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.