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A comparative study of the catalytic oxidative dehydrogenation of propane by a novel polyoxovanadate based open-framework material (Co-POV)-[Co 3 V 18 O 42 (H 2 O) 12 (XO 4 )]Á24H 2 O (X = V, S), which is composed of nanometer size vanadium oxide clusters interlinked by cobalt oxide {-O-Co-O-} motifs, showed that Co-POV has superior catalytic property as compared to its individual metal oxide constituents, vanadium oxide and cobalt oxide, and their mixture, with high propylene selectivity.

Catalytic properties of a series of new class of catalysts materials-[Co 3 (H 2 O) 12 V 18 O 42 (XO 4 )].24H 2 O (VNM-Co), [Fe 3 (H 2 O) 12 V 18 O 42 (XO 4 )].24H 2 O (VNM-Fe) (X = V, S) and [H 6 Mn 3 (H 2 O) 12 V 18 O 42 (VO 4 )].30H 2 O for the oxidative dehydrogenation of propane is studied. The open-framework nanostructures in these novel materials consist of three-dimensional arrays of {V 18 O 42 (XO 4The effect of change in the heterometallic center M (M = Mn, Co, Fe) of the linkers on the catalyst performance was studied. The catalyst material with Co in the linker showed the best performance in terms of propane conversion and selectivity at 350°C. The material containing Fe was most active but least selective and Mn containing catalyst was least active. The catalysts were characterized by Temperature Programmed Reduction (TPR), BET surface area measurement, Diffuse Reflectance Infrared Fourier Transform Spectroscopy, and X-ray Absorption Spectroscopy. TPR results show that all three catalysts are easily reducible and therefore are active at relatively low temperature. In situ X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure spectroscopy (EXAFS) studies revealed that the oxidation state of Co(II) remained unchanged up to 425°C (even after pretreatment). The reduction of Co(II) into metallic form starts at 425°C and this process is completed at 600°C.

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A mixed-valence vanadate, MgVV 2VIV 2O10·4H2O (1), has been synthesized hydrothermally and characterized by single-crystal X-ray diffraction, spectroscopic and thermogravimetric analyses, and temperature dependent magnetic measurements. The compound shows magnetic properties with domination of intrasheet exchange interactions versus intersheet interactions due to large distance between vanadate sheets. It represents a synthetic analogue of the mineral melanovanadite: Ca2VV 4VIV 4O20·10H2O. The framework structure in 1 consists of vanadium oxide layers cross-linked by {Mg (H2O)4} groups. The vanadium oxide layers are composed of edge shared {VIVO5} square pyramids, forming {V2O8} dimers, which share corners with {VVO4} tetrahedral units. Crystal data for 1: triclinic space group P1̅ with a = 6.3232(14) Å, b = 6.3917(14) Å, c = 7.9388(17) Å, α = 88.264(19)°, β = 67.428(16)°, γ = 79.433(20)°, V = 290.97(12) Å3, Z = 1.