One-step supramolecular construction of Lewis pair poly(ionic liquids) for atmospheric CO2 conversion to cyclic carbonates

Lewis pair catalyst is considered to be a cutting-edge tool for the low-energy activation and subsequent conversion of CO2, which, yet suffers from complex preparation and unclear design strategy. This work proposes a one-step strategy for precisely constructing Lewis pair heterogeneous catalysts through the coordination of amino-functionalized poly(ionic liquid) (PIL) and metal cations for atmospheric CO2 conversion to cyclic carbonates. Self-tunability in the strength and ratio of Lewis acidic/basic sites is imparted by the facile regulation of the type/content of metal ions (Zn2+/Co2+/Cu2+), which is crucial for promoting acid/base cooperation in CO2 cycloaddition. The synergy of M2+, Br- and C-2 proton on imidazolium ring with an optimum acid/base molar ratio of ca. 1.47 has been proved to activate CO2 and epoxides synchronously, inducing a promising catalytic activity with high yield (similar to 95 %) and selectivity (>99 %) of cyclic carbonates under atmospheric pressure and low temperature (<= 75 degrees C) without cocatalyst.

Automated summary

This study proposes a one-step strategy to construct Lewis pair heterogeneous catalysts for CO2 conversion through the coordination of amino-functionalized poly(ionic liquid) and metal cations. The strength and ratio of Lewis acidic/basic sites can be tuned by regulating the type/content of metal ions, enabling efficient acid/base cooperation in CO2 cycloaddition. The synergistic effect of M2+, Br-, and C-2 proton on the imidazolium ring activates both CO2 and epoxides, leading to high yields and selectivity of cyclic carbonates under atmospheric pressure and low temperature without cocatalyst.