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The efficiency of catalysts relies on comprehending the underlying kinetics that govern their performance. Under the steady‐state regime, the "rate" is referred to as the turnover frequency, where the reaction rate is first order with respect to catalysts. Here, we introduce the Maximum Kinetic Efficiency (MaxKinEff) model, grounded in collision theory, to predict efficiency based on maximum turnover frequency, ΓmaxTOF0 ${{\rm{\Gamma }}_{max\;TOF}^0 }$ and maximum turnover number, τmaxTON0 ${\tau _{max\;TON}^0 }$. The model was applied to molecular water oxidation using twenty‐six transition metal catalysts from the first (3d), second (4d), and third (5d) rows. A thorough investigation reveals that [Ru(pda)(Br‐py)2] (pda=1,10‐phenanthroline‐2,9‐dicarboxylate; Py=pyridinophane) exhibits a notable ΓmaxTOF0 ${{\rm{\Gamma }}_{max\;TOF}^0 }$ of 1176.87×10−5 s−1 due to its larger collision diameter (σRC) and lower activation energy (Ea). Importantly, the trend in the computed τmaxTON0 ${\tau _{max\;TON}^0 }$ values aligns with experimental TON, τexperimentalTON0 ${\tau _{experimental\;TON}^0 }$ validating the model's accuracy. For instance, [Cp*Ir(κ2‐N,O)NO3] is identified by MaxKinEff as a standout performer, with the normalized maximum computed TON, τmaxTON0 ${\tau _{max\;TON}^0 }$ resembling the experimental TON, τexperimentalTON0 ${\tau _{experimental\;TON}^0 }$ =2000. [ABSTRACT FROM AUTHOR]

This paper reports the photoelectrochemical (PEC) analysis and the photocatalytic activity for hydrogen production of ZnO/Al photoelectrodes prepared with 0.5, 1 and 5 wt% of Al. The photoelectrodes were obtained by the sol-gel method and used as active material on photocatalyst for hydrogen production under UV-light irradiation. By increasing the aluminium concentration, the band-gap of ZnO decreases, at the same time the photoluminescence intensity decreases too. On the contrary, the PEC test showed an increase in the photocurrent due to the Al presence, which improves the charge transfer because it is a better coupling of the electronic bands of ZnO and Al. The n-type of semiconductor was corroborated by OCP curves, while the electron-hole pair recombination was calculated by electrochemical measurements where Al incorporation diminished the recombination. The electron lifetime calculated from OCP curves increases with Al content, which favours the catalytic activity of ZnO/Al photoelectrodes indicating its efficiency. In concordance, Nyquist plots reveal that ZnO/Al photoelectrodes with highest amount of Al showed low charge transfer resistance. On the other hand, the presence of Al increased the number of active sites as calculated by Turnover frequency (TOF), which is favourable to carry out redox reactions. The photocatalytic activity for hydrogen production was almost 6.6 times higher with respect to ZnO because the presence of Al, which favored the increase of charges and a greater number of active sites. This result is in agree with the information obtained by PEC analysis, where also a higher amount of photocurrent was produced by the Al content in ZnO/Al. • Recombination constant and electron life parameters on ZnO/Al photoelectrodes increases as Al incorporation increases too. • Photocurrent increases due to the Al presence because of a better coupling of the electronic bands of ZnO and Al. • The presence of Al increased the number of active sites on ZnO/Al photoelectrodes enhancing the H 2 production. • The photocatalytic activity for H 2 production was almost 6.6 times with respect to ZnO because of the presence of Al. • Length of Debye and depletion layer of ZnO/Al film decrease as Al increases reducing the electron-hole pair recombination. [ABSTRACT FROM AUTHOR]

