氧化锰面体分子筛维纳米结构的形状控制合成.doc

Shape-Controlled Synthesis of Manganese Oxide Octahedral Molecular Sieve Three-Dimensional Nanostructures Direct architecture of complex nanostructures is desirable and still remains a challenge in areas of materials science. Due to their size- and shape-dependent electronic and optical properties, much effort has been made to control morphologies of transition metal oxide nanoparticles and to organize them into complicated 3D structures using templates. In particular, manganese oxides have attracted much attention because they have extensive applications in many chemical processes due to their porous structures, acidity, ion-exchange, separation, catalysis, and energy storage in secondary batteries. Using organic templates, such as trimethylamine (TMA), manganese oxides have been successfully organized into macroscopic rings and helices via sol gel processes. However, the methods mentioned above all need further purification, so impurities will be introduced. Subsequent procedures are needed to obtain pure products. Thus, facile and organic template-free methods are highly desired for synthesis of manganese oxide nanoparticles with complex 3D structures. Manganese oxide octahedral molecular sieves (OMS) are a class of microporous transition metallic oxides with various kinds of tunnel structures that can be synthesized via controlling synthetic conditions, such as temperature, concentration, pH, and cations. Manganese oxide molecular sieves are semiconducting mixed-valence catalysts that have distinct advantages over aluminosilicate molecular sieve materials for applications in catalysis due to the mixed-valence character. In particular, cryptomelane-type manganese oxide (OMS-2) nanoparticles can be easily prepared via reflux at lower temperatures. However, synthesis of OMS-2 nanoparticles with uniform shapes and organization of them into ordered 3D nanostructures is still a challenge and requires precise control over synthetic parameters, such as temperatu