Coupling Reaction Of CO2 Research Articles

The efficient and reusable imidazolium-organoboron catalysts for green CO2 insertion reactions in solvent-free under atmospheric and high-pressure conditions

Organoboron compounds that are available in industrial and scientific research were investigated as organocatalysts for the coupling reaction of CO2 into cyclic carbonates as fine chemicals in solvent-free and under sustainable green atmospheric and high-pressure conditions (1 atm and 1.6 MPa, 100 °C, 2 h). This work synthesized a series of imidazolium-organoboron catalysts (IBC1-IBC8) using the eco-friendly and metal-free methodology and characterized by various analysis techniques. These techniques were NMR (1H, 13C, and 11B), UV–Vis, FT-IR, Mass spectrometry, C/H/N analysis, and melting point measurement together with thermal gravimetric analysis (TGA-DTA), respectively. After that, the Lewis acidity of the synthesized imidazolium-organoboron catalysts, which is important for catalytic CO2 conversion studies, was investigated by the traditional Gutmann-Beckett test, and the Lewis acidity order of the target compounds was found at range 54.96–50.36 ppm. In the presence of 0.1 mol% imidazolium-organoboron catalyst (IBC8) and 0.2 mol% DMAP as co-catalyst, 4-chloromethyl-1,3-dioxalan-2-one was obtained as cyclic carbonate from epichlorohydrin in 44.9 % yield and 97.6 % selectivity (1 atm and 100 °C) and in an excellent 97 % yield with 98.9 % selectivity (1.6 MPa and 100 °C) in 2 h without any solvents. After the imidazolium-organoboron catalyst (IBC8) showed efficient catalytic conversion and high selectivity, the effect of different parameters, including the effect of substrate, Lewis acid-base, reaction time, reaction temperature, CO2 pressure, and catalyst amount, was studied for this catalyst. According to the obtained catalytic conversion results, it was also determined that the optimum Cat./ECH ratio for CO2 cycloaddition reactions is 1/1000.

Pyrolysis of 1,2-bis(2,4,6-tribromophenoxy)ethane: Theoretical and experimental research

1,2-Bis(2,4,6-tribromophenoxy)ethane (BTBPE), as a novel brominated flame retardant, is widely applied to various plastic products to improve flame resistance. In this paper, we have carried out theoretical and experimental studies on the pyrolysis of BTBPE. The density functional theory (DFT) method at M06/cc-pVDZ theoretical level was used to calculate thermodynamic and kinetic parameters, and the pyrolysis mechanisms of BTBPE were in detail analyzed based on theoretical calculation data and relevant experimental findings. In unimolecular pyrolysis reaction, concerted reaction mechanism with a four-membered ring transition state at low temperatures leads to high yields of 2,4,6-tribromophenol and vinyl 2,4,6-tribromophenol ether, and free radical reaction at high temperatures generates 2,4,6-tribromophenoxy and 2,4,6-tribromophenoxy-ethyl by direct breakage of the CO bond. The 2,4,6-tribromophenoxy radical can further catalyze BTBPE decomposition to form 2,4,6-tribromophenol and vinyl 2,4,6-tribromophenol ether. Reactions of the BTBPE molecule with H radicals mainly proceed via debromination, which results in the production of HBr and low-brominated congeners. The 2,4,6-tribromophenol and 2,4,6-tribromophenoxy undergo a CO coupling reaction to eliminate OH, which is the principal pathway for the generation of polybrominated diphenyl ethers (PBDEs). The formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) involves the self-condensation of 2,4,6-tribromophenoxys, debromination, rearrangement, and cyclization. The energy barrier of the reaction path forming PBDD is lower than that of the reaction path forming PBDFs. Therefore, the yield of brominated dibenzo-p-dioxin is higher than that of brominated dibenzofuran. The experimental results of pyrolysis are in good agreement with our theoretical research.

