This study presents a novel strategy to enhance the ion-ion selectivity of porous graphene membranes through electrochemical repair. The researchers developed a method to mask larger non-selective pores in large-area graphene using a 10-nm-thick electropolymerized conjugated microporous polymer (CMP) layer. This CMP layer, which has a strong π-π interaction with graphene, effectively reduces the contribution of non-selective pores, leading to a significant increase in Li+/Mg²⁺ selectivity from zero-dimensional pores to 300 with a high Li⁺ ion permeation rate. The electrochemical repair approach offers several advantages, including precise control over the thickness of the CMP mask layer, mechanical reinforcement of the graphene, and the ability to customize pore sizes. The resulting porous graphene membranes exhibit superior performance in ion-ion separation compared to state-of-the-art materials, making them a promising platform for various applications in energy, water, and chemical sectors.This study presents a novel strategy to enhance the ion-ion selectivity of porous graphene membranes through electrochemical repair. The researchers developed a method to mask larger non-selective pores in large-area graphene using a 10-nm-thick electropolymerized conjugated microporous polymer (CMP) layer. This CMP layer, which has a strong π-π interaction with graphene, effectively reduces the contribution of non-selective pores, leading to a significant increase in Li+/Mg²⁺ selectivity from zero-dimensional pores to 300 with a high Li⁺ ion permeation rate. The electrochemical repair approach offers several advantages, including precise control over the thickness of the CMP mask layer, mechanical reinforcement of the graphene, and the ability to customize pore sizes. The resulting porous graphene membranes exhibit superior performance in ion-ion separation compared to state-of-the-art materials, making them a promising platform for various applications in energy, water, and chemical sectors.