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1.
Top Curr Chem (Cham) ; 378(1): 11, 2020 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-31903506

RESUMO

The dramatic increase in atmospheric carbon dioxide (CO2) concentrations has attracted human attention and many strategies about converting CO2 into high-value chemicals have been put forward. Metal-organic frameworks (MOFs), as a class of versatile materials, have been widely used in CO2 capture and chemical conversion, due to their unique porosity, multiple active centers and good stability and recyclability. Herein, we focused on the processes of chemical conversion of CO2 by MOFs-based catalysts, including the coupling reactions of epoxides, aziridines or alkyne molecules, CO2 hydrogenation, and other CO2 conversion reactions. The synthesized methods and high catalytic activity of MOFs-based materials were also analyzed systematically. Finally, a brief perspective on feasible strategies is presented to improve the catalytic activity of novel MOFs-based materials and explore the new CO2 conversion reactions.


Assuntos
Dióxido de Carbono/química , Estruturas Metalorgânicas/química , Alcenos/química , Aminas/química , Aziridinas/química , Catálise , Compostos de Epóxi/química , Hidrogenação , Líquidos Iônicos/química
2.
Food Chem ; 306: 125611, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31606631

RESUMO

Aromatic secondary metabolites are closely related to quality attributes of postharvest fruit. In the present study, 20% CO2 was applied to strawberry fruit to investigate the regulation of elevated CO2 on aromatic secondary metabolites. The results showed that elevated CO2 delayed accumulations of anthocyanins, eugenol and lignin. Phenylalanine and tyrosine, the precursors of the above secondary metabolites, were 18.90% and 35.61%, respectively, lower in CO2-treated fruit compared with the control on day 6. Furthermore, enzyme activities and transcriptional profiles analysis showed pentose phosphate pathway and glycolysis were activated by elevated CO2 whereas the aromatic amino acids (AAAs) pathway was inhibited. These results indicated that elevated CO2 restricted carbon flux into aromatic secondary metabolism by inhibiting the AAAs pathway, leading to the decrease of phenylalanine and tyrosine, and thus, delayed the accumulation of aromatic secondary metabolites. In addition, the effect of elevated CO2 was eliminated after transferred CO2-treated fruit to air.


Assuntos
Fragaria/metabolismo , Antocianinas/análise , Antocianinas/metabolismo , Dióxido de Carbono/química , Eugenol/análise , Eugenol/metabolismo , Fragaria/química , Frutas/química , Frutas/metabolismo , Lignina/análise , Lignina/metabolismo
3.
Food Chem ; 307: 125550, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31639575

RESUMO

Modified atmosphere has widely been evident to contribute to fruit quality maintenance, however the correlation among these quality traits was less known. To explore main factors of elevated atmosphere and reduce the detection indexes, we exposed strawberry to either high O2 (80% O2 + 20% N2) or CO2 (20% CO2 + 20% O2 + 60% N2) atmosphere and compared quality characteristics. It was demonstrated that both atmospheres well maintained the fruit firmness, alleviated weight loss and decay rate. Elevated O2 maintained the polyphenolic contents and cell integrity by significantly decreasing superoxide and hydrogen peroxide levels. PCA analysis implied that HO treatment mainly affected oxygen metabolism while HCO affected carbon metabolism more. Significantly positive correlation was observed between weight loss, anthocyanin content and decay rate in elevated O2 and control groups. This study provided new insights into correlation and difference between impact of elevated O2 and CO2 to postharvest preservation.


