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Development of selective catalytic reduction (SCR) with alkali tolerance is an essential task to remove air pollution. The previously developed Fe- and H2SO4-induced CeO2exhibited high alkali tolerance while maintaining a high nitrogen oxide conversion (Khan, M.N.; Han, L.: Wang. P.; and Zhang, D. iScience, 2020. 23(6), 101173). In this work, we focused on understanding the influence of induced Fe and H2SO4in the continuous development and improvement of alkali tolerance catalysts. The roles of Fe and H2SO4in preventing alkali poisoning were investigated by using density functional theory calculations. Our results showed that a potassium species hindered the formation of Brønsted acid sites by occupying the lattice oxygen sites on the CeO2surface and inhibited the adsorption of the reductant, NH3. The induced Fe and H2SO4promoted the formation of oxygen vacancies and generated characteristic adsorption sites (SO4/Fe_CeO2_Vo) for the accumulation of multiple potassium atoms. Hence, the synergistic effect of Fe and H2SO4protects NH3adsorption sites on the CeO2surface from potassium poisoning of the catalyst. These findings can also give insight into understanding the similar ability of metal oxide-based catalysts with sulfate ion against alkali poisoning and open new ways in facilitating the tailored design of alkali tolerance catalysts for NH3–SCR.

Dynamic behavior of intermediate adsorbates, such as diffusion, spillover, and reverse spillover, has a strong influence on the catalytic performance in oxide-supported metal catalysts. However, it is challenging to elucidate how the intermediate adsorbates move on the catalyst surface and find active sites to give the corresponding products. In this study, the effect of the dynamic behavior of methoxy intermediate on methanol decomposition on a Pt/TiO2(110) surface has been clarified by combination of scanning tunneling microscopy (STM), temperature-programmed desorption (TPD), and density functional theory (DFT) calculations. The methoxy intermediates were formed by the dissociative adsorption of methanol molecules on Pt nanoparticles at room temperature followed by spillover to the TiO2(110) support surface. TPD results showed that the methoxy intermediates were thermally decomposed at >350 K on the Pt sites to produce CO (dehydrogenation) and CH4(C–O bond scission). A decrease of the Pt nanoparticle density lowered the activity for the decomposition reaction and increased the selectivity toward CH4, which indicates that the reaction is controlled by diffusion and reverse spillover of the methoxy intermediates. Time-lapse STM imaging and DFT calculations revealed that the methoxy intermediates migrate on the five-fold coordinated Ti (Ti5c) sites along the [001] or [11¯0]direction with the aid of hydrogen adatoms bonded to the bridging oxygens (Obr) and can move over the entire surface to seek and find active Pt sites. This work offers an in-depth understanding of the important role of intermediate adsorbate migration in the control of the catalytic performance in oxide-supported metal catalysts.

Inverse molecular design allows the optimization of molecules in chemical space and is promising for accelerating the development of functional molecules and materials. To design realistic molecules, it is necessary to consider geometric stability during optimization. In this work, we introduce an inverse design method that optimizes molecular properties by changing the chemical composition in the equilibrium geometry. The optimization algorithm of our recently developed molecular design method has been modified to allow molecular design for general properties at a low computational cost. The proposed method is based on quantum alchemy and does not require empirical data. We demonstrate the applicability and limitations of the present method in the optimization of the electric dipole moment and atomization energy in small chemical spaces for (BF, CO), (N2, CO), BN-doped benzene derivatives, and BN-doped butane derivatives. It was found that the optimality criteria scheme adopted for updating the molecular species yields faster convergence of the optimization and requires a less computational cost. Moreover, we also investigate and discuss the applicability of quantum alchemy to the electric dipole moment.

