OperandoDB-FTIR and DFT results certificate that the isobutane aromatization could be exclusively catalyzed by (Zn–O–Zn)²⁺Lewis acid site over Zn/HZSM-5.

We report herein the preparation, characterization, and catalytic performance of a series of heterogeneous catalysts featuring highly dispersed zinc sites on zeolitic SSZ-13 and ZSM-5 frameworks. The materials are evaluated in the CO₂-assisted oxidative ethane dehydrogenation, a very important reaction for the synthesis of platform chemicals. In particular, we find that Zn_2.92/SSZ-13 exhibits high reactivity in the conversion of C₂H₆ and CO₂ and high ethene selectivity. In line with the experimental results, we show that the selective character of the catalyst is due to the characteristic compositional structure of the support and its topology that can effectively confine CO₂ molecules. An in-depth molecular analysis via operando studies and DFT calculations shows that the rate-limiting step of the reaction with CO₂ is the second C–H bond dissociation to give C₂H₄. The addition of CO₂ effectively reduces the energy barrier of this step, favoring desorption of C₂H₄ while limiting byproduct formation. Overall, this work demonstrates the breakthrough potential of catalysts made of highly dispersed zinc species on zeolites in relevant transformations.

Because of their peculiar nitrogen-rich structure, carbon nitrides are convenient polydentate ligands for designing single atom-dispersed photocatalysts. However, the relation between catalysts’ textural properties and their photophysical–photocatalytic properties is rarely elaborated. Herein, we report the preparation and characterization of a series of single-atom heterogeneous catalysts featuring highly dispersed Ag and Cu species on mesoporous graphitic C₃N₄. We show that adjustment of materials textural properties and therefore metal single-atom coordination mode enables ligand-to-metal charge transfer (LMCT) or ligand-to-metal-to-ligand charge transfer (LMLCT), properties that were long speculated in single-atom catalysis but never observed. We employ the developed materials in the degradation of organic pollutants under irradiation with visible light. Kinetic investigations under flow conditions show that single atoms of Ag and Cu decrease the number of toxic organic fragmentation products while leading to a higher selectivity toward full degradation. The results correlate with the selected mode of charge transfer in the designed photocatalysts and provide a new understanding of how the local environment of a single-atom catalyst affects the surface structure and reactivity. The concepts can be exploited further to rationally design and optimize other single-atom materials.

Single-atom site catalysts can improve the rates and selectivity of many catalytic reactions. We have modified Pt ₁ /CeO ₂ single sites by combining them with molecular groups and with oxygen vacancies of the support. The new sites include hydrided (Pt ²⁺ -Ce ³⁺ H ^δ− ) and hydroxylated (Pt ²⁺ -Ce ³⁺ OH) sites that exhibit higher reactivity and selectivity to previous single sites for several reactions, including a ninefold increase in the reaction rate for carbon monoxide oxidation and a 2.3-fold improvement of propylene selectivity for oxidative dehydrogenation of propane. The atomic structure and reaction steps of these sites were determined with in situ and ex situ spectroscopy techniques and theoretical methods.

A series of Zn-modified Silicalite-1 (S-1) zeolites (Zn_x/S-1) were prepared by the wetness-impregnation method and applied in the catalytic conversion of isobutane. The structure and location of Zn species in Zn_x/S-1 were investigated using UV-Vis and N₂ physical adsorption. The acidity and origin of the acid sites in Zn_x/S-1 were studied by NH₃-temperature programmed desorption and Fourier-transform infrared analysis. The catalytic performance of Zn_x/S-1 for isobutane conversion was investigated in a fixed-bed microreactor. In the experiments, the acidity of S-1 zeolite was dramatically increased by modification with Zn, with both Lewis and Brønsted sites identified in Zn_x/S-1. The relationship between Brønsted acid sites and Zn–OH groups on ZnO clusters of Zn_x/S-1 was also revealed for the first time. Furthermore, Zn_x/S-1 catalysts exhibited excellent catalytic performances in both isobutane dehydrogenation and butene isomerization reactions. A high selectivity of total butene products ranging from 84.6 to 97.2 was achieved on the catalysts with different Zn loadings. Moreover, the linear correlation between isobutane conversion and the acid amount (determined by NH₃-TPD) confirmed that the weak-to-medium acid sites in Zn_x/S-1 should play a key role in isobutane conversion.