[Display omitted] • Loading effects of Ni 3 Fe/Al 2 O 3 catalyst analyzed for the CO 2 methanation reaction. • 55 wt% Ni 3 Fe/Al 2 O 3 is the most active and possesses surface alloy sites. • CO 2 methanation activity is closely related to the area of the surface alloy sites. • A suitable kinetic model and its parameters determined for 55 wt% Ni 3 Fe/Al 2 O 3. • Model parameters are thermodynamically consistency and statistically robust. A series of Al 2 O 3 -supported bimetallic Ni-Fe catalyst with Ni/Fe = 3 are prepared, characterized, and examined for CO 2 methanation to identify the total metal loading (Ni+Fe) that yields the maximum activity. The XRD patterns of all catalysts exhibit a noticeable peak shift, which suggests alloy formation and XPS studies reveal that the near-surface concentration of the reduced catalysts possess Ni/Fe ratios similar to those targeted. Analysis of the particle size distribution from TEM and degree of reduction from TPR clearly shows that an increase in metal loading results in a gradual decrease in effective dispersion. However, the catalyst with 55% total metal loading of Ni+Fe, 55Ni 3 FeAl, possessed the maximum surface metal sites and effective surface metal area, which is reflected in the highest activity of this catalyst during CO 2 methanation. Kinetic measurements of the CO 2 methanation reaction are obtained on 55Ni 3 FeAl at temperatures ranging from 513 to 533 K and ambient pressure under differential reactor conditions and in the absence of heat and mass transfer resistance. Several kinetic models are then considered to fit the reaction data for CO 2 methanation. The parameters of the models are determined by non-linear regression and analyzed for their thermodynamic consistency and statistical validity (R2, R2 adj , NRMSE and F - test). The kinetic data of CO 2 methanation on 55Ni 3 FeAl is adequately represented by a reaction model, where the surface reaction between molecularly adsorbed CO 2 and adsorbed H 2 appears to be the rate-determining step. The activation energy of this rate determining step was 136 kJ/mol. This kinetic model can then be used to design, analyze, and control different reactors where the most active Al 2 O 3 supported Ni-Fe catalyst with Ni/Fe = 3, 55Ni 3 FeAl, is used for the CO 2 methanation reaction. [ABSTRACT FROM AUTHOR]

Viologen-based covalent organic networks represent a burgeoning class of materials distinguished by their captivating properties. Here, supramolecular chemistry is harnessed to fabricate polyrotaxanated ionic covalent organic polymers (iCOP) through a Schiff-base condensation reaction under solvothermal conditions. The reaction between 1,1'-bis(4-aminophenyl)-[4,4'-bipyridine]-1,1'-diium dichloride (DPV-NH 2 ) and 1,3,5-triformylphloroglucinol (TPG) in various solvents yields an iCOP-1 and iCOP-2. Likewise, employing cucurbit[7]uril (CB[7]) in the reaction yielded polyrotaxanated iCOPs, denoted as iCOP-CB[7]-1 and iCOP-CB[7]-2. All four iCOPs exhibit exceptional stability under the acidic and basic conditions. iCOP-CB[7]-2 displays outstanding electrocatalytic Oxygen Evolution Reaction (OER) performance, demanding an overpotential of 296 and 332 mV at 10 and 20 mA cm -2 , respectively. Moreover, the CB[7] integrated iCOP-2 exhibits a long-term stable nature for 30 h in 1 m KOH environment. Further, intrinsic activity studies like TOF show a 4.2-fold increase in generation of oxygen (O 2 ) molecules than the bare iCOP-2. Also, it is found that iCOP-CB[7]-2 exhibits a high specific (19.48 mA cm -2 ) and mass activity (76.74 mA mg -1 ) at 1.59 V versus RHE. Operando-EIS study evident that iCOP-CB[7]-2 commences OER at a relatively low applied potential of 1.5 V versus RHE. These findings pave the way for a novel approach to synthesizing various mechanically interlocked molecules through straightforward solvothermal conditions., (© 2024 Wiley‐VCH GmbH.)

The catalytic cycles of a new generation of the GPx mimic, selenosubtilisin and tellurosubtilisin were illuminated via the density functional theory and solvent-assisted proton exchange procedure to show the indirect proton exchange through a hydrogen-bonded transfer network. The reactivity of selenosubtilisin and tellurosubtilisin toward methanethiol as a reduction step and hydrogen peroxide as an oxidation step was investigated. The results show that all steps of the proposed catalytic cycles are spontaneous and kinetically favorable. From the kinetics viewpoint, the oxidation of selenic acid (ΔG≠ = 23.86 kcal mol−1) and tellurenic acid (ΔG≠ = 20.66 kcal mol−1) is considered as the rate-determining steps. The comparison of the barriers for oxidation/reduction of the chalcogens shows a decay from the selenosubtilisin to tellurosubtilisin. On the basis of the turnover frequency calculations, the catalytic cycle of tellurosubtilisin is faster than that of selenosubtilisin, because of the lower span energy. To confirm the nature of bond cleavage/formation, during the catalytic reactions, topological analyses were applied by using the quantum theory of atoms in molecules procedure. The high values of the electron localization function and localized orbital locator at the transition state regions, calculated by the MultiWFN program, confirm the critical bond formation. [ABSTRACT FROM AUTHOR]

