Abstract: In the pursuit of the dual-carbon objectives, nuclear energy, recognized as a substitute for clean energy, has resulted in a growing demand for uranium resources. Consequently, the uranium-containing wastewater produced poses significant and substantial threats to environmental safety and public health. Photocatalytic technology, renowned for its remarkable efficiency in the removal of heavy metals and organic contaminants, has garnered widespread attention. Within this domain, graphitic carbon nitride (g-C₃N₄, CN) has emerged as a material of great interest, exhibiting considerable promise due to its distinct and exceptional photocatalytic properties. To broaden the photoresponse spectrum of graphitic carbon nitride and enhance the functional utility of additional active sites, a nitric acid exfoliation-salt templating methodology was employed to synthesize mesoporous graphitic carbon nitride composite material—Na-HNO₃-CN in this paper. The synthesized material Na-HNO₃-CN was comprehensively characterized through a series of advanced techniques, including scanning electron microscopy (SEM), brunauer-emmett-teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). Following these characterizations, its photocatalytic capabilities in the reduction of U(Ⅵ) were systematically investigated and analyzed. The experimental results show that Na-HNO₃-CN composite material possesses a three-dimensional porous honeycomb architecture. Compared with conventional graphitic carbon nitride, Na-HNO₃-CN exhibits substantial improvements in various properties: The specific surface area increases significantly from 5.38 cm³/g to 47.11 cm³/g, the pore volume expands from 0.12 cm³/g to 0.20 cm³/g, and the visible light absorption range extended appreciably from 450 nm to 550 nm, accompanies by a noticeable redshift in the absorption edge. Moreover, the photoelectric current response of Na-HNO₃-CN is considerably higher than that of the original CN material. Specifically, Na-HNO₃-CN with a Na to HNO₃ ratio of 3∶1 achieves a U(Ⅵ) removal rate of 95.59%, which is approximately 4.8 times higher than that of CN. The reduction reaction rate constant (0.019 8 min⁻¹) of 3∶1 Na-HNO₃-CN is 11 times that of the original CN (0.001 8 min⁻¹), indicating its superior and outstanding performance in the photocatalytic reduction of U(Ⅵ). The findings from this research not only highlight the remarkable performance of the Na-HNO₃-CN in the photocatalytic reduction of U(Ⅵ) but also provide valuable insights and offer new perspectives for the future development and design of high-efficiency photocatalytic materials. These results indicate the potential applications value of mesoporous graphitic carbon nitride composites in environmental remediation, particularly in the treatment and mitigation of uranium-contaminated wastewater, and suggest promising avenues for further research, exploration, and innovation within this field.