Photocatalytic, Oxidative Cleavage of C−C Bond in Lignin Models and Native Lignin

It is challenging to realize the selective C-C bond cleavage of lignin β-O-4 linkages for production of high-value aromatic chemicals due to its intrinsic inertness and complex structure. Here we report a light-driven, chlorine-radical-based protocol to realize the oxidative C-C bond cleavage in various lignin model compounds catalyzed by commercially available TPT and CaCl₂, achieving high conversion and good to high product yields at room temperature. Mechanistic studies reveal that the preferential activation of C_β-H bond facilitates the oxidation and C-C bond cleavage of lignin β-O-4 model via chlorine radical. Furthermore, this method is also applicable to the depolymerization of natural lignin extracts, furnishing the aromatic oxygenates from the cleavage of C_α-C_β bonds. This study provides experimental foundations to the depolymerization and valorization of lignin into high value-added aromatic compounds.