C O Bond Research Articles

Pt-N catalytic centres concisely enhance interfacial charge transfer in amines functionalized Pt@MOFs for selective conversion of CO2 to CH4

Improving ligand-to-active metal charge transfer (LAMCT) by finely tuning the organic ligand is a decisive strategy to enhance charge transfer in metal organic frameworks (MOFs)-based catalysts. However, in most MOFs loaded with active metal catalysts, electron transmission encounters massive obstacle at the interface between the two constituents owing to poor LAMCT. Herein, amines (–NH2) functionalized MOFs (NH2-MIL-101(Cr)) encapsulated active metal Pt nanoclusters (NCs) catalysts are synthesized by the polyol reduction method and utilized for the photoreduction of CO2. Surprisingly, the introduction of –NH2 (electron donating) groups within the matrix of MIL-101(Cr) improved the electron migration through the LAMCT process, fostering a synergistic interaction with Pt. The combined experimental analysis exposed the high number of metallic Pt (Pt0) in Pt@NH2-MIL-101(Cr) catalyst through seamless electron shuttling from N of –NH2 group to excited Pt generating versatile hybrid Pt-N catalytic centres. Consequently, these versatile hybrid catalytic centres act as electro-nucleophilic centres, which enable the efficient and selective conversion of CO bond in CO2 to harvest CH4 (131.0 µmol.g−1) and maintain excellent stability and selectivity for consecutive five rounds, superior to Pt@MIL-101(Cr) and most reported catalysts. Our study verified that the precise tuning of organic ligands in MOFs immensely improves the surface-active centres, electron migration, and catalytic selectivity of the excited Pt NCs catalysts encaged inside MOFs through an improved LAMCT pathway.

The role of water vapour on CO2 mobility on calcite surface during carbonation process for calcium looping: A DFT study

The presence of water vapour has been proven to stimulate carbonation for the calcium looping process, while its effect mechanism during the slow reaction stage still lacks insight understanding at the atomic level, where H2O molecules may interact with the product layer to affect the transportation of CO2. This study tried to reveal the role of water vapour on CO2 mobility on the calcite surface through density functional theoretical (DFT) calculation. H2O molecule has higher adherence to calcite surface than CO2, and it can react with CO3 to generate HCO3− and OH− ions. Then, the formed OH− ion above the surface layer can adsorb CO2. Moreover, H2O can also react with O2− defect to form OH− ions, and the OH ion at the deeper position can still adsorb CO2 through a two-step process with remarkable energy barriers. However, the formation of HCO3− can degrade the energy barriers to CO2 release from the calcite surface, owning to the weaker CO bond. Two directions of CO2 movement between anions were involved in this investigation, including crossing through the surface layer to the second layer and the movement inside the surface layer, where the higher mobility of CO2 from HCO3− to O2− ion occurs in both movement directions. For the case inside the surface layer, the movement from O2− ion to HCO3− has a higher energy barrier, indicating that the stimulation by H2O is a one-way effect, and the enhancement by H2O for CO2 mobility is caused by the reaction with CO32− other than O2− ion.

Quantifying the contribution of lignin to humic acid structures during composting

The transformation behavior of different types of lignin structure was investigated during composing with particular interest of revealing the contribution rate of lignin functional groups as well as their interaction to humic acids (HA). Rice straws, tree branches, and pine needles were selected as composting materials, because they predominantly contain G-S-H, G-S, and G-type lignin. Results showed that microorganisms were the driving force behind the conversion of lignin into HA. During composting, appeared different levels of cleavage, tearing, and fragmentation on the superficial lignin structures. In depth analysis of lignin transformation, lignin primarily consisted of aromatic groups, CO bonds, alkyl groups, hydroxyl groups and linkage between monomeric units (β-O-4, β-5 and β-β) in the early stage of composting. As lignin degraded, the CO bonds were gradually exposed. But due to their unstable nature, the CO bonds were prone to undergo changes with the cleavage of the aromatic rings at positions 2, 5, and 6 during composting. CO bonds could be converted into aromatic rings, alkyl groups, hydroxyl groups, and CO groups in HA. Through multiple linear regression analysis, it could be concluded that the CO bonds in G-type and S-type monomeric units contributed significantly to the aromatic rings, accounting for 30.4 % and 48.4 %, respectively. The main mechanism might be related to the cleavage of CO bonds and subsequent atomic rearrangement after the release of carbon atoms. This in-depth analysis filled the gap in the mechanism of HA formation during composting.

