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

Rare earth metal sandwiched Keggin-type heteropolyoxometalates, K11[RE(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.

Graphical abstractRare earth metal sandwiched Keggin-type heteropolyoxometalates, K11[RE(PW11O39)2] (RE = La, Ce, Pr, Nd, Sm, Eu, Dy and Y), were immobilized onto aminosilylated mesoporous silica SBA-15. The samples show higher catalytic efficiency than the bulk ones in heterogeneous epoxidation of cyclohexene with H2O2. The leaching of active species is negligible and the recycled catalysts retain high activity. Figure optionsDownload full-size imageDownload as PowerPoint slide