This study reports on one of the best heterogeneous catalysts for the dehydrogenation of dimethylamine–borane (DMAB). This new catalytic system consists of highly monodisperse Pd and Ru alloy nanoparticles supported by poly(N -vinyl-pyrrolidone) (PdRu@PVP). The prepared heterogeneous catalyst can be reproducibly formed using an ultrasonic reduction technique for DMAB dehydrogenation under mild conditions. For the characterization of PdRu@PVP nanomaterials, several spectroscopic and microscopic techniques were used. The prepared PdRu@PVP nanomaterials with an average particle size of 3.82 ± 1.10 nm provided an 808.03 h−1 turnover frequency (TOF) in the dehydrogenation of DMAB and yielded 100% of the cyclic product (Me 2 NBH 2) 2 under mild conditions. Furthermore, the activities of catalysts were investigated theoretically using DFT-B3LYP calculations. The theoretical results based on density functional theory were in favorable agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In a recent experimental research, the formation of naphthalene has been demonstrated by La-mediated acetylene bicyclo-oligomerization in the gas phase, and this is the first report of metal-activated acetylene bicyclo-oligomerization to form the naphthalene. In this work, the complete reaction mechanism has been systematically analyzed on the doublet potential energy surface by employing density functional theory (DFT), the results showed that the computational results were consistent with experimental dates. Among them, two possible reaction pathways were identified: (1) LaCH is formed by a second addition of acetylene molecule to LaCH followed by dehydrogenation (path (a)). (2) First, dehydrogenation of LaCH, followed by the addition of a second acetylene molecule (path (b)), we found that the optimum pathway was path (a). According to the thermodynamic point of view, the reaction is highly exothermic and favorable. In addition, sequential acetylene additions coupled with dehydrogenation showed that the bicycle-oligomerization reaction can occur. For further analysis of the observed kinetic behavior, the energetic span model was utilized and confirmed the TOF-determining transition state (TDTS) and TOF-determining intermediate (TDI) of the overall reaction. Finally, the optimum path was found and demonstrated. [ABSTRACT FROM AUTHOR]

There is great interest in reducing the size of zeolite particles, because this can improve their catalytic properties in various reactions. This work evaluates two faujasite-type X zeolites, one micrometric and one nanometric. Zeolites in the sodium form were exchanged ionically with methylammonium cations. The materials were then evaluated as catalysts in the Knoevenagel condensation reaction. Steric impediments restricted ion exchange in the micrometric zeolite and became more important with increasing cation volume. In the case of the nanometric sample, such impediments were less evident, because the smaller particle size provided greater access of exchanger cations, compared to the micrometric zeolite in which the sodium was inaccessible. The best catalytic performances were achieved with zeolites containing the monomethylammonium cation. The increased accessibility and diffusion of the reactants and products through the pores of the nanometric zeolite provided the best butyraldehyde conversions, independent of the exchanger cation. In order to increase accessibility to catalytic sites, several studies have been carried out in order to reduce the diameter of the particles of zeolites to the nanometer scale. This reduction can promote the increase in the activity of the catalysts in some reactions. Graphical Abstract: In order to increase accessibility to catalytic sites, several studies have been carried out in order to reduce the diameter of the particles of zeolites to the nanometer scale. This reduction can promote the increase in the activity of the catalysts in some reactions. [ABSTRACT FROM AUTHOR]

