Multinuclear systems for photo-induced production of green fuels: an overview of homogeneous catalysts based on transition metals

In the last century, humankind has based its energy demand on the extensive exploitation of fossil resources with the massive emission of CO2, resulting in problems such as pollution, the greenhouse effect, and, consequently, climate change. However, these resources are limited, and each year, their depletion is getting closer. Therefore, in the last few decades, scientific efforts have been focused on finding alternative ways to use and store green energy sources. The purpose of the present review is to present an overview of the most efficient multinuclear catalytic systems in the field of artificial photosynthesis based on reductive and oxidative mechanisms. In particular, it emphasizes the most recent improvements in homogeneous photocatalysis based on multimetallic complexes, illustrating the advantages of systems consisting of a linked catalyst(s) and photosensitizer(s) that can be employed to achieve high-energy demanding processes, such as the reduction of CO2 and water oxidation. Schematic representation of light-induced processes in artificial photosinthetic systems composed by multinuclear metal complexes.