Boosting Photocatalysis: Cu-MOF Functionalized with g-C3N4 QDs for High-Efficiency Degradation of Congo Red

In recent years, organic dye contamination has posed a significant threat to water safety. This study presents a novel composite photocatalyst comprising graphitic carbon nitride quantum dots (g-C3N4QDs) supported on a copper-based metal–organic framework (Cu-MOF) for efficient visible-light degradation of organic pollutants. The g-C3N4QDs were synthesized via a facile strategy and subsequently immobilized onto the Cu-MOF support. Comprehensive characterization including SEM, TEM, XRD, BET, UV-Vis DRS, PL, and EIS confirmed the successful formation of a heterostructure, revealing that an optimized loading of g-C3N4QDs significantly enhanced light absorption, facilitated charge separation, and increased the specific surface area, with the optimal composite exhibiting 273 m2/g compared to 112 m2/g for the pristine Cu-MOF. Electrochemical analyses indicated a 2.38-fold enhancement in photocurrent density and a reduced interfacial charge transfer resistance, reflecting superior electron–hole pair separation. Crucially, the optimized g-C3N4QDs/Cu-MOF composite demonstrated exceptional photocatalytic performance, achieving 96.6% degradation of Congo red (100 mg/L) within 30 min under visible light irradiation, substantially outperforming the 77.6% degradation attained by the pristine Cu-MOF. This enhancement is attributed to the synergistic effects of improved light harvesting, efficient interfacial charge transfer across the heterojunction, and an enlarged active surface area. The composite exhibits considerable potential as a high-performance and stable photocatalyst for purifying dye-contaminated wastewater.