Metalloporphyrins in bio-inspired photocatalytic conversions

Numerous natural systems contain porphyrin derivatives that facilitate important catalytic processes; thus, developing biomimetic photocatalytic systems based on synthetic metalloporphyrins constitutes a rapidly advancing and fascinating research field. Additionally, porphyrins are widely investigated in a plethora of applications due to their highly versatile structure, presenting advantageous photoredox, photophysical and photochemical properties. Consequently, such metallated tetrapyrrolic macrocycles play a prominent role as photosensitizers and catalysts in developing artificial photosynthetic systems that can store and distribute energy through fuel forming reactions. This review highlights the advances in the field of metalloporphyrin-based biomimetic photocatalysis, particularly targeting water splitting, including both hydrogen and oxygen evolution reactions, carbon dioxide reduction and alcohol oxidation. For each photocatalytic system different approaches are discussed, concerning either structural modifications of the porphyrin derivatives or the phase in which the process takes place, i.e. homogenous or heterogenous. The most important findings for each porphyrin-based photocatalytic reaction are presented and accompanied by the analysis of mechanistic aspects when possible. Finally, the perspectives and limitations are discussed, providing future guidelines for the development of highly efficient metalloporphyrin-based biomimetic systems towards energy and environmental applications.