CC Bond Cleavage Research Articles

Photocatalytic selective oxidation of glycerol to formic acid and formaldehyde over surface cobalt-doped titanium dioxide.

Glycerol is one of the most important biomass platform compounds that is a by-product of biodiesel production, and the selective cleavage of the CC bond of glycerol to produce liquid hydrogen carriers (i.e., formic acid and formaldehyde) offers a viable strategy to alleviate the currently faced energy shortages. However, the harsh reaction conditions, long reaction times, poor yields of liquid hydrogen carriers, and the tendency of peroxidation to carbon dioxide (CO2) make the selective CC bond cleavage of glycerol more challenging. Herein, we report the selective CC bond cleavage of glycerol to formic acid and formaldehyde using surface cobalt (Co)-doped titanium dioxide (TiO2) under light irradiation and ambient conditions. The optimized system exhibits a high conversion of glycerol (95%) and the yield of liquid hydrogen carriers reaches 78% (formic acid, 57%; formaldehyde, 21%) in 8h, effectively preventing their peroxidation to CO2. The outstanding photocatalytic performance is mainly attributed to the introduction of Co species and oxygen vacancies that promote the separation of photogenerated charges and holes and provide more adsorption sites for oxygen which are electron acceptors, respectively. In-depth investigations have shown that photogenerated holes and superoxide radicals are the main active species in this reaction. This work presents an effective and promising strategy for the efficient utilization of biomass resources.

Hydrothermal synthesis of bismuth cluster-modified covalent triazine framework composite photocatalysts with effective performance in selective C[sbnd]C bond cleavage of lignin

With regard to the low production of aromatic monomers generated from renewable resources, improving the selective CC bond cleavage in lignin could be the solution. Here, a novel CTF-Bi cluster photocatalyst was firstly prepared by hydrothermal method. A series of Bi/CTF composite photocatalysts varying in Bi cluster content were synthesized using confined growth techniques. CB-3 with a Bi addition of 0.075 g exhibited superior photocatalytic performance, achieving a high depolymerization rate of 78.4 % for lignin model compound, and benzoic acid, benzaldehyde, and phenyl formate were the three main products with the yield of 65.2 %, 81.4 %, and 52.6 %, respectively. Mechanistic studies demonstrated that the localized surface plasmon resonance (LSPR) could suppress the reconjunction of photogenerated electrons and holes, thus improving the photocatalytic efficiency. In addition, the conduction band (CB) and valence band (VB) positions of the photocatalyst affected the selective CC bond cleavage via influencing the production of free radicals. This research offers a novel approach for the selective depolymerization of lignin, which further improved depolymerization efficiency and product selectivity, contributing to advancements in both academic research and practical biomass conversion.

Production of highly oxidized starch in a flow cell using a nickel anode

This study emphasizes the potential of using sustainable and low-cost methods to process biopolymers, contributing to eco-friendly biorefinery technologies. In this context, the transformation of potato starch, a readily available biopolymer, into carboxylic acid starch (CAS) with high yield using an electrochemical process was achieved. As a result of the green transformation, the potato starch was oxidized into CAS, achieving 31 % oxidation of the available glycosyl groups. The transformation was conducted using a NiOOH anode in a FM01-LC flow cell, consuming 19 kWh/kg of energy per kilogram of modified starch. Different analytical techniques such as FTIR and NMR spectroscopies, iodine test, elemental analysis, Scanning Electron Microscopy (SEM) and acid base titration were used to characterize the electrolyzed samples. The results of these analyses revealed CC bond cleavage, opening of the glycosyl rings without significant degradation of the polymer structure. Data from the oxidation of model compounds, maltose and maltotriose at a nickel anode in the same medium supports that CC bond cleavage occurs at the ring carbons under these specific conditions. The use of a lab-scale flow cell with a higher electrode area and lower electrolyte volume improved energy efficiency, making this method affordable and easily scalable.

Collision-Induced Dissociations of Linear Hexose and Disaccharides with Linear Hexose at the Reducing End.

