Enzymes are molecules. So it's hardly surprising that biomimetic and bio-inspired chemistry approaches have essentially led to molecular catalysts. Recently, however, the bio-inspired approach is also being used by materials chemists, who are rightly taking the liberty of translating structural and functional information about the active sites of metallo-enzymes into new catalytic bio-inspired materials. In this lecture, the following examples are discussed in detail: (i) mixed oxides of manganese and calcium, inspired by the active site of photosystem II, which possess remarkable catalytic properties for the oxidation of water to oxygen; (ii) molybdenum sulfides which, like the active site of nitrogenases, catalyze the reduction of protons to hydrogen.
The bio-hybrid and artificial metallo-enzyme systems discussed in lectures 1 and 2 combined receptor proteins and molecular complexes. The molecular nature of the latter is not mandatory. Proteins can also be combined with solid materials. This is the case, for example, of the systems that can be prepared with ferritin. This protein, involved in cellular iron storage, has a large cavity in which hundreds and thousands of metal atoms can accumulate. It is therefore possible to precipitate particles of Pt, Pd or cerium oxides in this cavity. These assemblies are then studied for their catalytic properties (hydrogenation, catalase, peroxidase, etc.). Viruses are another class of biological "cages" that have been extensively studied. Gold nanoparticles or iron oxides can be precipitated onto them. These different artificial biological assemblies are discussed.
