Alkaline oxidation of 14C-labelled protolignin, formed from cinnamic acid in spruce and aspen twigs

Simultaneous determination of calycosin-7-O-β-D-glucoside, cinnamic acid, paeoniflorin and albiflorin in rat plasma by UHPLC-MS/MS and its application to a pharmacokinetic study of Huangqi Guizhi Wuwu Decoction

The purpose of this study was to develop a sensitive method for quantifying cinnamic acid in human plasma using UPLC–ESI–MS/MS. Cinnamic acid was separated using water containing 0.005% (v/v) formic acid and acetonitrile as a mobile phase by gradient elution at a flow rate 0.2 mL/min, equipped with a HALO-C18 column (2.1 × 100 mm, 2.7 μm). Quantitation of this analysis was performed on a triple quadrupole mass spectrometer employing electrospray ionization technique, operating in multiple reaction monitoring negative ion mode. The mass transitions were m/z 146.8 → 103.0 for cinnamic acid, and 432.9 → 225.0 for geniposide as internal standard. Liquid–liquid extraction and protein precipitation with ethyl acetate–methanol-1.2% acetic acid (4/16/1, v/v/v) were used in the sample extraction. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma constituents. The calibration curves for cinnamic acid in human plasma were 0.1–500 ng/mL and displayed excellent linearity with correlation coefficients (r) greater than 0.99. Both the intra- and inter-day precisions (CV%) were within 3.88% for human plasma. The accuracy was 99.34–106.69% for human plasma. In vitro plasma protein binding of cinnamic acid was 64.26 ± 1.89 and 65.50 ± 1.78% for the spiked human plasma concentrations of 100 and 1000 ng/mL, respectively. The developed analytical method satisfied the criteria of international guidance and could be successfully applied to the pharmacokinetic study of cinnamic acid after oral administration of Socheongryong-tang tablets to humans.

A rapid and selective hydrophilic interaction chromatography-mass spectrometry (HILIC-MS) method was developed to measure cinnamic acids in dried chili peppers (Capsicum annum) for the purpose of investigating the association between cinnamic acid levels and inhibition of Salmonella growth in the peppers. Trans-cinnamic and hydroxy-cinnamic acids were quantified in 15 varieties of chili peppers by the HILIC-MS method, using electrospray ionization in negative mode with multiple reaction monitoring for detection. Trans-cinnamic acid and 4-OH-cinnamic acid were found in all samples; highest concentrations were 0.81 and 7.15 ppm, respectively. The compound, 2-OH-cinnamic acid was not detected. Mean recoveries of the target compounds from spiked samples were greater than 79%. The pepper samples were evaluated for Salmonella growth inhibition after addition of moisture to the dried samples. No correlation was found between Salmonella growth inhibition and cinnamic acid content, suggesting that these cinnamic acids are not major inhibitory compounds in these peppers. Practical applications The HILIC-MS method developed for the analysis of dried chili peppers is a simple, sensitive method for organic acids and is applicable to any food matrix. Only extraction and automated filtration are employed to produce extracts for analysis. Ammonium formate buffer in the mobile phase, pH 6, enhances ionization of acids for negative ESI-MS detection relative to the degree of ionization from use of acidic mobile phases containing formic or acetic acid modifiers. The use of 4-Cl-benzoic acid as internal standard and evaluation of matrix effects from the dried pepper extracts are important for future research in similar applications. The HILIC chromatographic separation may separate critical peak pairs in pepper extracts that are not resolvable by reversed-phase HPLC.

ABSTRACTBackgroundIn patch testing, co‐reactivity between Myroxylon pereirae resin, colophonium and propolis is well recognised. One of the possible explanations is that these materials have common allergenic ingredients.ObjectivesTo identify the main ingredients in M. pereirae resin and colophonium samples used in the preparation of commercial patch test allergens and to compare their compositions with each other as well as with propolis.Materials and MethodsAnalyses were performed on M. pereirae resin and colophonium samples using gas chromatography–mass spectrometry/flame ionisation detection of the volatile components obtained by headspace SPME (solid phase microextraction).ResultsThe main ingredients in M. pereirae resin were benzyl benzoate, (E)‐nerolidol, benzoic acid, benzyl alcohol, (E)‐cinnamic acid, vanillin and (E)‐benzyl cinnamate. In colophonium, longifolene, caryophyllene oxide, acetone + formic acid, α‐terpineol and δ‐cadinene + calamenene were the major constituents.ConclusionsThe major ingredients of the volatile fractions of M. pereirae resin and colophonium are quite different; common haptens in volatile ingredients cannot readily explain co‐reactivity. M. pereirae resin has cinnamic acid‐ and benzoic acid derivatives in common with propolis and in addition (E)‐nerolidol and vanillin with Brazilian propolis and benzyl alcohol with Chinese propolis. Colophonium shares various ingredients with Brazilian propolis but few with the Chinese variety.