Assuntos
Armazenamento de Alimentos , Fragaria/química , Oxigênio/química , Antocianinas/metabolismo , Dióxido de Carbono/química , Fragaria/metabolismo , Frutas/química , Peróxido de Hidrogênio/metabolismo , Superóxidos/metabolismo
4.
Food Chem ; 308: 125555, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31655483

RESUMO

Saccharomyces cerevisiae flor yeast is used for the first time in sparkling wine-making. Twenty-six oenological variables and fifty-three volatile metabolites are quantified in the middle (P = 3 bar) and at the end (P = 6 bar) of the second fermentation, carried out in open and closed bottles. A heat-map of volatiles and the fingerprints obtained for ten chemical families and ten odorant series visualize the changes for each condition. Terpenes, fatty acids and volatile phenols increased their contents by pressure effect at the end of the study by 25.0, 7.8 and 2.2%, respectively. The remaining families decrease between 17.4% and 30.1% for furanic compounds and esters in the same stage. A Principal Component Analysis established that nine volatiles are mainly affected by pressure and five by fermentation stage. The use of ethanol-tolerant flor yeasts constitutes an innovative procedure for the enhancement of the sparkling wines diversification.


Assuntos
Dióxido de Carbono/química , Fermentação , Saccharomyces cerevisiae/metabolismo , Vinho/análise , Dióxido de Carbono/análise , Ésteres/análise , Odorantes/análise , Pressão
5.
Carbohydr Polym ; 227: 115380, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31590848

RESUMO

Old corrugated containers with low recyclability were used as raw materials to synthesize a series of aerogels with varying cellulose concentrations in NaOH/urea solution via a freeze-drying process. The resulting aerogels had a rich porous structure with specific surface areas in the range of 132.72-245.19 m2.g-1 and mesopore volumes in the range of 0.73-1.53 cm3.g-1, and were tested for CO2 sorption at ambient temperature and pressure, displaying excellent CO2 adsorption capacities in the range of 1.96-11.78 mmol.g-1. Furthermore, the CO2/N2 selectivity of aerogels decreased with decreasing specific surface area, which was mainly caused by the decrease in CO2 capture. In addition, the CO2 sorption capacity of the sample with 2% cellulose content, CA-2, exceeded the values reported so far for many other sorbents with higher specific surface areas, and showed reasonable cyclic stability for CO2 capture. Therefore, this adsorbent represents an attractive prospect for CO2 uptake at room temperature.


Assuntos
Dióxido de Carbono/química , Sequestro de Carbono , Celulose/química , Adsorção , Géis , Papel , Porosidade , Reciclagem , Hidróxido de Sódio/química , Ureia/química
6.
Top Curr Chem (Cham) ; 378(1): 6, 2019 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-31840192

RESUMO

Ferrites are a large class of oxides containing Fe3+ and at least another metal cation that have been investigated for and applied to a wide variety of fields ranging from mature technologies like circuitry, permanent magnets, magnetic recording and microwave devices to the most recent developments in areas like bioimaging, gas sensing and photocatalysis. In the last respect, although ferrites have been less studied than other types of semiconductors, they present interesting properties such as visible light absorption, tuneable optoelectronic properties and high chemical and photochemical stability. The versatility of their chemical composition and of their crystallographic structure opened a playground for developing new catalysts with enhanced efficiency. This article reviews the recent development of the application of ferrites to photoassisted processes for environmental remediation and for the synthesis of solar fuels. Applications in the photocatalytic degradation of pollutants in water and air, photo-Fenton, and solar fuels production, via photocatalytic and photoelectrochemical water splitting and CO2 reduction, are reviewed paying special attention to the relationships between the physico-chemical characteristics of the ferrite materials and their photoactivated performance.


Assuntos
Compostos Férricos/química , Luz Solar , Poluentes Atmosféricos/química , Dióxido de Carbono/química , Dióxido de Carbono/metabolismo , Catálise , Hidrogênio/química , Hidrogênio/metabolismo , Água/química , Purificação da Água
7.
Diving Hyperb Med ; 49(4): 298-303, 2019 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-31828749

