Hybrid Rh catalysts prepared with carbon nanotubes of different inner diameter

Hybrid catalysts have been prepared by the immobilization of a Rh diamine complex on four multiwall carbon nanotubes of different inner diameter (average inner diameter ranging from 4 to 10 nm). The complex has been tethered to the support by the reaction of the –Si(OCH3)3 functionality in the rhodium complex with phenol type –OH groups on the support surface, that have been created by oxidation with air. The hybrid catalysts have been tested in the hydrogenation of cyclohexene and carvone. In general terms, the obtained hybrid catalysts are more active than the Rh complex in homogeneous phase and they are recyclable. It has been found that the nanotubes dimensions have an influence in the catalytic properties. In the case of the thinner nanotubes (inner Ø ∼ 4 nm) the support has not a positive effect while the catalysts prepared with nanotubes of inner diameter around 7 nm give the best results.

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► Carbon NT’s of different dimensions are used for the heterogenization of a Rh complex.
► The hybrid catalysts are, in general, more active than the homogeneous Rh complex.
► An effect of the nanotubes diameter in the catalytic properties has been found.
► It seems that there is an optimum inner diameter of the nanotubes support.