Robust CA-GO-TiO2/PTFE Photocatalytic Membranes for the Degradation of the Azithromycin Formulation from Wastewaters.

We have developed an innovative thin-film nanocomposite membrane that contains cellulose acetate (CA) with small amounts of TiO2-decorated graphene oxide (GO) (ranging from 0.5 wt.% to 2 wt.%) sandwiched between two polytetrafluoroethylene (PTFE)-like thin films. The PTFE-like films succeeded in maintaining the bulk porosity of the support while increasing the thermal and chemical robustness of the membrane and boosting the catalytic activity of TiO2 nanoparticles. The membranes exhibited a specific chemical composition and bonding, with predominant carbon-oxygen bonds from CA and GO in the bulk, and carbon-fluorine bonds on their PTFE-like coated sides. We have also tested the membranes' photocatalytic activities on azithromycin-containing wastewaters, demonstrating excellent efficiency with more than 80% degradation for 2 wt.% TiO2-decorated GO in the CA-GO-TiO2/PTFE-like membranes. The degradation of the azithromycin formulation occurs in two steps, with reaction rates being correlated to the amount of GO-TiO2 in the membranes.

Copper(II)-polymer chelate grafted from magnetic mesoporous silica for the O-arylation of phenols via the Ullmann reaction

The present work describes the grafting of polymer-metal chelates (PMC) from Fe3O4@SBA-15 via the Surface Initiated-Atom Transfer Radical Polymerization (SI-ATRP) method. Fe3O4@SBA-15 were silylated by 2-bromo-2-methyl-N-(3-(trimethoxysilyl)propanamide (BTPAm) to give the surface-anchored ATRP initiator. Acrylamide (AAm) was polymerized from the Fe3O4@SBA-15 surface via the ATRP approach and trans-amidated with ethylenediamine to give poly(N-2-aminoethylacrylamide) grafted magnetic mesoporous silica, Fe3O4@SBA-g-PAE-AAm. The grafted chelating polymer ligand (CPL) was treated with an acetonitrile solution of Cu(OAc)2 to afford the Fe3O4@SBA-g-PAE-AAm-Cu(II). The grafted PMC was characterized by FT-IR, CP/MAS 13C NMR, thermo-gravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) analysis. The oxidation state of copper (+2) was confirmed using X-ray photoelectron spectroscopy (XPS). The catalytic activity of the grafted PMC was examined in the CO bond formation via the Ullmann-type O-arylation reaction between haloarenes and phenols after establishing the optimal reaction conditions. The excellent recyclability of the catalyst was shown by small deactivation over seven runs.

Effect of carbon quantum dots doping on structural, optical, and antibacterial properties of barium tungstate nanocomposite material

Local bacterial infection remains an increasingly severe threat to human health worldwide, and infection control is still a challenging task. Carbon Quantum Dots (CQSs) and barium tungstate show antibacterial properties. CQDs doped Barium Tungstate (BaWO4) are synthesized by using a hydrothermal route and their optical and antimicrobial activities against the Gram-positive bacteria staphylococcus aureus and optical properties were investigated. The UV–Vis reveals a shift in the bandgap from 3.62 eV to 2.93 eV due to doping of CQDs in BaWO4. The structure of the CQDs/BaWO4 were studied by XRD, which shows CQDs doped BaWO4 samples possess tetragona4 werelite structure with the preferred orientation of (112) identified by XRD at 26° having crystallite size ∼ 31 nm. Nanocomposite BaWO4/CQDs exhibit a spherical-like shape and are composed of Ba, O, W and C according to the design of the experiment. Zeta sizer of CQDs by DLS shows the size of CQDs is 7.65 nm. The FT-IR shows the presence of functional groups in doped material like CC, CO, and COOH bonds which indicate that the C-dots are functionalized with epoxy, carbonyl, hydroxyl, and carboxylic acid groups. Their elemental composition and surface morphology were studied by EDS which shows the percentage variation of CQDs in BaWO4, SEM results show the change in shape of the sample by adding CQDs to BaWO4. The TEM image proves the presence of doped material in the BaWO4. The PL spectra reveals the emission spectra shift towards a higher wavelength and absorption increases. The qualitative analysis shows the antimicrobial activity and enlargement of the inhibition zone and quantitative analysis confirms it.

