Graphitic Carbon Nitride (g-C₃N₄),as a metal-free two-dimensional nanomaterial,shows broad prospects in photocatalysis.In this study,alkali-exfoliated g-C₃N₄ was prepared from bulk g-C₃N₄ via treatment with sodium tert-butoxide.A series of composite materials were then synthesized by tuning the dosage of Graphene Quantum Dot (GQD).The morphology,structure,and composition of these samples were thoroughly characterized by XRD,FT-IR,SEM,UV-Vis,PL,and other techniques,and their photocatalytic performance was evaluated through the degradation of Methylene Blue (MB).The results indicate that,compared with bulk g-C₃N₄,the alkali-exfoliated samples shorten the carrier transport distance,while the introduction of GQD effectively suppresses the recombination of electron-hole pairs.When the GQD doping amount is 5.0%,the photocatalytic degradation efficiency of MB reaches 90.9%.Furthermore,free radical trapping experiments identify ·O₂^- and h⁺ as the main active species,and a possible photocatalytic mechanism for MB degradation is proposed.