Visible-light-active CeO₂–TiO₂–ZnO Z-scheme photocatalytic filters for simultaneous removal of indoor particulate matter and volatile organic compounds

Indoor air quality is increasingly compromised by the synergistic toxicity of particulate matter (PM) and volatile organic compounds (VOCs). Conventional purification technologies typically address these pollutants in isolation, suffering from energy inefficiencies and secondary fouling. This study presents a multifunctional, visible-light-active air purification medium engineered by immobilizing a ternary CeO₂–ZnO–TiO₂ Z-scheme nanocomposite onto porous glass fiber filters via a modified Pechini sol–gel dip-coating process. Morphological characterization reveals a hierarchically porous architecture that increases the specific surface area to 37.5 m² g⁻¹ without compromising aerodynamic permeability. Optoelectronic analysis confirms a bandgap reduction to 2.64 eV, enabling efficient photon harvesting under ambient LED illumination. The functionalized filter demonstrates exceptional multipollutant removal capabilities, achieving 82.1% filtration efficiency at the most penetrating particle size (MPPS) and > 80% degradation of gaseous toluene (50 ppm) within 90 min. Mechanistic studies suggest a direct Z-scheme charge transfer pathway that preserves the strong redox potentials of the constituent oxides. Furthermore, the filter exhibits high resistance to fouling under continuous dust loading (300 µg m⁻³) and stable performance over multiple regeneration cycles.