Reaction Of Dioxide Research Articles

Constrained C2 adsorbate orientation enables CO-to-acetate electroreduction.

The carbon dioxide and carbon monoxide electroreduction reactions, when powered using low-carbon electricity, offer pathways to the decarbonization of chemical manufacture1,2. Copper (Cu) is relied on today for carbon-carbon coupling, in which it produces mixtures of more than ten C2+ chemicals3-6: a long-standing challenge lies in achieving selectivity to a single principal C2+ product7-9. Acetate is one such C2 compound on the path to the large but fossil-derived acetic acid market. Here we pursued dispersing a low concentration of Cu atoms in a host metal to favour the stabilization of ketenes10-chemical intermediates that are bound in monodentate fashion to the electrocatalyst. We synthesize Cu-in-Ag dilute (about 1 atomic per cent of Cu) alloy materials that we find to be highly selective for acetate electrosynthesis from CO at high *CO coverage, implemented at 10 atm pressure. Operando X-ray absorption spectroscopy indicates in situ-generated Cu clusters consisting of <4 atoms as active sites. We report a 12:1 ratio, an order of magnitude increase compared to the best previous reports, in the selectivity for acetate relative to all other products observed from the carbon monoxide electroreduction reaction. Combining catalyst design and reactor engineering, we achieve a CO-to-acetate Faradaic efficiency of 91% and report a Faradaic efficiency of 85% with an 820-h operating time. High selectivity benefits energy efficiency and downstream separation across all carbon-based electrochemical transformations, highlighting the importance of maximizing the Faradaic efficiency towards a single C2+ product11.

Green Synthesis of Nd2sn2o7 Nanostructures Using Gum of Ferula Assa-Feotida for the Fabrication of 3a,4-dihydronaphtho[2,3-c]furan-1(3H)-One

Here, first, the Nd2Sn2O7 NPs were greenly generated in the participation of gum of ferula assa-feotida of SnCl4.5H2O and Nd(NO3)3. The uncontrolled release of CO2 by industrial processes that acidify the oceans and warm the planet has prompted scientists to try different methods to capture CO2 directly from wastewater sources. Considering the morphology of Nd2Sn2O7 NPs, an appropriate exterior layer for CO2 imbibition was created in all catalyst sites. Findings disclosed that Nd2Sn2O7 NPs positively affected the fabrication yield of 3a,4-dihydronaphtho[2,3-c]furan-1(3H)-one through a three-factor coupling reaction of alkynes, allylic chlorides, and carbon dioxide. The technique enjoyed profitable performance and forbearance of functional groups.

Electrocatalyst Microenvironment Engineering for Enhanced Product Selectivity in Carbon Dioxide and Nitrogen Reduction Reactions.

Carbon and nitrogen fixation strategies are regarded as alternative routes to produce valuable chemicals used as energy carriers and fertilizers that are traditionally obtained from unsustainable and energy-intensive coal gasification (CO and CH4), Fischer-Tropsch (C2H4), and Haber-Bosch (NH3) processes. Recently, the electrocatalytic CO2 reduction reaction (CO2RR) and N2 reduction reaction (NRR) have received tremendous attention, with the merits of being both efficient strategies to store renewable electricity while providing alternative preparation routes to fossil-fuel-driven reactions. To date, the development of the CO2RR and NRR processes is primarily hindered by the competitive hydrogen evolution reaction (HER); however, the corresponding strategies for inhibiting this undesired side reaction are still quite limited. Considering such complex reactions involve three gas-liquid-solid phases and successive proton-coupled electron transfers, it appears meaningful to review the current strategies for improving product selectivity in light of their respective reaction mechanisms, kinetics, and thermodynamics. By examining the developments and understanding in catalyst design, electrolyte engineering, and three-phase interface modulation, we discuss three key strategies for improving product selectivity for the CO2RR and NRR: (i) targeting molecularly defined active sites, (ii) increasing the local reactant concentration at the active sites, and (iii) stabilizing and confining product intermediates.

