Porphyrins and phthalocyanines as biomimetic tools for photocatalytic H2 production and CO2 reduction

The increasing energy demand and environmental issues caused by the over-exploitation of fossil fuels render the need for renewable, clean, and environmentally benign energy sources unquestionably urgent. The zero-emission energy carrier, H-2 is an ideal alternative to carbon-based fuels especially when it is generated photocatalytically from water. Additionally, the photocatalytic conversion of CO2 into chemical fuels can reduce the CO2 emissions and have a positive environmental and economic impact. Inspired by natural photosynthesis, plenty of artificial photocatalytic schemes based on porphyrinoids have been investigated. This review covers the recent advances in photocatalytic H-2 production and CO2 reduction systems containing porphyrin or phthalocyanine derivatives. The unique properties of porphyrinoids enable their utilization both as chromophores and as catalysts. The homogeneous photocatalytic systems are initially described, presenting the various approaches for the improvement of photosensitizing activity and the enhancement of catalytic performance at the molecular level. On the other hand, for the development of the heterogeneous systems, numerous methods were employed such as self-assembled supramolecular porphyrinoid nanostructures, construction of organic frameworks, combination with 2D materials and adsorption onto semiconductors. The dye sensitization on semiconductors opened the way for molecular-based dye-sensitized photoelectrochemical cells (DSPECs) devices based on porphyrins and phthalocyanines. The research in photocatalytic systems as discussed herein remains challenging since there are still many limitations making them unfeasible to be used at a large scale application before finding a large-scale application.

Automated summary

The increasing energy demand and environmental issues call for renewable and environmentally friendly energy sources. Photocatalytic production of H-2 from water and conversion of CO2 into chemical fuels have been extensively studied. This review focuses on the recent advances in photocatalytic systems containing porphyrin or phthalocyanine derivatives for H-2 production and CO2 reduction. Various approaches for improving photosensitizing activity and catalytic performance are discussed, as well as the development of heterogeneous systems using nanostructures, organic frameworks, and semiconductor sensitization. The research in photocatalytic systems remains challenging due to limitations for large-scale application.