SWCNT- and Cu-decorated UiO-66(Zr) nanocomposite as a highly active visible-light photocatalyst for efficient deep oxidative desulfurization of liquid fuels

A UiO-66(Zr)-based composite functionalized with single-walled carbon nanotubes (SWCNTs) and copper nanoparticles was synthesized and applied as a photocatalyst for oxidative desulfurization of dibenzothiophene (DBT) in liquid fuels under visible light irradiation. The photocatalysts were characterized using XRD, XPS, FT-IR, FE-SEM, PL, UV–Vis, EDX, TEM, BET, ESR, and DRS analysis. The influence of key parameters, photocatalyst loading, DBT concentration, sulfur-to-fuel ratio, O/S molar ratio, solvent-to-fuel ratio, and temperature, on DBT removal was systematically investigated. The 1Cu-UC composite exhibited the highest photocatalytic efficiency under optimized conditions, achieving complete (100%) DBT elimination within 120 min of visible-light illumination. The optimal values were: photocatalyst dose 2 g L −1 , initial DBT concentration 500 mg g −1 , sulfur-to-fuel ratio 0.5, oxidant-to‑sulfur ratio 9, and a reaction temperature of 50 °C. Its superior activity was attributed to its high BET surface area (599.20 m 2 g −1 ), efficient separation of the photogenerated electron–hole pairs, reduced bandgap energy (2.67 eV), and enhanced visible-light absorption. The catalyst demonstrated excellent stability, retaining more than 90% after five consecutive runs. The remarkable desulfurization is ascribed to synergistic interactions among Cu nanoparticles, SWCNTs, and the UiO-66(Zr) framework, facilitating electron transfer, the generation of reactive oxygen species (ROS), and the efficient DBT adsorption.