RESUMO

INTRODUCTION: Scrubbers in closed-circuit rebreather systems remove carbon dioxide (CO2) from the exhaled gas. In an attempt to be more user-friendly and efficient, the ExtendAir® non-granular, pre-formed scrubber cartridge has been developed. The cartridge manufacturer claims twice the absorptive capacity of granular CO2 absorbent, with less variability, lower work of breathing, and reduced exposure to caustic chemicals after a flood. To our knowledge there are no published data that support these claims. METHODS: Cartridge (ExtendAir®) and granular (Sofnolime® 797) scrubbers of equal volume and mass were tested five times in an immersed and mechanically ventilated O2ptima rebreather. Exercise protocols involving staged (90 minutes 6 MET, followed by 2 MET) and continuous (6 MET) activity were simulated. We compared: duration until breakthrough, and variability in duration, to endpoints of 1.0 kPa and 0.5 kPa inspired partial pressure of CO2; inspiratory-expiratory pressure difference in the breathing loop; and pH of eluted water after a 5 minute flood. RESULTS: Mean difference in scrubber endurance was 0-20% in favour of the ExtendAir® cartridge, depending on exercise protocol and chosen CO2 endpoint. There were no meaningful differences in endpoint variability, inspiratory-expiratory pressure in the loop, or pH in the eluted water after a flood. CONCLUSIONS: Cartridge and granular scrubbers were very similar in duration, variability, ventilation pressures, and causticity after a flood. Our findings were not consistent with claims of substantial superiority for the ExtendAir® cartridge.


Assuntos
Dióxido de Carbono/química , Dióxido de Carbono/metabolismo , Mergulho , Humanos , Pressão Parcial , Respiração , Dispositivos de Proteção Respiratória , Água
8.
Sci Total Environ ; 695: 133838, 2019 Dec 10.
Artigo em Inglês | MEDLINE | ID: mdl-31756859

RESUMO

Biological sequestration of CO2 for generating value added products is an emerging strategy. Succinic acid (SA) is an important C4 building block chemical, and its biological production via CO2 sequestration, holds many practical applications. This study presents an in-depth insight on SA production using isolated strain belonging to genus Citrobacter, more closely related to Citrobacter amalonaticus by considering critical process parameters such as different carbon sources at various initial concentrations, buffering agent (NaHCO3) concentrations and different pH conditions. The effect of H2 gas as an electron donor and availability of CO2 during SA production was also evaluated. The results from this work demonstrated that the isolated strain depicted the ability to utilize diverse carbon sources and highest SA production was achieved with sucrose as a substrate, indicating that reduced carbon substrates help in maximizing the redox potential. Incorporation of CO2 and H2 not only enhanced the production of SA but also affected the total acids profile favoring the production of SA over lactic, formic and acetic acids. Additional supply of CO2 and H2 led to maximum SA production of 12.07 gL-1, productivity of 0.36 gL-1 h-1 and SA yield of 48.5%. In control operation when no gases were supplied and in other test conditions where either of the gases were supplied, lactic acid was the major end product followed by acetic acid. The positive effect of CO2 for SA production provides scope for sustainable integration of SA and the CO2-generating biofuel industries or industrial side streams.


Assuntos
Dióxido de Carbono/metabolismo , Citrobacter/fisiologia , Ácido Succínico/metabolismo , Dióxido de Carbono/química , Sequestro de Carbono , Elétrons , Fermentação
9.
J Mass Spectrom ; 54(10): 791-801, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31652381

RESUMO

Supercritical fluid chromatography (SFC) has experienced a particular revival in recent years thanks to the development of robust and efficient commercial systems. Because of its physico-chemical properties, supercritical carbon dioxide (CO2 ) mixed with cosolvents and additives is particularly suitable for SFC to allow the elution of compounds of different polarities and more particularly complex lipids. Hyphenation with mass spectrometry (MS) is increasingly described in the literature but still requires many further developments in order to be as user-friendly as coupling with liquid chromatography. The basic concepts of SFC and MS hyphenation will be first considered. Then a representative example of method development in lipidomics will be introduced. In conclusion, the challenges and future needs in this field of research will be discussed.


