Synthesizing Interpenetrated Triazine‐based Covalent Organic Frameworks from CO<sub>2</sub>
Siquan Zhang, Loris Lombardo, Masahiko Tsujimoto, Zeyu Fan, Ellan K. Berdichevsky, Yong‐Sheng Wei, Kotoha Kageyama, Yusuke Nishiyama, Satoshi Horike
Abstract
Abstract Crystalline triazine‐based covalent organic frameworks (COFs) are aromatic nitrogen‐rich porous materials. COFs typically show high thermal/chemical stability, and are promising for energy applications, but often require harsh synthesis conditions and suffer from low crystallinity. In this work, we propose an environmentally friendly route for the synthesis of crystalline COFs from CO 2 molecules as a precursor. The mass ratio of CO 2 conversion into COFs formula unit reaches 46.3 %. The synthesis consists of two steps; preparation of 1,4‐piperazinedicarboxaldehyde from CO 2 and piperazine, and condensation of the dicarboxaldehyde and melamine to construct the framework. The CO 2 ‐derived COF has a 3‐fold interpenetrated structure of 2D layers determined by powder X‐ray diffraction, high‐resolution transmission electron microscopy, and select‐area electron diffraction. The structure shows a high Brunauer–Emmett–Teller surface area of 945 m 2 g −1 and high stability against strong acid (6 M HCl), base (6 M NaOH), and boiling water over 24 hours. Post‐modification of the framework with oxone has been demonstrated to modulate hydrophilicity, and it exhibits proton conductivity of 2.5×10 −2 S cm −1 at 85 °C, 95 % of relative humidity.