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A computational investigation of the catalytic reaction on multinuclear sites is very challenging. Here, using an automated reaction route mapping method, the single-component artificial force induced reaction (SC-AFIR) algorithm, the catalytic reaction of NO and OH/OOH species over the Ag-4(2+) cluster in a zeolite is investigated. The results of the reaction route mapping for H-2 + O-2 reveal that OH and OOH species are formed over the Ag-4(2+) cluster via an activation barrier lower than that of OH formation from H2O dissociation. Then, reaction route mapping is performed to examine the reactivity of the OH and OOH species with NO molecules over the Ag-4(2+) cluster, resulting in the facile reaction path of HONO formation. With the aid of the automated reaction route mapping, the promotion effect of H-2 addition on the SCR reaction was computationally proposed (boosting the formation of OH and OOH species). In addition, the present study emphasizes that automated reaction route mapping is a powerful tool to elucidate the complicated reaction pathway on multi-nuclear clusters.

In this paper, we investigated the effects of the Ga loading amount and H-2 treatment temperature for the reductive solid-state ion-exchange reaction on the generated Ga species in Ga-exchanged MFI zeolites (Ga-MFIs) as well as their catalysis for ethane dehydrogenation (EDH). For the formation of isolated Ga hydrides in the zeolites, [GaH](2+) ions were preferentially formed in the low-loading Ga-MFI (Ga/Al = 0.3) treated with H-2 at 550 degrees C, corresponding to the conventional preparation conditions, (Ga-MFI-0.3(550)), while the high Ga loading (Ga/Al = 1.0) and high-temperature H-2 treatment (800 degrees C) (Ga-MFI-1.0(800)) induced the formation of [GaH2](+) ions as the major Ga hydrides, as revealed by in situ Fourier transform infrared spectroscopy including the isotope experiment using D-2. In the context of other Ga species, such as Ga+ cations and partially reduced Ga oxides (GaOX), Ga+ cations and GaOX coexist in Ga-MFI-0.3(550), as indicated by pyridine adsorption experiments. On the other hand, GaOX was hardly observed and a larger amount of Ga+ cations was formed in Ga-MFI-1.0(800). The remaining Bronsted acid sites (BASs) were also characterized by the NH3 adsorption experiment. In the EDH reaction, Ga-MFI-1.0(800) exhibited high selectivity owing to low coke formation, resulting in the highest durability among the series of Ga-MFIs tested. Under the optimized conditions, Ga-MFI-1.0(800) exhibited the highest C2H4 formation rate among previously reported Pt-free catalysts. Based on the combined results of characterization, catalyst tests, and kinetic studies, the high selectivity and durability of Ga-MFI-1.0(800) can be ascribed to the low amount of the remaining BASs by isolated Ga species ([GaH](2+), [GaH2](+) ions and Ga+ cations) as well as the major formation of [GaH2](+) ions among isolated Ga hydrides.

The catalytic combustion of methane (CH4) at a low temperature is becoming increasingly key to controlling unburned CH4 emissions from natural gas vehicles and power plants, although the low activity of benchmark platinum-group-metal (PGM) catalysts hinders its application. Based on the automated reaction route mapping, we designed the main-group catalyst for low-temperature CH4 combustion with ozone (O3). The computational screening of the active site predicted the strong Brønsted acid sites (BASs) as promising ones. We experimentally demonstrated that the catalyst comprising strong BASs exhibited improved CH4 conversion at 200 °C, correlating with the theoretically predicted design concept. The main-group catalyst (proton-type beta zeolite) delivered a reaction rate, which was 442 times higher than that of a benchmark catalyst (5wt% Pd-loaded Al2O3), at 190 °C and exhibited higher tolerance to steam and SO2. Our strategy demonstrated the rational design of earth-abundant catalysts based on automated reaction route mapping.

Propane dehydrogenation has been a promising propylene production process that can compensate for the increasing global demand for propylene. However, Pt-based catalysts with high stability at ≥600 °C have barely been reported because the catalysts typically result in short catalyst life owing to side reactions and coke formation. Herein, we report a new class of heterogeneous catalysts using high-entropy intermetallics (HEIs). Pt-Pt ensembles, which cause side reactions, are entirely diluted by the component inert metals in PtGe-type HEIs. The resultant HEI (PtCoCu) (GeGaSn)/Ca-SiO

The oxidation of NO to NO2 and the subsequent reduction by NH3 via a NO+ intermediate over a proton-type chabazite zeolite (H-CHA) were investigated by the combination of in situ infrared (IR) spec...