Characterization of carbohydrate structures using mass spectrometry is a challenging task. Understanding the dissociation mechanisms of carbohydrates in the gas phase is crucial for characterizing these structures through tandem mass spectrometry. In this study, we investigated the collision-induced dissociation (CID) of glucose, galactose, and mannose in their linear forms, as well as the linear forms of hexose at the reducing end of 1-6 linked disaccharides, using quantum chemistry calculations and tandem mass spectrometry. Our results suggest that the dehydration reaction in linear structures is unlikely to occur due to the significantly high reaction barrier compared to those of C═O migration and C-C bond cleavage. We demonstrate that the different intensities of the cross-ring fragments observed in the CID spectra can be explained by the different transition state energies of C═O migration and C2-C3, C3-C4, and C4-C5 bond cleavages, and the branching ratios of the cross-ring fragments are significantly different between glucose and galactose. The application of the cross-ring fragments to oligosaccharides reveals that the stereoisomers of glucose and galactose in oligosaccharides can be differentiated based on the relative intensities of the cross-ring fragments produced by the C2-C3 bond cleavage and C3-C4 bond cleavage, a differentiation that cannot be achieved by conventional tandem mass spectrometry.

Interface-rich porous Fe-doped hcp-PtBi/fcc-Pt heterostructured nanoplates enhanced the C[sbnd]C bond cleavage of C3 alcohols electrooxidation

Efficient CC bond cleavage and the complete oxidation of alcohols are key to improving the efficiency of renewable energy utilization. Herein, we successfully prepare porous Fe-doped hexagonal close-packed (hcp)-PtBi/face-centered cubic (fcc)-Pt heterostructured nanoplates with abundant grain/phase interfaces (h-PtBi/f-Pt@Fe1.7 PNPs) via a simple solvothermal method. The open porous structure, abundant grain/phase interface and stacking fault defects, and the synergistic effect between intermetallic hcp-PtBi and fcc-Pt make h-PtBi/f-Pt@Fe1.7 PNPs an effective electrocatalyst for the glycerol oxidation reaction (GOR) in direct glycerol fuel cells (DGFCs). Notably, the h-PtBi/f-Pt@Fe1.7 PNPs exhibit an excellent mass activity of 7.6 A mgPt−1 for GOR, 4.75-fold higher than that of commercial Pt black in an alkaline medium. Moreover, the h-PtBi/f-Pt@Fe1.7 PNPs achieve higher power density (125.8 mW cm−2) than commercial Pt/C (81.8 mW cm−2) in a single DGFC. The h-PtBi/f-Pt@Fe1.7 PNPs can also effectively catalyze the electrochemical oxidation of 1-propanol (17.1 A mgPt−1), 1,2-propanediol (7.2 A mgPt−1), and 1,3-propanediol (5.2 A mgPt−1). The in-situ Fourier-transform infrared spectra further reveal that the CC bond of glycerol, 1-propanol, 1,2-propanediol, and 1,3-propanediol was dissociated for the complete oxidation by the h-PtBi/f-Pt@Fe1.7 PNPs. This study provides a new class of porous Pt-based heterostructure nanoplates and insight into the intrinsic activity of different C3 alcohols.

