More than Catalyst Recycling: Tuning Synthetic Photocatalytic Processes via Heterogenization on Silica and Alumina

The heterogenization of homogeneous photocatalysts on inert supports such as silica and alumina offers more than improved recyclability. Unlike semiconducting supports such as titanium dioxide, which can alter the photocatalyst behavior through electron injection, insulating oxides preserve the intrinsic photophysical and redox properties of the molecular species. However, such heterogenization is an opportunity to completely modify the physicochemical properties of the surrounding environment, thereby influencing excited-state properties and enhancing reactivity and stability as well as compatibility with green solvents and flow systems. In addition, advanced support design introduces further potential for selectivity or reactivity with gas, although these remain largely underexplored. While silica is widely used due to its tunability and surface area, alumina offers complementary properties but remains less developed. This review highlights the early stage, yet rapidly evolving landscape of heterogenized photocatalysts on silica and alumina, emphasizing the emerging functionalities that extend well beyond catalyst recovery.