Hollow tubular In2O3 modified carbon nitride for photocatalytic high-yield cleavage of lignin C–C bonds under 395 nm light

The selective cleavage of C α –C β bonds is of great significance to lignin valorization, and photocatalysis offers an eco-friendly pathway to achieve this process. Here, graphitic carbon nitride (g-C 3 N 4 ) modified with hollow tubular In 2 O 3 was constructed via the calcination method for the photocatalytic cleavage of lignin C α –C β bonds. MIL-68(In) was used as the precursor of In 2 O 3 , imparting a unique hollow tubular structure and a relatively large specific surface area. The hollow tubular structure is helpful for light penetration and scattering, as well as rapid migration of the lignin substrate. The Z-scheme g-C 3 N 4 /In 2 O 3 heterojunction exhibited 92.1% conversion (corresponding benzaldehyde yield: 82.4%) of the lignin model compound 2-phenoxy-1-phenylethanol (PP-ol), outperforming pure In 2 O 3 and g-C 3 N 4 by 40- and 2.3-fold, respectively, under 395 nm light illumination. By varying the illumination wavelength, the conversion and yields of the g-C 3 N 4 /In 2 O 3 composites were found to follow wavelength-dependent reactivities. Additionally, photogenerated holes are capable of converting PP-ol into benzoic acid, whereas 1 O 2 mainly converts PP-ol into benzaldehyde. This work could encourage the application of metal-organic frameworks in biomass conversion and provide insight into photocatalytic lignin valorization.