Reevaluating Mechano-driven Chemical Reactions: Insights from Ultrasonic, Piezo, and Contact-Electro Mechanisms

Mechano-driven chemical reactions offer a disruptive alternative to conventional thermally and photochemically initiated processes. However, conceptual ambiguities, particularly conflating sonochemistry with piezocatalysis, have obscured a coherent understanding of these mechanistic pathways. This review reexamines mechano-activation through a unified energy-transfer perspective, focusing on three representative mechanisms: sonochemistry, piezocatalysis, and contact-electro catalysis (CEC). We dissect how ultrasonic excitation spans a frequency- and intensity-dependent continuum, from low-frequency ultrasound (20–100 kHz) that enhances mass transport and interfacial effects, to high-frequency ultrasound (>100 kHz) capable of inducing bond cleavage via transient high-temperature and high-pressure microenvironments generated by acoustic cavitation. In contrast, piezocatalysis and CEC rely on mechanical-to-electrical transduction mechanisms via piezoelectric polarization or interfacial charge transfer, respectively, offering photonic- and adsorption-independent activation pathways with high catalyst recyclability. By re-evaluating the driving forces and energetic thresholds underlying each mechano-chemical pathway, this review clarifies the mechanistic boundaries and operational regimes of ultrasonics, piezoelectric, and contact-electro-induced reactions. Emphasis is placed on the critical role of material properties and the importance of decoupling mechanical and electronic descriptors. The review concludes by outlining key directions for the rational design of mechano-responsive materials and catalytic systems, offering new opportunities for sustainable catalysis and next-generation mechano-driven chemical reactions.