A novel ternary heterostructure based on g-C3N4/N-TiO2/Y1.97SiO5:Ce-0.03 was synthesized via thermal treatment and evaluated for the photocatalytic degradation of two antibiotic pollutants, chloramphenicol (CAP) and vancomycin (VAN), in aqueous solution. The composite was designed to function as a photoactive platform, in which Ce3+-doped Y2SiO5 acts as an internal light converter, emitting at similar to 430 nm upon UV excitation (365 nm) to enhance activation of the g-C3N4/N-TiO2 interface. Structural and morphological characterizations (WAXD, FTIR, XPS, TEM) confirmed the formation of a well-integrated heterostructure with strong interfacial interactions. The photocatalyst achieved near-complete removal of CAP (99.7 %) and VAN (100 %) under UV light, and also showed high efficiency under simulated solar irradiation and in real water matrices. These results demonstrate the synergistic light-conversion and charge-transfer properties of the composite, underscoring its potential as a sustainable and scalable solution for antibiotic pollutant removal in water treatment applications.