Ternary novel BiOI@MIL-88A(Fe)@g-C3N4 nanocomposite with core@shell structure was successfully synthesized by hydrothermal method. Fabricated photocatalysts were characterized and results confirmed the formation of MIL-88A(Fe)@g-C3N4 core@shell structure and subsequently BiOI decoration on the surface of MIL-88A(Fe)@g-C3N4. Photocatalytic performances of prepared samples were investigated for degradation of Acid Blue 92 (AB92), Rhodamine B (RhB) and phenol under visible irradiation. It is clearly demonstrated that the as prepared ternary BiOI@MIL-88A(Fe)@g-C3N4 composites exhibits exceptional visible-light photocatalytic activities for cationic, anionic as well as neutral pollutant molecules compared to the widely accepted outstanding g-C3N4. It is mainly proved that the exceptional photocatalytic efficiencies are comprehensively ascribed to the porous structure of MIL-88A(Fe)@g-C3N4, greatly promoted charge separation and introduced catalytic functions to the carrier-related redox reactions by decorating BiOI and coupling g-C3N4, to modulate holes and electrons. Additionally, studies performed using radical scavengers showed the main reactive species in the photocataytic reaction for all chemical pollutant degradation.