The major drawback of the strictly biomimetic approach is that it prevents the chemist from exploring a wide space of atoms and molecules to achieve the desired objective, since the principle is the strict copying of the active site. Another more interesting approach, known as "bio-inspired chemistry", relies on the fact that precise knowledge of the structure of an enzymatic active site can be exploited to invent catalysts whose operating principles are inspired by those of the active enzyme. This second variant allows the use of chemical elements or combinations of atoms which nature has neither explored for reasons of bioavailability, nor selected because of their toxicity during evolution, but which meet the specifications of the enzyme. Such catalysts offer numerous advantages. They are easy to synthesize and inexpensive to produce on a large scale. Unlike the enzymes on which they are based, they can be used in a wide range of organic solvents, some even in water, and at a wide range of temperatures and pressures. They are also less sensitive to oxidation in air.
Among their drawbacks, bio-inspired catalysts are often less active, less stable and less selective than enzymes. Soluble, they also suffer from a recurring problem in homogeneous catalysis, that of their integration into a technological process. Thus, the discovery of a promising molecular catalyst for industrial application often calls for its grafting onto an insoluble material. This concept was illustrated during this lecture by the development, carried out in our laboratory and published in the journals Science in 2009 and Angew. Chem. in 2011, of a nickel-based catalyst inspired by the active site of Ni and Fe hydrogenases. This complex, grafted onto carbon nanotubes, has remarkable catalytic properties for the reduction of protons to hydrogen and the oxidation of hydrogen, opening up interesting prospects for the development of electrolyzers and fuel cells without noble metals. A film recounting this adventure, directed by M. Chauvin with the collaboration of M. Fontecave and V. Artero, is shown during the lecture.
