Energy is the major challenge facing humanity in the 21st century. The increase in the world's population, the economic growth of the planet's major countries, the programmed disappearance of non-renewable energy sources (oil, coal, gas and even uranium), and the need to limit the production of greenhouse gases, mean that we urgently need to innovate in the field of energy technologies. This innovation will come from an ever-increasing coupling between fundamental and technological research. All the evidence suggests that, although our energy sources will be much more diversified in the future than they are today, the sun is the only one capable of providing the energy needed by mankind in a clean, sustainable way for billions of years.
One of the living world's most fascinating contributions to these issues is photosynthesis, which very efficiently converts solar energy into chemical fuels (sugars) using water as a source of electrons. Water is a very stable molecule and a poor reducing agent. It needs to be activated. Certain living organisms (cyanobacteria, algae, plants) have invented a unique and totally conserved catalyst, based on manganese and calcium, to couple two deprotonated water molecules and oxidize them to molecular oxygen.
The structures of the photosystem and the MnCa site were presented, enabling us to propose mechanisms for water oxidation. The understanding of this chemistry and the development of catalysts with the same chemical properties as the photosystem's MnCa site, for applications in the energy field, have for years led chemists to implement a bio-inspired approach to prepare coordination complexes capable of binding water and oxidizing it to oxygen. The history of this research was presented in full, with successive discussions of biomimetic polynuclear manganese complexes, then mono- and poly-nuclear ruthenium complexes, and finally the latest cobalt oxide-based materials proposed by D. Nocera at MIT (Science 2008 321 1072).
