Synergic Effect of Isolated Ce 3+ and Pt δ+ Species in UiO-66(Ce) for Heterogeneous Catalysis.

In this work, we have synthesized through an efficient electrostatic deposition a Pt single-atom catalyst (SAC) supported on a Ce-MOF. The basic solution employed in the impregnation process favors the deprotonation of the hydroxyl groups allocated on the clusters that can easily interact with the cationic Pt species. The resulting material, denoted as Pt/UiO-66(Ce), shows an increment of Ce content, as demonstrated by UV-vis and Ce L-edge XANES spectroscopy. These Ce species and their corresponding oxygen vacancies are able to accommodate very disperse Pt single sites. Moreover, Pt L-edge XANES and CO-FTIR spectroscopy confirm the cationic nature of the supported Pt (2+ < δ < 4+). For comparison purpose, we have synthesized and characterized a well-known Pt single-site catalyst supported on nanocrystalline ceria, denoted as Pt/CeO. Since the simultaneous presence of Ce and Pt on the MOF clusters were able to activate the oxygen molecules and the CO molecule, respectively, we tested Pt/UiO-66(Ce) for the CO oxidation reaction. Interestingly, this catalyst showed ∼six-fold increment in activity in comparison with the traditional Pt/CeO material. Finally, the characterization after catalysis reveals that the Pt nature is preserved and that the activity is maintained during 14 h at 100 °C without any evidence of deactivation.