Metalated porous porphyrin polymers as efficient heterogeneous catalysts for cycloaddition of epoxides with CO2 under ambient conditions

We have successfully synthesized a porphyrin based porous organic polymer (POP-TPP) from free-radical polymerization of tetrastyrylporphyrin monomer under solvothermal conditions. Besides high surface area (1200 m2/g) and high thermal stability, the obtained polymer features open metal chelating sites, and thus the catalytic activities of metalloporphyrins can be reasonably adjusted by introducing various metal ions. After metalation with Co3+, Zn2+, and Mg2+, the Co/POP-TPP, Zn/POP-TPP, and Mg/POP-TPP as heterogeneous catalysts are very active for cycloaddition of epoxides with CO2 to cyclic carbonates at ambient conditions with n-Bu4NBr as a nucleophilic additive. Particularly, under the relatively low CO2 concentration (15% in volume), the activity of heterogeneous Co/POP-TPP catalyst is even higher than that of the corresponding homogeneous Co/TPP catalyst. More importantly, there is no activity loss even if the Co/POP-TPP is recycled for 18 times. The excellent catalytic activity and superior recyclability of the obtained catalysts indicate that the porphyrin based porous organic polymer is a promising candidate for construction of efficient heterogeneous catalysts in the future.