Metal-assisted synthesis of salen-based porous organic polymer for highly efficient fixation of CO2 into cyclic carbonates

Abstract

There has been increasing interest in the utilization of CO₂ as an inexpensive and abundant C1 feedstock for producing high value-added commodity chemicals that would promote sustainable development as well as decrease atmospheric CO₂. Fixation of CO₂ into cyclic carbonates is an effective and economical utilization method that would alleviate the current excessive CO₂ emission situation. The development of catalysts with high catalytic efficiency and high recyclability is necessary but challenging. Herein, a series of metal–salen-functionalized porous organic polymers (M-salen-POP, M = Mn²⁺, Co²⁺, Ni²⁺) was synthesized through simple metal-assisted methods. Because of its porous nature and the presence of many active catalytic sites that are derived from Lewis acid metal ions in the framework, Co-salen-POP catalyzed the cycloaddition reaction of CO₂ and styrene oxide to obtain an exceptional 96% yield and 99% selectivity within 30 minutes under 100 °C and 1 MPa CO₂ atmosphere. After five cycles, its catalytic yield of styrene carbonate was maintained at 94% under the same conditions. Furthermore, other epoxides such as epichlorohydrin and phenyl glycidyl ether can be completely converted in 5 minutes at 100 °C and 1.0 MPa. The present work offers a facile, powerful, and effective strategy to construct highly efficient heterogeneous catalysts with abundant active sites for the fixation of carbon dioxide.