A Z-scheme WO₃–ZnO–TiO₂ nanocomposite coated filter for concurrent PM2.5 filtration and toluene photomineralization under visible light

Indoor air quality is increasingly compromised by particulate matter (PM) and volatile organic compounds (VOCs), posing compounded health risks in enclosed environments. Conventional purification technologies typically address these pollutants independently, relying on energy-intensive filtration or saturation-limited adsorption. Herein, a dual-functional air purification medium is developed by immobilizing a ternary WO₃–ZnO–TiO₂ nanocomposite onto porous borosilicate glass fibers via a scalable sol–gel dip-coating method. Structural and optical characterization (X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS)) confirms a well-coupled heterojunction with a reduced bandgap of 2.82 eV, enabling photoactivation under visible light (λ > 420 nm). Aerodynamic evaluation demonstrates that hierarchical surface roughness enhances the capture efficiency of 0.3 μm particles from ~ 45% to > 95%, with only a modest pressure drop increase (~ 25 Pa at 1.0 m s⁻¹). Photocatalytic testing using gaseous toluene (50 ppm) reveals > 90% degradation within 90 min under visible light, with an apparent rate constant (k_app) of 0.035 min⁻¹—seven times higher than pristine TiO₂. Carbon dioxide evolution indicates ~ 68% mineralization of degraded toluene. Importantly, the functionalized filter retains ~ 85% VOC removal efficiency under heavy particulate loading (300 µg m⁻³) and maintains ~ 90% activity over twelve consecutive cycles (24 h total runtime). These findings establish the WO₃–ZnO–TiO₂ coated filter as a mechanically robust, energy-efficient platform for simultaneous mitigation of particulate and gaseous indoor pollutants.