Atomic dispersion of metal species has attracted attention as a unique phenomenon that affects adsorption properties and catalytic activities and that can be used to design so-called single atom materials. In this work, we describe atomic dispersion of bulk Pd into small pores of CHA zeolites. Under 4% NO flow at 600 °C, bulk Pd metal on the outside of CHA zeolites effectively disperses, affording Pd2+ cations on Al sites with concomitant formation of N2O, as revealed by microscopic and spectroscopic characterizations combined with mass spectroscopy. In the present method, even commercially available submicrosized Pd black can be used as a Pd source, and importantly, 4.1 wt % of atomic Pd2+ cations, which is the highest loading amount reported so far, can be introduced into CHA zeolites. The structural evolution of bulk Pd metal is also investigated by in situ X-ray absorption spectroscopy (XAS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), as well as ab initio thermodynamic analysis using density functional theory (DFT) calculations.

Recently, Pd-exchanged CHA zeolites (Pd-CHA) have attracted attention as promising passive NOx adsorbers (PNAs) for reducing NOx emissions during the cold start period of a vehicle engine. In this work, the relationship between the local structures and the NO adsorption/desorption properties of the Pd cations in CHA zeolites was investigated. Pd cation formation and NO adsorption were theoretically explored by density functional theory (DFT) calculations for different paired Al sites in six-/eight-membered rings (6MR/8MR). Furthermore, we prepared a series of Pd-CHAs with different Pd loadings (0.5-5.4 wt%) and evaluated their NO adsorption/desorption properties by in situ infrared (IR) spectroscopy and temperature-programmed desorption (TPD) measurements. The increase in the Pd loading resulted in a shift in the NO desorption temperature toward a higher temperature regime. This phenomenon was ascribed to the increase in the proportion of less stable Pd cations, resulting in improved NO adsorption. Furthermore, the effect of Al distribution on the NO adsorption property of Pd-CHA was examined using CHA zeolites containing different proportions of paired Al sites in 6MR while maintaining similar Si/Al ratios (Si/Al = 12.0-16.5). The present study, based on a combination of theoretical and experimental techniques, shows that the NO adsorption/desorption properties over Pd-CHA can be tuned by controlling the Pd loading amount and the type of paired Al sites.

Keggin-type phosphomolybdic acid (PMo

Recently, Pd-exchanged CHA zeolites (Pd-CHA) have attracted attention as promising passive NOx adsorbers (PNAs) for reducing NOx emissions during the cold start period of a vehicle engine. In this work, the relationship between the local structures and the NO adsorption/desorption properties of the Pd cations in CHA zeolites was investigated. Pd cation formation and NO adsorption were theoretically explored by density functional theory (DFT) calculations for different paired Al sites in six-/eight-membered rings (6MR/8MR). Furthermore, we prepared a series of Pd-CHAs with different Pd loadings (0.5-5.4 wt%) and evaluated their NO adsorption/desorption properties by

We have carried out an experimental and theoretical study of CHA-zeolite supported indium (In)–oxo clusters that promote CH4 activation at room temperature. X-ray absorption fine structure (XAFS) measurements indicate the formation of multinuclear In–oxo clusters by the O2 activation of the In(I)-exchanged CHA zeolite prepared through reductive solid-state ion exchange (RSSIE). The structure of the In–oxo clusters and their locations were investigated in detail using ab initio thermodynamic analysis. The redox properties of the In species during RSSIE and the formation of the In–oxo clusters were also studied by temperature programmed reaction and in situ XAFS measurements. The reaction of CH4 on the O2-activated In-CHA zeolite was monitored using IR spectroscopy where adsorbed formic acid was generated at room temperature. The adsorption and C–H activation of CH4 on our plausible model of the In–oxo clusters were theoretically investigated using density functional theory calculations. We found that CH4 is likely to adsorb and react more easily on dinuclear In–oxo ions than on monomeric In–oxo ions and that the C–H bond cleavage reaction occurs via a heterolytic pathway rather than a homolytic pathway. This study reveals the potential of multinuclear In–oxo clusters as active sites for the transformation of CH4 to oxygenates under mild reaction conditions.

We investigated the hydration of hydrophobic epoxides and alkynes in water using 24 types of heterogeneous and homogeneous catalysts and found that Hbeta (Hβ) zeolite with a relatively high Si/Al ratio (Si/Al = 75), Hβ-75, is an effective catalyst. Hβ-75 showed wide substrate scope, good reusability, and applicability in gram-scale synthesis for both types of reactions. The effects of hydrophobicity, acidity, and the size of zeolite pores were also comprehensively studied through the hydration of hydrophilic and hydrophobic epoxides and alkynes with different molecular sizes using two types of zeolite (Hβ and HZSM5). The high yields obtained using the Hβ-75 catalyst in the hydration of hydrophobic epoxides and alkynes are attributed to the hydrophobic interaction between zeolite pores with the substrates, as well as the relatively large pore size.

