Covalent triazine networks are interesting candidates for organic electrocatalytic materials due to their tunable, durable and sustainable nature. However, the limited availability of molecular designs that ensure both two-dimensionality and functional groups in the π-conjugated plane has hindered their development. In this work, a layered triazine network composed of thiophene and pyridine ring was synthesized by the novel mild liquid phase condition. The resulting network showed layered nature since its intramolecular interaction stabilized its planar conformation. The connection on the 2-position of the heteroaromatic ring prevents steric hindrance. The simple acid treatment method could be used to exfoliate the networks, resulting in high yields of nanosheets. The planar triazine network showed superior electrocatalytic properties for the oxygen reduction reaction in the structure-defined covalent organic networks.