An oscillatory plug flow photoreactor facilitates semi-heterogeneous dual nickel/carbon nitride photocatalytic C–N couplings

Carbon nitride materials are effective photocatalysts, especially when combined with nickel in dual catalytic cross-coupling reactions. Scaling these processes to continuous operation is challenging due to issues with solid handling in flow reactors. Using an oscillatory pump and microstructured plug flow photoreactor, a stable suspension of the photocatalyst was achieved, preventing reactor channel clogging. Optimization of the oscillator properties ensured short residence times (20 min) and demonstrated recyclability over 10 cycles without activity loss. A scale-out demonstration yielded a model substrate on a 12 g scale (90% yield, 2.67 g h−1). The method was also successfully applied to gram-scale synthesis of an intermediate for tetracaine, an active pharmaceutical ingredient.