Double-Walled Covalent Organic Frameworks with High Stability.

Double-walled covalent organic frameworks, consisting of two same building blocks parallel to each other forming ladder-shape linkers, could enhance the stability of the frameworks and increase the density of functional sites, thus making them suitable for various applications. In this study, two double-walled covalent organic frameworks, namely DW-COF-1 and DW-COF-2, were successfully synthesized via imine condensation. The resulting DW-COFs exhibited a honeycomb topology, high crystallinity and stability. Particularly, DW-COF-2 showed excellent resistance toward boiling water, strong acid, and strong base, due to its double-wall structure, which limits the exposure of labile imine bonds to external chemical environments. The DW-COFs showed high porosity near 900 m2/g, making them suitable for gas storage/separation. The selective gas adsorption experiments showed that at 273 K and 1 atm pressure, DW-COF-1 and DW-COF-2 exhibited a good IAST selectivity towards CO2/N2 (15/85) adsorption, with selectivity values of 121.3 and 56.4 for CO2 over N2, respectively.