The local structure of WO3photocatalyst in the photoexcited metastable state created 150 ps after laser irradiation have been determined by pump-probe L3-edge EXAFS and constrained thorough search analysis. A highly distorted octahedral local structure was found where one of the shortest W-O bonds was further shortened to 1.66 Å while the other five bonds were rather elongated even though theoretical calculations predicted the reverse change. We discuss this contradiction and propose a possible structure for the metastable state.The local structure of WO3photocatalyst in the photoexcited metastable state created 150 ps after laser irradiation has been determined by pump-probe EXAFS and constrained thorough search analysis. A highly distorted octahedral local structure was found, especially one of the shortest W-O was further shortened. We discuss contradiction with theoretical calculation and propose a possible structure for the metastable state.

To elucidate the reaction mechanism and the origin of the enantioselectivity of the asymmetric dehydrative cyclization of allyl alcohol to cyclic ether catalyzed by a Cp-ruthenium complex and a chiral pyridinecarboxylic acid, (R)-X-Naph-PyCOOH, density functional theory (DFT) calculations were performed. According to the DFT calculations, the rate-determining step is the dehydrative σ-allyl formation step with ΔG‡= 18.1 kcal mol–1at 80 °C. This agrees well with the experimental data (ΔG‡= 19.01 kcal mol–1at 80 °C). The DFT result showed that both hydrogen and halogen bonds play a key role in the high enantioselectivity by facilitating the major R,SRu-catalyzed reaction pathway via a σ-allyl Ru intermediate to generate the major (S)-product. In contrast, the reaction is sluggish in the presence of the diastereomeric R,RRucatalyst with an apparent activation energy of 33.1 kcal mol–1; the minor (R)-product is formed via a typical π-allyl Ru intermediate and via a minor pathway for the cyclization step. In addition, the calculated activation Gibbs free energies, 14.4 kcal mol–1for I < 16.8 kcal mol–1for Br < 18.1 kcal mol–1for Cl, reproduced the observed halogen-dependent reactivity with the (R)-X-Naph-PyCOOH ligands. The origin of the halogen trend was clarified by a structural decomposition analysis.

The detailed structures of monomeric ReOxcatalysts supported on the CeO2surface and the reaction mechanism of the deoxydehydration (DODH) reaction were investigated by density functional theory calculations. After examining various ReOxHystructures over CeO2without substrate adsorption, the stable structure under the experimental condition at 400 K was determined to be the ReVIIO2species. The reaction mechanism of DODH was then investigated for the conversion of 1,4-anhydroerythritol to 2,5-dihydrofuran as a model reaction. Through the investigations of several reaction pathways, an oxygen vacancy-assisted mechanism, in which the starting structure is the ReIVO species and the oxidation state of the Re atom changes between +IV and +VI during the reaction, was postulated to be the most plausible pathway, considering the energies of the intermediates and the barrier height for the cleavage of the two C–O bonds.

To understand the influence of incongruent strain on heterogeneous catalysis, the effect of isotropic and anisotropic strains in the catalytic activity of terrace Ru(0001) and stepped Ru(1015) surfaces have been studied for the initial step of the Fischer–Tropsch (FT) reaction. Adsorption–strain relations have been investigated using the d-band model and the novel eigenstress model. The adsorption relation in the reactant state follows both models. The eigenstress model can predict similar qualitative changes in the adsorption energies without the need to calculate the d-band center of the slab. Activation energies also scale according to Brønsted–Evans–Polyani (BEP) relation. Some exemptions included new minimum energy pathways, which do not break the scaling relations but reinforce the mechanochemical effect of producing new chemical pathways with the strain. In addition, in the case of a compressed Ru(1015) surface, reactant adsorption energy does not scale with dissociation activation energy. This is explained by the heightened difference in the reactant interaction energy. These results offer a potential novel route to break the BEP relation in catalysis.

