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.