Celecoxib Catalyzed the Coupling Reaction of Epoxide and CO2

Abstract: In this study, high yields of various cyclic carbonates are obtained by employing the drug celecoxib to promote the coupling reaction of CO2 and epoxide using tetrabutylammonium bromide. This strategy enables the synthesis of benzoic acid, phenylpropiolic acid, and 2, 4- quinazolinedione. In addition, the model reaction mechanism is proposed.

Optimization of activity and selectivity for syngas-to-ethanol conversion on metal-based catalysts via the first-principles microkinetic simulations

Achieving high selectivity in converting syngas to ethanol has long been a challenging task, requiring identification of key factors favoring ethanol production over other by-products such as methane, methanol, and acetaldehyde. Herein, we perform systematic density functional theory (DFT) calculations and microkinetic simulations to shed light on the activity and selectivity trends of ethanol relative to three competing by-products in syngas conversion, which quantitatively unveils the key determining factors on the transition metal-based catalysts. The scaling relations involved are revealed as functions of the adsorption energies of C and O species (EC and EO), and the three-dimensional activity and selectivity surfaces are constructed quantitatively, indicating that the optimal condition (peak position) correspond to EC = -6.10 eV and EO = -5.70 eV. Furthermore, we find that ethanol activity at the peak is primarily constrained by the kinetic barriers of CH3O dissociation and the coupling reaction of CH3 and CO, while its selectivity can be enhanced by increasing the energy barrier of CH3 hydrogenation and strengthening the adsorption of CH3CHO. More significantly, following these rules, the single-atom metal alloy catalysts (i.e., Cu1Co, Cu1Ni) are identified that could serve as promising candidates for ethanol synthesis, which are superior to the common alloy-type catalysts. We believe that these insights further deepen the understanding of theoretical design of metal alloy catalysts in ethanol production.

Tailoring the catalytic microenvironment of CuO with hydrophobic CuSA2 for selective CO2 electroreduction to C2+ products

Advancing the Faraday efficiency (FE) and current density of Cu catalyzed electrochemical CO2 reduction (ECR) reaction to produce C2+ products is important for its practical applications. Constructing a hydrophobic interface to regulate the local reaction environment is an effective method to improve the selectivity of C2+ products, but it is limited by the low reaction current density. In this work, we fabricated a novel hydrophobic and ECR active copper stearate (CuSA2) decorated CuO nanoparticle catalyst (CuO/CuSA2) for ECR reaction toward C2+ products. As a result, the CuO/CuSA2 catalyst achieved an FE of 61.33 % and a partial current density of 429.33 mA cm−2 for C2+ products. The CuSA2 and CuO nanoparticle cooperate very well for the formation of C2+ products. The in-situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and electrochemical adsorption experiment indicated that the hydrophobic CuSA2 regulated the local ECR reaction environment. The local ∗CO2.- and *CO adsorption were strengthened by hydrophobic CuSA2 modification while the H2O adsorption was inhibited. CuO nanoparticle promotes *CO coupling reaction and enhances C2 intermediates (*OCCOH and *OC2H5) adsorption. Hydrophobic CuSA2 and CuO nanoparticle synergistically promote the generation of C2+ products. This work provides new insights into the design of hydrophobic CO2 reduction electrocatalysts for the preparation of C2+ products.

Nanoporous Copper for the Electrosynthesis of Cyclic Carbonates from CO2 and Epoxides

AbstractCyclic carbonates are often produced through catalytic coupling reactions of CO2 with epoxides under harsh conditions. Here, we present a highly active nanoporous copper (np‐Cu) cathode material for the electrosynthesis of cyclic carbonates in mild environments. Np−Cu material was drop casted on glassy carbon (np‐Cu/GC) as cathode electrode to perform galvanostatic electrosynthesis using a magnesium anode in CO2‐saturated acetonitrile with 0.1 M tetraethylammonium iodide. Very good yields have been obtained for 1,2‐butylene carbonate (BC, 74 ± 4 %) and propylene carbonate (PC, 62 ± 6 %). By varying the cathode electrode materials, low yields (≤ 20 %) on bare GC, but similar yields (76 ± 4 % BC and 63 ± 5 % PC) on polycrystalline Cu were achieved. Although the pore‐ligament structure is beneficial to enhance the CO2RR performance, its impact on the yield of cyclic carbonate is minimal. This implies that the activation of CO2 to the CO2⋅− radical anion is not the rate‐limiting step, but rather the ring closure of the final intermediate to form cyclic carbonates. Moreover, the np‐Cu/GC shows very good stability and reusability for the electrochemical‐organic test reaction. This study provides deeper insights into the reaction mechanism of cyclic carbonates formation on Cu‐based electrodes.