We focused on identifying a catalytic active site structure at the atomic level and elucidating the mechanism at the elementary reaction level of liquid-phase organic reactions with a heterogeneous catalyst. In this study, we experimentally and computationally investigated efficient C–H bond activation for the selective aerobic α,β-dehydrogenation of saturated ketones by using a Pd–Au bimetallic nanoparticle catalyst supported on CeO2(Pd/Au/CeO2) as a case study. Detailed characterization of the catalyst with various observation methods revealed that bimetallic nanoparticles formed on the CeO2support with an average size of about 2.5 nm and comprised a Au nanoparticle core and PdO nanospecies dispersed on the core. The formation mechanism of the nanoparticles was clarified through using several CeO2-supported controlled catalysts. Activity tests and detailed characterizations demonstrated that the dehydrogenation activity increased with the coordination numbers of Pd–O species in the presence of Au(0) species. Such experimental evidence suggests that a Pd(II)–(μ-O)–Au(0) structure is the true active site for this reaction. Based on density functional theory calculations using a suitable Pd1O2Au12cluster model with the Pd(II)–(μ-O)–Au(0) structure, we propose a C–H bond activation mechanism via concerted catalysis in which the Pd atom acts as a Lewis acid and the adjacent μ-oxo species acts as a Brønsted base simultaneously. The calculated results reproduced the experimental results for the selective formation of 2-cyclohexen-1-one from cyclohexanone without forming phenol, the regioselectivity of the reaction, the turnover-limiting step, and the activation energy.

A compact inertial electrostatic confinement (IEC) fusion neutron source was developed. Imaging tests using the cylindrical IEC neutron source were conducted with the indirect imaging plate (IP) method using dysprosium foil and an imaging plate. An array of B_4C powder contained in a stainless-steel blade and Cd pins was successfully imaged. To calculate thermal neutron flux of the device, we tested multiple types of IP and IP scanners with the indirect IP method to create a calibration curve, and it was confirmed that dental IP scanners, which are more widely used than industrial ones, can be applied to the indirect IP method.

We report a visible-light-induced copper-catalyzed highly enantioselective umpolung allylic acylation reaction with acylsilanes as acyl anion equivalents. Triplet-quenching experiments and DFT calculations supported our reaction design, which is based on copper-to-acyl metal-to-ligand charge transfer (MLCT) photoexcitation that generates a charge-separated triplet state as a highly reactive intermediate. According to the calculations, the allylic phosphate substrate in the excited state undergoes novel molecular activation into an allylic radical weakly bound to the copper complex. The allyl radical fragment undergoes copper-mediated regio- and stereocontrolled coupling with the acyl group under the influence of the chiral N-heterocyclic carbene ligand.

2,7-Bis(2-phenyl-1H-imidazol-4-yl)fluorenone (BPIFO) was synthesized as a new fluorenone derivative bearing two imidazole moieties, and it exhibited remarkable and reversible changes in photo physical properties through two-step deprotonation with a base and back protonation with an acid in dimethylsulfoxide, which were interpreted by DFT calculations.2,7-Bis(2-phenyl-1H-imidazol-4-yl)fluorenone (BPIFO) was synthesized as a new fluorenone derivative bearing imidazole moieties, and it exhibited remarkable and reversible changes in photo physical properties through two-step deprotonation with a base and back protonation with an acid in dimethylsulfoxide, which were interpreted by DFT calculations.

Quantitative evaluation of the antibacterial activity of conventional antibacterial agents in situ is difficult. In this study, we demonstrated that antibacterial activity can be quantitatively estimated from the photoluminescence intensity of pyrene fluorophores incorporated into tannic acid, a naturally occurring antibacterial agent.Quantitative evaluation of the antibacterial activity of conventional antibacterial agents in situ is difficult. In this study, we demonstrated that antibacterial activity can be quantitatively estimated from the photoluminescence intensity of pyrene fluorophores incorporated into tannic acid, a naturally occurring antibacterial agent.

