Photocatalytic transformations of lignocellulosic biomass into chemicals

As the largest renewable carbon resource, lignocellulosic biomass has great potential to replace fossil resources for the production of high-value chemicals, in particular organic oxygenates. Catalytic transformations of lignocellulosic biomass using solar energy have attracted much recent attention, because of unique reactive species and reaction patterns induced by photo-excited charge carriers or photo-generated reactive species as well as the mild reaction conditions, which may enable the precise cleavage of target chemical bonds or selective functionalisation of specific functional groups with other functional groups kept intact. Here, we present a critical review on recent advances in the photocatalytic transformation of lignocellulosic biomass with an emphasis on photocatalytic cleavage of C-O and C-C bonds in major components of lignocellulosic biomass, including polysaccharides and lignin, and the photocatalytic valorisation of some key platform molecules. The key issues that control the reaction paths and the reaction mechanism will be discussed to offer insights to guide the design of active and selective photocatalytic systems for biomass valorisation under mild conditions. The challenges and future opportunities in photocatalytic transformations of lignocellulosic biomass are also analysed.