Construction of a Metal-Silica Interface for Semihydrogenation of Alkynes.

Fabricating optimum surface structures represents an attractive approach for synthesizing supported catalysts with high activity and specific selectivity. New active sites could be flexibly constructed via the strong metal-support interaction under the redox condition. Herein, we demonstrated the formation of a new Rh-Si surface on a silica-modified carbon nanotube supported Rh catalyst under the high-temperature reduction condition as well as a thin amorphous silica coating layer and weak chemisorption toward the CO molecule. The electronic interactions between Rh and Si, along with the particular structure, guarantee desirable catalytic performance for the semihydrogenation of phenylacetylene under mild conditions. This facile approach might be extensively used in constructing new active sites with robust activity and specific selectivity in diverse heterogeneous catalysis systems.

The ligand effect of atomically precise gold nanoclusters in tailoring catalytic properties.

It is well known that surface ligands are vital layers for ligand-protected Aun nanoclusters. Improving the knowledge of the relationship between ligands and catalytic properties is a forefront research topic for Aun nanoclusters. Enormous effort has been devoted to realizing the ligand effect in synthesis, including well-controlled sizes and shapes as well as structural transformation. However, the crucial function of surface ligands has not been addressed yet in catalytic reactions. Here, this review mainly aims to summarize the recent progress concerning the influence of surface ligand layers on catalytic activity and selectivity, based on the various types of ligand protected Aun nanoclusters. Besides, the potential challenges and opportunities of Aun nanoclusters are indicated, mainly in terms of surface ligands to guide the improvement of catalytic performances.

Distinct chemical fixation of CO2 enabled by exotic gold nanoclusters.

Atomically precise metal nanoclusters, especially the metal nanoclusters with an exotic core structure, have given rise to a great deal of interest in catalysis, attributing to their well-defined structures at the atomic level and consequently unique electronic properties. Herein, the catalytic performances of three gold nanoclusters, such as Au38S2(S-Adm)20 with a body-centered cubic (bcc) kernel structure, Au30(S-Adm)18 with a hexagonal close-packed (hcp) core structure, and Au21(S-Adm)15 with a face-centered cubic (fcc) kernel structure, were attempted for the CO2 cycloaddition with epoxides toward cyclic carbonates. Due to the excess positive charge with a strong Lewis acidity and large chemical adsorption capacity, the bcc-Au38S2(S-Adm)20 nanocluster outperformed the hcp-Au30(S-Adm)18 and fcc-Au21(S-Adm)15 nanoclusters. Additionally, the synergistic effect between the gold nanocluster and co-catalyst played a crucial role in CO2 cycloaddition.

Distinct structure assembly driven by metal-ligand binding in Au23 nanoclusters and its relation to photocatalysis.

Here, we introduce two Au23 nanoclusters to unveil the significance of metal-ligand binding-induced assembly. The Au23 cluster protected by the thiolate ligand is packed in the shell-by-shell arrangement, while the Au23 cluster capped by dual ligands of thiolate and PPh3 is constructed from the assembly of Au4 tetrahedra. Furthermore Au23 from Au4 tetrahedron-based assembly is capable of converting absorbed visible light into more excitons, compared to Au23 from shell-by-shell assembly, thus exhibiting more efficient photocatalysis.

The precise editing of surface sites on a molecular-like gold catalyst for modulating regioselectivity.

It is extremely difficult to precisely edit a surface site on a typical nanoparticle catalyst without changing other parts of the catalyst. This precludes a full understanding of which site primarily determines the catalytic properties. Here, we couple experimental data collection with theoretical analysis to correlate rich structural information relating to atomically precise gold clusters with the catalytic performance for the click reaction of phenylacetylene and benzyl azide. We also identify a specific surface site that is capable of achieving high regioselectivity. We further conduct site-specific editing on a thiolate-protected gold cluster by peeling off two monomeric RS-Au-SR motifs and replacing them with two Ph2P-CH2-PPh2 staples. We demonstrate that the surface Au-Ph2P-CH2-PPh2-Au motifs enable extraordinary regioselectivity for the click reaction of alkyne and azide. The editing strategy for the surface motifs allows us to exploit previously inaccessible individual active sites and elucidate which site can explicitly govern the reaction outcome.