Anthraquinone Substituents Regulate the Ion-Transport Sites in iHOFs for Efficient Transport of Alkali-Metal Ions

The designability of crystalline framework materials holds promise for the development of stable solid-state electrolytes with high ionic conductivity. In this study, we present three anthraquinone-based ionic hydrogen-bonded organic frameworks (<b>iHOF-21-23</b>), which possess 2D sandwich-shaped hydrogen-bonding networks. By modulating the anthraquinone substituents, the three iHOFs exhibit distinct ion-transport sites. Specifically, both carbonyls in the structure of <b>iHOF-22</b> are ion-transport sites, whereas only one carbonyl in each of <b>iHOF-21</b> and <b>iHOF-23</b> is, and thus <b>iHOF-22</b> exhibits higher ionic conductivities. The ionic conductivities of Li⁺, Na⁺, and K⁺ of <b>iHOF-22</b> at 30 °C are 1.37 × 10^-4, 1.14 × 10^-4, and 9.76 × 10^-5 S cm^-1, respectively, which are 16-47% higher than those of <b>iHOF-21</b> and <b>iHOF-23</b>. The design of the iHOFs for multidimensional ion transport provides valuable insights for the development of solid-state electrolytes for various ion batteries.