Solvent Free Ambient Pressure CO2 Cycloaddition Catalyzed by Cobalt-Impregnated 2D-Nanofibrous COFs

Covalent organic frameworks (COFs) constitute an evolving class of permanently porous and ordered materials, and they have recently attracted increased interest due to their intriguing morphological features and numerous applications in gas storage, adsorption, and catalysis. However, their low aqueous stabilities and tedious syntheses generally hamper their use in heterogeneous catalysis. Nonetheless, a capable and water-stable heterogeneous catalytic system for coupling CO2/epoxides to generate industrially important cyclic carbonates is still of great interest. Herein, exceedingly water- and thermally stable 2D-cobalt-impregnated hydrazone-linked fibrous COFs are reported as a catalyst for CO2/epoxide coupling reactions at ambient pressure. The functionalized cobalt (Co)-doped COFs demonstrated excellent catalytic activities with the high TONs (80925) and TOFs (6466 h-1), outperforming reported heterogeneous catalysts for CO2/epoxide coupling at ambient pressure. We found that the Co2+ ions within the COF matrix catalyze CO2 cycloaddition through density functional theory calculations. We also confirmed the excellent structural stability and consistent activity of Co-doped COFs up to ten repeating cycles.