ACS Catalysis 最新文献

Intermetallic compounds serve as model catalysts for selective hydrogenation reactions, offering precise control over the active site composition(s), geometric and electronic structure. The addition of a third element to form a ternary intermetallic alters the exposed crystal facet(s), demonstrating a strategy to impart improved catalytic behavior in intermetallic catalysts. The site-specific substitution of a small fraction of Pd atoms with Au in pyrite-type PdSb₂ results in the preferential exposure of the (100) facet over the (111) facet. Electron back scattered diffraction and density functional theory calculations confirm the facet change upon the substitution of Pd with Au to form the ternary Pd_1–xAu_xSb₂ (0.075 ≤ x ≤ 0.25). The (100) facet demonstrates higher net alkene selectivity due to significantly weaker alkene binding compared to the (111) facet. Distinct from our prior work on chemical substitution to directly alter the active site composition, this work demonstrates the indirect modification of active sites via preferential facet exposure.

This work investigates Ru-CeO₂–TiO₂ catalysts for the CO₂ methanation reaction and compares their performance with that of previously studied Ru-CeO₂ systems. Despite the lower Ru loading, the TiO₂-containing catalysts exhibit a significantly higher activity. To understand this behavior, in situ X-ray absorption spectroscopy (XAS) was carried out at the Ru K-edge and Ce L₃-edge. Unlike Ru-CeO₂, which displays the reversible redox behavior of Ru, the Ru-CeO₂–TiO₂ catalysts show irreversible Ru reduction and a substantially higher fraction of Ce³⁺ species under all tested conditions (H₂, CO₂, H₂/CO₂). The stabilization of metallic Ru during methanation, together with the enhanced formation of Ce³⁺ promoted by TiO₂ through interfacial electronic transfer, accounts for the catalyst’s high activity. Complementary in situ DRIFTS measurements reveal the formation and rapid consumption of bidentate carbonates and formates. These species act as a key intermediate in methane formation. Overall, these findings highlight the crucial role of the mixed CeO₂–TiO₂ oxide in tuning the surface chemistry of the catalysts by stabilizing metallic Ru, enhancing ceria reducibility, and promoting efficient reaction pathways for CO₂ methanation. The manipulation of metal ↔ oxide–oxide interactions can be a very useful tool when dealing with the valorization of CO₂.

Copper catalysis offers an attractive earth-abundant alternative to noble-metal-based carbonylation, yet its application to aryl electrophiles remains severely limited due to the low redox flexibility of Cu(I) and the inhibiting effect of CO coordination. Here we report a photocatalyst-free strategy that overcomes these intrinsic limitations by exploiting in situ generated NHC-stabilized aryl-Cu(I) complexes as bifunctional catalytic species capable of both light absorption and aryl-group transfer. This platform enables the development of copper-catalyzed carbonylation of arylboronic esters using aryl thianthrenium salts as electrophilic coupling partners. The method exhibits a broad substrate scope and high functional-group compatibility, accommodating diverse electron-rich and electron-deficient aromatics as well as structurally complex late-stage scaffolds. This work introduces a generalizable design principle for activating aryl electrophiles under copper catalysis and establishes a dual-functional reactivity mode for Cu(I) species in carbonylation chemistry.