Hierarchical mesoporous MnO2 superstructures synthesized by soft-interface method and their catalytic performances

To obtain a highly efficient and stable heterogeneous catalyst in catalytic wet hydrogen peroxide oxidation, we have successfully synthesized hierarchical mesoporous manganese dioxide (MnO₂) superstructures by a facile and environmental friendly method on a soft-interface between CH₂Cl ₂ and H₂O without templates. The main crystal phase of as-prepared MnO₂ was proved to be ε-MnO₂ by X-ray diffraction techniques. The structure characterizations indicated that the hierarchical MnO₂ superstructures were composed of urchin-like MnO₂ hollow submicrospheres assembled by one-dimension nanorods building blocks with rich mesoporosity. The nitrogen sorption analysis confirmed that the as-synthesized MnO₂ has an average pore diameter of 5.87 nm, mesoporous volume of 0.451 cm³ g^-1, and specific surface area of 219.3 m² g^-1. Further investigations revealed that a possible formation mechanism of this unique hierarchical superstructure depended upon the synthesis conditions. The catalytic performances of the hierarchical mesoporous MnO₂ superstructures were evaluated in catalytic degradation of methylene blue in the presence of H ₂O₂ at neutral pH, which demonstrated highly efficient catalytic degradation of the organic pollutant methylene blue using hierarchical mesoporous MnO₂ superstructures as catalyst at room temperature. © 2014 American Chemical Society.