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[Display omitted] • Electron localization is the primary reason for the ineffective charge separation process at the porphyrin-based MOF ligands. • Introducing Cu species into the conjugated framework allows efficient electron transitions by delocalizing the π-electrons. • Cu-induced electron delocalization significantly enhances the removal rate of ciprofloxacin. • The delocalized π-electrons are transferred to the Cu site for efficient activation of PDS to generate OH and SO 4 − . Photocatalytic persulfate activation provides a promising approach for the elimination of persistent organic pollutants from water. This has been exemplified in porphyrin-based metal organic frameworks (PMOFs), which however come with ineffective electron transition within the porphyrin ligand. Herein, we present a Cu ion modification strategy capable of boosting electron transition by inducing electron delocalization under visible light. The introduction of Cu ions increased the degradation rate constant of ciprofloxacin (CIP) by nearly 44 times, surpassing most state-of-the-art photocatalysts. The in-situ characterizations and theoretical calculations suggest that π-electron localization constitutes the origin of ineffective electron transition in PMOFs. The introduction of Cu ions induces π-electron delocalization to intensify the π → π* transition, forming electron-rich centers of Cu to lower the energy barrier for O-O bond cleavage. This work offers fundamental insights into the electron transition within PMOFs, upon which the universal strategy is proposed for improved water decontamination performance via persulfate activation. [ABSTRACT FROM AUTHOR]