Simultaneous UPLC-MS/MS determination of four components of Socheongryong-tang tablet in human plasma: Application to pharmacokinetic study

Hydrogen is a promising clean energy source replacing largely consumed fossil fuels which emit greenhouse gases such as carbon dioxide causing global warming because water is the only substance after hydrogen burning and a wide variety of energies can be utilized for stable supply of hydrogen. However, hydrogen has serious drawbacks, low energy density and explosive nature, which promotes the use of hydrogen carriers to realize hydrogen storage and transportation with efficiency. Though some hydrogen carriers such as ammonia, liquid hydrogen, and methylcyclohexane have been reported, formic acid is increasingly attractive among them since it can be synthesized from carbon dioxide and hydrogen produced by water-splitting and is a nontoxic organic acid.A number of studies on hydrogen production from formic acid with metal complex catalysts have been developed[1], where a strong acidic solution is needed to decompose formic acid into hydrogen and carbon dioxide efficiently. Moreover, the reaction control is mainly conducted by pH, temperature and pressure. Thus, a simple reaction control alternative to these factors under mild condition is desirable in terms of safety and sustainability.We report herein hydrogen production based on formate decomposition using hybrid catalytic system composed of enzyme (FDH: formate dehydrogenase), photosensitizer (ZnTPPS: Zn (II) meso-tetra(4-sulfonatophenyl)porphyrin), hydrogen evolution catalyst (Pt-PVP: platinum nanoparticles dispersed by polyvinylpyrrolidone), NAD+ and methyl viologen (MV) as electron mediators as shown in Figure 1. By using this system, hydrogen production in neutral pH region was controlled with visible light irradiation.A mixed solution of 200 mM phosphate buffer (4.9 mL, pH 7.0) containing HCOONa (50 µmol), NAD+ (25 µmol), ZnTPPS (50 nmol), MV (250 nmol) and Pt-PVP (250 nmol) was deaerated by freeze-pump-thaw cycle repeated six times, and then gas phase was replaced by argon. 0.10 mL FDH (0.95U) was added to the solution. Finally, the solution was irradiated with 250 W halogen lamp at 30.5 oC. Gas phase was analyzed by gas chromatography to qualify and quantify produced hydrogen and carbon dioxide. Formate in the solution was also analyzed with ion chromatography.In this condition, hydrogen production and formate consumption were on the increase constantly and nearly equal, while apparent carbon dioxide production was half of them. The possible cause is that a part of the produced carbon dioxide which induces global warming was captured in the reaction solution as pH of the solution had been adjusted to 7.0. After 25-hour-irradiation, formate was converted into hydrogen completely. This result illustrates hydrogen production was derived from formate decomposition. In addition, the optimum pH for hydrogen production was investigated in this system ranging from pH 6.0 to pH 8.0. The highest catalytic activity was observed at pH 7.0 because formate oxidation catalyzed by FDH proceeded the most smoothly in the region of pH 7.0-8.0 and more adequate protons to be reduced were in this system at pH 7.0 than pH 8.0. Finally, Figure 2 shows the visible light response of gas production and formate consumption. Hydrogen was produced only in the presence of visible light irradiation whereas carbon dioxide production and formate consumption increased consistently. This means formate oxidation proceeded regardless of the visible light irradiation or non-irradiation producing carbon dioxide while photocatalytic hydrogen production from NADH regenerated by formate dehydrogenation was driven by visible light irradiation.A hybrid catalytic system for visible light-controlled hydrogen production from formate in neutral pH range was constructed successfully, leading to the unharmful and green utilization of formic acid as a useful hydrogen carrier.In this hybrid catalytic system, MV is used as an electron mediator for charge separation, which has been known to inhibit light absorption of photosensitizer due to the absorption overlap between MV• and ZnTPPS[2]. As a result, this system becomes slightly complicated including four redox reactions. Hence, hybrid photocatalytic system without MV will be constructed in the future for efficient and simple hydrogen evolution.Reference[1] W. H. Wang, Y. Himeda, J. T. Muckerman, G. F. Manbeck, E. Fujita, Chem. Rev. 2015, 115, 12936.[2] M. E. El-Khouly, E. El-Mohsnawy, S.Fukuzumi, J. Photochem. Photobiol. C. 2017, 31, 36. Figure 1

