Lignin oxidative depolymerization on graphitic carbon nitride -- explore the cleavage of β-5 linkage

As Net Carbon Zero and the development of the circular economy become critical global environmental issues, developing alternative green energy and chemical resources for fossil fuels are an area of significant research activity. Lignocellulosic biomass as the most abundant biomass throughout the world has aroused much attention as green energy and value added products source. As one of lignocellulosic biomass components, lignin which is comprised of different aromatic monomers is potential feedstock for value added chemicals production. However, the method and mechanism of the cleavage of linkages between monomers to obtain high-value monomers still remains to be further studied. Therefore this study focus on β-5 lignin model compound. In this study it was found that higher yield of aromatic products were obtained from β-5 lignin model compound photocatalytic conversion on carbon nitride comparing to P25’s. The final products of β-5 model compound were found by GC-MS. According to GC-MS analysis, the cleavage occurs at the carbon-carbon bond between the benzene ring and the α-carbon, producing two aromatic monomers. The above results reveal for the first time the products and possible mechanism of photocatalytic transformation of β-5 model compounds under carbon nitride.