Unveiling the mechanism and selectivity of the [3 + 2] cycloaddition reactions of nitrone with acetylene derivatives leading to anticancer 4-isoxazoline derivatives from the MEDT perspective

The [3 + 2] cycloaddition reactions of N-methyl-C-(2-furyl) nitrone (a) with a series of acetylene derivatives (4b), (5b), and (6b) have been studied at the B3LYP-D3/6-31G(d) computational level within the framework of Molecular Electron Density Theory. Topological analysis allows classifying the nitrone (a) as a zwitterionic (zw-) three-atom component (TAC) associated with high energy barrier. These 32CA reactions follow a one-step mechanism under kinetic control with highly asynchronous bond formation. Bonding Evolution Theory (BET) analysis indicates that no new covalent CO and CC bonds form at the transition states (TSs). Interestingly, the global electron density transfer (GEDT) between 0.08 and 0.18 e predicts low polar character of forward electron density transfer (FEDF) type with the electronic flux from the nitrone (a) to the acetylene derivatives. Electron localization function (ELF) and atom-in-molecules (AIM) topological analysis of the electron density at the TS structures characterize the non-concerted nature of these one-step zw-type 32CA reactions.

Performance Assessment of Novel Transparent Insulation Materials for Integrated Storage Collectors

Transparent insulation structures play a pivotal role in harnessing solar energy efficiently, akin to the greenhouse effect in the atmosphere. This study undertakes a systematic evaluation of a novel sorbitol- or bio-based polycarbonate (bio-PC) for thermal insulation (TI) structures and hot water collector systems. Employing optical and mechanical methods, the bio-PC was comprehensively characterized on the polymer film level. Subsequently, the technical and ecological performance of these structures in various hot water collectors and systems was rigorously modelled and simulated. Results indicated that the novel bio-PC exhibited superior properties compared to conventional materials like cellulose acetate or fossil-based PC, showcasing promising prospects for widespread adoption. Drawing parallels to the greenhouse effect of CO2, the functional principle of transparent insulation structures is rooted in high solar transmittance and infrared absorbance, primarily governed by carbon-oxygen bonds. While fossil-fuel based transparent insulation materials have been prevalent, they suffer from drawbacks such as average infrared absorbance and susceptibility to yellowing. In contrast, the newly introduced bottom-up biopolymer bio-PC, derived from sorbitol derivatives, offers a compelling alternative. The study sheds light on the potentials and limitations of bio-PC for transparent insulation structures in integrated storage or flat plate collectors, aiming to mitigate environmental impacts associated with traditional materials. Future research directions emphasize refining modelling tools and addressing input data deficiencies, particularly for life cycle analysis. Concurrently, efforts are directed towards enhancing simulation accuracy and reliability through concurrent measurements of collector systems equipped with bio-PC-based transparent insulation. This research underscores the critical role of innovative materials in advancing sustainable energy solutions, with bio-PC emerging as a promising candidate in the realm of transparent insulation technology.

Molten-salt-induced interpenetrated meso/macro porous structural hard carbon derived from chitosan for enhanced potassium ions storage

Hard carbon materials are commonly used as anode materials for environmentally friendly potassium-ion energy devices due to excellent development prospects. However, the poor conductivity and unsatisfactory rate performance of hard carbon limit their development. Herein, chitosan was chosen as the carbon precursor to prepare interpenetrated meso/macro-porous structural hard carbon (PC) formed by the template agent NaCl in the molten state at high temperature as the anode for potassium-ion batteries. PC with a high content of pyridinic N, pyrrolic N, and CO bonds can provide a high reversible capacity of 280.1 mAh g−1 at the current density of 0.05 A g−1, and show an improved rate performance of 173.8 mAh g−1 at 1.0 A g−1. Galvanostatic charge/discharge (GCD) curves do not exhibit an obvious plateau, indicating that surface adsorption is dominant in the potassium ions storage mechanism. The high K+ diffusion coefficient indicates that the interconnected meso/macro structure allows potassium ions to diffuse faster in PC. Therefore, using activated carbon (AC) as the cathode and PC as the anode, a potassium-ion hybrid capacitor (PIHC) is fabricated, which can achieve an energy density of 130 Wh kg−1 at the current density of 0.05 A g−1 and an energy density of 62 Wh kg−1 at 1.0 A g−1.

