Synergistic catalysis of metalloporphyrins and phosphonium ionic liquids for the efficient transformation of CO2 under ambient conditions

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Synergistic effect between different functional groups is of significant influence on the activity of catalysts, especially for bi- or multi-component catalysts. Herein, a binary catalyst composing of metalloporphyrin (MPP) and phosphonium ionic liquid (PIL) is developed. The influence of substitution groups in both MPP and PIL on the cycloaddition addition of carbon dioxide and epoxides was comprehensively studied. The results demonstrated that the introduction of both electron-donating and electron-withdrawing functional groups in 5,10,15,20-tetraphenylporphyrin (TPP) framework was unfavorable to CO2 transformation. Moreover, PIL cocatalyst with longer alkyl group could enhance the catalytic activity obviously. When Co3+ was used as the metal active center, the binary catalyst system (TPP/Ph3PHexBr) could endow cyclic carbonate with a quantitative yield under the ambient condition of 50 °C and 1 atm CO2 pressure. The turnover frequency (TOF) value could also be as high as 191.3 h–1. Our founding thus provides an insight into the design of binary catalysts for efficient transformation of CO2.