<p>Triazine (Tz)-based conjugated polymers with redox activity have drawn considerable attention as electrode materials for sustainable rechargeable batteries due to the features such as structural stability and electron-withdrawing nature of the Tz unit. However, it is rather challenging to synthesize highly redox-active Tz-based conjugated polymer electrodes under both ecological and cost-effective conditions. In this study, an ionothermal Friedel-Crafts reaction is developed for the efficient production of redox-active Tz-based conjugated polymers by using an AlCl₃-NaCl-KCl eutectic salt as a solvent-catalyst system and polycyclic aromatic compounds with cyanuric chloride as the starting monomers. As proof-of-concept, a series of Tz-based conjugated polymers were synthesized with high yields in the range of 74.8%–94.6%. The resulting Tz-based polymers exhibit excellent electrochemical performance when serving as the cathode materials in rechargeable Al batteries, Na batteries, and aqueous Zn batteries, including high capacities (141.8, 163.5, and 161.4 mAh g⁻¹, respectively), high operating voltage, as well as fast rate capability. Moreover, the ionothermal-synthesized Tz-based polymers also present much higher redox activity than their counterparts produced under traditional Friedel-Crafts reaction conditions. These results in this work offer a promising pathway to construct highly redox-active Tz-based conjugated polymer electrode materials for sustainable rechargeable batteries.</p>