Tubular aluminophosphate mesoporous materials containing framework silicon, vanadium and manganese

Aluminophosphate-based tubular mesoporous materials containing framework silicon, vanadium and manganese have been successfully synthesized. X-ray diffraction and transmission electron microscopy reveal that these solid products possess disordered arrays of tubular mesoporous channels which mimic the hexagonal MCM-41 structure. N₂ adsorption further suggests that these materials are relatively thermally stable, have an average free mesopore diameter of 35 Å and have high BET specific surface areas up to 700 m²/g. Electron probe microanalysis reveals that the overall P/Al ratio of these materials is less than unity and ²⁷Al and ³¹P MAS NMR shows that both tetrahedral and octahedral aluminum occur as well as tetrahedral phosphorous and hydroxylated phosphorus species, indicating a nonideal aluminophosphate framework. Incorporation of silicon results in a less disordered mesoporous structure and substantial increases in the relative amounts of tetrahedral aluminum and tetrahedral phosphorus. Transition metal ions can be incorporated up to V/Al = 0.10 for vanadium and Mn/Al = 0.20 for manganese. Electron spin resonance and diffuse reflectance ultraviolet-visible spectroscopies reveal that both vanadium and manganese are present as isolated species and suggest framework locations for these ions.