Transition-metal-free synthesis of 2-arylphenol via SNAr reaction of dibenzothiophene dioxide with KOH

Transition-metal-free synthesis of 2-arylphenol via SNAr reaction of dibenzothiophene dioxide with KOH

CeO2 Frustrated Lewis Pairs Improving CO2 and CH3OH Conversion to Monomethylcarbonate.

Frustrated Lewis pairs (FLPs), discovered in the last few decades for homogeneous catalysts and in the last few years also for heterogeneous catalysts, are stimulating the scientific community's interest for their potential in small-molecule activation. Nevertheless, how an FLP activates stable molecules such as CO2 is still undefined. Through a careful spectroscopic study, we here report the formation of FLPs over a highly defective CeO2 sample prepared by microwave-assisted synthesis. Carbon dioxide activation over FLP is shown to occur through a bidentate carbonate bridging the FLP and implying a Ce3+-to-CO2 charge transfer, thus enhancing its activation. Carbon dioxide reaction with methanol to form monomethylcarbonate is here employed to demonstrate active roles of FLP and, eventually, to propose a reaction mechanism clarifying the role of Ce3+ and oxygen vacancies.

Vibrational and electronic properties of Na2Ti6O13

AbstractSodium hexatitanate, Na2Ti6O13, in the form of elongated microcrystals, were synthesized by solid‐state reaction of titanium dioxide and sodium carbonate. The monoclinic structure was confirmed by X‐ray powder diffraction and selected area electron diffraction. Electron diffraction was used to determined zone axis and the crystal‐grown direction, which allowed to perform polarized Raman measurements. Energy band gap and the electronic transition were studied by UV–Vis diffuse reflectance and using Tauc relation. Density functional theory (DFT) calculations also revealed an indirect allowed bandgap transition and a good agreement between theoretical and experimental energy band gaps were demonstrated. For the first time, the assignment of the vibrational modes was carried out in the samples and thoroughly compared with theoretical data obtained from DFT calculations. The most relevant of the 60 predicted optical phonon modes of Na2Ti6O13 were experimentally observed and assigned to their symmetries.

Solvent-Free Coupling Reaction of Carbon Dioxide and Epoxides Catalyzed by Quaternary Ammonium Functionalized Schiff Base Metal Complexes under Mild Conditions.

A series of bifunctional Schiff base metal catalysts (Zn-NPClR, Zn-NPXH, and M-NPClH) with two quaternary ammonium groups were prepared for carbon dioxide (CO2) and epoxide coupling reactions. The effects of the reaction variables on the catalytic activity were systematically investigated, and the optimal reaction conditions (120 °C, 1 MPa CO2, 3 h) were screened. The performances of different metal-centered catalysts were evaluated, and Co-NPClH showed excellent activity. This kind of bifunctional catalyst has a wide range of substrate applicability, excellent stability, and can be reused for more than five runs. A relatively high TOF could reach up to 1416 h-1 with Zn-NPClH as catalyst by adjusting reaction factors. In addition, the kinetic study of the coupling reaction catalyzed by three catalysts (Zn, Co, and Ni) was carried out to obtain the activation energy (Ea) for the formation of cyclic carbonates. Finally, a possible mechanism for this cyclization reaction was proposed.

NaHCO3 as a carrier of CO2 and its enhancement effect on mineralization during hydrothermal alteration of basalt

Reaction of carbon dioxide (CO2) with minerals to generate stable carbonates, also known as CO2 mineralization, has been regarded as one of the most promising methods for safe and permanent carbon storage. As a promising feedstock, basaltic rock has gained special interest, and elevating basalt carbonation efficiency with the reduction of negative environmental impact is the main challenge for CO2 mineralization system development. Considering multiple potential positive effects of the CO2 carrier, NaHCO3, we conducted this study to experimentally evaluate the CO2 storage efficiency during water-basalt-NaHCO3 interactions under hydrothermal conditions at 200–300°C. The inclusion of NaHCO3 was confirmed to drastically promote the alteration of basalt, especially at higher temperatures. As revealed by experiments conducted at the saturated vapor pressure of water, the carbon storage efficiency at 300°C reached 75 g/kg of basalt in 5 days, which was 12 times higher than that at 200°C. In such hydrothermal systems, basalt was carbonated to generate calcite (CaCO3), where the Ca was mainly from plagioclase; Mg and Fe were incorporated into smectite, and Na in the saline system participated in the formation of Na silicates (i.e., analcime in the case of basalt). Due to the presence of additional Na in solution, all the released elements were consumed quickly with generation of secondary minerals in turn promoted basalt dissolution to release more Ca for CO2 storage. This study illuminated the role of NaHCO3 in basalt carbonation and provided technical backup to the design of advanced CO2 mineralization systems.

