Selective photocatalytic aerobic oxidative cleavage of lignin C-O bonds over sodium lignosulfonate modified Fe3O4/TiO2

Lignocellulose shows significantly potential in sustainable conversion to high-quality fuel and valueadded chemicals with the demands for realizing the rapid cycle of carbon resources and helping to reach carbon neutrality in nature. Selective tailoring of a-O-4, 8-O-4, etc. linkages in lignin has always been viewed as "death blow" for its depolymerization. Herein, novel sodium lignosulfonate (SL) modified Fe3O4/TiO2 (SL-Fe3O4/TiO2) spherical particles have been developed and used as catalysts for selectively photocatalytic oxidative cleavage of organosolv lignin. As expected, 80% selective conversion of lignin in C2-C4 esters has been achieved, while C-O bonds in lignin model compounds can be effectively cleaved. Other than normal hydroxyl radical-mediated photocatalytic depolymerization of lignin over TiO2-based materials, in this contribution, mechanism studies indicate that photogenerated holes and superoxide anion radicals are main active species, which trigger the cleavage of a/8-O-4 bond, and the isotope labeling study confirms the crucial factor of C8-H dehydrogenation in cleavage of 8-O-4 bonds. & COPY; 2023 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences Published by Elsevier B.V. All rights reserved.