(600cu) Zeolitic Imidazole Framework-8 Catalysts in the Conversion of CO2 to Chloropropene Carbonate

The catalytic conversion of CO₂ to cyclic carbonates and polycarbonates over conventional solid catalysts, including zeolites and mesoporous oxides, is well-known. However, the development of superior performance catalysts requires new materials with fundamentally different structural, compositional, adsorption and transport properties than those of conventional zeolites, metal oxides or metal phases. In this respect, zeolitic imidazolate frameworks (ZIFs), have emerged as novel crystalline microporous materials with highly desirable properties, such as uniform micropores, high surface areas, and open porous framework structures with large accessible pore volumes making them potentially interesting candidates for adsorption and catalytic applications. In particular, the catalytic activity of ZIF-8 and amine-functionalized ZIF-8 catalysts in the synthesis of chloropropene carbonate from CO₂ and epichlorohydrin is demonstrated. In contrast to hitherto known catalysts, ZIF-8 catalysts displayed high epoxide conversions, and moderate to high selectivities to chloropropene carbonate at reaction temperatures as low as 70°C. No co-catalysts or solvents were required during the reaction. The incorporation of ethylenediamine in ZIF-8  enhanced its catalytic performance due to the higher CO₂ adsorption capacity of the amine-functionalized samples. The ZIF-8 catalysts however, lost their distinctive crystalline structure and superior catalytic performance when attempts were made to recycle them after use.