Performance of a biomimetic oxidation catalyst immobilized on silica particles

•We immobilized an oxidation catalyst, a cobalt porphyrin, on silica particles.•The activity was investigated and compared to earlier findings on gold and silicon.•We found the activity was the same as on gold and 10 times higher as on silicon.•High background hydroquinone oxidation was observed by magnetic silica particles.•Orientation and organization of supported catalyst are of importance for activity.

A biomimetic oxidation catalyst, cobalt porphyrin with thiol linkers, was chemically conjugated to silica particles and utilized in the oxidation of hydroquinone to benzoquinone. The cobalt porphyrin/silica particle catalyst was characterized with Inductively Coupled Plasma (ICP) and X-ray Photoelectron Spectroscopy (XPS). The catalytic performance of the cobalt porphyrin molecules was compared to previous results for the same catalyst grafted to a gold surface and on silicon wafers. The measured catalytic activity, after background correction, was 100 times higher than that of its homogeneous counterpart, 10 times higher than that on a silicon wafer, and almost the same as that on a gold surface. The turnover frequency rates after 400 h are still comparable with initial rates reported for homogeneous porphyrins and salophens, whereas the use of particles as support increases the active surface area, which removes the limitations for scale-up associated with the previously used silicon wafers and gold surfaces.

Graphical abstractA biomimetic oxidation catalyst, cobalt porphyrin (CoTPP), was chemically grafted on silica particles and further used in oxidation of hydroquinone to benzoquinone. The activity was compared to earlier findings on gold and silicon wafers. It was found that the activity is the same as that on gold wafers, 10 times higher as that on silicon wafers, and it outperformed its homogenous counterpart by a factor of 100.Figure optionsDownload full-size imageDownload high-quality image (84 K)Download as PowerPoint slide