Zn-Doped Porous Graphitic Carbon Nitride: A High-Performance Catalyst for the Photodegradation of Pharmaceuticals and Personal Care Products

In this study, photocatalytically active graphitic carbon nitride (GCN) photocatalysts with varying amounts of zinc salts were synthesized using a solvent-free, scalable, and eco-friendly method. The photocatalysts were characterized using X-ray powder diffraction, scanning electron microscopy, nitrogen sorption, thermogravimetric analysis, UV–vis diffuse reflectance, and time-resolved photoluminescence (TRPL) spectroscopy. The addition of zinc to the GCN yields materials (GCN:Zn) with an enhanced surface area up to ca. 150 m²/g. Moreover, Zn incorporation affects the electronic structure of GCN and improves the electron transfer rate in the materials. The GCN:Zn materials show significantly improved photocatalytic activity for the degradation of pharmaceutical and personal care products (PPCPs) such as sulfamethoxazole (SMX), tetracycline (TET), and triclosan (TC) compared to zinc-free GCN. Although the degradation efficiency exceeds 98%, mineralization of the PPCPs is moderate (45–53%) due to the formation of stable intermediates. The treated effluents are nontoxic to Escherichia coli and Staphylococcus xylosus, indicating that no harmful intermediates form during the photocatalytic degradation of the PPCPs. The GCN:Zn photocatalysts demonstrate excellent reusability and stability for the degradation of PPCP over four cycles with minimal loss in activity, showcasing their potential for sustainable water treatment applications.