Thermal decomposition of alkenes: role of allylic C-C bond cleavage

Thermal decomposition of alkenes is critical in many chemical processes. In the alkene moiety, allylic CC bonds are significantly weaker than alkylic and vinylic CC bonds. To address literature discrepancies in the rate of allylic CC bond cleavage, the current work investigates the thermal decomposition of two prototype molecules, namely 1-hexene (k1) and 4-methyl-1-pentene (k2). The formation of product allyl radicals is tracked using a highly sensitive UV laser diagnostic to determine the rate coefficients of k1 and k2 over 1178–1359 K in a shock tube. Both reactions exhibit a positive Arrhenius temperature dependence, with the decomposition of 4-methyl-1-pentene occurring 1.5–3 times faster than that of 1-hexene. Values of k1 adopted in literature models vary by an order of magnitude.By integrating our previous measurements of 1-butene and 1-pentene decomposition (Zhou et al., 2024), this work establishes a comprehensive set of rate rules that encompasses the decomposition of allylic-primary (P), allylic-secondary (S21 and S22), and allylic-tertiary (T) CC bonds. At 1200 K, the decomposition of a tertiary allylic CC bond (kT) occurs 42 times faster than that of the primary CC bond (kP). Notably, our established rate rules caution against commonly adopted analogies between the rate coefficients of the thermal decomposition of 1-butene and 1-pentene, as kS21 proceeds 3–7 times faster than kP.The implementation of these rate rules in various kinetic models of alkenes and biofuels greatly enhances the accuracy of their predictions. This work thus contributes to a deeper understanding of the mechanisms underlying soot formation during from the combustion of unsaturated fuels.

Observation of oxygenated intermediates in functional mimics of aminophenol dioxygenase

Aminophenol dioxygenases (APDO) are mononuclear nonheme iron enzymes that utilize dioxygen (O2) to catalyze the conversion of o-aminophenols to 2-picolinic acid derivatives in metabolic pathways. This study describes the synthesis and O2 reactivity of two synthetic models of substrate-bound APDO: [FeII(TpMe2)(tBu2APH)] (1) and [FeII(TpMe2)(tBuAPH)] (2), where TpMe2 = hydrotris(3,5-dimethylpyrazole-1-yl)borate, tBu2APH = 4,6-di-tert-butyl-2-aminophenolate, and tBuAPH2 = 4-tert-butyl-2-aminophenolate. Both Fe(II) complexes behave as functional APDO mimics, as exposure to O2 results in oxidative CC bond cleavage of the o-aminophenolate ligand. The ring-cleaved products undergo spontaneous cyclization to give substituted 2-picolinic acids, as verified by 1H NMR spectroscopy, mass spectrometry, and X-ray crystallography. Reaction of the APDO models with O2 at low temperature reveals multiple intermediates, which were probed with UV–vis absorption, electron paramagnetic resonance (EPR), Mössbauer (MB), and resonance Raman (rRaman) spectroscopies. The most stable intermediate at −70 °C in THF exhibits multiple isotopically-sensitive features in rRaman samples prepared with 16O2 and 18O2, confirming incorporation of O2-derived atom(s) into its molecular structure. Insights into the geometric structures, electronic properties, and spectroscopic features of the observed intermediates were obtained from density functional theory (DFT) calculations. Although functional APDO models have been previously reported, this is the first time that an oxygenated ligand-based radical has been detected and spectroscopically characterized in the ring-cleaving mechanism of a relevant synthetic system.

3D hollow superstructures endow PdAg electrocatalyst with selective ethanol electrooxidation

Direct ethanol fuel cells (DEFCs) have been considered as future power devices for many portable applications. The ethanol oxidation reaction (EOR), that is, a multielectron process, suffers from low efficiency owing to the high selectivity to the 4e− pathway (C2 pathway) and low selectivity to the 12e− pathway (C1 pathway). The preparation of efficient catalysts with high C1 pathway selectivity is regarded as a promising and fascinating field. Herein, we first advance a one-pot synthesis of 3D PdAg superstructures (SSs) with a hollow interior and ultrathin nanosheet shell. PdAg SSs achieve a mass activity of 5.27 A mg−1 for the alkaline EOR and a Faraday efficiency of 22.7 % for the C1 pathway, which is 5.7 and 7.5 times higher than that of commercial Pd/C, respectively. Mechanism studies confirm that the construction of the Pd-Ag system greatly facilitates the oxidation of the C1 intermediates (*CH3 and *CO) and enhances the CC bond cleavage ability of the catalyst. This work not only highlights an active Pd-based catalyst for the selective EOR, but also sheds light on the formation of 3D open nanostructure via self-assembly of 2D nanosheets.

