A₂B₂-Type Zinc(II) Porphyrin-Modified Organic Polymers with Flexible Linkers for Efficient Fixation of CO₂ to Cyclic Carbonate

Two A2B2-type zinc(II) porphyrin-modified organic polymers Poly(ZnEtPpI2/BDDA) and Poly(ZnMePpI2/BDDA) were synthesized by the free-radical copolymerization of flexible 1,4-butanediol diacrylate (BDDA) with novel A2B2-type zinc(II) porphyrins ZnEtPpI2 and ZnMePpI2, respectively. The characterizations of both were carried out successfully. The two organic polymers had abundant dual-function sites (Zn2+ and I–) and excellent adsorption capacity for solvent, showing high catalytic activity for the CO2 fixation to cyclic carbonate under the conditions of 120 °C and 1.0 MPa CO2. Specifically, Poly(ZnEtPpI2/BDDA) displayed the highest catalytic activity with a TOF of 1480 h–1 for the cycloaddition of CO2 and epichlorohydrin (ECH) and wide applicability for different epoxides. Moreover, the Poly(ZnEtPpI2/BDDA) showed excellent stability and could be recycled at least 7 times. Finally, the kinetic experiments confirmed that Poly(ZnEtPpI2/BDDA) was a promising catalyst with a relatively low activation energy (35.3 kJ/mol) for the fixation of CO2 to cyclic carbonate.