Engineering stable active Cu0-Cuσ+ sites via in situ surface reconstruction over Cu/CeO2 catalyst for the hydrogenation of carbon-oxygen bonds

Cu/CeO2 catalysts have been wildly used for the hydrogenation of carbon-oxygen bonds reactions due to their excellent catalytic performance. It is widely accepted that the Cu0-Cuσ+ interface could be the primary active sites during the reaction, but how to form and maintain highly dispersed such species remains challenging under the reaction conditions of high temperature and H2 partial pressure. In this work, we proposed an effective strategy to construct stable Cu0-Cuσ+ interface sites over the Cu/CeO2 catalysts by in situ N2O-involved oxidation treatment. It was evidenced that the sequential oxidation-reduction by N2O and H2 broke the grain boundaries of Cu nanoparticles and therefore facilitated the formation of the active Cu0-Cuσ+ sites, leading to an enhanced activity. However, a rapid deactivation was observed after this temporary enhancement due to the aggregation of copper species. We further introduced some additional cerium species during catalyst preparation. The 16Cu/CeO2-1Ce catalyst prepared by post-impregnation of 1 wt% cerium achieved a stable performance of 90.6% MA conversion after the N2O-involved oxidation treatment, which was much higher than that of 26.2% over the 16Cu/CeO2 catalyst. It was demonstrated that the strong interaction between the formed CeO2 and reconstructed Cu species prevented the metal sintering and increased the fraction of the Cu0-Cuσ+ sites. This method that combined in situ N2O-involved oxidation treatment and cerium modification may offer potential in engineering stable active sites for high-performance catalysts in the hydrogenation of carbon-oxygen bonds.

Selective hydrodeoxygenation of 5-hydromethylfurfural to 2,5-dimethylfuran over PtFe/C catalyst

2,5-dimethylfuran (DMF), a promising biomass-derived fuel, is synthesized via the hydrodeoxygenation of 5-hydroxymethylfurfural (HMF). This study focuses on the inherent activity of a 5Pt5Fe/C catalyst for HMF hydrodeoxygenation to DMF. The catalyst exhibited exceptional performance, achieving a remarkable DMF yield of 99.6 %. It displayed specific selectivity for C = O bond hydrogenation and CO bond cleavage in diverse substrates, producing high yield of 2-methylfuran from furfural and furfury alcohol, and high yield of toluene from benzaldehyde, benzyl alcohol. In-depth characterizations unveiled valuable insights into the 5Pt5Fe/C catalyst's properties, emphasizing a harmonious balance between metal and acid sites due to the interactive synergy between Pt and Fe species, enhancing hydrodeoxygenation activity. Additionally, the catalyst demonstrated satisfactory stability, maintaining a commendable DMF yield over five reaction cycles despite observed changes.

Hydrodeoxygenation of biomass-derived fatty acids and esters to biofuels on RuRe/ZSM-5 catalysts: Synergistic effects of ReOx and Brønsted acid sites

The hydrodeoxygenation of fatty acids and esters is a critical pathway to produce biofuels. We report an efficient RuRe/ZSM-5(18) catalyst for hydrodeoxygenation of methyl laurate, the selectivity of n-C12H26 reached up to 95.2 % at complete conversion under the reaction conditions of 200 °C, 3 MPa H2, 3 h. The contribution of ReOx and acid sites was discussed from the perspective of dynamics and thermodynamics. ReOx was available for the adsorption of substrate and intermediates, the acidity from ReOx species and ZSM-5 are conducive to the cleavage of CO bond. The synergistic effects of ReOx and Brønsted acid sites induced Ru0 species to be electron-deficient, which preferred to adsorb aldehyde group in a linear adsorption configuration and facilitated for the hydrogenation of the aldehyde intermediate to alcohol, followed by dehydration to produce hydrocarbons. Thus, RuRe/ZSM-5(18) catalyst presented superior activity and chemoselectivity in the hydrodeoxygenation of methyl laurate as well as a series of fatty acids and esters without loss in carbon numbers in reactant.

