Tailorable Synthesis of Heterogeneous Enzyme-Copper Nanobiohybrids and application in selective oxidation of benzene to phenol
A protein-direct synthetic route to make nanobiohybrids containing copper nanoparticles (CuNPs) using an enzyme in combination with a copper sulfate in aqueous media at room temperature has been described. Enzyme-Cu(ii) intermediates, rapidly generated in aqueous media, are transformed, induced by the enzyme structure, to facilitate the formation of a particular Cu species, tailoring the size of nanoparticles formation depending on the experimental conditions, e.g. pH, reducing step, amount of enzyme or incubation time. This controlled-synthesis allows the preparation of tailor-made nanobiohybrids of Cu(0)NPs, Cu(0)/Cu2ONPs, Cu2ONPs or Cu3(PO4)2 NPs at multimilligram scale. The catalytic performance of the novel CuNPs nanobiohybrids was evaluated in the selective C-H functionalization of benzene by direct monohydroxilation using hydrogen peroxide as green oxidant at mild conditions, aqueous media and moderate temperature. Optimization in the amount of hydrogen peroxide, the presence of co-solvent, temperature was performed, obtaining the production of 17 mM phenol with 83% selectivity using Cu-CALB-PHOS-NR nanobiohybrid as catalyst.