Insights into the CO-mediated deactivation mechanism for dimethyl ether carbonylation reaction over a H-MOR catalyst

Dimethyl ether (DME) carbonylation to methyl acetate (MAc) catalyzed by H-MOR catalyst has aroused wide interest due to its high efficiency as an emerging method for ethanol production. However, the rapid deactivation of H-MOR catalyst results in great challenges for its industrial application, urging a clear understanding of the intricate carbonylation deactivation mechanism. Herein, we discover a CO-mediated deactivation mechanism over H-MOR catalyst, which is beyond the traditional understanding that deactivation is originated from DME/methanol-to-hydrocarbon (DTH/MTH) chemistry. It is revealed that the coupling reaction of CO or MAc with olefins accelerate the catalyst deactivation, and methyl cyclopentenones (MCPOs) are first identified as the key intermediates for aromatic cokes formation over H-MOR catalyst. A more comprehensive mechanism for DME carbonylation deactivation is proposed based on the understanding. This study would provide valuable insights into understanding the carbonylation process and offer potential directions for developing carbonylation catalysts with enhanced stability.

Silver Metal-Organic Framework Derived N-Doped Carbon Nanofibers for CO2 Conversion into β-Oxopropylcarbamates.

Developing efficient heterogeneous catalysts for chemical fixation of CO2 to produce high-value-added chemicals under mild conditions is highly desired but still challenging. Herein, we first reported an approach to prepare a novel catalyst (Ag@NCNFs), featuring Ag nanoparticles (NPs) embedded within porous nitrogen-doped carbon nanofibers (NCNFs), via growing a Ag metal-organic framework on one-dimensional electrospun nanofibers followed by pyrolysis. Benefiting from the abundant nitrogen species and porous structure, Ag NPs is well dispersed in the obtained Ag@NCNFs. Catalytic studies indicated that Ag@NCNFs exhibited excellent catalytic activity for the three-component coupling reaction of CO2, secondary amines, and propargylic alcohols to generate β-oxopropylcarbamates under mild conditions with a turnover number (TON) of 16.2, and it can be recycled and reused at least 5 times without an obvious decline in catalytic activity. The reaction mechanism was clearly clarified by FTIR, NMR, 13C isotope labeling, control experiments, and density functional theory calculations. The results suggest that Ag@NCNFs and 1,8-diazabicyclo[5.4.0]undec-7-ene can synergistically activate propargylic alcohol to react with CO2, and then the generated α-alkylidene cyclic carbonate was invaded by secondary amine to produce β-oxopropylcarbamate. Importantly, to the best of our knowledge, this is the first experimental and theoretical investigation on this reaction.

Organocatalysts for the Synthesis of Cyclic Carbonates under the Conditions of Ambient Temperature and Atmospheric CO2 Pressure

2–(1H–1,2,4–Triazol–3–yl)phenol (CAT–1) was used as an organocatalyst for the coupling reaction of CO2 and epoxides at an ambient temperature and atmospheric CO2 pressure (1 bar). This compound has a structure in which a hydrogen bond donor, a hydrogen bond acceptor, and another hydrogen bond donor are adjacent in sequence in a molecule. The binary catalytic system of CAT–1/nBu4NI showed TON = 19.2 and TOF = 1.60 h−1 under 1 bar CO2 at room temperature within 12 h using 2–butyloxirane. Surprisingly, the activity of CAT–1, in which phenol and 1H–1,2,4–triazole are chemically linked, showed a much greater synergistic effect than when simply mixing the same amount of phenol and 1H–1,2,4–triazole under the same reaction conditions. In addition, our system showed a broad terminal and internal epoxide substrate scope.

