The structure determination of metal nanoclusters protected by ligands is critical in understanding their physical and chemical properties, yet it remains elusive how the metal core and ligand of metal clusters cooperatively contribute to the observed performances. Here, with the successful synthesis of Au₄₄TBPA₂₂Cl₂ cluster (TBPA = 4-tert-butylphenylacetylene), the structural isomer of previously reported Au₄₄L₂₈ clusters (L denoted as ligand) is filled, thereby providing an opportunity to explore the property evolution rules imparted by different metal core structures or different surface ligands. Time-resolved transient absorption spectroscopy reveals that the difference in the core structure between Au₄₄TBPA₂₂Cl₂ and Au₄₄L₂₈ can bring nearly 360 times variation of excited-state lifetime, while only 3–24 times differences in excited-state lifetimes of the three Au₄₄L₂₈ nanoclusters with identical metal core but different ligands are observed, which is due to much stronger impact of the metal core than the surface ligands in the electronic energy bands of the clusters. In addition, the Au₄₄ clusters protected by alkyne ligands are shown to be highly effective toward the electrochemical oxidation of ethanol, compared to the Au₄₄ clusters capped by thiolates, which is ascribed to smaller charge transfer impedance of the former clusters. We anticipate that the study will enhance the process in controlling the nanomaterial properties by precisely tailoring metal core or surface patterns.

Precise mono-doping of metal atom into metal particles at a specific particle position (e.g., the central site) in a highly controllable manner is still a challenge. In this work, we develop a highly controllable strategy for exchanging a single Ag atom into the central gold site of Au₁₃Ag₁₂(PPh₃)₁₀Cl₈ (Ph = phenyl) nanoclusters. Interestingly, a “pigeon-pair” cluster of {[Au₁₃Ag₁₂(PPh₃)₁₀Cl₈]·[Au₁₂Ag₁₃(PPh₃)₁₀Cl₈]}²⁺ is obtained and confirmed by electrospray ionization mass spectrometry (ESI-MS), thermogravimetric analysis (TGA) and single crystal X-ray diffraction (SCXRD) analysis. The experimental results and density functional theory (DFT) calculations suggest that the single-metal-atom exchanging from [Au₁₃Ag₁₂(PPh₃)₁₀Cl₈]⁺ to [Au₁₂Ag₁₃(PPh₃)₁₀Cl₈]⁺ occurs at the central position through the side entry of the μ₃-bridging Cl atoms. Finally, the effects on the electronic structure and properties caused by the single-atom exchange at the central site are shown by the enhancement of fluorescence and catalytic activity in the photocatalytic oxidation of ethanol.

We evaluated bismuth doped cerium oxide catalysts for the continuous synthesis of dimethyl carbonate (DMC) from methanol and carbon dioxide in the absence of a dehydrating agent. Bi_xCe_1-xO_δ nanocomposites of various compositions (x = 0.06-0.24) were coated on a ceramic honeycomb and their structural and catalytic properties were examined. The incorporation of Bi species into the CeO₂ lattice facilitated controlling of the surface population of oxygen vacancies, which is shown to play a crucial role in the mechanism of this reaction and is an important parameter for the design of ceria-based catalysts. The DMC production rate of the Bi_xCe_1-xO_δ catalysts was found to be strongly enhanced with increasing O_V concentration. The concentration of oxygen vacancies exhibited a maximum for Bi_0.12Ce_0.88O_δ, which afforded the highest DMC production rate. Long-term tests showed stable activity and selectivity of this catalyst over 45 h on-stream at 140 ℃ and a gas-hourly space velocity of 2,880 mL·g_cat^-1·h^-1. In-situ modulation excitation diffuse reflection Fourier transform infrared spectroscopy and first-principle calculations indicate that the DMC synthesis occurs through reaction of a bidentate carbonate intermediate with the activated methoxy (-OCH₃) species. The activation of CO₂ to form the bidentate carbonate intermediate on the oxygen vacancy sites is identified as highest energy barrier in the reaction pathway and thus is likely the rate-determining step.