Fabrication of Carboxylic Acid and Imidazolium Ionic Liquid Functionalized Porous Cellulosic Materials for the Efficient Conversion of Carbon Dioxide into Cyclic Carbonates

Cellulosic poly(ionic liquid)s ([Cellmim][Br]) with a degree of substitution (DS) in the range of 0.32–0.89 were synthesized successfully via the homogeneous transesterification reaction of cellulose with 1-(2-methoxyacetyl)-3-methyl imidazole bromide IL ([Mmim][Br]) in a DBU/DMSO/CO2 solvent system. The structure and properties of these novel materials have been fully characterized. Cellulosic poly(ionic liquid) POF polymers (POF-[Cellmim][Br]) were then obtained by an in situ crosslinking reaction without adding an exterior catalyst. The porosity and properties of the POF-[Cellmim][Br] materials can be modulated. The POF-[Cellmim][Br] materials functioned as green, efficient, and highly active catalysts for cycloaddition reactions of epoxides and carbon dioxide under solvent-free and co-catalyst-free conditions. These reactions gave high yields (up to 97%), and the catalyst can be easily separated with excellent reusability and no significant change to its structure. A plausible reaction mechanism for the cycloaddition reaction of epoxide and carbon dioxide by the POF-[Cellmim][Br] catalyst is proposed based on the experimental results. This work provided a new strategy to prepare cellulosic-PIL POF materials and offered a platform to understand the cooperative effects of porous properties and nucleophilic anions on the cycloaddition reaction of carbon dioxide and epoxides.

Benzimidazolium‐Decorated Metalloporphyrin Molecule and Polymer: a Reliable Preparation Method and Application in Catalyzing the Cycloaddition Reaction of CO2and Epoxides

AbstractDue to the synergistic effect of central metal and halide anion, cationic metalloporphyrins and derivatives exhibit outstanding catalytic activities for the cycloaddition reaction of epoxides and carbon dioxide. Herein, a generic strategy was developed to synthesize the benzimidazolium‐containing metalloporphyrin molecule and polymer. To demonstrate the method feasibility, we firstly synthesized the molecule1H, in which the benzimidazole groups were in‐site constructed by the cyclization of 5,10,15,20‐(4‐carboxyphenyl)‐porphyrin (H2TCPP) witho‐diaminobenzene (PEA). After post‐synthetic ionization and metallization, I−and Zn2+were introduced as the nucleophile and Lewis acid, respectively. The structure of1ZnILwas confirmed by single crystal X‐ray diffraction analysis. By using the similar conditions of model reaction,H2TCPPwas copolymerized with 1,2,4,5‐tetraaminobenzene (BTA) to prepare the polymerP‐1ZnIL. The prepared cationic molecule1ZnILand polymerP‐1ZnILshowed comparable activities in catalyzing the cycloaddition of carbon dioxide with epoxides to cyclic carbonates compared to the reported bifunctional catalysts based on metalloporphyrins.

