Heterogeneous Photoredox Catalysis in Water Using Photocatalyst-Functionalized Glass Particles

Heterogeneous photocatalysis is a viable alternative method for sustainable chemistry regarding the synthesis of molecules and polymers. The nature of homogeneous photocatalysts in solution often leads to contamination of products, a constant need to replace catalysts, and higher waste production. The transition to a heterogeneous platform becomes more appealing as it overcomes the limitations encountered when using catalysts in solution, thus becoming more effective in polymer synthesis. Our heterogeneous technique of photocatalytic polymer brushes functionalized on micron-scale silicon dioxide (SiO2) glass beads is covalently attached to the surface which in turn allows easy separation, cleaning, and reusability of these photocatalysts for several consecutive reactions. However, while attempting to convert the system to more biocompatible conditions, the polymer brush functionalized glass beads were demonstrated to be ineffective in aqueous environments. Possible reasons for the reduced efficiency could be hydrolysis causing the photoactive polymer brushes to degraft. This presentation illustrates the different approaches to address this problem through the addition of a diblock copolymerization as well as the changing of the silane group for the functionalization of the glass surface. Implementation of a diblock copolymerization within the polymer brushes proved to positively affect the efficiency of the heterogeneous photocatalyst in an aqueous environment and improved recyclability due to reduced hydrolysis. As a result, this allows polymer brushes a new, versatile approach toward heterogeneous photocatalysts in water while also providing a promising outlook toward more user-friendly and biocompatible chemistries using visible light.