Oxygenolytic cleavage of 1,2-diols with dioxygen by a mononuclear nonheme iron complex: Mimicking the reaction of myo-inositol oxygenase

A mononuclear iron(II) complex, [(TpPh2)FeII(OTf)(CH3CN)] (1) (TpPh2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate, OTf = triflate) has been isolated and its efficiency toward the aliphatic CC bond cleavage reaction of 1,2-diols with dioxygen has been investigated. Separate reactions between 1 and different 1,2-diolates form the corresponding iron(II)-diolate complexes in solution. While the iron(II) complex of the tetradentate TPA (tris(2-pyridylmethyl)amine) ligand is not efficient in affecting the CC cleavage of 1,2-diol with dioxygen, complex 1 displays catalytic activity to afford carboxylic acid and aldehyde. Isotope labeling studies with 18O2 reveal that one oxygen atom from dioxygen is incorporated into the carboxylic acid product. The oxygenative CC cleavage reactions occur on the 1,2-diols containing at least one α-H atom. The kinetic isotope effect value of 5.7 supports the abstraction of an α-H by an iron(III)-superoxo species to propagate the CC cleavage reactions. The oxidative cleavage of 1,2-diolates by the iron(II) complex mimics the reaction catalyzed by the nonheme diiron enzyme, myo-inositol oxygenase.

Investigation of cyclopentene + OH and cyclopentene thermal decomposition reactions

This study presents the first high-temperature measurements of cyclopentene+OH→k1Products reaction over 856 – 1258 K and 1.03 – 4.33 bar. The determined rate coefficients of k1 exhibited Arrhenius temperature dependence with an activation energy ∼ 3.3 kcal mol−1 and negligible pressure dependence. Rate coefficients of OH + cyclopentene are faster than OH + 1-pentene but comparable to OH + 2-pentene, highlighting the significance of allylic CH bonds in these reactions. At 1258 K, our rate coefficient is ∼ 30 % slower than the average room-temperature measurement, indicating the role of OH-addition pathways at low temperatures. Site-specific rate coefficients and branching ratios are determined, with H-abstraction at the allylic CH site accounting for ∼68 % of the reaction and alkylic CH bond contributing ∼22 %. Our measured k1 may be given as (unit: cm3molecule−1s−1):k1=1.64×10−10e(−1660T)Cyclopentene decomposition reaction (cyclopentene→k2cyclopentadiene+H2) is studied over 1186–1472 K and 1.17 – 1.38 bar. Time-resolved yields of the product, cyclopentadiene, are monitored using a sensitive UV laser diagnostic near 220 nm. Absorption cross-sections of cyclopentadiene, measured in two separate mixtures, showed weak positive temperature dependence (8.7 – 9.8 × 10−18 cm2molecule−1) over 961 – 1326 K. Our rate coefficients of k2 exhibited a positive Arrhenius temperature dependence with an activation energy of ∼ 54.7 kcal mol−1. At 1300 K, the decomposition of cyclopentene proceeds 5.5 and 28 times faster than that of cyclopentadiene and cyclopentane, respectively. Our measured k2 may be expressed as (unit: s−1):k2=2.55×1012e(−27,527.6T)The pentagonal structure of cyclopentene influences its H-abstraction and decomposition reactions distinctively. While H-abstraction by OH follows a mechanism akin to cyclohexene and linear alkenes, with comparable rate coefficients at allylic CH bonds, the penta-ring structure significantly impacts the decomposition mechanism. Cyclopentene decomposition predominantly produces cyclopentadiene and H2 in a ring-conserving manner, differing from the cleavage of allylic-alkylic CC bonds in the decompositions of 1-alkenes and cyclohexene.

