In recent years, graphitic carbon nitride (g-C₃N₄) has been developed greatly in the domain of water treatment. We adopted one-step calcination to enhance the light absorption of g-C₃N₄ with melamine-sponge (MS). A novel form of photocatalysts (gCNMx, x = 0.1, 0.2 and 0.3) were successfully prepared. The color of gCNMx changed with addition of MS. Experimental analysis demonstrated that C-doping and N vacancies increased the capacity of light absorption of gCNM0.2, and further increased efficiency of photothermal conversion and photogenerated holes. The sterilization efficiency of gCNM0.2 could rival a variety of metal photocatalysts. Moreover, the preparation of gCNM0.2 was cost-effective and environmental-friendly. Interestingly, the inactivation efficacy of gCNM0.2 for S. aureus depended heavily on the photogenerated holes, however, the decisive force toward S. typhimurium was photothermal conversion.