Understanding the Mechanocatalytic Conversion of Biomass: A Low-Energy One-Step Reaction Mechanism by Applying Mechanical Force

On the way to establishing biomass as a renewable and environmentally friendly source to cover the ever-increasing global demand on energy and chemicals, one great challenge is the efficient depolymerization of cellulose. Enhanced conversion rates have been discovered in ball-milling experiments, thus opening a mechanocatalytic approach. However, an understanding of the impact of mechanical forces on the acid-catalyzed cleavage of glycosidic bonds at the molecular level is still missing. Herein, we contribute such fundamental insight based on atomistic modeling. Mechanically stressing the macromolecular back-bone radically changes the depolymerization pathway from a complex high-harrier reaction upon thermal activation to a low-energy single-step mechanocatalytic process. In addition to revealing a regioselective increase in basicity under a mechanical force, our results provide molecular-level explanations of the experimental findings and might therefore guide rational ways to improve such mechanocatalytic processes.