Covalent Organic Framework with Frustrated Bonding Network for Enhanced Carbon Dioxide Storage

Two-dimensional covalent organic framework (COF) materials can serve as excellent candidates for gas storage due to their high density of periodically arranged pores and channels, which can be tethered with functional groups. However, post-functionalization tends to disturb the structure of the COF; thus, it is attractive to develop synthetic approaches that generate built-in functionalities. Herein, we develop a new strategy for the construction of 2D-COFs with built-in, unreacted periodic bonding networks by solvent-directed divergent synthesis. Tetraphenylethane (TPE), which combines both π-rigidity for stacking and rotational flexibility, is selected as the central core for COF construction. By solvent control, two distinct COF structures could be constructed, arising from a [4 + 4] condensation pathway (TPE-COF-I) or an unusual [2 + 4] pathway (TPE-COF-II). TPE-COF-II contains unreacted linker units arranged around its pores and shows greatly enhanced carbon dioxide adsorption performance (23.2 wt %, 118.8 cm3 g–1 at 1 atm, 273 K), which is among the best COF materials for CO2 adsorption reported to date.