Pre-Activation as a Route for Tuning the Kinetics of Mechanochemical Transformations.

Learning to control reaction kinetics is essential for translating any chemical technology into real-world application. Based on time-resolved in situ powder X-ray diffraction data, we demonstrate the opportunity to tune mechanochemical reaction rates through the pre-activation of the starting reagents. For three model co-crystal systems, the pre-activation of the most stable reagent yields up to a ca 10-fold increase in the reaction rate, whilst negligible kinetic enhancement is seen when the less stable reagent is pre-activated. Moreover, we demonstrate how the polymorphic outcome of mechano-co-crystallization is also sensitive to pre-activation of the starting material. Our results suggest that reproducibility of mechanochemical processes requires detailed understanding over the origin and history of reagent powders, whilst providing a new conceptual framework to design and control mechanochemical reactions.