Bisphenol S-doped g-C3N4 nanosheets modified by boron nitride quantum dots as efficient visible-light-driven photocatalysts for degradation of sulfamethazine

•The novel metal-free BNQDs/BPS-CN photocatalysts are successfully synthesized.•The photocatalysts show superior photocatalytic activities and stability in photodegradation of sulfamethazine.•Enhanced visible light absorption and charge transfer from BNQDs/BPS-CN are recorded.•A pathway for photocatalytic degradation of sulfamethazine is proposed. Antibiotics may pose a great risk to ecosystem and human health. Photocatalysis, as a low-cost and environmentally friendly technology is widely used for the removal of antibiotics from wastewater. Graphitic carbon nitride (g-C3N4) has shown promising prospects in visible light photocatalysis, while its photocatalytic performance is greatly limited because of the sluggish charge separation and transfer. In this work, metal-free boron nitride quantum dots (BNQDs) modified bisphenol S (BPS)-doped g-C3N4 nanosheets (BNQDs/BPS-CN) heterojunction was synthesized to overcome these defects and applied in photodegradation of sulfamethazine (SMZ, a typical antibiotic) under the visible light. Multifarious characterization methods were used to explore the structure, porosity, elemental composition, optical performances, photo-electrochemical properties and photocatalytic performances of as-prepared BNQDs/BPS-CN composites. The degradation efficiency of SMZ with BNQDs/BPS-CN-4 composite reaches 100% within 60 min, and the rate constant is 13.7 times higher than that of pure g-C3N4. This phenomenon is because of the shrinking band gap width and the introduction of electronegative BNQDs, which is conducive to the absorption of visible light and high-efficiency separation of photoexcited charge carriers. Meanwhile, the results of free radical trapping experiments and electron spin resonance characterization prove that the photogenerated holes and superoxide radicals play predominant roles in the photodegradation of SMZ. This study proposes an effective mechanism for the construction of novel visible-light-driven photocatalysts using metal-free two-dimensional materials and quantum dots, which can be applied in the treatment of organic contaminants.