[Ru(II)Cp((R)-Cl-Naph-PyCOOH)]PF6((R)-1) catalyzes the dehydrative cyclization of (E)-hept-2-ene-1,7-diol (2) to 2-vinyltetrahydro-2H-pyran (3) with a 97:3 S/Renantiomer ratio. Complex (R)-1is in equilibrium between two diastereomers (R,RRu)-1(AR) and (R,SRu)-1(AS). A difference of turn over efficiency between the ASand ARcycles is thought to be the origin of the high enantioselectivity. The ASgives a major enantiomeric product (S)-3, according to the results of detailed mechanistic investigation via i) X-ray crystallographic analysis of related complexes, ii) NMR experiments using allylic alcohol 2, OH-lacking 2-mimic 4, d-labeled (S)-4-1d, enantiomerically enriched hept-6-ene-1,5-diol (6) as branched isomer of 2, and OH-lacking 6-mimic 5, iii) substrate structure/reactivity and selectivity relationships, iv) deuterium-labeling experiment, v) kinetics via calorimetric analysis, and vi) ligand structure/reactivity and selectivity relationships. AScaptures 2via hydrogen and halogen bonds. Oxidative addition in an H2Oinmode leads to a macrocyclic σ-allyl intermediate. Here, an efficient nC(7)OH/π*C(3)=C(2)trans-annular (TA) interaction facilitates an SN2′ nucleophilic addition of OH in an OHTAmanner to furnish (S)-3. Contrary to the AS, ARcannot capture 2using the halogen bond and slowly operates to give (R)-3. A conventional π-allyl-complex-involved mechanism is ruled out by a contradiction in the result of ii) and iii).Mechanism of dehydrative asymmetric allylic cyclization catalyzed by a Cp-ruthenium complex of chiral pyridinecarboxylic acid was investigated. A reaction pathway has been proposed, in which a R,SRu-configrated stereoisomer of σ-allyl complex is smoothly formed through a substrate/catalyst complex assisted by a halogen bond between chloro group with nucleophlic substituent on the substrate to give the major enantiomer of the product.

Recently, mechanical ball milling was applied to chitin depolymerization. The mechanical activation afforded higher selectivity toward glycosidic bond cleavage over amide bond breakage. Hence, the bioactive N-acetylglucosamine (GlcNAc) monomer was preferentially produced over glucosamine. In this regard, the force-dependent mechanochemical activation–deactivation process in the relaxed and pulled GlcNAc dimer undergoing deacetylation and depolymerization reactions was studied. For the relaxed case, the activation energies of the rate-determining steps (RDS) proved that the two reactions could occur simultaneously. Mechanical forces associated with ball milling were approximated with linear pulling and were introduced explicitly in the RDS of both reactions through force-modified potential energy surface (FMPES) formalism. In general, as the applied pulling force increases, the activation energy of the RDS of deacetylation shows no meaningful change, while that of depolymerization decreases. This result is consistent with the selectivity exhibited in the experiment. Energy and structural analyses for the depolymerization showed that the activation can be attributed to a significant change in the glycosidic dihedral at the reactant state. A lone pair of the neighboring pyranose ring O adopts a syn-periplanar conformation relative to the glycosidic bond. This promotes electron donation to the σ*-orbital of the glycosidic bond, leading to activation. Consequently, the Brønsted–Lowry basicity of the glycosidic oxygen also increases, which can facilitate acid catalysis.

Au nanoparticles supported on the manganese oxide octahedral molecular sieve OMS-2 can efficiently catalyze α,β-dehydrogenation of β-N-substituted saturated ketones using O2as the terminal oxidant. However, despite the utility of this reaction, the active sites and the reaction mechanism remain unclear. Here, the reaction mechanism for the Au/OMS-2-catalyzed aerobic α,β-dehydrogenation of 1-methyl-4-piperidone was investigated mainly by using density functional theory (DFT) calculations. From control experiments under various reaction conditions, we found that O2plays an important role in the α,β-dehydrogenation over Au nanoparticles. Thus, we attempted to clarify the mechanism for the α,β-dehydrogenation of 1-methyl-4-piperidone on Au nanoparticle catalysts by DFT calculations using Au cluster models. The reaction was found to cleave the C–Hαand C–Hβbonds in that order. An O2molecule adsorbed on the negatively charged Au cluster caused by charge transfer from OMS-2 was found to be sufficiently activated to abstract the Hαatom in the 1-methyl-4-piperidone substrate. This indirect Hαabstraction by the activated O2was energetically more favorable than direct Hαabstraction by the Au cluster. The subsequent Hβabstraction was found to be promoted by adsorbed oxygen species (i.e., HOO, OH, and O) formed after the Hαabstraction. The reaction mechanism proposed in this study provides general insight into the aerobic C–H bond activation by supported Au catalysts.