C[sbnd]C bond cleavage in the electrooxidation of 2,3-butanediol controlled by an ionic liquid modifier

In heterogeneous catalysis, ionic liquids (ILs) are used as chemical modifiers to control selectivity. In our work, we aim to apply the same concept to electrocatalytic systems. As a model reaction, we studied the electrooxidation of 2,3-butanediol on the low-index Pt(111), Pt(100) and Pt(110) surfaces in an acidic environment. We used the IL 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([C2C1Im][OTf]) dissolved in an aqueous electrolyte as a catalyst modifier. The reaction mechanisms were investigated by electrochemical infrared reflection absorption spectroscopy (EC-IRRAS). The oxidation of 2,3-butanediol is highly structure dependent. On all three surfaces, the two products formed are acetoin and diacetyl, i.e. either one or two alcohol functionalities are oxidized. However, we observe distinct features on the different surfaces with respect to activity, potential window of oxidation, and selectivity. Only the Pt(100) surface is active towards CC bond cleavage. The latter reaction leads to the formation of COads and poisoning of the catalyst. Modification of this surface by addition of the IL leads to an increase of the selectivity for acetoin from 51 % to 78 % (at 1.1 VRHE). In addition, CC bond cleavage is suppressed, no CO is formed, and the surface remains active for the target reaction. We attribute these effects to the reversible and structure dependent adsorption of the [OTf]− anions on the Pt surfaces and additional interionic interactions. Our results demonstrate the potential of ILs to control selectivity in electrocatalytic reactions.

Dry reforming of ethane over titania-based catalysts for higher selectivity and conversion to syngas

Ethane, one of the key components of shale gas, is a valuable feedstock for the production of syngas (CO + H2) via the CC bond cleavage during dry reforming of ethane (DRE) reaction. Selective catalysts are needed to direct this reaction pathway against the competing CH bond cleavage for ethylene formation. In this study, Fe, V and Rh oxides supported on TiO2 catalysts were prepared by impregnation method. The catalysts were tested for DRE with the main target of enhancing selectivity to syngas (CO and H2) and reducing byproducts (methane and ethylene) formation. The catalysts were characterized using X-ray diffraction, scanning electron microscopy, NH3/CO2 temperature programmed desorption and H2-temperature programmed reduction. Temperature programmed oxidation was utilized to characterize the coke contents of the spent catalysts. The catalysts were evaluated for DRE reaction in a fixed-bed reactor at the temperature range from 500 °C to 650 °C and CO2/ethane ratio from 2:1 to 10:1 (mol/mol). It was found that ethane conversion over the three catalysts increased in the order Rh/TiO2 > Fe/TiO2 > V/TiO2. Rh/TiO2 catalyst exhibited > 99 % ethane conversion, 36 % and 61 % yields of H2 and CO, respectively, at 650 °C and CO2/ethane ratio of 5.0. The high conversion of ethane was mainly attributed to the enhanced dispersion of Rh oxides on the TiO2 support coupled with the balanced surface acidic and basic sites. The Rh catalyst facilitated CC bond dissociation of ethane thereby forming methyl intermediates which then reacted with adsorbed CO2, thereby enhancing higher syngas production during DRE reaction.

Electrochemical oxidation of glucose in alkaline environment—A comparative study of Ni and Au electrodes

The glucose oxidation reaction (GOR) was studied on Au and Ni electrodes by cyclic voltammetry (CV), rotating disk electrode (RDE) measurements coupled with Koutecky–Levich analysis, Differential Electrochemical Mass Spectrometry (DEMS), in situ Fourier Transform Infrared spectroscopy (FTIRS) and High Performance Liquid Chromatography (HPLC) analysis of the reaction products after electrolysis in potentiostatic mode under continuous flow conditions. This study allowed to identify the reaction products and propose tentative reaction mechanisms. On gold, glucose is adsorbed on metallic sites through its anomeric function (C1) resulting in the formation of gluconate as the main GOR product at potentials close to 0.6 V vs. RHE, with a selectivity towards gluconate close to 100% and a projected faradaic efficiency of ca. 70%. The conversion rate is rather low, close to 20%, due to poisoning of the surface, leading to a strong deactivation. At potentials above 0.7 V vs. RHE, the selectivity towards gluconate decreases and non-selective GOR oxidation proceeds through CC bond cleavage. On nickel, the GOR occurs at high potentials (close to 1.2 V vs. RHE) on Ni(OH)2 and NiOOH sites, and proceeds through C1C2 bond breaking, resulting in arabinose and formate. At higher potentials, the selectivity towards arabinose decreases, formate being the main reaction product.