Reversibility of the Phosphoroclastic Split of Pyruvate (Utter, M. F., Lipmann, F., and Werkman, C. H. (1945) J. Biol. Chem. 158, 521–531) Chester Hamlin Werkman (1893–1962) was born in Fort Wayne, Indiana. His career in science began at Iowa State University in 1920 when he became a graduate student under Robert E. Buchanan, an internationally recognized microbiologist. Werkman's interest in bacteria stemmed from the fact that he thought of them as simple models for studying the basic chemical transformations involved in living processes. He completed his dissertation in 1923 and remained with Buchanan until he was offered a faculty position at the University of Massachusetts in 1924. However, he returned to the Department of Bacteriology at Iowa State a year later and remained there as a faculty member for the rest of his life. Upon returning to Iowa State, Werkman's research interests underwent a slow evolution. Initially he continued to publish papers related to his thesis work on immunology and vitamins, but soon he developed an interest in food microbiology and the role of vitamins as growth factors for bacteria. During the early 1930s, the Iowa State agricultural experimental station started investigating the use of bacterial fermentation to dispose of farm waste, and Werkman became involved in this effort. This resulted in his publication of a series of papers describing organic techniques to isolate and quantify the products of various fermentation processes. Soon Werkman became interested in investigating the intermediate mechanisms of these fermentations and embarked on what would become a lifelong study of reaction intermediates in bacteria. One of Werkman's most important contributions to physiological microbiology was done with his graduate student, Harland G. Wood. Werkman and Wood established the existence of heterotrophic carbon dioxide fixation (the concept that all organisms, not just plants or specialized bacteria, can utilize CO2), which could be summarized by the “Wood Werkman reaction.” CO2+CH3COCOOH⇌COOHCH2COCOOH Werkman and Wood used 13C-labeled compounds to confirm heterotrophic carbon dioxide fixation and also to study the utilization of carbon in metabolism. To do this, they built a mass spectrometer and a 72-foot thermal diffusion column (to produce concentrated 13C) in the elevator shaft of the science building. They published their first detailed papers on the use of 13C-labeled compounds in the Journal of Biological Chemistry (JBC) (1Wood H.G. Werkman C.H. Hemingway A. Nier A.O. Heavy carbon as a tracer in heterotrophic carbon dioxide assimilation..J. Biol. Chem. 1941; 139: 365-376Abstract Full Text PDF Google Scholar, 2Wood H.G. Werkman C.H. Hemingway A. Nier A.O. The position of carbon dioxide carbon in succinic acid synthesized by heterotrophic bacteria..J. Biol. Chem. 1941; 139: 377-381Abstract Full Text PDF Google Scholar). These and other papers by Wood will be the subject of a future JBC Classic. In 1938, Merton Franklin Utter (1917–1980) joined Werkman's laboratory as a graduate student. Utter, who was born in Westboro, Missouri, had just graduated from Simpson College in Indianola, Iowa. The first paper he published with Werkman was entitled “The Preparation of an Active Juice from Bacteria” (3Wiggert W.P. Silverman M. Utter M.F. Werkman C.H. Preparation of an active juice from bacteria..Iowa State Coll. J. Sci. 1940; 14: 179-186Google Scholar). This was a very modest title considering that active enzyme systems had not yet been isolated from bacteria. Werkman and Utter used these bacterial extracts and 13C-labeled compounds to further investigate carbon dioxide fixation, which is the subject of the JBC Classic reprinted here. The Wood Werkman reaction had already established that carbon dioxide could be combined with aC3 compound, but the existence of a C1 + C2 reaction had not been demonstrated. Werkman and Utter knew that the phosphoroclastic split, in which