Singlet oxygen in environmental catalysis: Mechanisms, applications and future directions

Singlet oxygen (1O2) is an energetically excited form of oxygen characterized by its high energy and strong electrophilic nature. It is naturally occurring and plays an increasingly important role in diverse fields, including chemical synthesis, medical applications and environmental restoration. However, uncertainties in detection techniques, production pathways and response mechanisms pose significant challenges, hindering the full understanding and effective application of 1O2. This review highlights the importance of 1O2 as a reactive oxygen species (ROS) in both biological and environmental contexts. It begins with an overview of techniques for detecting singlet oxygen, followed by a detailed examination of various systems capable of generating 1O2, including peroxymonosulfate activation, Fenton-like reactions, photocatalysis and electrocatalysis. The review then explores potential applications of singlet oxygen, including selective organic synthesis, bacterial inactivation and selective oxidation processes. Finally, it discusses the current challenges and future opportunities in 1O2 generation and applications. The purpose of this review is to enhance the understanding of advanced oxidation processes involving singlet oxygen and their practical applications.