Hydrogen-bonded structure of hydrated water in polyvinyl pyrrolidone aqueous solution investigated by X-ray absorption and emission spectroscopy

Polyvinylpyrrolidone (PVP) is a hydrophilic polymer that is widely used in various biomedical applications owing to its excellent biocompatibility. It has been suggested that water-polymer interactions play a key role in controlling biocompatibility, although the molecular-level consequences of these interactions remain unknown. In this study, the hydrogen-bonded structures of water molecules hydrating PVP were investigated using X-ray absorption spectroscopy (XAS) and X-ray emission spectroscopy (XES). XAS spectral profiles revealed that the CO bonds in highly concentrated PVP aqueous solutions have at least two states: one where hydrogen bonds are formed with water molecules and the other where they are not. In the XES profile of water extracted from a solution with a stoichiometric ratio of nw = 1.0, increased hydrogen bonding and hydrogen bond distortion were identified from the enhancement of 1b1′ and 3a1 peaks, respectively. Because it is difficult for water molecules to form strong hydrogen-bonded structures in tetrahedral coordination at nw = 1.0, these findings suggest that the presence of strong hydrogen bonds between the CO sites and water prevents the formation of tetrahedrally coordinated hydrogen-bonded structures among water molecules.

Solar-Light-Driven Photocatalytic Oxidative Coupling of Phenol Derivatives over Bismuth-Based Porous Metal Halide Perovskites.

The selective oxidative coupling of phenol derivatives, involving carbon-carbon (C-C) and carbon-oxygen (C-O) bond formation, has emerged as a critical approach in the synthesis of natural products. However, achieving precise control over the selectivity in coupling reactions of unsubstituted phenols utilizing solar light as the driving force remains a big challenge. In this study, we report a series of porous Cs3Bi2X9 (X=Cl, Br, I) photocatalysts with tailored band gaps and compositions engineered for efficient solar-light-driven oxidative phenol coupling. Notably, p-Cs3Bi2Br9 exhibited about 73 % selectivity for C-C coupling, displaying a high formation rate of 47.3 μmol gcat -1 h-1 under solar radiation. Furthermore, this approach enables control of the site-selectivity for phenol derivatives on Cs3Bi2X9, enhancing C-C coupling. The distinctive porous structure and appropriate band-edge positions of Cs3Bi2Br9 facilitated efficient charge separation, and surface interaction/activation of phenolic hydroxyl groups, resulting in the kinetically preferred formation of C-C over C-O bond. Mechanistic insights into the reaction pathway, supported by comprehensive control experiments, unveiled the crucial role of interfacial charge transfers and Lewis acid Bi sites in stabilizing phenolic intermediates, thereby directing the regioselectivity of diradical couplings and resulting in the formation of unsymmetrical biphenols.

Coupling electron donors with proton repulsion via Pt-N3-S sites to boost CO2 reduction in CO2/H2 fuel cell

A fuel cell involving CO2/H2 is an appealing energy system to convert CO2 into synthetic fuels as well as to generate electricity using only waste heat. However, overcoming the inherent activation barrier of CO2 to improve the CO2 conversion rate in CO2/H2 fuel cell is still challenging. Herein, we report a synergistic electron-donor and proton-repulsion group composed of Pt-N3-S-C sites to simultaneously modulate the electronic structure and CO2-protonation ability of Ru nanoclusters (RuNC) in RuNC/Pt-N3-S-C catalyst. Experiments combined with theoretical calculations indicate that Pt-N3-S sites not only function as electron donors to Ru nanoclusters to cooperatively induce the orbital hybridization of Ru 3d and the antibonding orbitals of CO2, affording the dissociation of CO bonds in CO2, but also as electronic structure “modulator” to create new active sites on the surface of RuNC to effectively activate molecular CO2. More importantly, an internal polarization field between Pt-N3-S-C and RuNC additionally makes single atom Pt sites repel protons while Ru atoms serve as proton capturers via hydrogen spillover effect, resulting in accelerated protonation of CO2. Consequently, the catalyst exhibits highly improved catalytic activities for CO2 reduction with a conversion rate of 559.1 μmol gcat−1 h−1. This approach helps with fine tuning the electronic structures and catalytic CO2 protonation ability of catalysts for thermal-coupled electrocatalysis.

