Unravelling key phenomena in ball milling reactions toward fundamental principles-a minireview tutorial

Mechanochemistry is an emerging solvent-free approach in which chemical and supramolecular processes are driven by mechanical forces acting on solid reagents. In particular ball milling, a central approach within mechanochemistry, can generate nanoscale domains and activate reactivity through mechanical energy, offering a green and energy-efficient alternative to conventional solution-based methods. Unlike solution chemistry-whose principles are well established-the mechanisms underlying ball milling processes remain under active investigation. Ball milling reactions obey the same thermodynamic principles and underlying molecular mechanisms as solution-based reactions; however, the dominant energy inputs differ significantly. In ball milling, energy is delivered locally and intermittently through mechanical impacts rather than uniformly via thermal activation. Combined with the absence of solvent, the presence of lattice defects, and solid-state constraints, these factors can substantially alter reaction kinetics, accessible pathways, and product distributions. The purpose of this minireview-tutorial is to present, from my perspective, the contributions of my collaborators and myself toward understanding the unique phenomena associated with ball milling. We hope these insights will help advance the establishment of the fundamental principles of ball milling.