The photocatalytic water splitting activity of a wide-bandgap material, Ga2O3, is greatly boosted with the addition of a Zn and Rh-Cr co-catalyst at optimum loadings. To date, however, the exact roles of the co-catalysts and particularly the origin of their synergistic functions have not been clarified. Herein, we present how the optimum Zn loading on Ga2O3 leads to creation of a ZnGa2O4/Ga2O3 heterojunction favorable for charge separation through information on the occupied and unoccupied electronic states of Zn and Ga elucidated by X-ray absorption and emission spectroscopic methods. The function of Rh-Cr as an electron sink and reduction site was proven by photocatalytic experiments using an electron scavenger (Ag+) and by learning where Ag deposits and its effects on photocatalytic activity. Finally, perturbation of the Zn electronic structure by photoactivation was evidenced by modulation excitation X-ray absorption spectroscopy. Importantly, Rh-Cr markedly enhanced the level of the perturbation, serving as proof of the direct communication and synergy between the electronic states of Zn, present in ZnGa2O4, and Rh-Cr deposited on Ga2O3.

The study of the formation, characterization, and functionality of isolated surface hydrides on solid materials is a formidable task because of the complexity of solid surfaces and the difficulty of analyzing structures in solids. Herein, we found the formation of indium (In) hydride species supported by CHA zeolites. The In hydrides were formed by treatment of an In-exchanged CHA zeolite (In-CHA) with H2 at high temperatures (>773 K). In situ Fourier transform infrared (FTIR) spectroscopy and density functional theory (DFT) calculations revealed that an [InH2]+ ion on a framework anionic site is a plausible structure. In-CHA exhibited high selectivity and durable catalytic activity for the nonoxidative dehydrogenation of ethane for at least 90 h. Kinetic and in situ spectroscopic studies as well as transition state (TS) calculations suggested that [InH2]+ ions serve as catalytically active sites for selective dehydrogenation using In-CHA.

We have carried out an experimental and theoretical study of CHA-zeolite supported indium (In)-oxo clusters that promote CH4 activation at room temperature. X-ray absorption fine structure (XAFS) measurements indicate the formation of multinuclear In-oxo clusters by the O2 activation of the In(i)-exchanged CHA zeolite prepared through reductive solid-state ion exchange (RSSIE). The structure of the In-oxo clusters and their locations were investigated in detail using ab initio thermodynamic analysis. The redox properties of the In species during RSSIE and the formation of the In-oxo clusters were also studied by temperature programmed reaction and in situ XAFS measurements. The reaction of CH4 on the O2-activated In-CHA zeolite was monitored using IR spectroscopy where adsorbed formic acid was generated at room temperature. The adsorption and C-H activation of CH4 on our plausible model of the In-oxo clusters were theoretically investigated using density functional theory calculations. We found that CH4 is likely to adsorb and react more easily on dinuclear In-oxo ions than on monomeric In-oxo ions and that the C-H bond cleavage reaction occurs via a heterolytic pathway rather than a homolytic pathway. This study reveals the potential of multinuclear In-oxo clusters as active sites for the transformation of CH4 to oxygenates under mild reaction conditions.

Carbon supported Pd@Pt core-shell nanoparticles catalyst was prepared in a flow reactor toachieve enhanced catalytic activities with low Pt loading for the acceptorless dehydrogenative synthesis of pyrimidines. Spectroscopic (XAS analysis) and microscopic (HAADF-STEM) techniques reveled that the core-shell structure was formed by the applied preparation method. The Pd@Pt/PVP (polyvinylpyrrolidone)/C catalyst showed the activity for the three component one pot synthesis of pyrimidines through a series of consecutive reactions including oxidation of alcohols, C C, and C N coupling, followed by heterocyclization and dehydrogenation employing various primary alcohols, secondary alcohols, and amidines. The reaction mechanism on Pd@Pt/PVP/C catalyst was explored by comparison with the control experiments.

In this work, proton-exchanged *BEA zeolite with a high Si/Al ratio of 75 (Hβ-75), was demonstrated as an effective catalyst for the acetalization of glycerol with carbonyl compounds. This catalyst system was applicable to various substrates and reusable for at least 4 times with slight decrease in activity. The turnover frequency, based on acid site concentration, increased as a function of Hβ Si/Al ratio, indicating the importance of the zeolite hydrophobic surface properties. The origin of the high efficiency exhibited by Hβ-75 is quantitatively discussed based on kinetic studies, hydrophobicity, and acid site concentration.