Engineering building blocks of covalent organic frameworks for boosting capacitive charge storage

Engineering building blocks of covalent organic frameworks (COFs) with tailored active sites and microstructures is efficient in boosting capacitive energy storage. Herein we craft imine-linked COFs built from tri-arylamine knots and di-aldehyde linkers via a well-established Schiff-base condensation. The resulting COFs show enriched redox responses and diverse morphologies including nanoparticles, hollow spheres, and crystalline fibers by altering the knot planarity and the substitutes on linkers. It is disclosed that the coplanarity of building blocks and intramolecular H-bonding dominate the stacking modes of COFs, and accordingly their mi-crostructures, and electrochemical performance. Among such COFs, a hydroquinone-enriched nanofiber-like COF delivers the highest specific capacitance of 235 F g(-1) at 0.5 A g(-1), which outperforms the most COF-based electrodes reported previously, due to its high planarity, intramolecular H-bonding, ultrahigh specific surface area, and abundant electroactive moieties. This work may unlock an alternative approach to the modularization of pseudocapacitive COFs by enriching redox-active centers and tuning microstructures.

Automated summary

Engineering customized active sites and microstructures in covalent organic frameworks (COFs) is an efficient way to enhance capacitive energy storage. In this study, imine-linked COFs were crafted from tri-arylamine knots and di-aldehyde linkers using Schiff-base condensation. By altering the planarity of the knots and the substitutes on the linkers, the resulting COFs exhibited enriched redox responses and diverse morphologies including nanoparticles, hollow spheres, and crystalline fibers. The study revealed that the coplanarity of building blocks and intramolecular H-bonding played a crucial role in determining the stacking modes, microstructures, and electrochemical performance of COFs. Among the studied COFs, a hydroquinone-enriched nanofiber-like COF displayed the highest specific capacitance of 235 F g(-1) at 0.5 A g(-1), surpassing previously reported COF-based electrodes due to its high planarity, intramolecular H-bonding, ultrahigh specific surface area, and abundant electroactive moieties. This work provides an alternative approach to modulating pseudocapacitive COFs by enriching redox-active centers and tuning microstructures.