Insight into the Formation and Catalytic Mechanism of “CO Pool” during Electrocatalytic Conversion of CO2

The OC-CO coupling reaction, requiring pairs of *CO or *CHO intermediates absorbed on adjacent Cu sites, is the key elementary reaction during the electrocatalytic conversion of CO2 towards C2 products, where the harsh demand of adjacent *CO cause the transmission and preservation of CO species become the critical step of CO coupling reaction. Among the reported M-Cu (M=Ag, Au, Zn, etc....) tandem catalysts and Cu+-Cu sites, CO goes through the route of “generation-desorption-transmission-deeply reduction” over the catalytic surface. Despite the in-depth studies of the various site’s composition, morphological structures, and catalytic sites arrangement on Cu-based catalysts, the migratory manner on the electrode surface and the concentration and reactivity of CO in the double layer is still obscure, which are essential steps for CO spillover on the surface of Cu-based catalysts and further coupling reactions, as well as the underlying causes of the poor selectivity of CO/C2 products. At the same time, in situtechniques with temporal resolution are still lacking for probing the overflow and inter-diffusion of CO in the double layer.In this study, based on the rotating disk electrode, we developed an effective means for in situ monitoring of the transport and electrochemical properties of CO in the diffusion layer. Based on theoretical analysis of the electrochemical interface CO species transfer path and time-resolved RRDE techniques, we proved that most of the CO intermediates are favorable to transferred and then reserved in the diffusion layer, leading to an enhanced concentration of CO over equilibrium concentration, and finally benefitted the transmission and reactivity of CO species. By analyzing the reaction chain, combined with in situ ATR-SEIRAS monitor and theoretic calculation, the chemical potential was proved to be enhanced by introducing the “CO pool”, which could be resonated in the reaction chain, raised an increased entropy production and finally led to a resonance-enhanced concentration of by-intermediates, finally strengthening the activity of whole chain-system. Figure 1

Tetrabutylammonium bromide/triethanolamine deep eutectic solvents with double hydrogen bond as efficient catalysts for fixation of CO2 in cyclic carbonates under mild conditions

AbstractBACKGROUNDCarbon dioxide is not only a major greenhouse gas but also an important carbon resource, which is abundant, renewable, low cost and non‐toxic. The coupling reaction of CO2 with epoxides has shown great potential in the field of chemical carbon fixation due to its 100% atomic utilization efficiency. Deep eutectic solvents (DESs) based on tetrabutylammonium bromide (TBAB) were evaluated for cycloaddition reaction of CO2 with propylene oxide (PO) to propylene carbonate (PC). Density functional theory (DFT) was used to calculate the catalytic performance of DES in CO2 cycloaddition reaction.RESULTSThe utilization of DES containing triethanolamine (TEA) as hydrogen bond donor significantly shortened the reaction time. Under optimal reaction conditions (30 mmol PO, 5 mol% TBAB/TEA (1:1) DES, 1.0 MPa CO2, 90 °C, 2 h), high PC yield (98%) was obtained. DFT calculations revealed that TBAB/TEA (1:1) DES was used as the catalyst for the coupling reaction between PO and CO2, with the ring‐opening process serving as the rate‐determining step and energy barrier of 17.9 kcal mol−1. TBAB/TEA (1:1) DES exhibited excellent recyclability and could be reused more than five times.CONCLUSIONTBAB/TEA (1:1) DES is a highly efficient homogeneous catalyst for the synthesis of cyclic carbonates through the cycloaddition reaction of CO2 and epoxides. The synergistic catalytic effect of the double hydrogen bonds between DES and Br anions is the reason for its high efficiency. © 2023 Society of Chemical Industry.

Solvent- and Co-Catalyst-Free Cycloaddition of Carbon Dioxide and Epoxides Catalyzed by Recyclable Bifunctional Niobium Complexes.

