Photocatalyst g-C3N4 for efficient cleavage of lignin C-C bonds in micellar aqueous medium

Depolymerizing lignin to prepare aromatic high-value chemicals is beneficial to solve the problem of energy shortage and waste of resources. However, cleavage of lignin C-C bonds still faces greater challenges due to the recalcitrance of C-C bonds in lignin. Photocatalysis is considered to be a promising way to break lignin C-C bonds under mild conditions. Here, the micellar aqueous medium (SDS) composed of sodium lauryl sulfonate and water was prepared. 1, 2-Diphenylethanol (lignin model compound, Dpol) and dioxanesolv poplar lignin can be well dispersed in SDS-8 (mass fraction of 0.08% for sodium lauryl sulfate). Photocatalyst g-C3N4 can efficiently break the lignin C-C bonds in SDS-8 and very high photocatalytic efficiency can be obtained. A small amount of acetic acid can further improve photocatalytic efficiency. The main products produced by photocatalytic breaking lignin C-C bonds are benzaldehyde and benzoic acid. The mechanism of photocatalytic cleavage of lignin C-C bonds mainly follows a photogenerated electron-hole coupled redox mechanism. Thereinto, the hydrogen provided by SDS-8 has powerfully promoted photocatalytic efficiency. Our work provides a new direction for photocatalytic cleavage of lignin C-C bonds into aromatic high-value chemicals.