Quantitative measurement of the number of active surface sites on two-dimensional (2D) catalysts is one of the most crucial points in heterogeneous catalysis because it is used to determine the turnover frequency (TOF), which refers to the catalytic activity of model catalysts. However, because of the difficulty in identifying the effective active surface area on 2D heterogeneous catalysts, there is still the assumption that each metal atom is an active site. To shed light on these issues and to bridge the activity gaps between 2D and three-dimensional (3D) heterogeneous catalysts, we present an experimental approach that uses Pt nanoparticle (NP) arrays on a thin silicon wafer probed with CO pulse chemisorption, a widely used surface-sensitive technique, to determine the number of active sites and the area of the effective active surface. A Pt thin film and Pt NP arrays with two different NP sizes (i.e., 2.1 and 4.5 nm) were prepared as model systems for 2D catalysts. The effective active metal surface area determined using CO pulse chemisorption for these 2D catalysts is 53-79% of the apparent metal surface area that was obtained by measuring the surface area based on scanning electron microscopy images. This discrepancy between the active and apparent surface area is attributed to the presence of hydrocarbon contamination and organic capping layers on the catalysts. The results indicate that estimating the active sites of 2D catalysts by apparent surface area is reasonably in agreement with the number measured by chemisorption that is used to characterize 3D nanocatalysts. This experimental technique on 2D catalysts can be expected to provide information for extracting the true TOF of product molecules on 2D catalysts in gas-phase catalytic reactions. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Alumina-supported bimetallic Pt-Pd catalysts proved to be more active in the complete oxidation of methane than monometallic systems (Pt/AlO, Pd/AlO). The maximum activity of the bimetallic catalysts was achieved at ~40 at.% Pt in Pd on the catalyst surface. After the oxidation reaction, redistribution of platinum and palladium was observed in the active component of the catalysts with the degree of redistribution depending on the initial Pt: Pd ratio. [ABSTRACT FROM AUTHOR]

Highlights: [•] Homogeneous and heterogeneous oxido–peroxido W(VI) complexes catalyze the oxidation of olefins. [•] H2O2, urea hydrogen peroxide and tert-butyl hydroperoxide as oxidant. [ • ] The substrate conversion and selectivity are very sensitive to the complex structure and the reaction conditions. [•] The mechanistic pathways for the epoxidation are presented. [Copyright &y& Elsevier]

Highlights: [•] Oxidations catalyzed by tris(pyrazol-1-yl)methane metal complexes are reviewed. [•] Homogeneous and supported C-scorpionate complexes catalyze the oxidation of alkanes. [•] Epoxide formation from alkenes is efficiently catalyzed by C-scorpionate complexes. [•] Rhenium C-scorpionate complexes catalyze the Baeyer–Villiger oxidation of ketones. [•] The mechanistic pathways for the oxidative functionalizations are presented. [ABSTRACT FROM AUTHOR]

Highlights: [•] Metalloenzyme-catalyzed aliphatic carbon–carbon bond cleavage reactions recently identified. [•] Substrates vary in terms of their O2 reactivity in the absence of enzyme. [•] Reaction pathways depend on the nature of the substrate; metal versus substrate reactivity with O2. [•] Regioselectivity of carbon–carbon bond cleavage influenced by nature of metal ion. [•] Model systems providing insight into structure/reactivity relationships. [ABSTRACT FROM AUTHOR]

Abstract: Over the past five years, Ga(III) and most notably In(III) precursors have attracted a growing interest for application in ROP catalysis of cyclic esters, primarily lactide, and may now be considered as potentially efficient ROP initiators of cyclic esters/carbonates. Despite their higher cost (vs. Al), Ga and In derivatives exhibit key attractive features including: (i) Ga(III) and In(III) are biocompatible metal centers and (ii) their precursors are typically more stable than organoaluminum species in polar media. The present contribution reviews discrete Ga(III) and In(III) compounds thus far developed as ROP initiators of cyclic esters/carbonates. The very few reports on Ga(III)-mediated ROPs of cyclic ethers are also included. In addition to the ROP performances of such species, the synthesis and structural characterization of these initiators are also provided and thoroughly discussed with, whenever appropriate, the establishment of structure/reactivity relationships and mechanistic pathways. [Copyright &y& Elsevier]

Intrinsic catalytic activities (TOF values) in CH complete oxidation under lean conditions were estimated as a function of Pt and Pd particle sizes (d) for two series of Pt/AlO and Pd/AlO catalysts. Comparison of TOF ~ f(d) relationships revealed significant difference between Pt and Pd catalysts. For Pt catalyst TOF showed tendency to increase by 2-3 times with increasing particle size from 1 to ca 3 nm and remained constant, when Pt particles became larger than 3 nm. On the other hand, for Pd catalyst TOF increased almost linearly when particle size grew from 1 to 20 nm. These different tendencies were attributed to the different mechanisms of CH oxidation over Pt and Pd catalysts: Langmuir-Hinshelwood and Mars-Van Krevelen respectively. [ABSTRACT FROM AUTHOR]

