Hydrothermal synthesis and characterisation of two novel large-pore framework vanadium silicates

Two new large-pore sodium vanadium silicates, denoted AM-15 and AM-17 (Aveiro-Manchester, structures number 15 and 17) with framework composition Na6Si14V4O39 and Na4CaSi10V2O27, respectively, are reported. Electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR) and diffuse reflectance ultraviolet-visible (DR UV/Vis) spectroscopy reveal that as-prepared AM-15 contains both V-IV and V-V in a square pyramidal and tetrahedral coordination, respectively, while AM-17 contains predominantly octahedral V-IV The thermal stability of AM-15 in air is modest (ca. 380 degreesC), while AM-17 is stable up to 450 degreesC. The acid-base and redox properties of AM-17 have been assessed by the conversion of isopropanol and ethanol oxidation, respectively. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).