Photoexcited Single-Electron Transfer for Efficient Green Synthesis of Cyclic Carbonate from CO₂

It is attractive but challenging to produce high-value-added cyclic carbonates at ambient condition by the 100% atom-economic photocatalytic cycloaddition of CO 2, which is limited by the insufficient understanding of the catalytic mechanism. Here, by taking Mg-MOF-74 as a model system, we propose the photoexcited catalyst can generally activate CO 2 via single-electron-transfer mechanism, leading to the rapid formation of • CO 2 – radical. Subsequently, beneficial for the activation of inert CO 2, the energy barrier of the rate-determining step (RDS) of the whole cycloaddition, i.e., the CO 2 attacking step, significantly decreases, resulting in the feasible synthesis of cyclic carbonates under ambient condition. With the combination of synchrotron radiation in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), in situ electron spin resonance (ESR) spectroscopy, and the density functional theory calculation, the reaction process and corresponding key intermediates are systematically investigated, revealing the CO 2 activation to be the most energy consumption steps in cyclic carbonate production, rather than the ring-opening of epoxide, thus furnishing new insights into photocatalytic CO 2 cycloaddition.