CO2, as a cheap and abundant renewable C1 resource, can be used to synthesize high value-added chemicals. In this paper, a series of bifunctional metallic niobium complexes were synthesized and their structures were characterized by IR, NMR and elemental analysis. All of these complexes have been proved to be efficient catalysts for the coupling reaction of CO2 and epoxides to obtain cyclic carbonates under solvent- and co-catalyst-free conditions. By using CO2 and propylene oxide as a model reaction, the optimal reaction conditions were systematically screened as: 100 °C, 1 MPa, 2 h, ratio of catalyst to alkylene oxide 1:100. Under the optimal reaction conditions, the bifunctional niobium catalysts can efficiently catalyze the coupling reaction with high yield and excellent selectivity (maximum yield of >99% at high pressure and 96.8% at atmospheric pressure). Moreover, this series of catalysts can also catalyze the coupling reaction at atmospheric pressure and most of them showed high conversion of epoxide. The catalysts have good substrate suitability and are also applicable to a variety of epoxides including diepoxides and good catalytic performances were achieved for producing the corresponding cyclic carbonates in most cases. Furthermore, the catalysts can be easily recovered by simple filtration and reused for at least five times without obvious loss of catalytic activity and selectivity. Kinetic studies were carried out preliminarily for the bifunctional niobium complexes with different halogen ions (3a(Cl-), 3b(Br-), 3c(I-)) and the formation activation energies (Ea) of cyclic carbonates were obtained. The order of apparent activation energy Ea is 3a (96.2 kJ/mol) > 3b (68.2 kJ/mol) > 3c (37.4 kJ/mol). Finally, a possible reaction mechanism is proposed.

Mechanistic insight into the carboxylic derivatives formation from CO2 and ethylene over iron(0)-based catalyst

Since the 1980s, nickel/palladium-based catalysts have been extensively studied for the coupling reactions of CO2 and ethylene. In this study, the CO2 and ethylene coupling mediated by the iron(0)-based catalyst with a bis(dicyclohexylphosphino)ethane (dcpe) ligand was systematically investigated by means of DFT calculations. The DFT functionals were first subjected to a benchmark test in order to describe an iron-catalyzed reaction with a two-state reactivity (TSR). For the Fe/dcpe catalytic system, the formation of the five-membered iron-lactone 3 follows a stepwise route, which is easy to occur with a low energy barrier of 13.8 kcal/mol. The competing reactions by CO2 insertion and β-H elimination determine the fate of the five-membered iron-lactone 3, which may lead to the formation of three different products, including the formation of i) succinic acid, ii) iso-methylmalonic acid, and iii) acrylic acid. The calculated TOFs showed that CO2 insertion into the five-membered iron-lactone 3 is more likely to occur (1.67 h−1 for the formation of succinic acid) compared with the β-H elimination leading to iso-methylmalonic acid and acrylic acid. Interestingly, β-H elimination can be effectively facilitated by addition of the electrophiles, and a comparable TOF of 0.042 h−1 was obtained for the formation of methyl acrylate in the presence of CH3I. Unlike nickel-/palladium-catalyzed CO2 and ethylene coupling reactions, all four iron(0)-catalyzed reaction routes investigated herein showed a two-state reactivity scenario involving spin crossover between triplet and quintet PESs. This study provides a mechanistic understanding of the intriguing iron(0)-catalyzed CO2 and ethylene coupling reactions, which may shed some light on the development of green catalysts for CO2 utilization.

Selective synthesis of dimethyl carbonate via the coupling reaction of CO2 and alcohols by the synergistic catalysis of silver sulfadiazine and superbase

The three-component coupling of methanol, CO2 and propargyl alcohol to manufacture dimethyl carbonate (DMC) provides a new, thermodynamic favorable and green chemical synthesis route. In this work, to overcome the problems of low DMC yield and slow conversion rate of intermediates, the synergistic catalytic strategy of silver sulfadiazine and superbase is developed to improve the reaction efficiency. The effect of various parameters i.e. catalyst and cocatalyst types, catalyst loading, solvent, temperature, proportion of raw materials, pressure and time on the coupling reactions is investigated in detail. Under the optimal conditions, the selectivity of DMC is 89.5% with the yield of 55.6%. And the effect of alkyne derivative α-monosubstituted propargyl alcohol on the efficiency and selectivity of DMC are studied also. The mechanism study shows that propargyl alcohols with different structures apparently affect the reaction process, and the synergistic catalysis of silver sulfadiazine/1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) is the reason for the high yield and selectivity of DMC.

