Introducing hydroxyl groups as cellulose-binding sites into polymeric solid acids to improve their catalytic performance in hydrolyzing cellulose

Porous polymeric solid acids bearing hydroxyl and sulfonic acid groups, synthesized from aromatic monomers via the Friedel-Crafts “knitting” polymerization, could efficiently hydrolyze cellulose. • Bifunctional porous polymeric solid acids were synthesized for hydrolyzing cellulose. • Friedel-Crafts polymerization followed by sulfonation was used to synthesize the solid acids. • Hydroxyl groups as cellulose-binding sites enhanced catalytic performance of the solid acid. • Porous structure (large surface area) is crucial to the catalytic activity of the solid acids. Effective hydrolysis of cellulose to glucose is a crucial step to produce fuels and chemicals from lignocellulosic biomass. Solid acids are promising alternatives of cellulases and homogenous acids for hydrolyzing cellulose. In this study, porous polymeric solid acids bearing hydroxyl and sulfonic acid groups were fabricated for cellulose hydrolysis in water through the low-cost Friedel-Crafts “knitting” polymerization of hydroxyl-containing aromatic monomers followed by sulfonation. The synthesized bifunctional solid acids could effectively hydrolyze microcrystalline cellulose (Avicel) to glucose by as high as 93 % at 120 °C within 48 h and ball-milled Avicel by 98 % at 120 °C in 24 h. The evidence from this study indicated that the outstanding catalytic performance of the solid acids was attributed to the porous structure (large surface area) and the presence of the hydroxyl (cellulose-binding group) in the solid acids.