Construction of Hierarchical Porous Polycyanurate Networks with Cobaltoporphyrin for CO2 Adsorption and Efficient Conversion to Cyclic Di- and Tri-Carbonates

Abstract

A new porphyrin-based cyanate monomer 5,10,15,20-tetrakis(4-cyanatophenyl)-porphyrin (TCP) was synthesized, from which a porous polycyanurate network PCN–TCP was constructed by means of one-step thermal cyclotrimerization reaction. The substantial porphyrins in the PCN–TCP network enable the coordination with cobalt (Co) ions to create a cobaltoporphyrin-supported porous catalyst (Co@PCN-TCP) with a BET surface area of 689 m2 g–1 and ultramicropores (0.55 nm), micropores (1.15 nm), and mesopores (2.11–5.23 nm). At 273 K and 1.0 bar, Co@PCN-TCP uptakes 13.0 wt % CO2 with a high CO2/N2 selectivity (IAST, 79.1). Using Co@PCN-TCP as a heterogeneous catalyst, high conversions for cycloaddition reactions between CO2 and various epoxides are achieved. Particularly, silicon- and sulfite-containing cycloaliphatic di- and tri-epoxides with a large molecular volume and steric hindrance also readily react with CO2 to obtain the corresponding cyclic di- and tri-carbonates with satisfactory conversions of 91.6–92.1 and 89.4%, respectively. The resultant novel cyclic di- and tri-carbonates are potential raw materials for producing isocyanate-free polyurethanes. In addition, the reaction conversions are almost unchanged after repeatedly using Co@PCN-TCP, exhibiting excellent recovery and reusability.