While
magnetic supports have been widely used to immobilize homogeneous
catalysts in organic chemistry, this strategy has so far found very
little application in photocatalysis. Indeed, magnetic supports are
dark colored, and thus compete for photon absorption with photocatalysts
themselves. We have developed a series of core–shell Fe(0)-silica
nanoparticles as supports for immobilizing the photosensitizer Ru(bpy)3
2+, featuring various silica shell thicknesses16–34
nm SiO2on 9 nm Fe cores. The supports and the resulting
photocatalytic systems were studied for their magnetic, optical, and
catalytic properties in the context of the photooxidation of citronellol,
and we found that thicker silica shells lead to higher catalytic activity.
We correlated this effect as well as Ru(bpy)3
2+ fluorescence and singlet oxygen generation to the absorption properties
of the supports. We were able to reuse our optimal system three times
with minimal loss of activity and achieved turnover numbers largely
surpassing the performance of homogeneous Ru(bpy)3
2+. This work highlights the role of material design in the
conception of new supports for applications in heterogeneous photocatalysis.
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