Shear properties and failure mechanisms of adhesive bonded composite joint: Effect of glass particle reinforcement

AbstractHigh‐performance composite structures and effective joining processes are important for shipbuilding, and aerospace sectors to perform better in challenging situations. The importance of this study is to analyze the effect of glass powder‐modified adhesive and joining techniques such as co‐curing (CC), co‐bonding (CB), and secondary bonding (SB) on flexural, shear, and free vibrational characteristics such as natural frequency and damping factor for glass fiber‐reinforced polymer (GFRP) composites. Results revealed that, compared to SB and CB composite joints, 1 wt.% glass powder‐modified CC composite single lap joints (SLJ) enhanced the shear properties by 103.04% and 111.74%, respectively, due to rougher surface formation in the adhesive layer. As a result, it enhanced the fiber's adhesion to the matrix. On the other hand, CC bonded joints with 1 wt.% of glass powder exhibited the highest flexural strength (85.99 Mpa). The experimental free vibrational analysis showed that 1 wt.% glass powder CC composite had a high natural frequency, whereas higher wt.% glass powder increased the damping properties due to the matrix and fiber interaction. The current research reveals that CC technique with 1 wt.% of glass powder provided a significant improvement to the adhesively bonded composite's mechanical and free vibrational characteristics.Highlights Four distinct wt.% of glass powder were used to prepare the glass powder‐modified adhesive by sonication. SLJ glass fiber‐reinforced polymer composite joints were fabricated through CC, CB, and SB techniques Maximum shear and flexural strength were found at CC SLJ 1 wt.% glass powder. CC SLJ 1 wt.% glass powder enhanced better vibrational behavior. Failure surface analysis was conducted using FE‐SEM images.

Efficient hydrodeoxygenation of tetrahydrofuran 2,5-dicarboxylic acid to adipic acid over Pt-MOx catalysts: An experimental and computational study

The production of adipic acid (AA) from the ring-opening hydrogenolysis (hydrodeoxygenation - HDO) of tetrahydrofuran 2,5-dicarboxylic acid (THFDCA) by metal-metal oxide catalysts (Pt-MOx/TiO2 and Pt/MOx) was evaluated. Correlations between AA yield, or products distribution, and the type of active centers in the catalyst surface were established by studying the type (MOx: WOx, MoOx, and ZrOx), the amount of metal oxide (MOx:Pt molar ratio), and the reaction temperature (180ºC, 220ºC, and 240ºC) in Pt-MOx/TiO2 and Pt/MOx. The activity results show that only the catalysts that contain both Pt and Mo produced AA at 220ºC, with yields of 24% for Pt-MoOx/TiO2 (4 wt% Pt, 1:1 Mo:Pt molar ratio) and 34% for 4 wt% Pt/MoO3. At 180ºC, these catalysts exhibited high selectivity towards reducing the carboxyl group. Computational studies using DFT suggest that this behavior is due to the preferential interaction between the oxygen vacancy (O-VAC) in MoO3 and the CO bond in the carboxyl group in 2-hydroxyadipic acid (2-HAA), the first observed intermediate from the HDO of THFDCA. Coverage of this adsorption configuration decreases at temperatures above 200ºC, where the interaction between the alcohol group in the 2 C position in 2-HAA and the Brønsted acid site (BAS) on the surface of MoO3 is preferred. This latter interaction could promote the acid-catalyzed dehydration of the alcohol group to obtain AA. Increasing the amount of Mo to 5:1 Mo:Pt in Pt-MoOx/TiO2 and decreasing the Pt content to 0.1 wt % in Pt/MoO3 decreases the selectivity to alcohols, increasing the AA yield to 55% at 220ºC and 65% at 240ºC for both catalysts. This enhancement in performance is consistent with the findings from the DFT studies. To our knowledge, this is the highest yield reported for AA production from THFDCA or FDCA by metal-metal oxide catalysts.