Abstract: To develop a single stage water–gas shift reaction (WGS) catalyst for compact reformers, Pt/CeO2, Pt/ZrO2, and Pt/Ce(1−x)Zr(x)O2 catalysts have been applied for the target reaction. The CeO2/ZrO2 ratio was systematically varied to optimize Pt/Ce(1−x)Zr(x)O2 catalysts. Pt/CeO2 showed the highest turnover frequency (TOF) and the lowest activation energy (E a) among the catalysts tested in this study. It has been found that the reduction property of the catalyst is more important than the dispersion for a single stage WGS. Pt/CeO2 catalyst also showed stable catalytic performance. Thus, Pt/CeO2 can be a promising catalyst for a single stage WGS for compact reformers. [Copyright &y& Elsevier]

Abstract: The potential energy surface (PES) corresponding to the reaction NO2(2A1) with CO(1∑+) catalyzed by Ir+ has been investigated by using density functional theory (DFT). Minimum energy crossing points (MECPs) on the potential energy surfaces are located by using the methods of Harvey et al. The possible spin inversion processes are discussed by means of spin–orbit coupling (SOC) calculations. As a result, the values of the SOC constants at 4/2MECP1 and 5/3MECP2 are 617 and 1187cm−1, respectively. The latter is found to be the energetically favored channel. The energetic span (δE) model coined by Kozuch was applied in this cycle to obtain some kinetic information. The turnover frequency (TOF) determining transition state (TDTS) and TOF determining intermediate (TDI) were confirmed, and the TOF was calculated by the AUTOF program at different temperatures. [Copyright &y& Elsevier]

Abstract: This paper describes the properties of new X zeolite catalysts, whose anions are compensated by different methylammonium cations. The properties of these catalysts, with varying degrees of exchange, are compared with those of Y zeolites containing the same cations. For steric reasons, cation exchange was restricted to the faujasite supercavity, and the degree of ion exchange decreased with the radius of the organic cation. The basicity of the catalysts was analyzed using X-ray photoelectron spectroscopy (XPS) and the Knoevenagel condensation reaction, with good correlation obtained between the results of the two methods. The best catalytic activity was observed for the faujasite with the highest aluminum content (X zeolite), exchanged using the monomethylammonium cation. The better performance of this catalyst was attributed to its basicity, as well as the available micropore volume. [Copyright &y& Elsevier]

Herein, green and non-toxic bismuth sulphide@graphitic carbon nitride (Bi 2 S 3 @g-C 3 N 4) nanosheets (NCs) were firstly synthesized by ultrasonicated-assisted method and characterized with different tool. Bi 2 S 3 @g-C 3 N 4 NCs antimicrobial activity tested against three types of microbes. As well the heterostructured Bi 2 S 3 @g-C 3 N 4 NCs was investigated for removing dye and hexavalent chromium under visible light and showed high efficiency of photocatalytic oxidation/reduction higher than g-C 3 N 4 alone, attributing to lower recombination photogenerated electron-hole pairs. Bi 2 S 3 @ g-C 3 N 4 NCs showed high antimicrobial efficiencies against Staphylococcus aureus (S. aureus) as a Gram positive bacterium, Escherichia coli (E. Coli)as a Gram negative bacterium and Candida albicans (C. albicans) and that the disinfection rates are 99.97%, 99.98% and 99.92%, respectively. The core mechanism is that the bacterial membrane could be destroyed by reactive oxygen species. The Bi 2 S 3 @g-C 3 N 4 NCs is promising for environmental disinfection including water and public facilities disinfection and solar photocatalytic depollution. Turnover number (TON) and Turnover frequency (TOF) are used as concise assessment indicator for photocatalytic efficiency. [Display omitted] • Bi 2 S 3 @g-C 3 N 4 NCs were successfully synthesized by ultrasonicated-assisted method. • Bi 2 S 3 @g-C 3 N 4 nanosheets (NCs) exhibited enhanced photocatalytic removal of dyes and Cr (VI). • Bi 2 S 3 @g-C 3 N 4 NCs had a high antibacterial efficiency against different microbes. • The Bi 2 S 3 @g-C 3 N 4 NCs is promising for environmental materials for disinfection and purification. • TON and TOF are used as concise assessment indicator for photocatalysis processes. [ABSTRACT FROM AUTHOR]