Assuntos
Cromatografia com Fluido Supercrítico/métodos , Lipídeos/análise , Espectrometria de Massas em Tandem/métodos , Acetatos/química , Técnicas Biossensoriais , Dióxido de Carbono/química , Limite de Detecção , Reprodutibilidade dos Testes , Solventes/química
10.
Top Curr Chem (Cham) ; 377(6): 32, 2019 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-31654264

RESUMO

Metal-organic frameworks (MOFs) are an emerging class of porous crystalline materials attracting attention for their vast array of topologies as well as potential applications in gas storage, heterogeneous catalysis, and molecular sensing. In most cases, organocarboxylates (or corresponding carboxylic acids) are the most common building block, achieving well-defined metal-carboxylate coordination motifs in MOF structures. However, organosulfonates (or corresponding sulfonic acids) have been less well studied in MOF chemistry, probably owing to the weak coordination tendency of the sulfonate oxygens toward metal centers. This review summarizes the research on organosulfonate-based porous crystalline MOFs in recent years. The construction of most porous organosulfonate MOFs relies on using either a second N-donor ligand or carboxylate-sulfonate bifunctional ligands. Despite occupying more confined porosity than the carboxylate counterpart, the permanent porosity in organosulfonate MOFs is often highly polar and hydrophilic. Thus, organosulfonate MOFs often exhibit improved proton/Li+ conductivity as well as CO2 affinity compared with their carboxylate-based counterparts. In addition, the application of organosulfonate MOFs in molecular sensing, molecular sieving, catalysis, and anion exchange are discussed in this review as well.


Assuntos
Estruturas Metalorgânicas/química , Ácidos Sulfônicos/química , Dióxido de Carbono/química , Ácidos Carboxílicos/química , Catálise , Estruturas Metalorgânicas/síntese química , Porosidade
11.
Chem Biodivers ; 16(12): e1900401, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31654480

RESUMO

The complement system participates in host defense by eliminating microorganisms and triggering inflammation. However, insufficient control or exacerbated complement activation contributes to inflammatory diseases. Since promising antioxidant and anti-inflammatory activities have been identified in Arctium lappa L. extracts, this study aims to explore the effect of A. lappa extracts on the lectin pathway (LP) of complement activation. Four extracts were obtained by supercritical extraction using scCO2 with or without ethanol as co-solvent, at different temperatures and pressures (E1: 2.2 mg/mL, E2: 2.6 mg/mL and E3: 2.0 mg/mL, E4: 1.5 mg/mL). To evaluate the effect of A. lappa extracts on the LP activation, an ELISA assay using mannose binding lectin pathway of complement was carried out with C4 detection. All extracts showed a concentration-dependent inhibitory effect on the activation of complement by the LP. The following IC50 were observed for E1, E2, E3 and E4: 179.4 µg/mL, 74.69 µg/mL, 119.1 µg/mL and 72.19 µg/mL, respectively. Our results suggest that A. lappa extracts are potential candidates for the treatment of inflammatory disorders that are complement-related.


Assuntos
Arctium/química , Cromatografia com Fluido Supercrítico/métodos , Proteínas do Sistema Complemento/metabolismo , Lectinas/metabolismo , Extratos Vegetais/química , Arctium/metabolismo , Dióxido de Carbono/química , Proteínas do Sistema Complemento/agonistas , Lectinas/antagonistas & inibidores , Folhas de Planta/química , Folhas de Planta/metabolismo , Temperatura Ambiente
12.
Phys Chem Chem Phys ; 21(42): 23346-23354, 2019 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-31620729

RESUMO

While aromatic amino acids in their deprotonated form have been well characterized by IR and photoelectron spectroscopies, no information is available on the neutral dehydrogenated radicals and, in particular, on their stability when the deprotonation site is changed. This is investigated by observing the neutral fragment issued from either simple photodetachment or dissociative photodetachment of the deprotonated aromatic amino acids phenylalanine, tyrosine, and tryptophan. We show that the dehydrogenated radicals of aromatic amino acids produced upon photodetachment of molecules deprotonated on the carbonyl group dissociate without barrier, leading to the formation of CO2 and a radical amine. However, when the system is deprotonated on functional groups located on the chromophore, the radicals produced by photodetachment are stable, indicating the important photostabilizing role played by functional groups.


