(100) surface-exposed CeO2 nanocubes as an efficient heterogeneous catalyst in the tandem oxidation of benzyl alcohol, para-chlorobenzyl alcohol and toluene to the corresponding aldehydes selectively

Abstract

A new synthesis strategy has been developed to synthesize exclusively (100)-surface-exposed CeO₂ nanocubes (∼90 nm), formed through three dimensional (3D) self-assembly of smaller ceria nanocrystal building blocks, as an efficient heterogeneous catalyst for multiple selective oxidation reactions. To compare the effect of morphology on catalysis, 1D CeO₂ nanorods have also been tested in parallel. The as-synthesized CeO₂ nanocubes acted as a breakthrough catalyst in the quantitative conversion of benzyl alcohol and para-chlorobenzyl alcohol with absolute selectivity to their respective aldehydes (>99%) under very mild reaction conditions in water at 35 °C. The same ceria nanocubes acted as an efficient catalyst in the oxidation of toluene to benzaldehyde selectively. The preferentially exposed (100) surfaces, the presence of a high concentration of oxygen vacancies (2.11 × 10²¹ cm⁻³), the small size of the nanoscale building blocks and the corresponding high surface area and porosity have been reasoned to produce the observed high catalytic activity parameter and turn over frequency (TOF). Further characterization of the recovered catalysts after five cycles confirmed the retention of the original morphology, crystal structure and, most importantly, catalytic properties with no significant activity loss, confirming the possibility of repeated use of the present CeO₂ nanocubes without compromising their intrinsic qualities.