Iron-catalyzed azidation of cyclobutanol by C[sbnd]C bond cleavage

An iron-catalyzed ring-opening azidation of cyclobutanols through CC bond cleavage is disclosed for the first time. A range of tertiary cyclobutanols are tolerated providing γ-carbonyl-containing secondary alkyl azides. The method provides a straightforward approach for introducing azide group into aliphatic chain of organic molecules. A plausible mechanism involving radical-mediated sequential CC bond cleavage and C−N3 bond formation is proposed.

Revealing the biological significance of multiple metabolic pathways of chloramphenicol by Sphingobium sp. WTD-1

Chloramphenicol (CAP) is an antibiotic that commonly pollutes the environment, and microorganisms primarily drive its degradation and transformation. Although several pathways for CAP degradation have been documented in different bacteria, multiple metabolic pathways in the same strain and their potential biological significance have not been revealed. In this study, Sphingobium WTD-1, which was isolated from activated sludge, can completely degrade 100 mg/L CAP within 60 h as the sole energy source. UPLC-HRMS and HPLC analyses showed that three different pathways, including acetylation, hydroxyl oxidation, and oxidation (C1-C2 bond cleavage), are responsible for the metabolism of CAP. Importantly, acetylation and C3 hydroxyl oxidation reduced the cytotoxicity of the substrate to strain WTD-1, and the C1-C2 bond fracture of CAP generated the metabolite p-nitrobenzoic acid (PNBA) to provide energy for its growth. This indicated that the synergistic action of three metabolic pathways caused WTD-1 to be adaptable and able to degrade high concentrations of CAP in the environment. This study deepens our understanding of the microbial degradation pathway of CAP and highlights the biological significance of the synergistic metabolism of antibiotic pollutants by multiple pathways in the same strain.

Effect of acid sites modification on the catalytic combustion of 1,2-dichloroethane: Revealing the synergy between NbOx and CeO2

1,2-Dichloroethane are primarily sourced from the emissions of the chlor-alkali industry, resulting in severe pollution of soil, air, and water. In this work, Nb/CeO2 catalysts were prepared by impregnation method, and their performance for EDC oxidation was evaluated. The addition of Nb improved the activity, selectivity, and stability of CeO2. Nb was highly dispersed on CeO2 surface in the form of NbOx, and partially entered the lattice of CeO2. This caused lattice distortion and more surface defects, thereby increasing the number of oxygen vacancies. NbOCe bonds formed in between Nb and CeO2 weakened the CeO bonds and enhanced lattice oxygen mobility. The presence of NbOx increased the number of Lewis acid (NbO) and Brønsted acid (Nb-OH) sites, which facilitated the cleavage of CCl and CC bonds. Increased acidity promoted the removal of Cl species in the form of HCl and effectively mitigated the chlorine poisoning of CeO2. In-situ DRIFTS results indicated that EDC oxidation on Nb/CeO2 catalysts followed a Mars-van Krevelen mechanism and progressed via the pathway of alcoholate → formate/methoxy → COx.

Computational exploration on hydroxyl and sulfate radicals-induced aqueous degradation of imipramine

In the present work, hydroxyl (•OH) and sulfate radicals (SO4•−)-induced aqueous degradation of imipramine (IMI) was theoretically probed by carrying out density functional theory (DFT) calculation. Among the initial reactions of •OH (SO4•−) toward IMI, the hydrogen abstraction (HA) reactions occurring on saturated carbon atoms of the alkylamine side chain are the most favorable, followed by the addition (AD) reactions involving unsaturated carbon positions, and the HA reactions related to unsaturated carbon atoms are the most unfavorable. The most favorable subsequent reactions for the initial AD and HA intermediates can afford the hydroxylation, oxidation, dehydrogenation, CN or CC bond cleavage products of IMI, while the corresponding ring-opening reactions occur hard. The stronger oxidizing ability of SO4•− was predicted in comparison with •OH. The cationic form of IMI has lower reactivity than IMI.H2O and O2 molecules may exert a significant influence over aqueous degradation of IMI.