pyruvic acid is split to make acetyl phosphate and formic acid, was common in Escherichia coli. CH3COCOOHPyruvic acid+H3PO4⇌CH3COOPO3H2acetyl phosphate+HCOOHformic acid If they could prove that this reaction was reversible, it would be an example of a C1 + C2 addition. Although the C1 compound in the reaction is formic acid rather than carbon dioxide, formic acid is in equilibrium with carbon dioxide and hydrogen in E. coli, so carbon dioxide fixation is ultimately involved in the reaction. Werkman and Utter teamed up with Fritz Lipmann (the author of a future JBC Classic), who had just discovered the role of acetyl phosphate in metabolism. To prove the reversibility of the reaction, they added 13C-labeled formic acid to E. coli extracts and tested for 13C in the resulting pyruvic acid. In separate experiments they added CH 133COOH and adenyl pyrophosphate (which would react to form labeled acetyl phosphate) to the extracts. In both cases the pyruvic acid formed contained 13C, demonstrating the reversibility of the phosphoroclastic split and the occurrence of C1 + C2 carbon dioxide fixation. As a final test they added 13CO2 to whole cell suspensions of E. coli and showed that the bacteria produced 13C-labeled pyruvic acid. After earning his Ph.D. with Werkman in 1942, Utter was appointed instructor in bacteriology at Ohio State. In 1944 he was offered an assistant professorship at the University of Minnesota and moved to Minneapolis. He moved again in 1946, this time to Cleveland, Ohio, to become an associate professor of biochemistry at Western Reserve University School of Medicine. Utter was promoted to professor in 1956 and became chairman of the biochemistry department in 1965. He remained as chairman until 1976 and then devoted all of his time to research and teaching in the Department of Biochemistry. Utter was also an associate editor for the JBC and helped to guide the journal's editorial policies during its rapid expansion. Utter continued to study metabolism and soon became interested in gluconeogenesis, which is where he made his most significant contribution to biochemistry. For many years it was believed that the synthesis of glucose (gluconeogenesis) occurred by the reversal of the Embden-Meyerhof pathway in glycolysis. Utter demonstrated that this was incorrect by discovering phosphoenolpyruvate carboxykinase and pyruvate carboxylase, two enzymes that are involved in the conversion of pyruvate to phosphoenolpyruvate in a sequence of reactions that differ from those in glycolysis. Utter, along with Bruce Keech, also provided one of the first examples of allosteric control of an enzyme when he demonstrated that acetyl-CoA regulates pyruvate carboxylase activity. 1All biographical information on Chester Hamlin Werkman was taken from Refs. 4Brown R.W. Biographical Memoir of Chester Hamlin Werkman. 44. National Academy of Sciences, Washington, D. C.1974: 328-358Google Scholar and 5Singleton R. From bacteriology to biochemistry: Albert Jan Kluyver and Chester Werkman at Iowa State..J. Hist. Biol. 2000; 33: 141-180Crossref PubMed Scopus (10) Google Scholar. 1All biographical information on Chester Hamlin Werkman was taken from Refs. 4Brown R.W. Biographical Memoir of Chester Hamlin Werkman. 44. National Academy of Sciences, Washington, D. C.1974: 328-358Google Scholar and 5Singleton R. From bacteriology to biochemistry: Albert Jan Kluyver and Chester Werkman at Iowa State..J. Hist. Biol. 2000; 33: 141-180Crossref PubMed Scopus (10) Google Scholar., 2All biographical information on Merton Franklin Utter was taken from Ref. 6Wood H.G. Hanson R.W. Biographical Memoir of Merton Franklin Utter. 56. National Academy of Sciences, Washington, D. C.1987: 474-499Google Scholar. 2All biographical information on Merton Franklin Utter was taken from Ref. 6Wood H.G. Hanson R.W. Biographical Memoir of Merton Franklin Utter. 56. National Academy of Sciences, Washington, D. C.1987: 474-499Google Scholar.