N-heterocyclic carbene-pyridine ligand coordinated Mo(II) complexes catalyzed synthesis of cyclic carbonates from carbon dioxide and epoxides

A variety of zero-valent molybdenum complexes and divalent molybdenum complexes with N-heterocyclic carbenes (NHC)-pyridine ligands were synthesized, and their catalytic activities and performances in the cycloaddition reaction of epoxides and carbon dioxide (CO2) were investigated. It was found that the divalent molybdenum complexes show high catalytic activity in the synthesis of cyclic carbonates from epoxide and CO2 in comparison with zero-valent molybdenum complexes. The divalent molybdenum complexes combined with tetrabutylammonium iodide (TBAI) can effectively transform various terminal epoxides and internal epoxides under 30–80 ℃ and 5–10 bar of CO2 pressure. The mechanic experiments by FT-IR and HRMS spectrometry reveal the reaction pathway of binary system in combination of divalent molybdenum complexes with TBAI.

Multifunctional Eu3+‐coordination polymer for highly selective recognition of Fe3+ and MnO4− ions in water and efficient catalytic fixation of carbon dioxide

A stable multifunctional Eu3+‐coordination polymer formulated as [Eu(Htzpia)(H2tzpia)]n (Eu‐CP‐1) has been successfully constructed by the reaction of Eu3+ ion with the new organic ligand 5‐(3‐(tetrazol‐5‐yl) phenyl) isophthalic acid (H3tzpia) under hydrothermal condition. Eu‐CP‐1 displays a 2D coordination network, in which 1D uniform chains with (μ‐COO)3 bridges are interlinked by the Htzpia and H2tzpia spacers. The 2D networks are associated into 3D architectures through hydrogen bonding interactions. Eu‐CP‐1 displays excellent luminescence property and exhibits good stability in water. Thus, Eu‐CP‐1 can be used to detect Fe3+ ions and MnO4− ions with high sensitivity and selectivity through luminescence quenching effect. Due to the presence of open metal sites, free oxygen/nitrogen atoms, and NH groups of tetrazole rings, Eu‐CP‐1 can act as an effective heterogeneous catalyst for the cycloaddition reaction of carbon dioxide with epoxides under eco‐friendly and solvent‐free conditions. Interestingly, Eu‐CP‐1 is highly recyclable and reusable for up to five cycles without an obvious loss in sensing or catalytic efficiency. In addition, the possible relevant mechanisms are also investigated. This work should aid in expanding potential application prospects of the lanthanide CPs in the fields of contaminated ions detection and CO2 cycloaddition.

Determining the optimal conditions for the synthesis nano CaTiO3 square prepared from natural dolomite rocks

Due to the importance of ceramic materials, especially of the perovskite type, this study included the synthesis of calcium titanate using dolomite as a natural calcium source from the Iraqi environment. Firstly, the work included preparing of calcium sulfate dihydrate from dolomite using dilute sulfuric acid, and then studying the optimal conditions for the formation of calcium titanate (CaTiO3) through the reaction of titanium dioxide with calcium sulfate dihydrate. The optimum conditions included: the ratio of titanium to calcium which was 1:0.5, 1:1, 1:1.5 and 1:2, respectively, as well as, the calcination temperature (1000, 1200 and 1300 °C) and finally the calcination time (1 and 2 h). The formation of calcium titanate was tracked by X-ray diffraction, and the results demonstrated that the optimum conditions are 1:1 at a calcination temperature of 1300 °C for 2 h. Moreover, the work included converting calcium titanate into calcium titanate nanoparticles using an environmentally friendly method which was achieved by using ultrasound on a liquid composed of calcium titanate in deionized water. The formation of calcium titanate nanoparticles was proved by TEM, which showed the formation of regular and irregular square-like nanoparticles with an average particle size of 55 nm. From an industrial point of view, this method is considered to be of low cost for the production of high cost nano-calcium titanate.

