In this work, a costeffective and ecofriendly calciumdoped Fe 2 O 3 (CaFe 2 O 3 ) with abundant oxygen vacancies was fabricated using a scalable precipitationcalcination method to activate peroxymonosulfate (PMS) for wastewater purification. Density functional theory calculations revealed that the incorporation of Ca 2 into the Fe 2 O 3 structure enhances the electron transfer from Fe 2 O 3 to PMS, facilitating the activation of PMS. The degradation of Rhodamine B by 5%CaFe 2 O 3 proceeded with a reaction constant 8 times higher than that of pristine Fe 2 O 3 . This can be attributed to the increased generation of 1 O 2 and O 2 , increased specific surface area and enhanced electrical conductivity. The applicability of the 5%CaFe 2 O 3 PMS system was investigated including its operating parameters and stability, and the intermediates involved in the reaction were identified. The 5%CaFe 2 O 3 PMS system exhibited excellent degradation efficiency in natural water samples. This work opens up new perspectives for designing highly efficient catalysts and renders iron oxides potential candidates for environmental remediation.