Interface-Engineered S-Scheme Heterojunction of g-C ₃ N ₄ Quantum Dots and NH ₂ –UiO-66 for Superior Visible-Light Photocatalysis

S-scheme heterojunctions have emerged as highly potential photocatalysts owing to their unique capability to promote efficient spatial separation of photoinduced charge carriers while simultaneously preserving the stable redox potentials required for pollutant degradation. In this study, g-C 3 N 4 QD/NH 2 –UiO-66 S-scheme heterojunction was synthesized using in situ growth and hydrothermal processes. Compared with bare g-C 3 N 4 QDs and NH 2 –UiO-66, the g-C 3 N 4 QD/NH 2 –UiO-66 S-scheme heterojunction displays improved photocatalytic efficiency toward ciprofloxacin (CIP) degradation under visible-light irradiation, achieving a degradation ratio of 81.25% for CIP. The fabricated g-C 3 N 4 QD/NH 2 –UiO-66 also shows remarkably enhanced photocatalytic H 2 production performance, reaching a H 2 evolution rate of 1296 μmol h –1 g –1, which is approximately 12.7 times and 2.3 times that of g-C 3 N 4 QDs and NH 2 –UiO-66, respectively, demonstrating a pronounced synergistic effect between the two components. Furthermore, trapping experiments indicate that the primary reactive species involved in the photodegradation procedure are • O 2 – and • OH. XPS, HRTEM, and UV–vis DRS have confirmed that the g-C 3 N 4 QD/NH 2 –UiO-66 S-scheme heterojunction exhibits a tight interface, enhanced charge transfer, and improved visible-light utilization efficiency. Experimental results combined with theoretical calculations further clarified the possible photodegradation mechanism. This work presents a novel strategy for efficient photocatalysis by rationally constructing an S-scheme heterojunction with boosted charge separation.