“…Cellulose and hemicellulose are polysaccharides that are readily converted into fuels and chemicals, such as hydroxymethylfurfural or sugar alcohols such as xylitol, through straightforward acid catalysis (5,10), while lignin is a complex aromatic polymer network whose valorization is challenging because of its inherent recalcitrance (1,5). Presently, lignin is separated from biomass at a rate of approximately 70 to 100 million metric tons/year through pulping or biorefining processes (11,12), but most isolated lignins have a dark color, strong odor, broad molecular weight distribution, and limited reactivity (5,(13)(14)(15), which restricts them to low-value applications (e.g., fillers for tires, asphalt, or concrete) (16,17). Furthermore, there is substantial variability in the composition, chemical structure, cost, and environmental impact of technical lignins due to differences among feedstocks and pulping/refining techniques (13,(18)(19)(20).…”