Tailoring morphology of MgO catalyst for the enhanced coupling reaction of CO2 and glycerol to glycerol carbonate

Developing efficient halogen-free catalysts is still a significant challenge for adsorption and activation of CO2 and further preparing glycerol carbonate. Herein, we successfully developed heterogeneous MgO catalyst via morphology-oriented regulation to catalyze the coupling reaction of glycerol and CO2. Specifically, cubic MgO displays more low-coordinated O2– originated from the unique atomic arrangement of (111) facet, resulting in abundant strong basic sites and surface oxygen vacancies. These strong basic sites promote the adsorption of CO2 to form thermodynamically stable monodentate carbonates near the oxygen vacancies. In addition, nearby surface oxygen vacancies could further enhance the transfer of electrons into the anti-bonding orbitals of CO2 molecules. The synergistic catalytic effect between the strong basic sites and the surface oxygen vacancies significantly facilitates the cycloaddition reaction (the most critical step in the coupling reaction). Therefore, under the optimal reaction conditions (140 °C, 2 MPa CO2, and 4 h), the MgO-C catalyst showed 83 % glycerol conversion and 44 % glycerol carbonate selectivity.

Insight into the effect of anions on cycloaddition of CO2 catalyzed by carboxylate anion-based ionic liquids: A theoretical study by QM and MD

Elucidating the mechanism of carbon dioxide (CO2) cycloaddition reaction catalyzed by ionic liquid (ILs) facilitates the rational design of efficient IL catalysts at the molecular level. To date, a great deal of research has been devoted to the halogen-containing ILs, however, the catalytic mechanism of halogen-free ILs remains unclear. In this contribution, an exhaustive theoretical study of the coupling reaction of CO2 with epichlorohydrin (ECH) catalyzed by three halogen-free ILs has been carried out for the first time by combining density functional theory (DFT) calculations with molecular dynamics (MD) simulations. Meanwhile, the effect of carboxylate anion structure on catalytic activity is deeply investigated. The final results provide a comprehensive catalytic mechanism of carboxylate anion-based ILs. The most favorable mechanism involves three steps, i.e., ring-opening of ECH, CO2 insertion, and ring-closure to form the product. Among them, the ring-opening of ECH is the rate-determining step (RDS). Additionally, the analytical results of the independent gradient model based on Hirshfeld partition (IGMH) and atoms in molecules (AIM) suggest that the electrophilic activation from carboxylate anions plays a critical role in promoting the ECH ring-opening process. The electrophilic activation of anions is investigated for the first time in this work. The results indicate that incorporating electrophilic groups into anions is a promising pathway to develop new robust and efficient halogen-free ILs.

Azaboratrane as an exceptionally potential organocatalyst for the activation of CO2 and coupling with epoxide

• The energy barrier for the CO 2 activation in the presence of AZAB is 9.35 kcal/mol. Also, the activation step is the rate-determining step of the coupling reaction of CO 2 with ethylene oxide. • The rate constant for the activation step and TOF for the coupling reaction of CO 2 with ethylene oxide is 0.0898 L/mol/s, and 1.74 × 10 9 , respectively. • The activation energy decreases to a great extent in the presence of polar solvents. Consequently, the rate constant value for the activation step increases to 3.8 × 10 3 L/mol/s in acetonitrile. • The coupling of CO 2 with epichlorohydrin is kinetically and thermodynamically more feasible than other epoxides. Excessive use of fossil fuels resulted in a massive increase in CO 2 concentration in the atmosphere, which led to serious environmental issues. Thus, necessary steps need to be employed to alleviate the excessive amount of CO 2 from the atmosphere, and converting CO 2 into industrially valuable chemicals (e.g., cyclic carbonates) could be the best possible strategy. But the stability of the CO 2 molecule poses an extreme challenge in this approach. Owing to the thermodynamic stability of the CO 2 molecule, an exclusive bicyclic compound, azaboratrane (AZAB), has been theoretically investigated in the present work. The density functional theory (DFT) based studies were conducted to probe the catalytic action of the AZAB. The plausible mechanisms for the coupling reaction of CO 2 with epoxides were proposed and investigated. The effects of the solvents on the CO 2 coupling with epoxides in the presence of AZAB were also studied. Finally, a comparative analysis of different azatranes has been conducted to showcase the novelty of the presented catalyst. The result shows that the coupling reaction proceeds via CO 2 activation mechanism. The energy barrier for the activation was 9.35 kcal/mol, which further decreases to a great extent in the presence of highly polar solvents. Also, the calculated rate constant for the activation step was 0.08 L/mol/s. The rate constant tends to increase by increasing the temperature and polarity of the solvent. Thus, AZAB is found to be a potential catalyst for CO 2 activation and its coupling with epoxides.

