Synergistic donor-acceptor GQD@g-C3N4 for the enhanced photodegradation of bisphenol a under visible light.

Metal-free photocatalysts activated under visible solar irradiation offer a promising and sustainable approach for the efficient remediation of organic contaminants in the environment. However, developing a highly efficient metal-free visible light photocatalyst remains a significant challenge, primarily due to the rapid recombination of photogenerated carriers and the inherently low specific surface area. Here, we designed a dual-modified MCNUGQD photocatalyst using a green synthesis approach to address these two critical challenges. The π-π stacked interface of graphene quantum dots (GQDs) and exfoliated carbon nitride (CN) promotes photogenerated carriers separation, enhancing electron utilization efficiency. The synergistic effects of GQDs grafting and efficient nanosheet exfoliation achieved the complete removal of 1 mg/L bisphenol A (BPA) within 5 min, achieving a high reaction rate constant of 0.983 min-1 and a total organic carbon (TOC) removal efficiency of 44.5%, under the optimized conditions. Moreover, MCNUGQD demonstrated excellent adaptability under various environmental conditions and maintained high reusability over four consecutive recycling tests. This study highlights that metal-free visible-light photocatalysts can outperform metal-based/modified systems and further demonstrates their practical applicability and potential for future development.