Self-assembled multilayer iron(0) nanoparticles (NPs, 6–10 nm), namely, sulfur-modified Au-supported Fe(0) [SAFe(0)], were developed for ligand-free one-pot carbon–carbon/carbon–nitrogen bond-forming reactions. SAFe(0) was successfully prepared using a well-established metal–nanoparticle catalyst preparative protocol by simultaneous in situmetal NP and nanospace organization (PSSO) with 1,4-bis(trimethylsilyl)-1,4-dihydropyrazine (Si-DHP) as a strong reducing agent. SAFe(0) was easy to handle in air and could be recycled with a low iron-leaching rate in reaction cycles.

The ring-opening process was generally considered as the rate-determining step for aromatic volatile organic compound photocatalytic degradation. A sophisticated and intensive degradation pathway is critical to the poor removal efficiency and low mineralization. In the present contribution, we successfully tailored and identified the ring-opening pathway of toluene elimination by electron delocalization in a borocarbonitride photocatalyst. By means of modulation of the dopant coordination configuration and electron geometry in the catalyst, the lone electrons of carbon transform into delocalized counterparts, sequentially elevating the interaction between the toluene molecules and photocatalyst. The aromatic ring of toluene can be attacked directly in the effect of electron delocalization without engendering additional intermediate species, significantly facilitating the removal and mineralization of toluene. This unprecedented route-control strategy alters the aromatic-ring-based reaction behavior from toluene to CO2and paves a way to purify the refractory pollutants from the top design.

A binder plays an important role in stabilizing the electrode structure and improving the cyclic stability of batteries. However, the traditional binders are no longer satisfactory in lithium–sulfur (Li–S) batteries because of their failure in accommodating the large volume changes of sulfur and trapping soluble intermediate polysulfides, thus causing severe capacity decay. In this work, we prepared a multifunctional binder for Li–S batteries by merely modifying the acacia gum (AG), a low-cost biomass polymer, with l-cysteine under mild conditions. Owing to the introduced amino and carboxyl branches by the l-cysteine, the modified AG shows enhanced polysulfide trapping ability and can effectively restrain the shuttling of polysulfides. In addition, the introduction of branches can help form a cross-linked 3D network with better mechanical strength and flexibility for adhering sulfur and accommodating the volume changes of cathode materials. As a result, compared with the normally used polyvinylidene fluoride binder and the unmodified AG binder, the l-cysteine-modified AG binder effectively enhanced the rate capability and cycling stability of the Li–S batteries directly using sulfur as the cathode, showing a promising way to prompt the practical use of Li–S batteries.

The mechanism of the aza-aldol reaction between boron aza-enolate and benzaldehyde is investigated by using density functional theory calculations. The result shows that the syn-Eisomer is preferentially formed, consistent with experimental observations. The six-membered ring transition state (TS) with the boat form leads to the Eisomer, while the more unstable chair TS does to the Zisomer. The preference of the synisomer is determined by the interactions between the substituents of aza-enolate and benzaldehyde. Structural distortion and intrinsic reaction coordinate analyses of simplified model systems provide insights into the origin of the relative stability of the rate-determining TS with boat and chair forms. The boat TS is an early TS; thus, minimal structural distortions of the reactant are required to reach this TS. The Lewis pair interactions between the boron and imine groups during B–N elimination also influenced the relative stability of the TSs. This interaction involves the nitrogen lone pair in the boat TS, while the π(N═C) orbital is involved in the chair TS. The Lewis pair with the lone pair stabilizes the TS more than that with the π orbital. The boron aza-enolate with 9-BBN generates an ate complex and forms C–C bonds sequentially, whereas that with Bpin does not generate an ate complex and exhibits the concerted formation of B–O and C–C bonds. Thus, the higher electrophilicity of boron such as 9-BBN enhances the reactivity by facilitating the formation of the ate complex. A reaction design is proposed to reverse the syn/antiselectivity. Proof-of-concept DFT calculations suggested that the modification of the imine group would change the relative stability of the boat/chair TSs and give the anti-product.

