Carbon-based elastic foams supported redox-active covalent organic frameworks for flexible supercapacitors

The construction of macroscopic and free-standing three-dimensional (3D) objects with intriguing mechanical properties from covalent organic frameworks (COFs) is challenging but of great significance toward their development in wearable energy storage devices. Herein, a COF/carbon composite foam is elaborately designed by in situ implanting COF crystallites along the surface of carbon network via Schiff base reaction, yielding an intimate mixing of both phases. Within the 3D architecture, the interconnected carbon skeleton ensures a fast electron transfer and good mechanical performance with high compressibility and good fatigue resistance (50 cycles at 70% strain). Another, the COF decoration enriches porous structures and affords sufficient active sites. When used as self-supported electrodes for supercapacitor devices, the as-fabricated COF/carbon composite foam delivers a high capacitance of 129.2 F g(-1) at 0.5 A g(-1) and shows superior long cycling stability with ca. 100% capacitance retention after 20,000 cycles at 10 A g(-1). More importantly, such an elastic, robust, and active composite foam can be assembled into flexible supercapacitors showing an excellent capacitive stability even under serious compressing or bending deformation, demonstrating a great potential in the state-of-the-art wearable devices.