A new mesoporous Mn and Ta mixed oxides (Mn-Ta oxide) with 2D-hexagonal ordering were successfully synthesized by soft template method, and their characterization was performed using small-angle powder X-ray diffraction (XRD) measurement, N2 adsorption-desorption isotherm measurement and transmission electron microscopy (TEM) observation.
Tantalum chloride and manganese chloride were dissolved in ethanol containing poly (alkylene oxide) block copolymer HO(CH2CH2O)20(CH2CH(CH3)O)70(CH2CH2O)20H (Pluronic P-123). After vigorous stirring, the resulting sol solution was aged so that template could be formed by self-assembling the poly block copolymer during drying. Then the dry solid obtained was calcined in air to remove the organic template, obtaining the Mn-Ta oxide. The N2 adsorption-desorption isotherm of the product was typical type-IV pattern characteristic of many mesoporous materials. The estimated BET surface area was 106 m2g-1, and the pore size distribution was centered around ca. 4.8 nm. Small-angle powder XRD pattern measured using Cu Kα radiation showed a sharp diffraction peak corresponding to d spacing 7.5 nm together with low-intensity peaks assigned to mesoporous materials. The wall thickness was estimated to be 3.9 nm from the d spacing and the pore size. The mesoporous structure of the prepared Mn-Ta oxide was observed directly by TEM measurement. The 2D-hexagonal arrangement of mesopores could be clearly seen.
Since there are few previous reports concerning the ordered 2D-hexagonal mesoporous oxide composed with two different transition metals, the application of the Mn-Ta oxide would be expected.