Within the context of electron transfer during the catalytic water oxidation reaction, the Ir-based system is among the most active. The reaction, mimicking photosynthesis II, requires the use of an electron acceptor such the Ce4+ cation. This complex reaction, involving adsorbed water at the interface of the metal cation and Ce4+, has mostly been studied in homogenous systems. To address the ambiguity regarding the gradual transformation of a homogenous system into a heterogeneous one, we prepared and studied a heterogeneous catalyst system composed of IrO2, with a mean particle size ranging from about 5 Å to 10 Å, dispersed on a TiO2 anatase support, with the objective of probing into the different parameters of the reaction, as well as the compositional changes and rates. The system was stable for many of the runs that were conducted (five consecutive runs with 0.18 M of Ce4+ showed the same reaction rate with TON > 56,000) and, equally importantly, was stable without induction periods. Extraction of the reaction rates from the set of catalysts, with an attempt to normalize them with respect to Ir loading and, therefore, to obtain turnover frequencies (TOF), was conducted. While, within reasonable deviations, the TOF numbers extracted from TPR and XPS Ir4f were close, those extracted from the particle shape (HR-STEM) were considerably larger. The difference indicates that bulk Ir atoms contribute to the electron transfer reaction, which may indicate that the reaction rate is dominated by the reorganization energy between the redox couples involved. Therefore, the normalization of reaction rates with surface atoms may lead to an overestimation of the site activity. [ABSTRACT FROM AUTHOR]

Herein, green and non-toxic bismuth sulphide@graphitic carbon nitride (Bi 2 S 3 @g-C 3 N 4 ) nanosheets (NCs) were firstly synthesized by ultrasonicated-assisted method and characterized with different tool. Bi 2 S 3 @g-C 3 N 4 NCs antimicrobial activity tested against three types of microbes. As well the heterostructured Bi 2 S 3 @g-C 3 N 4 NCs was investigated for removing dye and hexavalent chromium under visible light and showed high efficiency of photocatalytic oxidation/reduction higher than g-C 3 N 4 alone, attributing to lower recombination photogenerated electron-hole pairs. Bi 2 S 3 @g-C 3 N 4 NCs showed high antimicrobial efficiencies against Staphylococcus aureus (S. aureus) as a Gram positive bacterium, Escherichia coli (E. Coli)as a Gram negative bacterium and Candida albicans (C. albicans) and that the disinfection rates are 99.97%, 99.98% and 99.92%, respectively. The core mechanism is that the bacterial membrane could be destroyed by reactive oxygen species. The Bi 2 S 3 @g-C 3 N 4 NCs is promising for environmental disinfection including water and public facilities disinfection and solar photocatalytic depollution. Turnover number (TON) and Turnover frequency (TOF) are used as concise assessment indicator for photocatalytic efficiency., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Metal-catalyzed alkyne [2+2+2] cycloadditions provide a variety of substantial aromatic compounds of interest in the chemical and pharmaceutical industries. Herein, the mechanistic aspects of the acetylene [2+2+2] cycloaddition mediated by bimetallic half-sandwich catalysts [Cr(CO)3IndRh] (Ind = (C9H7)−, indenyl anion) are investigated. A detailed exploration of the potential energy surfaces (PESs) was carried out to identify the intermediates and transition states, using a relativistic density functional theory (DFT) approach. For comparison, monometallic parent systems, i.e., CpRh (Cp = (C5H5)−, cyclopentadienyl anion) and IndRh, were included in the analysis. The active center is the rhodium nucleus, where the [2+2+2] cycloaddition occurs. The coordination of the Cr(CO)3 group, which may be in syn or anti conformation, affects the energetics of the catalytic cycle as well as the mechanism. The reaction and activation energies and the turnover frequency (TOF) of the catalytic cycles are rationalized, and, in agreement with the experimental findings, our computational analysis reveals that the presence of the second metal favors the catalysis. [ABSTRACT FROM AUTHOR]