Aluminum Porphyrin-Based Ionic Porous Aromatic Frameworks Having High Surface Areas and Highly Dispersed Dual-Function Sites for Boosting the Catalytic Conversion of CO<sub>2</sub> into Cyclic Carbonates
Min Chen, Xiangying Liu, Yiying Yang, Wei Xu, Kechi Chen, Rongchang Luo
Abstract
Multifunctionalization of porous organic polymers toward synergistic CO 2 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 CO 2 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 m 2 ·g –1 ), abundant hierarchical micro–mesopores, and prominent CO 2 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 CO 2 cycloaddition to perform with diluted CO 2 (15% CO 2 in 85% N 2, 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.