Using milling balls as catalysts – Understanding the novel concept of direct mechanocatalysis

2026-07-22

I propose a novel concept of catalysis neither utilizing light, thermal heating nor an electric potential as in conventional catalysis, but simply mechanical energy. In this mechanochemical approach, mechanical energy is provided by the collision of milling balls inside a ball mill. The catalyst is neither dissolved (as in homogenous catalysis), nor a powder or bed of shaped bodies (as in heterogeneous catalysis), but the milling ball itself. I want to study how even in the absence of any solvent, solid reactants can be brought into reactions mechanocatalytically - only using milling balls that refresh their catalytically active surface constantly during their continuous collisions. I want to showcase this concept for a type of reactions that is commonly in the hand of homogeneous catalysis – C-C-cross coupling reactions catalysed by Pd, Cu or Ni. Understanding this novel concept involves 1) identifying reactions and reactants that can be applied to direct mechanocatalysis, 2) elaborating how mechanochemical reaction parameters such as milling speed, ball size and ball roughness replace common reaction parameters such as concentration or type of solvent and 3) elucidating the underlying mechanisms by employing in situ characterization techniques that allow for the monitoring of the reaction directly inside the moving milling vessels. I believe direct mechanocatalysis to be ground-breaking as it involves reactants that can hardly be brought into reaction via conventional approaches because of low solubility or limited stability in solution. The proposed solid-state approach will be fundamentally different from the conventional solution-based procedures, and I foresee new reactions to be possible. This approach is highly sustainable as it makes the use of any solvent obsolete and may develop to a new type of catalysis due to the exceptionally facile catalyst separation after synthesis; simply taking the milling ball out of the vessel.

Germany

2025-12-01