Efficient and Selective C–C Bond Cleavage of a Lignin Model Using a Polyimide Photocatalyst with High Photooxidation Capability

Lignin represents the most abundant and sustainable aromatic resource to produce value-added aromatics. However, an efficient and selective cleavage of recalcitrant C–C bonds in lignin under mild conditions remains challenging. Photocatalysis has emerged as a promising strategy for such a C–C bond cleavage under ambient conditions, although the activity and selectivity need to be further improved. Herein, using polyimide as a photocatalyst, we report an efficient and selective C–C bond cleavage in a β-O-4 lignin model under visible light at room temperature. The lignin model was converted into aromatic products with >99% substrate conversion and >99% C–C bond cleavage selectivity, which are superior to previously reported photocatalytic systems. Experimental investigations together with theoretical calculations indicated that the superior performance of the polyimide photocatalyst was attributed to its strong photooxidation capability and efficient charge carrier separation efficiency. Mechanistic studies revealed that the dehydrogenation of the lignin model driven by photogenerated holes was the rate-determining step. This work provides useful guidance for the design of high-performance photocatalysts for selective C–C bond cleavage of lignin.