Materials for selective photo-oxygenation vs. photocatalysis: preparation, properties and applications in environmental and health fields

Abstract

This perspective paper compares the properties and applications in the environmental and health fields of organic photosensitizers (embedded in solid organic or inorganic inert supports) and TiO₂-based photocatalysts. The basic principles of photosensitization and photocatalysis are recalled and the properties of the reactive oxygen species (ROS) produced under irradiation in both cases are reviewed. Various families of organic photosensitizers (PSs) and their immobilization on different supports are then described. The properties of these materials are summarized. A section is dedicated to their applications in fine chemistry, disinfection, photodynamic therapy (PDT), degradation of persistent pollutants in water and solvent-free oxygenation of selected chemicals. After a short reminder of the latest reviews on TiO₂-based photocatalysis, some selected applications of supported TiO₂ materials are reported in the fields of water treatment, active photocatalytic indoor air remediation/disinfection and passive materials designed not only for self-cleaning but also for removal of air pollutants and microorganisms. Both types of materials are quite complementary and their advantages/drawbacks are highlighted. The selectivity and extended lifetime of singlet oxygen (¹O₂) produced under visible light by PS-containing materials make them highly attractive for the selective oxygenation of persistent pollutants in wastewater containing complex matrices or for PDT. On the other hand, TiO₂-based photocatalysts have been devoted to the complete mineralization of pollutants. However, their use in a large field under visible irradiation is still to be developed.