Crystalline Anionic Germanate Covalent Organic Framework for High CO₂ Selectivity and Fast Li Ion Conduction

The metalloid-centered covalent organic framework has attracted great interest from both its structure and application. Heavier elements have seldomly been incorporated in the covalent organic frameworks, even if they exhibit special structural features and properties. Herein, we reported the first crystalline germanate covalent organic framework with hexacoordinated germanate linked by an anthracene linker. The existence of counterion lithium ions in the framework provides a high CO₂ uptake of 88.5 cm³ g⁻¹ at 273 K and a high CO₂/N₂ selectivity of 101. A significantly improved lithium ion conductivity of 0.25 mS cm⁻¹ at room temperature was observed due to the soft germanium center.