Single-site biomimetic amino acid complexes for the benign oxidation of hydrocarbons and alcohols

Zeolite encapsulated amino acid complexes such as Fe-proline, Fe-histidine and Cu-valine have shown significant promise in the selective oxidation of hydrocarbons such as cyclohexane and benzylic alcohols. This novel encapsulation procedure, which involves building a zeolite (host) around a pre-formed and structurally defined amino acid complex (guest), results in the generation of isolated single-sites for catalytic oxidations. IR and UV–Vis techniques were used for structure determination as well as establishing the integrity of the synthesised complexes. Preliminary results indicate that complexes were formed by coordination to the nitrogen atom of the amino group and the oxygen atom of the carboxylate group to the metal. The hydrophobic/hydrophilic nature of the zeolite, coupled with the high activity of the neat complex, generates highly active and selective single-site heterogeneous catalysts for the production of cyclohexanone, an important precursor to the production of commodity chemicals such as adipic acid and ?-caprolactam