MnOx Nanoparticles Supported on a New Mesostructured Silicate with Textural Porosity

Abstract

A two-step synthesis of a novel mesostructured silicate, KIL-2, and its manganese-containing analogue, Mn/KIL-2, has been developed. KIL-2 possesses interparticle mesopores with pore dimensions between 5 and 60 nm and a surface area of 448 m(2). The mesopores are formed by the aggregation of silica nanoparticles, which creates a network with interparticle voids. The particle size and the pore diameters depend on the temperature of the ageing step (first step) and on the solvothermal treatment in ethanol (second step), respectively. Mn/KIL-2 contains octahedrally coordinated Mn(3+) (80%) and tetrahedrally coordinated Mn(2+) (20%) ions. Mn(3+) ions are present in the extra-framework MnO(x) nanoparticles with typical dimensions of 2 nm, which are homogeneously distributed throughout the material. Mn(2+) ions occur as isolated manganese framework sites. The material is also able to retain its structure characteristics after the hydrothermal treatment in boiling water. Because of its non-toxic nature and cost-effective synthesis, Mn/KIL-2 thus exhibits properties that are needed for an environment-friendly catalyst.