Molecular engineering of interplanar spacing via π-conjugated phenothiazine linkages for high-power 2D covalent organic framework batteries

Two-dimensional covalent organic frameworks (2D-COFs) represent an attractive platform for organic electrodes, yet they suffer from infe-rior power capability caused by poor Li+ intercalation in densely TC-TC stacked interlayers. Herein, featuring nonplanar TC-conjugated hetero-aromatic linkages, phenothiazine with butterflyconformation is integrated as a structural scaffold to instantly tune packing topology and interplanar distance. Corrugated 2D-COF maintaining aroma-ticity and crystallinity is formed with good electroactivity, enlarged d-spacing, and accessibility to interior Li+-interactive sites, which re-sults in remarkable capacity of 220-773 mAh g-1 at high rates ranging from 100 to 3,200 mA g-1 with a good cycle life, bridging the perfor-mance gap between power and energy. Mechanistic studies reveal a dual storage mechanism with dominating capacitive storage pro-moted by TC-Li+ interactions, as well as enhanced redox activity of car-bonyls for better chemical accessibility. These findings elucidate inherent effects of molecular-level d-spacing regulation enabled by heteroaromatics, presenting a new design concept of interlayer engi-neering for organic porous energy storage materials.

Automated summary

By introducing nonplanar heteroaromatic linkages, such as phenothiazine, into two-dimensional covalent organic frameworks (2D-COFs), the packing topology and interplanar distance can be tuned, resulting in a porous 2D-COF with good electroactivity, enlarged d-spacing, and accessibility to interior Li+-interactive sites. This design concept of interlayer engineering provides a new strategy for organic porous energy storage materials.