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Polydispersed Ag species-modified TiO2 samples with abundant oxygen vacancies were successfully prepared through the calcination of atomically precise Ag33 nanocluster-loaded TiO2 at an optimal temperature under a nitrogen atmosphere. The ligands of the Ag33 nanoclusters are removed by extracting lattice oxygen from TiO2 during the calcination, leading to the formation of CO2, SO2, and H2O vapor. This process simultaneously induces Ag species sintering on the surface of TiO2. The resulting nanocomposites exhibited excellent catalytic activity for the reduction of nitroarenes with NaBH4 as the reductant. This is attributed to the produced Ag species on the oxygen-deficient TiO2, which act as active centers for the catalytic process. [ABSTRACT FROM AUTHOR]

Using ligand-protected metallic nanoclusters with atomic precision as catalysts and elucidating its ligand effect in the catalysis are the prerequisites to deepen the structure-catalysis relationship of nanoclusters at the molecular level. Herein, a series of Ag 33 nanoclusters protected with different thiolate ligands (2-phenylethanethiol, 4-chlorobenzyl mercaptan, and 4-methoxybenzyl mercaptan as precursors) were synthesized and used as heterogeneous catalysts for the conversion of nitroarenes to arylamine with NaBH 4 as reductant. The obtained nanoclusters exhibited ligand-dependent catalytic activity, with benzyl thiolate ligands distinctly superior to the phenethyl thiolate ligands. DFT calculations revealed that the ligand regulated catalytic activity of the nanoclusters was ascribed to the H-π and π-π interactions between the ligands and the substrates, owing to the presence of phenyl rings in these structures. This work highlighted the importance of the ligands on the metallic nanoclusters in catalysis and provides a strategy to regulate the catalytic activity by utilizing weak interactions between the catalysts and the substrates.