Depolymerization of Lignin by Homogeneous Photocatalysis

AbstractLignin, a major component of lignocellulose, constitutes the largest source for the production of aromatic building blocks, and offers considerable potential to serve as an entry to biobased products. During the past decades, substantial research activity has been noted in the pursuit of sustainable catalytic methods for accessing lignin-derived platform chemicals. However, the highly cross-linked and irregular structure has hindered the development of efficient and predictable deconstruction strategies from this renewable source. A majority of the developed methods for lignin depolymerization require harsh conditions including high-pressure atmospheres of gases, high temperatures, and prolonged reaction times. Considering the recent renewed interest in photocatalysis as a means for the mild and operationally simple generation of open-shell intermediates, it is not remarkable that such reaction manifolds have also been implemented towards lignin depolymerization. The tremendous potential of visible light photocatalysis for harnessing sustainable energy sources and reducing waste streams will certainly have an enduring impact in future green chemistry innovation.KeywordsAerobic oxidationC−C bond cleavageC−O bond cleavageLigninPhotoredox catalysisSustainable chemistry