Bimetallic zeolitic imidazolate framework derived magnetic catalyst for high-efficiency CO2 chemical fixation

Metal-organic framework (MOF) derived porous carbons are known as desirable catalysts for carbon dioxide (CO2) catalytic conversion. However, practical CO2 utilization processes are severely hampered by their powder form and relatively poor activities. Herein, we demonstrate the rational synthesis of ZnO and/or metallic Co embedded in N-doped porous carbon by one-step pyrolysis of bimetallic MOF, Co/Zn-ZIF. The optimized catalyst exhibits remarkable activity and recyclability towards the coupling reaction of CO2 and epoxides owing to hierarchical pore, good CO2 uptake and sufficient active sites. More importantly, its catalytic performance can be well maintained even under dilute CO2 (15%), humid environment or light irradiation instead of heating. These results pave a way to develop highly efficient materials for practical CO2 catalytic conversion.

Highly Enhanced Aromatics Selectivity by Coupling of Chloromethane and Carbon Monoxide over H-ZSM-5.

The transformation of methane into high value-added chemicals such as aromatics provides a more desired approach towards sustainable chemistry but remains a critical challenge due to the low selectivity of aromatics and poor stability. Herein, we first report a coupling reaction of CH3 Cl and CO (CCTA) based on methane conversion, which achieves extremely high aromatics selectivity (82.2 %) with the selectivity of BTX up to ca. 60 % over HZSM-5. The promoting effects have been demonstrated on other zeolites especially 10-membered rings (10 MR) zeolites. Multiple characterizations show that 2,3-dimethyl-2-cyclopentene-1-one (DMCPO) is generated from acetyl groups and olefins. Furthermore, isotopic labeling analysis confirms that CO is inserted into the DMCPO and aromatics rings. A new aromatization mechanism is proposed, including the formation of the above intermediates, which conspicuously weakens the hydrogen transfer reaction, leading to a considerable increase of aromatics selectivity and a dramatic drop in alkanes.

Highly Enhanced Aromatics Selectivity by Coupling of Chloromethane and Carbon Monoxide over H‐ZSM‐5

AbstractThe transformation of methane into high value‐added chemicals such as aromatics provides a more desired approach towards sustainable chemistry but remains a critical challenge due to the low selectivity of aromatics and poor stability. Herein, we first report a coupling reaction of CH3Cl and CO (CCTA) based on methane conversion, which achieves extremely high aromatics selectivity (82.2 %) with the selectivity of BTX up to ca. 60 % over HZSM‐5. The promoting effects have been demonstrated on other zeolites especially 10‐membered rings (10 MR) zeolites. Multiple characterizations show that 2,3‐dimethyl‐2‐cyclopentene‐1‐one (DMCPO) is generated from acetyl groups and olefins. Furthermore, isotopic labeling analysis confirms that CO is inserted into the DMCPO and aromatics rings. A new aromatization mechanism is proposed, including the formation of the above intermediates, which conspicuously weakens the hydrogen transfer reaction, leading to a considerable increase of aromatics selectivity and a dramatic drop in alkanes.