LAUSR

We report a QM/MM computational study of the cycloaddition between carbon dioxide (CO2) and styrene oxide in two different metal–organic frameworks (MOFs), Co-MOF-74 and Mg-MOF-74, to obtain atomic-level insights into the catalytic mechanism. The results suggest that both reactions begin by forming Lewis acid–base pairs between the epoxide and an open metal site and between CO2 and a phenolate moiety in the linker. Consequently, higher electrophilic and nucleophilic reactivities are conferred on the epoxide and CO2 (CO2(A)), respectively, thereby facilitating the initial ring-opening of the epoxide moiety. The ring-opening process is followed by the adsorption of a second CO2 molecule (CO2(B)), which is necessary for the subsequent ring closure to occur. In the case of Co-MOF-74, the binding of CO2(B) to the alkoxide oxygen increases the flexibility of the substrate moiety, enabling the cyclization pathway in which CO2(A) is incorporated into the final product. In contrast, the carbonate intermediate in t...