Engineered oligomeric-phase carbon nitride/WO3 Z-scheme photocatalysts for enhanced degradation of pharmaceutical contaminants in natural water under visible light

• WO 3 /carbon nitride photocatalyst was prepared for water treatment. • Oligomeric-phase carbon nitride in the photocatalyst enhanced its performance. • Increased superoxide anion radical contribution enhanced photocatalytic performance. • Improved photocatalysis of 14 pharmaceuticals were achieved under real water. In this study, we have synthesized oligomeric-phase carbon nitride/WO 3 (o-WCN) Z-scheme photocatalysts to enhance reactive species (RS) generation and photocatalytic efficiency under visible-light irradiation compared to more traditional graphitic-phase (g-WCN) and polymer-phase (p-WCN) catalysts. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used for structural analysis of photocatalyst confirming that o-WCN contained a higher proportion of terminal amine-rich oligomeric carbon nitride (o-CN) structures, leading to a more negative conduction band minimum (CBM) compared to other WCNs. Although charge transfer rate was fastest in g-WCN followed by p-WCN and o-WCN, o-WCN demonstrated superior overall photocatalytic performance (i.e., 4.82-fold) due to enhanced generation of the superoxide anion radicals (O 2 •− ), driven by its highly negative CBM. In water sampled from a water treatment facility, o-WCN exhibited remarkable efficiency in removing pharmaceutical contaminants, with a 25-fold reduction in half-life (t 1/2 ) compared to WO 3 and notable advantages over other reported photocatalysts. These findings highlight the importance of carbon nitride (CN) phase tuning when developing Z-scheme carbon nitride/WO 3 (WCN) photocatalysts for environmental applications and confirm the practical applicability of o-WCN for efficient water treatment.