Tunable one-pot syntheses of hexagonal-, cubic-, and lamellar-mesostructured vanadium-phosphorus oxides

Hexagonal-, cubic-, and lamellar-mesostructured vanadium-phosphorus oxides were hydrothermally synthesized by using V metal as a reducing agent and a V source. The respective phases were tunably synthesized in the ranges of pH 2.63-2.95, 3.00-3.36, and 3.45-4.45. It is suggested that the formation of these mesostructured materials depends on the solution species of vanadium and phosphorus. The unit cell constants of hexagonal, cubic, and lamellar phases were determined to be a = 5.05 nm, a = 8.54 nm, and c = 3.22 nm, respectively. IR spectroscopy, XRD, and elemental analyses show that hexagonal- and cubic-mesostructured materials possess an amorphous wall of vanadium-phosphorus oxides and their PN ratios were 0.99 and 0.76, respectively. On the other hand, the lamellar mesostructured material possessed more crystalline layers of vanadium-phosphorus oxide with a PN ratio of 0.50. The cetyltrimethylammonium templates could be exchanged with K+ or Cs+.