Assuntos
Aminoácidos Aromáticos/química , Aminas/química , Ânions/química , Dióxido de Carbono/química , Luz , Fenilalanina/química , Fotólise , Prótons , Triptofano/química , Tirosina/química
13.
Anticancer Res ; 39(10): 5473-5481, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31570441

RESUMO

BACKGROUND/AIM: Aerial parts and seeds of the neem tree (Azadirachta indica) have long been used in traditional medicine such as Ayurveda for health-related purposes. Our interest in neem bioactives lies in their potential use as standalone anticancer agents, or as adjuvants to standard therapy. The aim of the present study was to explore a supercritical CO2 extract (SCNE) of neem leaf and a prominent liminoid in neem leaf, nimbolide, for epigenetic activity. MATERIALS AND METHODS: Human colorectal cancer cell lines (HCT116 and HT29) were cultured for 48 h in the presence of neem extract or nimbolide and evaluated for growth inhibition and evidence of suppression of histone deacetylation and DNA methylation. RESULTS: Both SCNE and nimbolide suppressed the proliferation of colon cancer cells by inducing epigenetic modifications. CONCLUSION: Neem leaf contains bioactive constituents which modify epigenetic activity.


Assuntos
Azadirachta/química , Neoplasias Colorretais/tratamento farmacológico , Epigênese Genética/efeitos dos fármacos , Extratos Vegetais/farmacologia , Folhas de Planta/química , Dióxido de Carbono/química , Dióxido de Carbono/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Metilação de DNA/efeitos dos fármacos , Células HCT116 , Células HT29 , Humanos , Limoninas/farmacologia
14.
Chem Biodivers ; 16(11): e1900357, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31573145

RESUMO

The ginger extract obtained with supercritical CO2 fluid was purified by molecular distillation (MD), and the chemical compositions, antioxidant and cytotoxic activities of ginger extract and its distillates were investigated. Analysis revealed that the ginger extract was rich in terpene hydrocarbons, along with oxygenated terpenes and other non-volatile compounds. The MD distillates were prepared in a series of stages and the active compounds like terpenes and gingerols could be separated by MD. The major compounds of the distillates purified by MD at 40 °C, 80 Pa and 60 °C, 80 Pa were terpene hydrocarbons. Additional distillates obtained by MD at 80 °C, 80 Pa and 100 °C, 60 Pa were predominated by terpene hydrocarbons and oxygenated terpenes. Until the operating conditions of MD reached 150 °C and 2 Pa, some non-volatile compounds were concentrated in the final distillate. Moreover, antioxidant activities and the cytotoxic effects on three human cancer cells in final MD distillate were superior to other extracts, and this phenomenon could be mainly supported by the phenols. The MD could be used to prepare ginger distillates with better antioxidant and cytotoxic activities.


Assuntos
Antineoplásicos Fitogênicos/farmacologia , Antioxidantes/farmacologia , Compostos de Bifenilo/antagonistas & inibidores , Dióxido de Carbono/química , Gengibre/química , Picratos/antagonistas & inibidores , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/isolamento & purificação , Antioxidantes/química , Antioxidantes/isolamento & purificação , Proliferação de Células/efeitos dos fármacos , Destilação , Ensaios de Seleção de Medicamentos Antitumorais , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Extratos Vegetais/isolamento & purificação , Células Tumorais Cultivadas
15.
Chem Commun (Camb) ; 55(90): 13546-13549, 2019 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-31647068

RESUMO

Drugs containing amine groups react with CO2 to form crystalline ammonium carbamates or carbamic acids. In this approach, both the cation and anion of the salt, or the neutral CO2 adduct, are derived from the parent drug, generating new crystalline versions in a 'masked' or prodrug form. It is proposed that this approach may serve as a valuable new tool in engineering the physical properties of drugs for formulation purposes.


