Centrosymmetric Nanomaterials for Bending Vibration Driving Flexocatalysis: Mechano-Chemical Coupling Mechanism and...

Flexocatalysis is an emerging mechano-catalytic paradigm that converts mechanical stimuli into chemical energy via strain-gradient-induced electric polarization. Unlike conventional piezocatalysis, which is restricted to non-centrosymmetric crystals, flexocatalysis can operate in centrosymmetric, amorphous, polymeric, and porous dielectrics because non-uniform deformation locally breaks inversion symmetry, significantly expanding the material library for mechanically driven catalysis. However, the field remains in its early stages, and the mechanistic boundaries between flexocatalysis and coexisting pathways, such as piezocatalysis, tribocatalysis, sonocatalysis, and ultrasound-assisted photocatalysis, remain unclear, particularly under ultrasonic excitation. This review presents the physical fundamentals of flexoelectricity, the catalytic consequences of strain-gradient-induced polarization, and experimental criteria for distinguishing flexocatalysis from other mechanocatalytic pathways. It also systematically compares major classes of flexocatalytic materials, including centrosymmetric oxides, 2D layered materials, ferroelectrics, polymers and hydrogels, metal-organic frameworks (MOFs), and amorphous materials, highlighting that morphology and strain-gradient engineering matter as much as intrinsic flexoelectric coefficients. Furthermore, it proposes a framework for mechanistic attribution based on material symmetry and electronegativity, and identifies non-ultrasonic mechanical inputs as a promising route to isolate pure flexoelectric contributions. Finally, major challenges and future directions are discussed, aiming to provide a mechanistically rigorous framework for guiding the application-oriented design of flexocatalysts.