Convenient and efficient route of the synthesis of [3-14C] cinnamic acid is reported. [1-14C]Benzoic acid, prepared by carbonation of Grignard reagent with [14C]carbon dioxide, was reduced to [1-14C]benzyl alcohol. In the enzymatic step this alcohol was selectively oxidised to [1-14C]benzaldehyde using enzyme YADH (Ec. 1.1.1.1) and immediately condensed with malonic acid. This combined chemical and enzymatic approach allows to obtain [3-14C]cinnamic acid with radiochemical yield higher than 50% in respect to the starting alcohol.

Formic acid and ethanol oxidation reactions on noble metals were extensively studied in the past. However it is still unknown how the catalytic activity of Pd-Pt alloys towards formic acid and ethanol scale with composition. In case of formic acid oxidation, palladium is active at low electrode potentials, where platinum is quickly poisoned by strongly adsorbed CO. On the contrary, for ethanol oxidation, only platinum is active. Thus the activity of the alloys should scale with composition. However multitude of effects, such as surface morphology, segregation and changes in electronic properties make the relationship between composition of Pt-Pd alloys and catalytic activity a complicated one. Oxidation of formic acid on Pt, Pd and Pd-Pt alloys follows a so-called “dual pathway” mechanism, namely formic acid can undergo dehydrogenation leading directly to CO2 (not involving strongly adsorbed CO, COads, as an intermediate) or dehydration leading to formation of COads and its possible further oxidation to CO2. Direct path (dehydrogenation) is operative at relatively low potentials but, in case of Pt, strongly adsorbed COads quickly blocks the surface sites, causing overall low activity of Pt in formic acid oxidation at low potentials. On the contrary for Pd the poisoning by COads at low potentials is much slower and the direct path (dehydrogenation) is operative to a much large extend. As a result Pd is significantly more active than Pt towards formic acid oxidation at low potential. In case of Pt-Pd alloys additional factors, related to surface morphology, must be considered: the number of adjacent Pd atoms required to adsorb formic acid molecule and number of adjacent Pt atoms required to form CO from formic acid. In particular is known that COads cannot be formed from formic acid on isolated Pt atoms, because at least two adjacent Pt atoms are required to dehydrate formic acid molecule and form COads, a phenomenon known as the “ensemble effect”. As a result such isolated Pt atoms can be much more active towards formic acid oxidation directly to CO2, and low Pt concentration Pd-Pt nanoalloys favor formation of such sites, a so called “third body effect”. Also changes in electronic properties, due to Pt-Pd interactions, cannot be excluded. In particular we observed changes in onset potential of formic acid and in the catalytic current density. The changes in surface morphology can to a large extend explain the changes in catalytic currents, and the only observation tentatively suggesting the changes in electronic properties are the difference between Pd and Pd-Pt nanoalloys catalytic activity observed in the cathodic scan. However the changes in formic acid oxidation potential cannot be fully explained by surface morphology. As a result we explain the changes in formic acid oxidation potential based on changes in the electronic properties of the Pd-Pt surface due to interactions between Pt and Pd. In case of ethanol electrooxidation on Pt-Pd alloys similar factors, as mentioned above, must be considered. Additionally we used Differential Electrochemical Mass Spectrometry to distinguish between the possible ethanol oxidation products at different electrode potentials. Most common products of ethanol oxidation on Pt and Pt-Pd is carbon dioxide, acetic acid and acetaldehyde. Although it is known that all of these products are produced during the process of ethanol oxidation, the details of this reaction are still unknown, and how the ethanol oxidation mechanism change with Pt-Pd alloy composition. The use of DEMS allowed us to address those issues and to elucidate the changes in reaction mechanism when Pt is diluted by Pd. Better understanding of the mechanism of ethanol electrooxidation can help to develop new, more active catalysts for low temperature direct ethanol fuel cells. This project was funded from Polish National Science Centre budget based on decision number DEC-2013/09/B/ST4/00099

Formic acid is recognized as a promising hydrogen carrier. It readily decomposes to release hydrogen (and carbon dioxide) in the presence of apposite catalysts. The main deficiency of this practice is that the reverse reaction, the hydrogenation of carbon dioxide to formic acid is an uphill reaction necessitating extreme conditions. Carbon dioxide should be converted to bicarbonate salts since their hydrogenation is reasonable for storing hydrogen. The related approach has a drawback as formate salts are produced. The latter has lower weight percentage of hydrogen and they must be converted to formic acid. The goals of our research were to separate formate salt from the reaction mixture and to convert it to formic acid. In this paper, we present a process that combines the advantages of both methodologies—formic acid is the carrier, but the hydrogen is charged to a bicarbonate ion. This stage completes the formic acid cycle (FAC), which could operate as a continuous process for the production and storage of hydrogen. Additional research, including proper rescaling and optimization, should be carried out in order to assess the potential of such a process as a basis for replacing the present day combustion of fossil fuels with hydrogen usage in fuel cells.

