Ionic liquids-based ionic metal-organic frameworks (MOFs): A single catalyst with dual active centers for the cycloaddition of carbon dioxide

Abstract

The conversion of CO₂ to cyclic carbonates is a promising approach for chemical fixation of CO₂ and the development of robust catalysts is still a big challenge. This work suggested ionic liquids (ILs)-based ionic metal-organic frameworks (MOFs) using a bisimidazole-based IL as organic link. The introduction of ILs made the ionic MOFs dual active center catalysts (ILs and metal ions). Experiments indicated that the catalytic activity of the ionic MOFs using indium ion (In^3 +) as metal center was superior to that of those with zinc ion (Zn²⁺) as metal node due to the stronger electrophilicity of In³⁺ than Zn²⁺, making In-based ionic MOFs more effectively activate the epoxide ring, which was verified by the results of theoretical calculations. Moreover, a high chloropropene carbonate yield (98.1 %) could be obtained without the addition of co-catalysts under the optimum conditions (0.1 MPa CO₂, 5.4 % catalyst, 80 °C for 7 h).