Influence of divalent metal ions on CO2 valorization at room temperature by isostructural MOF-74 materials

Abstract

At present, the concentration of carbon dioxide (CO2) has increased to unprecedented levels. The valorization of CO2 into high value-added chemicals can be a very interesting alternative to stabilize the concentration of this atmospheric pollutant while the current energy transition takes place. The well-known M-MOF-74 family (M= Mg, Co, Ni, Cu and Zn) have been evaluated as heterogeneous catalysts to carry out several cycloaddition reactions at room temperature with several epoxides (epichlorohydrin; 1,2-epoxyhexane and styrene oxide) as substrate, to evaluate the influence of the metal in this reaction. Zn-MOF-74 showed the highest catalytic activity, always with conversion and selectivity values above 93% regardless of the epoxides studied and the carbonates obtained, due to the higher acid character of the Zn2+ ion. Therefore, it is confirmed that the influence of the metal is key in this reaction, despite the fact that Cu-MOF-74 with an adsorption capacity of 5 mmol/g of CO2 (45 ◦C, 5 bar) converts 26% of styrene oxide under the conditions evaluated compared to ZnMOF-74, which is the material with the lowest adsorption capacity (3 mmol/g of CO2) and shows a conversion of 93%.