Unit Synthesis Approach for Creating High Dimensionally Structured Complex Metal Oxides as Catalysts for Selective Oxidations

摘要

Solid-state catalysts for selective oxidations have been prepared by simple traditional protocols including impregnation, precipitation, solid-state reaction, and so on. Although these catalyst preparation protocols are convenient to form new or improved catalysts, a huge number of practical experiments have been inevitably necessary. This situation will be even more difficult because solid-state catalysts become increasingly complex in order to introduce multifunction. It is time that catalyst researchers should devote their efforts to establish new synthetic methodology to improve the situation and ultimately create new catalysts. Here, we propose a new catalyst synthesis approach, that is, unit synthesis, to produce high dimensionally structured crystalline complex metal oxide catalysts. By applying this synthesis methodology, we have been able to synthesize several new crystalline complex metal oxides active for catalytic selective oxidations. In this Perspective, crystalline Mo_(3)VO_(x ) oxides and crystalline porous material based on ε-Keggin polyoxometalates (POM) are introduced as successful examples of the unit synthesis. We found that the former shows extremely high catalytic activity for ethane oxidation to ethane and acrolein oxidation to acrylic acid with molecular oxygen and the latter for methacrolein oxidation to methacrylic acid.