One-pot oxidation–acetalization strategy for photocatalytic cleavage of C–C bonds in lignin model compounds over phosphorus-doped carbon nitride

Abstract

Photocatalytic depolymerization of lignin into aromatic compounds is of great significance but extremely challenging, hindered by the stable interunit C–C bonds with high dissociation energies. Herein, we developed a phosphorus-doped carbon nitride (P_x-CN) photocatalyst for the selective cleavage of C_α–C_β bonds in lignin model compounds under visible light at room temperature. This approach achieves a nearly complete conversion (>99.9%) of 2-phenoxy-1-phenylethanol, along with high yields of benzaldehyde dimethyl acetal (91.1%) and benzyl formate (56.3%). Mechanistic investigations reveal that the activation of the C_β–H bond is crucial for the transformation to occur. Meanwhile, the introduction of phosphorus accelerates the separation efficiency of charge carriers, thereby enhancing the photocatalytic performance of the P_x-CN. This work demonstrates the potential of phosphorus-doped carbon nitride for the high-selectivity photocatalytic cleavage of the C–C bond in lignin to aromatic chemicals.