Continuous flow catalysis with a biomimetic copper(II) complex covalently immobilized on graphite felt

The catecholase activity of a copper(II) complex coordinated by a tripodal pyrazole-based ligand was investigated in continuous flow catalysis. The covalent immobilization of the complex on the surface was achieved by a two steps method. First, the porous graphite felt support is functionalized by electrochemical reduction of 4-carboxymethyl-benzenediazonium salts. Second, the complex is covalently immobilized by esterification reaction between the COOH-containing linker and a primary alcohol group present on the C6 chain of the ligand. The two steps of the immobilization process were optimized by using nitro-containing molecules and cyclic voltammetry analyses. The copper complex exhibits higher catecholase activity in continuous flow catalysis than in solution with a 50 times lower amount of catalyst, underlining the advantages of the flow procedure. The presence of H2O2 is detected after catalysis, showing that the four-electron reduction of dioxygen to water does not occur unlike the natural enzyme.