During the hydrogenation of CO2to methanol over mixed-oxide catalysts, the strong adsorption of CO2and formate poses a barrier for H2dissociation, limiting methanol selectivity and productivity. Here we show that by using Co-containing dual-atom oxide catalysts, the poisoning effect can be countered by separating the site for H2dissociation and the adsorption of intermediates. We synthesized a Co- and In-doped ZrO2catalyst (Co–In–ZrO2) containing atomically dispersed Co and In species. Catalyst characterization showed that Co and In atoms were atomically dispersed and were in proximity to each other owing to a random distribution. During the CO2hydrogenation reaction, the Co atom was responsible for the adsorption of CO2and formate species, while the nearby In atoms promoted the hydrogenation of adsorbed intermediates. The cooperative effect increased the methanol selectivity to 86% over the dual-atom catalyst, and methanol productivity increased 2-fold in comparison to single-atom catalysts. This cooperative effect was extended to Co–Zn and Co–Ga doped ZrO2catalysts. This work presents a different approach to designing mixed-oxide catalysts for CO2hydrogenation based on the preferential adsorption of substrates and intermediates instead of promoting H2dissociation to mitigate the poisonous effects of substrates and intermediates.

Metal nanoclusters (NCs) have unique properties because of their small size, which makes them useful as catalysts in reactions like cross-coupling. Pd-catalyzed oxidative amination, which involves dehydrogenative C–N bond formation, uses Pd complexes as the active species. It is known that the catalytic conditions involve the formation of Pd(0) species from Pd NCs, but the precise role of Pd NCs in the transformations has not been established. In this study, we investigated the characteristic properties of Pd NCs in oxidative amination of 1,3-dienes. The reaction achieved direct amination of commercially accessible 1,3-dienes with secondary aromatic amines, providing a variety of nitrogen containing 1,3-dienes. The compound was applicable to radical polymerization to provide the nitrogen-fabricated 1,3-diene–based polymer, which exhibited a different thermal stability compared to aliphatic nitrogen-fabricated diene polymers. In addition to the synthetic utility, by combining X-ray absorption fine structure and small-angle X-ray scattering analysis, we revealed amines and 1,3-dienes affected metal leaching from the Pd nanoparticles and stabilization of Pd NCs in the catalytic reaction. Additionally, DFT calculation suggested that the catalytic intermediate contained multiple adjacent Pd atoms and was responsible for formation of an σ-allylic intermediate that is difficult to form with the use of Pd complexes. These results could be used to understand the underlying phenomenon in the oxidative coupling reaction and develop Pd NCs-based dehydrogenation.

In this work, we tested a setup of X-ray fluorescence (XRF) excited by proton-induced quasi-monochromatic X-rays (proton-induced XRF (PIXRF)) as a low-radiation dose analytical technique for precious cultural heritage samples. The low-dose performance of the PIXRF is experimentally assessed in comparison with the performance of a conventional XRF. For this assessment, we prepared test samples, which simulated original Japanese paintings with copper-bearing pigments. By introducing a figure-of-merit, the PIXRF is found to potentially give a better performance in terms of the radiation dose to the sample and the limit of detection, albeit the degraded multi-elemental analytical capability. PIXRF can be a cost-effective method to perform low dose measurements of precious samples, if introduced in an existing PIXE facility.