Efficient depolymerization of sodium lignosulfonate assisted by sulfur migration

Lignosulfonate (LS), as the most abundant technical lignin, is hard to depolymerize due to highly condensed structure. To overcome the limitation, in this work, NiMoO4/Al2O3 catalyst with regulated acidity/hydrogenation activity was developed for highly efficient LS depolymerization. Results show that the performance of NiMoO4/Al2O3 was improved by sulfur migration. Meanwhile NiMo alloy contributed to the good stability during LS depolymerization. The NiMoO4/Al2O3 was favor for the intermediate compounds production by the cleavage of CO and CC bonds, which intermediate compounds were eventually hydrogenated to monomers by highly active MoS2. Also, NiMoO4/Al2O3 and sulfonic groups play a synergistic role in the sulfur migration (only 39.1% bio-oil yield obtained by MoS2/Al2O3). After reacting at 300 °C for 4 h, 81.7% of bio-oil yield with 95% desulfurization rate were obtained. Thus, it was demonstrated that an inexpensive catalyst was developed which can efficiently catalyze the depolymerization of lignosulfonate.

Inhibition of terminal C[sbnd]C bonds cleavage drives high selectivity of n-alkane hydroisomerization

Herein we develop a solvent-free one-pot synthesis strategy to simultaneously modify the size effect of metal sites and structural acidity on bifunctional catalysts to in-situ grow platinum nanoparticles (Pt-NPs ∼ 1 nm and ∼ 20 nm) of disparate sizes in the molecular sieve framework without relying on any ligand assistance, causing skeletal defects while exhibiting excellent catalytic performance in n-alkane hydroisomerization. It maintains almost 100 % isomerization selectivity at conversions below 90 %, with performance far superior to that of the conventional catalysts (Pt-NPs ∼ 1 nm). The reason for high selectivity and high liquid yields was revealed by structural characterizations and density functional theory calculations, i.e., the inhibition of terminal CC bond cleavage over n-dodecane chains adsorbed on the defect-containing catalysts and the higher energy barrier of transition state for producing gaseous small molecules, while the size of Pt-NPs may not be the main factor in determining the performance of n-alkane hydroisomerization.

Breaking the C[sbnd]C bond of glucose on tungsten oxide-based catalysts in aqueous phase

In chemistry, selective activation of CC bonds enables the direct production of valuable chemicals from widely available and inexpensive natural materials but remains a fundamental challenge due to their kinetic inertness. The selective cleavage of CC bond in glucose by tungsten oxide-based catalysts in aqueous phase pioneers a path for converting cellulose biomass into valuable ethylene glycol. However, debates regarding the active phase and how it selectively breaks the C6 into C2 fragments have persisted for over a decade. In this study, we present a comprehensive mechanistic investigation by modeling three potential active phases, i.e. the reduced WO3-x surface, the dissolved tungstic acid, and tungsten bronze, in explicit solvent waters. By constrained molecular dynamics simulations, we have demonstrated that the low-coordinated W center can chelate with glucose, forming a metallacyclic complex with a 5-membered ring after the protonation of carbonyl group. The formation of 5-membered ring serves as the premise for the selectivity to C2 fragments via homolytic cleavage of CC bond. Furthermore, the reduced W5+ center is suggested to be crucial in facilitating the cleavage process by stabilizing the dissociated C4 intermediates via a redox process. In conclusion, we propose that the surface decoration of reduced and low-coordinated W sites can act as active heterogeneous catalysts for the selective conversion of cellulose in aqueous phase. These recent findings have the potential to provide valuable insights and strategies for CC bond activation in both biomass conversion and organic synthesis.