Sustainable production of formic acid from biomass and carbon dioxide

Water-assisted oxygen activation during gold-catalyzed formic acid decomposition under SCR-relevant conditions

The association of formic acid in both carbon dioxide and ethane at 298−318 K and 48−100 bar has been studied using Fourier transform infrared (FTIR) spectroscopy. The equilibrium constant, K, between dimer and monomer of the formic acid was obtained by examination of the carbonyl stretching band for formic acid. The concentrations of formic acid studied ranged from 1.0 to 8.4 mmol/L. In general, the results show that an increase in density causes an increase in the concentration of the formic acid monomer, which results in a decrease in K. The dimerization constant is significantly higher in ethane than in carbon dioxide. This result is a consequence of an enhanced interaction between formic acid (solute) and carbon dioxide (solvent) compared to the interaction between formic acid (solute) and ethane (solvent). Furthermore, the modified lattice-fluid hydrogen-bonding model (MLFHB) has been used to interpret the effects of density on the K. The influence of the carbon dioxide and ethane solvents on the eq...

The processing of cryogenic ices consisting of water and carbon monoxide by different types of radiation is known to lead to the formation of carbon dioxide, formic acid, formaldehyde, and also methanol. In this study, we have investigated these reactions upon electron irradiation with energies between 2 and 20 eV, an energy range typically found in secondary electrons. This is the first time that the reactions have been monitored with a sufficiently fine step width in energy to resolve and identify the primary electron–molecule interactions leading to the specific products. This enables us to elucidate reaction mechanisms by linking these primary electron–molecule interactions to final products. In these reactions, HCO• and HOCO• radicals are key intermediates. Our results show that the HCO• intermediate predominantly leads to formaldehyde, while HOCO• is intermediate to the formation of formic acid. Noticeably, the formation of both formaldehyde and formic acid is enhanced within characteristic energy ranges by resonant electron attachment processes. In contrast, the reactions leading to carbon dioxide show no resonant energy dependence but can be traced back to nonresonant neutral dissociation processes. This reveals that carbon dioxide is linked to neither of these two intermediates. This is in contrast to prior experimental studies, which have proposed that carbon dioxide is formed by loss of a H• radical from HOCO•. However, our results confirm theoretical studies that have predicted that carbon dioxide formation from HOCO• is not very efficient, because HOCO• presents an energetic well and quickly loses any excess energy it might have in an ice matrix. Instead, we provide evidence that the primary electron–molecule interaction leading to the formation of carbon dioxide in cryogenic ices of water and carbon monoxide is the neutral dissociation of water into O atoms and H2. The so-formed O atoms then react directly with carbon monoxide to yield carbon dioxide.

The methylation of amines for the synthesis of methylamines and dimethylamines as platform chemicals has been attempted mostly by homogeneous catalysts with acid additives. However, there are scarcely any reports on heterogeneous catalytic methylation reactions except for a routine approach under high temperature and high pressure of CO2 and H-2 gases for extended reaction times. Here we report a heterogeneously catalyzed selective methylation of aromatic amines using reactive and nontoxic formic acid as the only source for the construction of methyl groups, under ambient pressure in an additive-free one-pot reaction condition. Equal proportions of Pd and Ag in the PdAg/Fe3O4/N-rGO catalyst deliver highly selective amine methylation without aromatic ring hydrogenation, as the strained Pd in the alloy is combined with the graphene-derived support, preventing nanoparticle agglomeration and the action of magnetite as a promoter. Both N-methylation and N, N-dimethylation of various substituted aromatic amines were performed with complete conversion and excellent 90-97% selectivity by controlling the reaction times in the range of 10-24 h at 140 degrees C without unwanted aromatic ring hydrogenation. Furthermore, the developed bimetallic catalyst provided high yields (88-91%) of methylation with CO2+H-2 gas under high pressure, which are as good as the results of homogenous catalysts with an acid additive. To the best of our knowledge, our use of this environmentally friendly methodology is the first time that this durable heterogeneous catalyst has readily performed highly selective methylation at ambient pressure, which is attractive for industrial applications.