As a novel class of robust redox-active organic polymers, covalent triazine frameworks (CTFs) are highly promising cathode materials for lithium-ion batteries. However, the low electronic conductivity, low redox potentials, and poor electrochemical stability greatly limit their applications. Through a TfOH-catalyzed cyano-trimerization reaction, herein, a novel phenothiazine-based CTF, MPT-CTF, and its composite MPT-CTF@CNT have been successively achieved with superior rate capability, high and stable working potentials, and a high capacity of up to 297 mA h g⁻¹@0.4 A g⁻¹. This work provides a feasible route for the application of CTFs in organic cathode materials.