Synthesis, characterization and catalytic application of SBA-15 immobilized rare earth metal sandwiched polyoxometalates

Rare earth metal sandwiched Keggin-type heteropolyoxometalates, K₁₁RE(PW₁₁O₃₉)₂] (RE–PW₁₁, RE = La, Ce, Pr, Nd, Sm, Eu, Dy and Y), were anchored onto aminosilylated mesoporous silica SBA-15 and the resulting RE–PW₁₁/APTS/SBA-15 materials were characterized by ICP, FT-IR, XRD, N₂ adsorption, ³¹P MAS NMR and TEM. The RE–PW₁₁ clusters preserve their structure in the surface-modified mesopores. The catalytic activity of RE–PW₁₁ clusters was tested on heterogeneous oxidation of cyclohexene by H₂O₂. The interaction between RE–PW₁₁ and amino groups grafted on the channel surface of SBA-15 leads to strong immobilization of RE–PW₁₁ due to the introduction of the rare earth metal centre, which is against the leaching during the reaction.