A New Aluminum Porphyrin-Based Porous Hyper-Cross-Linked Polymer Modified by Imidazolium Salts for Cooperative Conversion of CO2 into Cyclic Carbonates under Mild Conditions

Abstract

Metalloporphyrin-based porous organic polymers that behave as advanced biomimetic nanoreactors have drawn continuous attention for heterogeneous CO₂ cycloaddition conversion in the past decades. However, the use of homogeneous onium salts, usually acting as nucleophilic cocatalysts, may increase the cost of product purification and cause additional environmental problems. In this contribution, a new aluminum porphyrin-based porous hyper-cross-linked polymer modified by imidazolium salts (denoted as Im@Al-HCP) has been successfully constructed for the first time. The two-step process of hyper-cross-linking reaction combined with postsynthetic modification endows the catalyst with a large surface area (about 213 m²·g^–1), good CO₂ adsorption capacity (up to 1.45 mmol·g^–1), and highly dispersed cooperative active sites. Accordingly, bifunctional Im@Al-HCP exhibits an outstanding catalytic activity, good recyclability, and broad substrate generality without cocatalysts and solvents under mild conditions. In particular, a high turnover frequency (TOF) value of up to 5000 h^–1 can be acquired, which far exceeds that of most reported heterogeneous catalysts under identical conditions. In addition, the as-made heterogeneous catalyst can be recycled for at least six times without an obvious loss in catalytic activity. This work not only bring some inspirations for the construction of multifunctional catalysts but also provides great potential for industrial applications of CO₂ cycloadditions.