RESUMO
Transforming lignin into aromatic monomers is critically attractive to develop green and sustainable energy supplies. However, the usage of the additional catalysts like metal or base/acid is commonly limited by the caused repolymerized and environmental issues. The key step is to mediate electron transfer in lignin to trigger lignin C-C/C-O bonds cleavage without the catalysts mentioned above. Here, we report that the ionic liquids [BMim][ClO4] was found to trigger lignin electron transfer to cleave the C-C/C-O bonds for aromatic monomers without any additional catalyst. The proton transfer from [BMim]+ to [ClO4]- could polarize the anion and decrease its structure stability, upon which the active hydroxyl radical generated and induced lignin C-C/C-O bonds fragmentation via free radical-mediated routes with the assistance of photothermal synergism. About 4.4 wt% yields of aromatic monomers, mainly composed of vanillin and acetosyringone, are afforded in [BMim][ClO4] under UV-light irradiation in the air at 80 °C. This work opens the way to produce value-added aromatic monomers from lignin using an eco-friendly, energy-efficient, and simple route that may contribute to the sustainable utilization of renewable natural resources.