Assuntos
Aminas/química , Compostos de Amônio/química , Carbamatos/química , Dióxido de Carbono/química , Ânions/química , Cátions/química , Cristalografia por Raios X , Modelos Moleculares , Estrutura Molecular , Sais/química
16.
J Dairy Sci ; 102(12): 10855-10866, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31548058

RESUMO

In recent years, using dairy phospholipids (PL) as functional ingredients has increased because PL have nutritional benefits and functional properties. In this study, a novel 2-step supercritical fluid extraction (SFE) process was used to extract whey protein phospholipid concentrate (WPPC), a dairy co-product obtained during the manufacture of whey protein isolate, for PL enrichment. In the first step, nonpolar lipids in WPPC were removed using neat supercritical carbon dioxide (S-CO2) at 41.4 MPa and 60°C. In the second stage, the feasibility of using the polar solvent ethanol as a co-solvent to increase the solubility of S-CO2 extraction solvent was explored. A 3 × 3 × 2 factorial design with extraction pressure (35.0, 41.4, and 55.0 MPa), temperature (40 and 60°C), and concentration of ethanol (10, 15, and 20%) as independent factors was used to evaluate the extraction efficiency providing the most total PL, and the best proportion of each individual PL from the spent solids collected during S-CO2 SFE. All lipid fractions were analyzed using thin-layer chromatography and high-performance lipid chromatography. The total amount of PL extracted from WPPC was significantly affected by ethanol concentration; the extraction pressure and temperature were nonsignificant. The optimal SFE condition for generating a concentrated PL lipid fraction was 35.0 MPa, 40°C, and 15% ethanol concentration; the highest amount of extracted PL averaged 26.26 g/100 g of fat. Moreover, adjusting SFE condition allowed successful recovery of a high concentration of sphingomyelin, phosphatidylcholine, and phosphatidylethanolamine, giving averages of 11.07, 10.07, and 7.2 g/100 g of fat, respectively, 2 to 3 times more than conventional solvent extraction. In addition, exhausted solids obtained after the SFE process were enriched with denatured proteins (72% on dry basis) with significantly more water-holding capacity and emulsifying capacity than untreated WPPC. Overall, this 2-stage SFE process using neat S-CO2 and ethanol has the greatest potential to produce a PL-rich lipid fraction from WPPC.


Assuntos
Cromatografia com Fluido Supercrítico/métodos , Fosfolipídeos/isolamento & purificação , Proteínas do Soro do Leite/química , Dióxido de Carbono/química , Cromatografia em Camada Delgada , Etanol/química , Fosfolipídeos/química , Solubilidade , Solventes/química , Temperatura Ambiente
17.
Phys Chem Chem Phys ; 21(38): 21370-21380, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31531468

RESUMO

Density functional theory modelling has been used to design Mo and W-based catalysts MoIII(tBu)(CO) and WIII(tBu)(CO) for CO2 hydrogenation and HCOOH dehydrogenation, which are bio-mimics of the active site of formate dehydrogenase. Based on DFT calculations, the molybdenum and tungsten based complexes are good catalysts in the +3 oxidation state for CO2 hydrogenation with free energies of 24.03 and 21.31 kcal mol-1, respectively. Such a low barrier indicates that our newly designed Mo and W-based complexes are very efficient for CO2 hydrogenation or HCOOH dehydrogenation catalysis. Overall, our computational results provide in depth insights that can serve as a great tool for the design and development of new and efficient molybdenum and tungsten based catalysts for CO2 hydrogenation or HCOOH dehydrogenation.


Assuntos
Materiais Biomiméticos/química , Dióxido de Carbono/química , Complexos de Coordenação/química , Formiato Desidrogenases/química , Formiatos/química , Modelos Moleculares , Catálise , Domínio Catalítico , Hidrogenação , Ligantes , Molibdênio/química , Oxirredução , Termodinâmica , Tungstênio/química
18.
Chemosphere ; 237: 124527, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31549649

RESUMO

Electrochemical reduction of CO2 has been demonstrated as one of the promising technologies to reduce the greenhouse effect. In this study, nano-prism assembled hierarchical CuO microspheres (Prism-CuO) were designed and used for CO2 electroreduction. The Prism-CuO coated gas diffusion electrode showed high activity for CO2-to-formate conversion with overpotential as low as ∼200 mV, and achieved maximum faradaic efficiency of 65.1% at -1.6 V vs. Ag/AgCl. Moreover, it maintained the stable performance for continuous 20 h of electrolysis. The better performance was mainly attributed to the unique prism feature as it provided abundant corner- and edge-based low-coordinated active reaction sites. These sites could further arouse strong local-electric field to lower the barrier of CO2 adsorption and motivate CO2 activation by accelerating charges transfer process. The result implied designing the nano-prism constructed hierarchical framework would be an efficient strategy to develop the advanced electrocatalyst for efficient CO2 reduction in aqueous solution.


