Cellulase-Inspired Solid Acids for Cellulose Hydrolysis: Structural Explanations for High Catalytic Activity

This work presents a detailed structure–activity analysis of a polymeric solid acid catalyst used in cellulose hydrolysis. In contrast to previous work, our studies show that the high catalytic activity is likely not due to hydrogen bonding between C–Cl moieties at the polymer surface and cellulose fibers. Instead, we report that such C–Cl bonds hydrolyze readily under polymer functionalization conditions to produce C–OH groups on the exterior of the solid acid beads. Furthermore, continued C–Cl to C–OH substitution under cellulose or cellobiose hydrolysis conditions releases HCl from the resin, which contributes to cellulose hydrolysis. Overall, the presented studies stress the need for detailed, quantitative analysis of polymer structures and spatial distribution of functional groups in order to correctly interpret the catalytic results obtained with polymer-based solid acids.