Kinetic study of photoreactions in an automatic single-liquid-slug oscillatory flow platform

Herein, an automatic single-liquid-slug oscillatory flow platform was established for the kinetic investigation of photochemical reactions. Reaction parameters including concentration, reaction time, light intensity, pressure, and temperature were controlled precisely in an automatic manner, and the reaction outcomes were obtained accurately via, integration of an online HPLC. With the reaction kinetics measurement performed for the photocatalytic oxidation of citronellol by Ru(bpy)₃Cl₂ at a volume scale of 50 μL, it was demonstrated that the single-liquid-slug oscillatory flow method was capable of achieving material and time savings of 70 % and 38 % respectively as compared to the conventional batch method, and of 80 % and 62 % respectively as compared to the continuous flow method. The four reaction orders manifesting the effects of the substrate concentration, photocatalyst concentration, light intensity, and oxygen pressure, respectively, were attained as well as the photoreaction rate constant. Furthermore, the kinetic data obtained under a series of temperatures also shed light on the photoreaction mechanism which exhibited a relationship between the photoreaction rate constant and temperature that deviated from the Arrhenius law. The approach developed in this work is especially useful for the kinetic studies of photoreactions with relatively slower intrinsic reaction kinetics, achieving a more resource-efficient practice with higher repeatability and accuracy.