Halogen-Substituted Zinc Porphyrin-Based Covalent Triazine Frameworks for Efficient Catalytic CO₂ Cycloaddition to...

The cycloaddition of carbon dioxide (CO₂) with aziridines represents a promising approach to produce high-value-added industrial products and offer potential for mitigating CO₂-related global warming issues. However, high temperature and/or high pressure are required for traditional thermally driven cycloaddition of CO₂ with aziridines by employing so-far reported catalysts, and more efficient catalysts need to be developed for mild procedures. Herein, we construct three zinc porphyrin-based covalent triazine frameworks (ZnDBP-CTFs), including ZnHDBP-CTF and halogen-substituted ZnDBP-CTFs (ZnClDBP-CTF and ZnBrDBP-CTF) at porphyrin meso positions, and investigate their catalytic activity in CO₂ cycloaddition to aziridines. Interestingly, different electron-withdrawing halogen atoms in the ZnDBP-CTFs skeleton not only tune the Lewis acidity of the coordinated zinc center but also vary the BET surface area of the materials. Encouragingly, under mild conditions (1 atm CO₂, 70°C), the ZnBrDBP-CTF with bromine atoms substituted at meso positions of porphyrin rings exhibits remarkable catalytic performance with the reaction rate reaching 16.35 mol mol^-1 h^-1, which is among the state-of-the-art cases for catalytic CO₂ cycloaddition to aziridines. This study demonstrates that ZnDBP-CTFs can be rationally tuned by incorporating various halogen atoms at the meso positions of the porphyrin units, thereby providing a robust strategy for modulating the catalytic activity of metalloporphyrin-based CTFs.