Assuntos
Dióxido de Carbono/química , Cobre/química , Microesferas , Adsorção , Catálise , Difusão , Técnicas Eletroquímicas , Eletrodos , Formiatos , Oxirredução
19.
Chemosphere ; 226: 924-933, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31509922

RESUMO

-While sulfate radical (SO4-)-based processes are useful to degrade acetaminophen (ACE), studies of using peroxymonosulfate (PMS) to degrade ACE are quite limited. In addition, although Co is validated as the most effective metal for activating PMS, very few Co catalysts have been developed and investigated for activating PMS to degrade ACE. Since carbon is a promising substrate to support Co nanoparticles (NPs) to form Co/carbon composite catalysts, most existing carbon substrates require delicate fabrications. As biochar is an easy-to-obtain but versatile carbon material, pyrolysis of Co/lignin affords an advantageous Co-impregnated biochar (CoIB) as an attractive catalyst for PMS activation. Specifically, as CO2 substitutes N2 as a reaction medium for pyrolysis of Co/lignin, the syngas production from pyrolysis can be substantially improved and a magnetic CoIB is afforded. This CoIB consists of evenly-distributed Co nanoparticles (NPs) impregnated in carbon matrices of biochar, and possesses several superior characteristics, such as high porosity, large surface area and magnetism, enabling CoIB a promising catalyst for activating PMS to degrade ACE. CoIB also shows a much higher catalytic activity of PMS activation than CoIBN2, and Co3O4 for degrading ACE. CoIB is also recyclable for activating PMS to effectively degrade ACE for multiple cycles. The ACE degradation pathway by this CoIB-activated PMS is proposed according to the degradation products. These findings validate that CoIB is assuredly an advantageous heterogeneous catalyst, which can be easily prepared from pyrolysis of Co/lignin in CO2 with concomitant enhanced syngas production for effectively activating PMS to degrade ACE.


Assuntos
Acetaminofen/química , Dióxido de Carbono/química , Carvão Vegetal/química , Cobalto/química , Lignina/química , Peróxidos/química , Pirólise , Catálise
20.
Chemistry ; 25(57): 13078-13082, 2019 Oct 11.
Artigo em Inglês | MEDLINE | ID: mdl-31402524

RESUMO

The Fe protein of nitrogenase catalyzes the ambient reduction of CO2 when its cluster is present in the all-ferrous, [Fe4 S4 ]0 oxidation state. Here, we report a combined structural and theoretical study that probes the unique reactivity of the all-ferrous Fe protein toward CO2 . Structural comparisons of the Azotobacter vinelandii Fe protein in the [Fe4 S4 ]0 and [Fe4 S4 ]+ states point to a possible asymmetric functionality of a highly conserved Arg pair in CO2 binding and reduction. Density functional theory (DFT) calculations provide further support for the asymmetric coordination of O by the "proximal" Arg and binding of C to a unique Fe atom of the all-ferrous cluster, followed by donation of protons by the proximate guanidinium group of Arg that eventually results in the scission of a C-O bond. These results provide important mechanistic and structural insights into CO2 activation by a surface-exposed, scaffold-held [Fe4 S4 ] cluster.


Assuntos
Azotobacter vinelandii/química , Dióxido de Carbono/metabolismo , Proteínas com Ferro-Enxofre/química , Oxirredutases/metabolismo , Dióxido de Carbono/química , Catálise , Nitrogenase/química , Oxirredução , Oxirredutases/química , Prótons
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