The Performance of a Biomimetic Oxidation Catalyst Immobilised on Gold and Silica Substrates

• Thiol-functionalized cobalt porphyrins were used as a model system for investigating catalytic activity in homo-geneous and heterogeneous oxidation catalysis. Self-assembled monolayers of thiol-functionalized cobalt porphyrins were prepared on a gold surface and served as heterogeneous catalysts. The immobilization of the molecules prevented the strong inactivation observed for their homogeneous congener. As a result, the turnover number permolecule in heterogeneous catalysis was at least 100 times higher than that of the corresponding homogeneouscatalyst. It is atypical for a heterogenized catalyst to outperform its homogeneous congener. The properties of themolecular layers were characterized on the molecular level by means of X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy (SPM). The results demonstrate that the performance of these biomimetic catalysts can be dramatically improved if the catalyst arrangement can be controlled on the molecular level. In order to further investigate the influence of the substrate on the catalytic performance, monolayers of the cobalt porphyrins were grafted onto silica surfaces. The observed catalytic activity together with the surface analytical results are interpreted in relation to the supporting substrate. Preliminary results from this investigation (silicon wafer) show that the catalytic activity is similar to that of gold substrates.

Ämnesord

NATURVETENSKAP  -- Kemi -- Organisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Organic Chemistry (hsv//eng)

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