Dual-functional Ti-MOF/g-C₃N₄ engineered PVDF membranes for photocatalytic self-cleaning and high-flux water...

The ubiquitous presence of emerging contaminants (ECs) such as antibiotics and synthetic dyes in aquatic systems necessitates advanced remediation technologies. However, conventional polyvinylidene fluoride (PVDF) membranes often suffer from severe fouling and rapid flux decline due to their inherent hydrophobicity, severely limiting their long-term applicability. This study presents the rational design of Ti-MOF/CN/PVDF composite membranes via integrated solvothermal synthesis of Ti-MOF/g-C₃N₄ (CN) heterojunctions and nanoparticle-regulated phase inversion. Comprehensive characterization (XRD, XPS, SEM-EDS, BET, AFM) confirmed the successful fabrication of the heterojunction membrane. XPS and XRD analyses confirmed the formation of covalent bonds at the (Ti-O-N) interface and lattice strain induced by the nanoparticle filler, effectively suppressing PVDF crystallization. Ti-MOF/CN exhibits a unimodal particle size distribution (D50 ≈ 400 nm) and high BET specific surface area (72.44 m² g^-1). Its uniform dispersion in PVDF increases the membrane pore size from 28.1 nm in pristine PVDF to 38.7 nm at 1 wt% Ti-MOF/CN, significantly enhancing the overall porosity. The top-performing M3 composite membrane demonstrated exceptional multifunctionality: it achieved retention rates exceeding 90% for multiple dyes (Rhodamine B, Methyl Blue, Malachite Green) and antibiotics (Tetracycline). Long-term retention experiments were conducted on complex wastewater containing mixed dyes, alongside photodegradation tests under simulated solar radiation conditions (AM 1.5G, 100 mW cm^-2). Results indicate over 95% retention of mixed pollutants. Visible light irradiation significantly enhances the M3 membrane's FRR to 91.6%, further demonstrating the Ti-MOF/CN composite membrane's robust long-term operational stability and self-cleaning capability for photocatalytic degradation of aqueous pollutants.