Efficient synthesis of imines using carbon nitride as photocatalyst

Abstract

Heterogeneous photocatalytic systems can provide green organic synthesis at cost-effective processes. In the present work, an efficient, environment-friendly and sustainable heterogeneous photocatalyst, the metal-free exfoliated carbon nitride (GCN-T), is used in the oxidative self-coupling of benzylamine (BZA) to produce N-benzylidenebenzylamine (BZI) within the visible light range of irradiation (LEDs with λmax = 417 nm) under mild reaction conditions. The issue of selectivity is successively addressed with complete conversion of BZA achieved upon 45 min of reaction, under irradiation, for 97 % selectivity towards BZI production. Electron paramagnetic resonance (EPR) spectroscopy is used to investigate the main reactive species involved in the photocatalytic reaction. This analysis revealed that superoxide and singlet oxygen radicals played the leading role in the amine conversion in the heterogeneous photocatalytic mechanism. A reaction pathway is proposed to include all identified species generated during the oxidative self-coupling of BZA under visible light irradiation. The results described here add to the portfolio of customisable heterogeneous photocatalytic solutions towards efficient solar synthesis.