Reactions based on transition-metal-catalyzed C–O bond cleavage have attracted much attention as a new synthetic method. Until now, several intermolecular reactions via C–O bond cleavage of aryl ethers, alkenyl ethers, esters, and others have been reported. Here we report an unprecedented C–O bond cleavage of 3-phenoxy acrylic acid derivatives, followed by intramolecular C–O bond formation with alkynes. This reaction gave 2,3-disubstituted benzofurans having useful functional groups—silyl substituents and acrylic acid derivatives—at the 2- and 3-positions, respectively. This report also described theoretical (DFT) insights into the mechanism.

The mechanism of C–H activation of methane by liquid indium, which is the first step of the dehydrogenative conversion of methane to higher hydrocarbons, was investigated using density functional theory calculations. In the first-principle molecular dynamics trajectory at the experimental temperature (1200 K), low-coordinated indium atoms continuously appear on the disordered liquid surface. The C–H cleavage is endothermic on clean surfaces, while the low-coordinated indium atoms reduce the endothermicity significantly. In small indium clusters, which are models of low-coordinated atoms on a surface, the calculated activation energy is much smaller than that on the clean surface. The energy level of the methane C–H σ* orbital is reduced by the interaction with the indium 5pσ orbitals. In2shows the lowest activation energy and exothermicity in the C–H bond cleavage.

Reaction mechanisms of hydrosilylation of ketone and alkene with tertiary silane using the Wilkinson-type catalyst were theoretically investigated on the basis of density functional calculations using ωB97XD functional. Previously proposed three mechanisms, the Chalk–Harrod (CH) mechanism, the modified Chalk–Harrod (mCH) mechanism, and the outer-sphere mechanism were examined. Besides, we also found two mechanisms, the alternative CH (aCH) mechanism and the double hydride (DH) mechanism. In the aCH mechanism, a four-coordinate rhodium hydride complex formed through the elimination of R3Si–Cl is a catalytically active species. In the DH mechanism, the active species is a six-coordinate complex with two Rh–H bonds. For the C═O double bond hydrosilylation, the rate-determining steps of the aCH and DH mechanisms are both acetone insertion into the Rh–H bond, and the order of the activation barrier is DH < aCH ≈ CH < mCH. For the C═C double bond hydrosilylation, except for the mCH pathway whose rate-determining step is the hydrosilane addition reaction, the rate-determining steps of the CH, aCH, and DH pathways are Si–C reductive elimination reactions. The order of the energy barrier is DH ≈ mCH < aCH ≈ CH. In the outer-sphere mechanism, no stable intermediate or transition state was found. Consequently, we concluded that the DH mechanism is adopted as the mechanism for the Rh-catalyzed hydrosilylation of the carbonyl group while the mCH or DH mechanism is adopted as the mechanism for alkenes under conditions where their active intermediates are formed. The present result revises a hypothesis that the hydrosilylation of the carbonyl group is in general accomplished by the mCH mechanism. The active species in the DH mechanism has one more extra Rh–H bond compared to that of the other pathways, and its interaction with a silyl group, trans-influence, and small steric effect are the origin of the highly efficient catalytic activity, which was not reported before.

Low-temperature complete oxidation of ethylene by the mesoporous silica-supported Pt catalyst is a forefront technology for food preservation. Public implementations of the Pt catalyst have already begun, and spectroscopy analyses on the catalytic mechanism have been reported. In this study, density functional theory calculations were conducted to clarify the potential energy profile and electronic mechanism of the catalytic reaction. Based on the experimental findings, a reaction pathway was proposed for ethylene oxidation up to CO2formation via the HCHO intermediate. Among several possibilities, a reaction pathway via ethylene dioxide species is energetically plausible for the C–C bond cleavage to generate HCHO. Particular focus was given to the electronic effect of the silica support in the ethylene dioxide route. The reservoir effect, in which the siloxide groups take electrons from the Pt moiety, reduces the activation energy of the C–C bond cleavage step by taking electrons from the σ(C–C) orbital.