Anthraquinone-Based Covalent Organic Framework Nanosheets with Ordered Porous Structures for Highly Reversible Sodium Storage

Incorporating redox-active quinones with linkers to form covalent organic frameworks (COFs) could effectively improve their electrochemical performances when used as electrode materials. Their stable frameworks are able to inhibit dissolution of quinone in the organic electrolyte, and ordered porous structures enhance the ion diffusion rate. Condensing redox-active quinones with linkers containing more replaceable sites could increase the redox-active moieties in COF electrode materials, which would effectively increase their specific capacities. Herein, 2,6-diaminoanthraquinone (DAAQ) was condensed with the hexachlorocyclotriphosphazene (HCCP) linker containing six replaceable sites of −Cl to form ordered porous DAAQ–HCCP COF. All of the −Cl sites of the HCCP linker were replaced by redox-active DAAQ during condensation reaction, significantly increasing the content of electroactive moieties in the framework. Benefiting from the stable framework and ordered porous structures, DAAQ–HCCP COF exhibits higher cycling stability than DAAQ and outstanding rate performance when used as the anode for sodium-ion batteries. The prepared COF displays specific capacities of 88 mA h g–1 at 100 mA g–1 after 100 cycles and 72 mA h g–1 at 2000 mA g–1 after 1000 cycles. The present work provides a new strategy to design COF with more redox-active sites for organic rechargeable batteries.