Nitrogen–Oxygen Co-Doped Porous Carbons from Flexible Covalent Organic Frameworks for Supercapacitors

Abstract

Aromatic systems ensure that the building blocks of covalent organic frameworks (COFs) tend to be rigid and exhibit good regularity, conjugation, and symmetry. However, flexible structures are more prone to deformation than rigid building blocks, in other words, it is very challenging to construct COFs with flexible building blocks. Three 2D flexible COFs with 3 + 3 structures are synthesized in this study using a solvothermal method with rigid/flexible building blocks. In addition, the effect of planarity variation of the building blocks on the structure and properties of the COFs is investigated. Subsequently, using high-temperature carbonization, three COFs are used as precursors to prepare nitrogen–oxygen codoped porous carbon materials. The nitrogen–oxygen codoping system and the well-developed porous structure substantially improve the adsorption and electrochemical properties of the materials. In particular, the large number of active sites in the porous system not only enhances the infiltration ability but also improves the diffusion and transport of electrolyte ions and charges within the electrode sheet. The specific capacitance of TAPB-TFPT-COF-700 is 183.9 F g^–1 at a current density of 1 A g^–1, demonstrating excellent specific capacitance and rate performance. In addition, the three porous carbon materials show excellent cycling stability after 2000 charge/discharge cycles.