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 CH2Cl2 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 cm(3) g(-1), and specific surface area of 219.3 m(2) 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 H2O2 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.