Nitrogen-rich covalent organic polymers and potassium iodide for efficient chemical fixation of CO into epoxides under mild conditions

Resource utilization of carbon dioxide (CO 2 ) to add value to the chemicals used in the preparation of cyclic carbonates has gained significant interest in sustainable chemistry and environmental preservation. Herein, new nitrogen-rich urea covalent organic polymers ( NUP-1 , NUP-2 , NUP-3 ) with multiple urea groups simultaneously acting as acidic nodes were designed and synthesized in a simple method. These synthesized NUPs were characterized using FT-IR spectroscopy, 13 C CP MAS NMR, SEM, PXRD, TGA, XPS spectroscopy, CO 2 adsorption and nitrogen adsorption-desorption. The novel NUP-3 catalyst was particularly effective in the cycloaddition reactions having obtained a 93% yield of cyclic carbonate after 24 h at 90 °C with 0.1 MPa of pressure, using 1.0 mol% of KI and 70 mg of NUP-3 . The results showed that the functionalized NUP-3 used as a catalyst for the cycloaddition reaction of CO 2 and epoxide with an alkali-metal salt, exhibited good activity under mild conditions. In addition, a mechanistic insight into the effects of urea groups on the activation of both epoxide and CO 2 was gained using DFT calculations. The synergistic interaction of KI and NUPs plays an important role in the fixation reaction of CO 2 and epoxides.