Selective photocatalytic synthesis of benzaldehyde in microcapillaries with immobilized carbon nitride

Photocatalysis on microfluidic reactors can be an environmental-friendly strategy to conventional chemical synthesis methods to find selective and efficient processes to produce high value-added molecules. In this work, we report for the first time a fluoropolymer microcapillary system with an immobilized metal-free thermal modified carbon nitride (GCN-T) catalyst. This strategy enabled a user-friendly, plug-and-plug selective chemistry using an external UV light (λ = 392 nm) and aqueous solutions. To intensify the Benzaldehyde (BAL) production, we explored the microfluidic photocatalytic conversion of Benzyl alcohol (BA). We obtained 0.20 mM of BAL using immobilized GCN-T after 2.4 min of residence time. The results were benchmarked against the same reactor using suspended catalysts and against a conventional batch reactor. Immobilized GCN performed similarly to suspended GCN in the microfluidic reactor (0.18 mM of BAL). We increase BAL yield by 9-fold after 2.4 min using suspended GCN in a microfluidic reactor comparing to a batch reactor. The stability of immobilized photocatalyst was confirmed in reuse studies where 0.20 and 0.17 mM of BAL were produced after one and four utilization runs, respectively. We anticipate this can be related to the presence of a high concentration of particles closer to the microreactor's inner wall, allowing the effective activation of GCN particles with UV irradiation. The immobilization of the catalyst avoided its blockage in the microfluidic channels and enabled the reuse without any further separation. To the best of our knowledge, this is the first report using the microcapillary film reactor and immobilized carbon nitride for the selective photocatalytic synthesis of BAL.