“…Nevertheless, CO2 is an unreactive molecule and high energy barrier of the noncatalyzed cycloaddition associated with CO2 is necessary for the reaction to occur spontaneously [7,8]. So far, a plethora of catalytic systems for producing cyclic carbonates has been successfully developed in order to reduce the activation energy of the cycloaddition reaction, including metal oxides [9,10], alkali metal salts [11,12], metal-salen complexes [13,14], metal-organic framework (MOF) [15,16], microporous polymer [17], graphitic carbon nitride [18,19] and ionic liquids [20][21][22][23][24].…”