Glass wool supported ruthenium complexes: versatile, recyclable heterogeneous photoredox catalysts

The present study describes the development of heterogeneous photoredox catalysts based on ruthenium complexes anchored onto a glass surface (glass wool). These easy-to-handle, inexpensive and reusable fiber-like materials allow Ru-based photoredox catalysis in the heterogeneous phase. Here we report the synthesis and characterization of these new materials, and evaluate their remarkable photocatalytic activity to engage in aerobic photooxidative reactions. In particular, the oxidative hydroxylation of arylboronic acids and the singlet oxygen-mediated photooxidation of 9,10-dimethylanthracene (DMA) and 2-ethylfuran are achieved with excellent yields (>95%) within 6 h of irradiation using blue LEDs (lambda similar to 450 nm). Further, the materials can be reused at least 6 times without any significant loss of activity, thus revealing their high stability and recyclability. The strategy takes advantage of the broad knowledge on Ru-based photocatalysis while adding the recovery and reuse benefits of heterogeneous catalysis. Additionally, these materials are promising alternatives for flow photochemistry. This approach that allows attachment of Ru complexes onto glass wool can be extended for use to other transition-metal complexes as photoredox catalysts.