Basic-functionalized Ionic Porous Organic Polymers: Triple Roles in One for Highly Efficient and Recyclable Carboxylative Cyclization of CO2 under Mild Conditions.

The transformation of carbon dioxide (CO2) into high-value chemicals is a significant step towards achieving the goal of "carbon neutrality". α-methylene cyclic carbonate, as an intermediate for the synthesis of many important organic compounds, is widely employed in industrial productions. In this work, a series of ionic porous organic polymers (IPOPs) with different basic-functionalized anions were successfully synthesized and adjusted to have certain BET surface areas and high contents of ion sites by post-modification. These basic-functionalized IPOPs could exhibit excellent catalytic performance for carboxylative cyclization of CO2 at 30 oC and 1 bar in presence of silver salts, eliminating the use of extra organic bases. In the whole catalytic reaction, the basic-functionalized anions could play triple roles: enriching CO2 for further transformation, activating the hydroxyl groups of substrates to improve the catalytic performance, while coordinating with Ag atom to stabilize and regenerate catalyst. Notably, the catalytic system of DCX-4-Tet/Ag2O exhibited excellent recyclability, and the yield of α-alkylidene cyclic carbonate was well maintained at 99% after 5 cycles. To the best of our knowledge, the catalytic system was the first example of basic-functionalized IPOPs that played multiple roles for highly efficient CO2 cyclization under mild conditions without any extra organic bases.