High-efficiency photo-oxidation of thioethers over C60@PCN-222 under air

Abstract

The selective oxidation of primary thioethers to sulfoxides is an important reaction in the production of pharmaceuticals, agrochemicals, and other valuable fine chemicals. However, the achievement of high conversion and selectivity towards sulfoxide during thioether oxidation under mild conditions still remains a great challenge. In this study, we found a new method to overcome the abovementioned challenge by applying the C₆₀@PCN-222 composite as a catalyst in the photo-oxidation of thioethers. The C₆₀@PCN-222 composite was obtained by the integration of guest C₆₀ molecules and a porous porphyrin-based metal–organic framework (MOF), PCN-222; we proposed that the photogenerated electron–hole separation of PCN-222 could be significantly enhanced through the encapsulation of C₆₀ molecules with a large, highly delocalized π-conjugation, which provided a great contribution to the high conversion and selectivity of this type of reaction. Under air and low optical power (50 mW cm⁻²) conditions at room temperature, the composite exhibited excellent catalytic performance; we further explored the underlying mechanism of action of this photocatalyst by investigating the reactive oxygen species via ESR spectral analysis and adjusting the experimental conditions. It has been revealed that superoxide radicals, generated by electron transfer from a photoexcited MOF to the C₆₀ molecules, serve as the main active species for the oxidation.