Theoretical Studies of Molecular Reactions at the Air–Water Interface: Recent Progress and Perspective

Water microdroplets have been shown to possess unique properties. For instance, compared to bulk water, microdroplets can accelerate chemical reactions by several orders of magnitude and trigger reactions that cannot occur in bulk water. These phenomena have generated significant interest in various fields like atmospheric science, green synthesis, and materials preparation. These unique properties and phenomena are associated with reactions at the air–water interface; however, the underlying mechanisms remain unclear. Studying the microscopic details of phenomena at the air–water interface remains a substantial experimental challenge. Meanwhile, molecular dynamics (MD) simulations and related computational methods provide powerful tools for studying chemical reactions at the air–water interface. This review aims to summarize processes and reactions at the air–water interface from the perspective of theoretical simulations. First, we discuss the physical and chemical properties of the air–water interface. Subsequently, we systematically introduce simulation methods and strategies for four categories of interfacial reactions: (a) simulations of near-barrierless chemical reactions, (b) simulations of chemical reactions with some energy barriers, (c) simulations of chemical reactions employing high-level quantum chemical methods, and (d) simulations of photochemical reactions. Finally, we focus on simulating thermal chemical and photochemical reactions at the air–water interface, with particular emphasis on atmospheric chemistry. The thermal chemical reactions discussed involve Criegee intermediates, nitrogen-containing compounds, and chlorine-containing compounds, while the photochemical reactions discussed include H₂O₂ and phenol. The results discussed here enable an improved understanding of the simulation methods and strategies for chemical reactions at the air–water interface, as well as atmospheric processes.