Constructing N-Coordinated Co and Cu Single-Atomic-Pair Sites toward Boosted CO2 Photoreduction

The visible-light-driven photocatalytic reduction reaction of carbon dioxide (CO2) (CO2RR) to value-added fuels presents a feasible approach to curb anthropogenic CO2 emissions and mitigate the increasing energy crisis. However, developing photocatalysts with excellent performance still remains a great challenge in this field. Herein Co,Cu,N-codoped carbon nanoparticles (Co1Cu1/NC) were fabricated through the pyrolysis of zeolitic imidazolate framework (ZIF-8) with Cu(NO3)2 adsorbed inside the cavities and CoTBPP decorated over the surface of ZIF. Spherical aberration-corrected high-angle annular dark-field scanning transmission electron microscopy and electron energy loss spectroscopy measurements disclose the dual-metal single-atomic nature of Co1Cu1/NC consisting of atomically dispersed Co–Cu pair sites on a nitrogen-doped carbon support. Extended X-ray absorption fine-structure analysis reveals the tetra-N-coordinated nature of each metal in Co1Cu1/NC (N2–Co–N2–Cu–N2). For the purpose of comparative study, Co,N- and Cu,N-codoped carbon nanoparticles (Co1/NC and Cu1/NC) also with single atomic site nature have been fabricated following the same route. The as-prepared Co1Cu1/NC exhibits highly effective photocatalytic CO2-to-CO reduction with a considerably high CO-generating yield of 22.46 mmol g–1 and a CO selectivity of 83.4% after 2 h of visible-light irradiation. Experimental characterizations and in particular theoretical calculations disclose the close association of the remarkable CO2RR catalytic activity of Co1Cu1/NC with the synergetic effect of the Co–Cu atomic-pair sites, which facilitate the conversion of CO2 to CO via lowering the energy barrier for the formation of the *COOH intermediate. This work paves a new avenue for the rational design and construction of atomic-pair photocatalysts with boosted performance.

Effects of Metal–Support Interaction in the Electrocatalysis of the Hydrogen Evolution Reaction of the Metal-Decorated Titanium Dioxide Supported Carbon

It has been found that the electrocatalytic properties of metallic nanoparticles supported on transition metal oxides are affected by the existing strong metal–support interaction (SMSI). Herein, the effects of SMSI on the electrocatalysis of the hydrogen evolution reaction (HER) were investigated in acid electrolyte by using Pt and Ag nanoparticles supported on carbon and titanium oxide (TiO2). High-resolution transmission electron microscopy (HR–TEM) images showed that Pt and Ag nanoparticles present a spherical shape at the TiO2 support and an average size distribution of around 4.5 nm. The X-ray photoelectron spectroscopy (XPS) results for Pt/TiO2/C and Ag/TiO2/C evidenced higher amounts of surface oxides in the metallic particles, when compared to the materials supported on carbon. Consistently, electrode polarization and electrochemical impedance results revealed that both metal–TiO2 and metal–C-supported catalysts were more active in catalyzing the HER than the corresponding carbon-supported materials, with Pt presenting better results. These differences in the HER activities were related to the electronic effects of the TiO2/C substrate on the Pt and Ag metals, introduced by strong metal-support (SMSI) in the metal–TiO2/C catalysts.

Functionalized β-Cyclodextrins Catalyzed Environment-Friendly Cycloaddition of Carbon Dioxide and Epoxides

Ammonium, imidazole, or pyridinium functionalized β-cyclodextrins (β-CDs) were used as efficient one-component bifunctional catalysts for the coupling reaction of carbon dioxide (CO2) and epoxide without the addition of solvent and metal. The influence of different catalysts and reaction parameters on the catalytic performance were examined in detail. Under optimal conditions, Im-CD1-I catalysts functionalized with imidazole groups were able to convert various epoxides into target products with high selectivity and good conversion rates. The one-component bifunctional catalysts can also be recovered easily by filtration and reused at least for five times with only slight decrease in catalytic performance. Finally, a possible process for hydroxyl group-assisted ring-opening of epoxide and functionalized group- induced activation of CO2 was presented.

Rapid Analysis of α-Tocopherol and Its Oxidation Products Using Supercritical Carbon Dioxide and Proton Transfer Reaction Ionization Mass Spectrometry.

