日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Structural analysis, porous properties, synthesis, formation mechanism and catalytic acitivity of nobel type of octahedral molecular sieve, crystalline orthorhombic and trigonal Mo and V mixed metal oxide, were reported. These orthorhombic and trigonal Mo₃VO_x have a layered structure with a slab comprising 6- and 7-membered rings of {MO₆} octahedral and pentagonal {(M)M₅O₂₁} units with a {MO₇} pentagonal bipyramidal unit and five edge-sharing {MO₆} octahedra. The layered 7-membered rings produce channel structure with a diameter of ca. 0.4 nm, and this channel could be empty by the thermal treatment. Small molecules as CO₂, methane, N₂, Kr and ethane can enter into this pore, although bigger molecules like butane and hexane can not enter. Because these metal oxides are based on Mo and V which could easily be oxidized and reduced, the pore property could be reversibly and continuously tuned by the redox treatments. Both compounds are produced by a hydrothermal reaction of solution containing Mo and V. By analyzing the reaction solution, we propose building block synthesis mechanism. The pentagonal {(M)M₅O₂₁} unit of Mo is produced in the solution and this building block reacts with other Mo and V to form the orthorhombic and trigonal Mo₃VO_x. Furthermore, both orthorhombic and trigonal Mo₃VO_x catalyze several selective oxidation reaction such as acrolein to acrylic acid and alcohols to carbonyl derivatives.