The present work focuses on development of polymeric composite membranes-based on polyvinylidene fluoride incorporated with aminopropyltrimethoxysilane (APTMS) functionalized TiO2/g-C3N4 nanoparticles, which was synthesized and characterized using FTIR, XRD, FE-SEM, EDAX, and XPS. A phase-inversion technique was used to integrate the APTMS-functionalized TiO2/g-C3N4 nanoparticles into PVDF membrane. To remove methylene blue dye (MB) efficiently, this work combines the two approaches, concentrating on photocatalytic degradation, adsorption, and kinetics. APTMS-functionalized TiO2/g-C3N4/PVDF, a selective adsorbent, was developed and assessed utilizing different adsorption isotherm models, such as Freundlich and Langmuir. APTMS-functionalized TiO2/g-C3N4 showed better MB degrading efficiency than that of TiO2/g-C3N4-PVDF composites. The photocatalytic activity of APTMS-functionalized TiO2/g-C3N4-PVDF composite was optimized under visible light, following a pseudo-first-order kinetic model. It was also found that the photocatalyst developed has possesses catalytic activity even after five consecutive cycles. A Box–Behnken design using response surface methodology (RSM) was applied, and found that the maximum removal of MB was achieved with 93.89% at optimum conditions: MB concentration = 10 mg/L, TiO2 dosage = 0.3315 g, and irradiation time = 70 min. These findings highlight that the potential of APTMS-functionalized TiO2/g-C3N4-PVDF composites membrane acts as an effective and cost-efficient solution for MB removal from wastewater, contributing to sustainable environmental remediation.