A triphasic photocatalytic reactor employing a mesoporous carbon nitride photocatalyst and aerobic O2 was assembled to operate under continuous flow conditions. This reactor design allows for facile downstream processing and reusability in multiple flow cycles. The selective aerobic oxidation of alcohols and amines was chosen to demonstrate the applicability and performance advantage of this flow approach compared to that of conventional batch photochemistry. This precious-metal-free photocatalytic flow system operates under benign reaction conditions (visible light, low pressure, and mild temperature) and will stimulate the exploration of other oxidative reactions in a sustainable, scalable, and affordable manner.