 to C18-3-4-1). 31P MAS NMR spectra show that phosphorus has four types of chemical environments in the cubic mesostructured zirconium oxophosphate framework and three types of chemical environments in mixed or hexagonal zirconium oxophosphate mesophases.