We have developed a rapid and sensitive analytical method for α-tocopherol and its oxidative products by combining online hyphenation of supercritical fluid extraction-supercritical fluid chromatography (SFC) with proton transfer reaction (PTR) ionization mass spectrometry (MS). α-Tocopherol is a well-known antioxidant that plays a vital role in the antioxidant defense system in plant cells. However, studies on the cellular mechanisms of α-tocopherol have been limited owing to the lack of a rapid analytical method, which limits the comparison of plant cells incubated in various conditions. Additionally, complex sample preparation and long chromatography separation times are required. Moreover, the majority of the involved molecules are a combination of isomers, which must be separated before applying tandem MS. α-Tocopherol produces the α-tocopheroxyl radical in the first step of its antioxidant function; another ion with the same mass may also be generated from the source. SFC separation effectively distinguished the observed ions from their oxidative products in the sample and those produced during the ionization reaction process. This method enabled the measurement of α-tocopherol and its oxidative products such as α-tocopheroxyl radical and α-tocopheryl quinone in approximately 3 min per sample, including the time required for sample preparation.

Bifunctional Nb-N-C atomic catalyst for aqueous Zn-air battery driving CO2 electrolysis

Designing efficient and cost-effective bifunctional catalysts is desirable for carbon dioxide and oxygen reduction reactions (CO2RR and ORR) to address carbon neutralization and energy conversion. Herein, a bifunctional CO2RR and ORR catalyst for aqueous Zn-air battery (ZAB) self-driving CO2RR electrolysis is developed using atomically dispersed niobium anchored onto N-doped ordered mesoporous carbon (Nb-N-C). The Nb-N-C atomic catalyst demonstrates aqueous CO2RR activity with CO Faradaic efficiency up to 90%, ORR activity with a half-wave potential of 0.84 V vs. reversible hydrogen electrode, and ZAB activity with a peak power density of 115.6 mW cm−2, owing to the high Nb atom-utilization efficiency and ordered mesoporous structure. Furthermore, two-unit ZABs in series, serving as the power source for the self-powered CO2 electrolysis system, continuously convert CO2 to CO with average productivity of 3.75 µmol h−1 mgcat−1 during the first 10 h. Moreover, theoretical calculations exhibit that atomic Nb anchored to N-doped carbon can form Nb-N coordination bonds, effectively reducing the energy barriers of potential-determining *COOH for CO2RR and *O formation for ORR.

New Co and Mn Catalysts Bearing ONO Ligands Containing Nucleophile for the Coupling of CO2 and Propylene Oxide

A series of novel ONO ligands bearing an ionic pendant-armed (hereinafter indicated as ONONu, where Nu corresponds to an anionic nucleophile) were synthesized, characterized, and successfully coordinated to cobalt and manganese precursors. New air-stable cobalt (III) complexes (1–6) and manganese (II) complexes (7 and 8) were obtained and characterized. Single crystal X-ray diffraction analysis of the Co(III) compound 5 confirmed the presence of two quaternized ligands coordinated to the metal and iodide as counterion. These novel complexes were revealed to be active catalysts in the coupling reaction of carbon dioxide and propylene oxide (PO) in different degrees of success. Among these, the manganese complex 8 afforded the best results towards the formation of propylene carbonate (PC) with a productivity of 256 kg PC/(kg cat·h), achieving a TON of 4860.

Generation of (E)-β-trifluoromethyl vinylsulfonohydrazides under photocatalysis and their anti-bacteria activity

Trifluoromethylation/sulfonylation of alkynes from trifluoromethyl thianthrenium triflate and sulfur dioxide under extremely mild reaction conditions provides a facile access to trifluoromethyl-substituted vinyl sulfonohydrazides in moderate to good yields. This multicomponent reaction of trifluoromethyl thianthrenium triflate, alkynes, sulfur dioxide and hydrazines proceeds efficiently under visible light irradiation in the presence of photocatalyst at room temperature with broad substrate scope and excellent functional group compatibility. This reaction is highly stereoselective, and only (E)-isomers are obtained. Additionally, these trifluoromethyl-substituted vinyl sulfonohydrazides are further evaluated for anti-bacteria activity. In vitro activities of these compounds against Staphylococcus aureus (G+) and Escherichia coli (G−) are examined.