Mix and match: The pentagonal [Mo(6)O(21)](n-) polyoxomolybdate building block assembles with other sources of Mo, V, and Sb ions to form an orthorhombic Mo-V-Sb oxide. The first single-crystal X-ray analysis of an orthorhombic Mo-V-based oxide, a promising catalyst for light alkane selective oxidation known as the "M1 phase", revealed the structure of the compound.

Crystalline microporous oxides such as zeolites are indispensable materials in various applications ranging from industrial processes to everyday life, such as catalysts, ion-exchange materials, and molecular sieves.[1] Most of them contain tetrahedrally coordinated metal atoms, but octahedrally coordinated metal centers have recently attracted much attention as building blocks of crystalline microporous metal oxides.[2] Manganese oxides (pyrolusite, hollandite, todorokite, and romanechite) with micropores are the only crystalline porous materials based solely on octahedra (octahedral molecular sieves). These manganese oxides contain microtunnel pores consisting of {MnO 6 } octahedra that share edges and corners.[3]Here we describe a novel type of octahedral molecular sieve, namely, crystalline orthorhombic Mo 3 VO x (x = 11.2), in which the microchannel is constructed by seven-membered rings of corner-sharing MO 6 (M = Mo or V) octahedra. It is isostructural to orthorhombic MoVNbTeO compounds, [4] which are very active and selective oxidation catalysts for light alkanes.[5] These mixed metal oxides have a layered orthorhombic structure with a slab composed of six-and seven-membered rings of corner-sharing {MO 6 } octahedra and pentagonal {(M)M 5 O 27 } units with a {MO 7 } pentagonal bipyramid and five edge-sharing {MO 6 } octahedra, where M is Mo, V, or Nb. The layered six-and seven-membered rings form channel structures. The Te atom is believed to be located both in the six-and seven-membered rings [4] and block the channel. Recently, we succeeded in preparing an orthorhombic Mo 3 VO x compound that contains only Mo and V, [6] in which the channel is expected not to be blocked (Figure 1). [7] Aperture diameters of the seven-and six-membered rings are estimated to be about 0.33-0.37 nm and about 0.25-0.28 nm, respectively. [8] The orthorhombic Mo 3 VO x mixed-metal oxide was synthesized from a reaction mixture of ammonium heptamolybdate (NH 4 ) 6 Mo 7 O 24 ·4 H 2 O, and vanadyl sulfate VOSO 4 ·n H 2 O (Mo/V 4:1) in H 2 O under hydrothermal conditions.[6] The crude material contained an amorphous phase as a byproduct, which was removed by washing the products with an aqueous solution of oxalic acid. Water and NH 3 in the micropores were removed by calcination under air without collapse of the structure, as confirmed by thermogravimetry (TG), temperature-programmed desorption (TPD), and X-ray diffraction studies. The TG data and TPD revealed a weight loss in the range of 320-460 K corresponding to water evaporation and

A new type of polyoxometalate-based porous material was successfully synthesized. The new material is the first fully inorganic Keggin-type polyoxometalate-based microporous material with intrinsically ordered open micropores and is the third member of the small family of octahedral molecular sieves (OMSs). Twelve MoO6 or VO6 octahedra surround a central VO4 tetrahedron to form ε-Keggin polyoxometalate building blocks (ε-VMo9.4V2.6O40) that are linked by Bi(III) ions to form crystalline Mo-V-Bi oxide with a diamondoid topology. The presence of a tetrahedral shape of the ε-Keggin polyoxometalate building block results in arrangement of microporosity in a tetrahedral fashion which is new in OMSs. Owing to its microporosity, this Mo-V-Bi oxide shows zeolitic-like properties such as ion-exchange and molecule adsorption.

Two new ε-Keggin-type polyoxometalate-based 3D frameworks, Na1.5H11.4[ε-Zn(II)Mo(V)10.9Mo(VI)1.1O40{Zn(II)}2] and (NH4)2.1H7.5[ε-Mn(II)0.2Mo(V)6Mo(VI)6O40{Mn(II)}2], are prepared, and their structures are determined by powder X-ray diffraction, Fourier transform infrared, Raman spectroscopy, and elemental analysis. ε-Keggin-type polyoxomolybdate units, [ε-ZnMo12O40] and [ε-Mn0.2Mo12O40], are linked with Zn(2+) and Mn(2+), respectively, in a tetrahedral fashion to form 3D frameworks. They show zeolite-like ion-exchange properties and redox properties. The ε-Keggin-based 3D framework shows high chemical composition diversity and can incorporate different elements in the framework.

NH3-SCR (selective catalytic reduction) is important process for removal of NOx. However, water vapor included in exhaust gases critically inhibits the reaction in a low temperature range. Here, we report bulk W-substituted vanadium oxide catalysts for NH3-SCR at a low temperature (100–150 °C) and in the presence of water (~20 vol%). The 3.5 mol% W-substituted vanadium oxide shows >99% (dry) and ~93% (wet, 5–20 vol% water) NO conversion at 150 °C (250 ppm NO, 250 ppm NH3, 4% O2, SV = 40000 mL h−1 gcat−1). Lewis acid sites of W-substituted vanadium oxide are converted to Brønsted acid sites under a wet condition while the distribution of Brønsted and Lewis acid sites does not change without tungsten. NH4+ species adsorbed on Brønsted acid sites react with NO accompanied by the reduction of V5+ sites at 150 °C. The high redox ability and reactivity of Brønsted acid sites are observed for bulk W-substituted vanadium oxide at a low temperature in the presence of water, and thus the catalytic cycle is less affected by water vapor.