Advantages in Using Inexpensive CO₂ To Favor Photocatalytic Oxidation of Benzylamines

In this work, we investigate using carbon dioxide (CO₂) as an inexpensive reaction medium during the photocatalytic oxidative coupling of primary amines to the corresponding imines. As a model system, we study the reaction of benzylamines in acetonitrile over a potassium poly­(heptazine imide) photocatalyst (K-PHI). We use CO₂ or argon (Ar) to saturate the reaction solution and the reactor headspace, and blue light (461 nm) to drive the reaction. When compared to the more expensive Ar, CO₂ boosts the conversion rate by creating a reaction intermediate with better electron donor properties. We also validate the influence of water content on the imine formation efficiency, and we observe higher catalytic activity of K-PHI, compared to a standard mesoporous graphitic carbon nitride (mpg-CN).