Multifunctionalization of porous organic polymers toward synergistic CO2 catalysis has drawn much attention in recent decades, but it still faces many challenges. Herein, we develop a facile, simple, and efficient strategy to obtain a series of aluminum porphyrin-based ionic porous aromatic frameworks (iPAFs), which are considered excellent bifunctional catalysts for converting CO2 into cyclic carbonates without any cocatalyst under mild and solvent-free conditions. By increasing the amounts of tetraphenylmethane fragments in the porphyrin backbones, the cooperative effect between Lewis acidic metal centers and nucleophilic ionic sites has been enhanced and then the significant improvement of catalytic activity can be achieved owing to the high surface areas (up to 719 m2·g-1), abundant hierarchical micro-mesopores, and prominent CO2 adsorption capacities (up to 1.8 mmol·g-1 at 273 K) as well as highly dispersed dual-function sites. More fascinatingly, high-active AlPor-iPAF-3 enables CO2 cycloaddition to perform with diluted CO2 (15% CO2 in 85% N2, v/v) or under ambient conditions. Therefore, this postsynthetic modification procedure in combination with the framework dilution strategy provides a new approach to fabricating high-surface-area metalloporphyrin-based porous ionic polymers (PIPs) with hierarchical structures, which is conducive to improving the accessibility of multiple active sites around substrates.
Keywords: CO2 cycloaddition; cyclic carbonates; ionic porous aromatic frameworks; metalloporphyrin; postsynthetic modification.