Ce Decoration-Enhanced Singlet Oxygen Generation of Titanium-Oxide Clusters for Photocatalytic Oxidation of Aromatic Alcohols.

In photocatalysis, the nature of reactive oxygen species plays a pivotal role in determining product selectivity. Yet, selective generation of singlet oxygen (1O2) is particularly desirable for achieving targeted photooxidations. Herein, two new nanosized titanium-oxide clusters (TOCs) doped with Ce, Ti14Ce2 and Ti4Ce2, were synthesized and explored in the selective photocatalytic oxidation of benzyl alcohols to benzaldehydes under mild conditions. Interestingly, the titanium-oxide core of Ti14Ce2 is recognized as a fragment of anatase TiO2, positioning Ti14Ce2 as a molecular model for Ce-doped TiO2 nanoparticles. Ce-doping effectively reduces the bandgap energy of the clusters, enabling visible-light absorption and enhancing their photocatalytic properties. Moreover, it promotes efficient energy transfer to O2 for 1O2 generation by increasing spin-orbit coupling. Both clusters exhibited high activity and selectivity in the oxidation of benzyl alcohols to benzaldehydes under visible-light irradiation. Our findings not only expand the TOC family with novel Ce-doped members but also offer insights into designing photocatalysts at the atomic level to enhance 1O2 generation for selective photo-oxidations.