Stable, metal-free, visible-light-driven photocatalyst for efficient removal of pollutants: Mechanism of action.

A low-cost and metal-free semiconductor-based photocatalyst driven by visible light has attracted great interest for water remediation. A relatively larger-surface area carbon nitride consisting of thin nanosheets is synthesized, firstly adopting melamine (M), cyanuric acid (C), urea (U) and dimethyl sulfoxide (DMSO) as the starting materials to form the supramolecular carbon nitride MCU(DMSO)-C3N4. Physical, chemical, and optical properties of the resulting samples were characterized. The photocatalytic performance of the MCU(DMSO)-C3N4 was evaluated under visible light irradiation using rhodamine B (RhB), tetracycline hydrochloride (TC), and ciprofloxacin (CIP) as target pollutants. Results showed that MCU-C3N4 exhibited much higher photocatalytic activity than pure g-C3N4, and when M, C, and U in DMSO with certain molar ratio (1:1:1) exhibited the highest activity. The larger surface area with more active reaction sites, increased bandgap with stronger REDOX ability, and higher separation efficiency of photogenerated electron-hole pairs contributed to higher photocatalytic activity. The photo-degradation is dominant by the active species (h+ and O2-) and converted product (OH). This exploration of MCU(DMSO)-C3N4 may open a window to the design of low-cost and highly efficient photocatalysis degradation systems for various wastewater treatments.