Structure effects of imidazolium ionic liquids on integrated CO2 absorption and transformation to dimethyl carbonate

The integration of chemical absorption of CO2 and in situ transformation to highly valuable chemicals is a promising process as an alternative toward fossil fuels. Here, three imidazolium ionic liquids (ILs), 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium 1,2,4-triazole ([Bmim][Tz]), and 1-butyl-2,3-dimethylimidazolium 1,2,4-triazole were synthesized to absorb and activate CO2 by the formation of CO2-adducts, which can be in situ converted into dialkyl carbonates with alcohols (ROH, R = CH3, C2H5, and C4H9) in solvent diiodomethane under ambient temperature and pressure. The results show [Bmim][Tz] exhibits the best CO2 absorption capacity and dimethyl carbonates (DMC) yield, where CO2 capacity is up to 0.216 gCO2/gIL and DMC yield (based on methanol) is as high as 20.2 %. The structures of imidazolium ILs have significant effects on the absorption of CO2 and subsequent transformation process. Fourier transform infrared and carbon nuclear magnetic resonance spectroscopies demonstrate ILs structures influence binding sites for CO2 absorption, which can combine with CO2 to form CO2-adducts, zwitterion [Bmim-CO2], and [Tz-CO2]−. Furthermore, density functional theory calculations verify the structure effects (binding sites and steric hindrance) of ILs on the activation of CO2 and methanol, through the elongated CO bond lengths of CO2-adducts and O-H bond lengths of methanol in IL-methanol complexes, respectively, leading to different DMC yields. The integrated process is promising for the energy-efficient capture and utilization of CO2 under ambient conditions.

Precise regulation of Mo2N–TiO2 deposited Pt nanoparticles induced synergistic effect for the hydrogenation of cinnamaldehyde

The amalgamation of an appropriate cocatalyst is a proficient technique to expand the efficacy of precious Pt-based catalytic materials. In this study, Mo2N–TiO2 with regularly distributed Mo2N particles were simply prepared for the deposition of precious Pt nanoparticles (NPs). Numerous techniques were implemented to thoroughly explore, how synthesis method influence the bulk structural, interfacial and cata1ytic features of the as-prepared 3 wt%Pt/TiO2 and 3 wt%Pt/Mo2N–TiO2 catalytic materials. The catalytic results obviously show that the 3 wt%Pt/Mo2N–TiO2 catalyst has exceptional hydrogenation performance when compared to 3 wt%Pt/TiO2 catalyst. The 3 wt%Pt/Mo2N–TiO2 catalyst displayed high conversion (72.4 %) of cinnamaldehyde (CAL) with a maximum selectivity (82.1 %) towards CO bond. The excellent hydrogenation performance is attributed to the synergistic interaction taking place between Pt NPs and Mo2N entities of 3 wt%Pt/Mo2N–TiO2. Also, the enhanced standardized dispersal of Pt NPs on the Mo2N–TiO2 surface causes more exposed Pt0 sites on the 3 wt%Pt/Mo2N–TiO2 surface, which is productive for the improved activation and conversion of CO bond of CAL to yield COL. In addition, the 3 wt%Pt/Mo2N–TiO2 catalyst retained its higher catalytic activity for consecutive five successive rounds without substantial loss in either conversion or selectivity.

Electrocatalytic Reduction of CO2 to CO by Molecular Cobalt-Polypyridine Diamine Complexes.

Cobalt complexes have previously been reported to exhibit high faradaic efficiency in reducing CO2 to CO. Herein, we synthesized capsule-like cobalt-polypyridine diamine complexes [Co(L1)](BF4)2 (1) and [Co(L2) (CH3CN)](BF4)2 (2) as catalysts for the electrocatalytic reduction of CO2. Under catalytic conditions, complexes 1 and 2 demonstrated the electrocatalytic reduction of CO2 to CO in the presence or absence of CH3OH as a proton source. Experimental and computational studies revealed that complexes 1 and 2 undergo two consecutive reversible one-electron reductions on the cobalt core, followed by the addition of CO2 to form a metallocarboxylate intermediate [CoII(L)-CO22-]0. This crucial reaction intermediate, which governs the catalytic cycle, was successfully detected using high resolution mass spectrometry (HRMS). In situ Fourier-transform infrared spectrometer (FTIR) analysis showed that methanol can enhance the rate of carbon-oxygen bond cleavage of the metallocarboxylate intermediate. DFT studies on [CoII(L)-CO22-]0 have suggested that the doubly reduced species attacks CO2 on the C atom through the dz2 orbital, while the interaction with CO2 is further stabilized by the π interaction between the metal dxz or dxz orbital with p orbitals on the O atoms. Further reductions generate a metal carbonyl intermediate [CoI(L)-CO]+, which ultimately releases CO.