Challenges related to energy shortages and environmental pollution are driving extensive research in catalysis. Flexocatalysis, which extends flexoelectricity to mechanocatalysis, is a promising mechanism for catalytic processes. Owing to its size-dependent effects, flexoelectricity has become particularly significant and plays a dominant regulatory role in chemical reactions within nanocatalysis. In this study, we integrated flexocatalysis with peroxymonosulfate (PMS) activation for efficient water purification. The simulation results show that flexoelectric polarization can induce a strong flexoelectric field in δ-MnO2 nanosheets. This built-in electric field subsequently drives the migration of electrons and holes to the reaction interface, thereby activating PMS and promoting rapid generation of reactive species for the degradation of organic pollutants. At low concentrations of flexoelectric catalysts, we achieved excellent degradation efficiency that was 6.6 times greater than that obtained through the thermal activation of PMS. This study demonstrated that flexoelectricity can function as a switch for PMS activation and offers a promising approach for sustainable water remediation.