Energy storage materials have advanced renewable energy technologies. Herein, we described the one-pot synthesis of covalent organic frameworks (COFs)/graphitic carbon nitride (g-C₃N₄) nanocomposite. The condensation of melamine and benzene-1,3,5-tricarboxyaldehyde with and without g-C₃N₄ offered the synthesis of COF and COF/g-C₃N₄. Furthermore, N-doped carbon and N-doped carbon/g-C₃N₄ were synthesized via the carbonization of COF and COF/g-C₃N₄, respectively. The materials i.e., before and after carbonization were used as electrode materials for supercapacitors and lithium-ion batteries (LIBs). They showed specific capacitance of 211, 257.5, 450, and 835.2 F·g^–1 for COF, COF/g-C₃N₄, N-doped carbon, and N-doped carbon/g-C₃N₄, respectively. Asymmetric supercapacitor device using N-doped carbon/g-C₃N₄ exhibited good energy (45.97 Wh·kg^–1) with high power (659.3 W·kg^–1). The N-doped C/g-C₃N₄ electrode was also applied for LIBs, offering a discharge capacity of 390 mAh·g^–1 (at 50 mA·g^–1).