Product Selectivity Research Articles

Aromatics Alkylated with Olefins Utilizing Zeolites as Heterogeneous Catalysts: A Review

The alkylation reaction of aromatic compounds gains considerable attention because of its wide application in bulk and fine chemical production. Aromatics alkylated with olefins is a well-known process, particularly for linear alkylbenzene, phenyloctanes, and heptyltoluene production. As octane boosters and precursors for various petrochemical and bulk chemical products, a wide range of alkylated compounds are in high demand. Numerous unique structures have been proposed in addition to the usual zeolites (Y and beta) utilized in alkylation procedures. The inevitable deactivation of industrial catalysts over time on stream, which is followed by a decrease in catalytic activity and product selectivity, is one of their disadvantages. Therefore, careful consideration of catalyst deactivation regarding the setup and functioning of the process of catalysis is necessary. Although a lot of work has been carried out to date to prevent coke and increase catalyst lifespan, deactivation of the catalyst is still unavoidable. Coke deposition can lead to catalyst deactivation in industrial catalytic processes by obstructing pores and/or covering acid sites. It is very desirable to regenerate inactive catalysts in order to remove the coke and restore catalytic activity at the same time. Depending on the kind of catalyst, the deactivation processes, and the regeneration settings, each regeneration approach has pros and cons. In this comprehensive study, the focus was on discussing the reaction mechanism of 1-octene isomerization and toluene alkylation as an example of isomerization and alkylation reactions that occur simultaneously, shedding light in detail on the catalysts used for this type of complex reaction, taking into account the challenges facing the catalyst deactivation and reactivation procedures.

Hydrogen and Solid Carbon Production via Methane Pyrolysis in a Rotating Gliding Arc Plasma Reactor

Plasma‐induced methane pyrolysis is a promising hydrogen production method. However, few studies have focused the decomposition of pure methane as a discharge gas. Herein, a rotating gliding arc reactor was used for the conversion of methane (discharge gas and feedstock) into hydrogen and solid carbon. Methane conversion, gaseous product selectivity, and energy usage efficiency(specific energy requirement for hydrogen production(SER)) were investigated as functions of operating parameters, e.g., specific energy input(SEI), residence time, and reactor design. SEI was positively(almost linearly) correlated with methane conversion and hydrogen yield and negatively correlated with SER. Conversion and efficiency of energy usage increased when reactor designs providing higher thermal densities were used. With the increasing flow rate of methane at constant SEI, the reaction volume and, hence, the residence time of the gas inside the reaction zone increased, which resulted in methane conversion and hydrogen selectivity enhancement. The solid carbon featured four distinct domains, namely graphitic carbon, turbostratic carbon, few‐layer graphene, and amorphous carbon, which indicated a nonuniform temperature distribution in the reaction zone. But it seems that graphitic carbon dominates amorhphous one. This study highlights the potential of rotating gliding arc plasma systems for efficient methane conversion into hydrogen and valuable solid carbon products

Research on Deoxygenation Pyrolysis of Larch Based on Microwave Heating

Aiming at problems such as low energy utilization efficiency and the high oxygen content of liquid products in the process of conventional biomass conversion to prepare liquid fuels, the deoxygenation pyrolysis technology route of larch based on microwave heating was proposed in this paper. Two kinds of calcium–iron composite oxygen carriers, including Ca2Fe2O5 with iron ore structure and CaFe2O4 with spinel structure, were successfully synthesized. The results showed that the selectivity of ideal products was improved under the action of single iron-based oxygen carriers; however, the deoxygenation effect was undesirable. Under the action of CaFe2O4, the selectivity of aromatics was increased to 27.17% and the selectivity of phenols was decreased to 36.46%, which mainly existed in the form of O1P with low oxygen content. The oxygen content of bio-oil was reduced to 27.70% and the calorific value was increased to 29.05 MJ/kg, thus leading to a great improvement in the quality of liquid products. After the pyrolysis reaction, the Fe2P3/2 XPS peak of CaFe2O4 shifted to a higher binding energy and was characterized as higher valence of iron oxide, which proved its “oxygen grabbing” capacity in microwave pyrolysis. The deoxygenation conversion of larch without an external hydrogen supply was achieved.

Reductive Transformation of CO2 to Organic Compounds

AbstractCarbon dioxide is a major greenhouse gas and a safe, abundant, easily accessible, and renewable C1 resource that can be chemically converted into high value‐added chemicals, fuels and materials. The preparation of urea, organic carbonates, salicylic acid, etc. from CO2 through non‐reduction conversion has been used in industrial production, while CO2 reduction transformation has become a research hotspot in recent years due to its involvement in energy storage and product diversification. Designing suitable catalysts to achieve efficient and selective conversion of CO2 is crucial due to its thermodynamic stability and kinetic inertness. From this perspective, the redistribution of charges within CO2 molecules through the interaction of Lewis acid/base or metal complexes with CO2, or the forced transfer of electrons to CO2 through photo‐ or electrocatalysis, is a commonly used effective way to activate CO2. Based on understanding of the activation/reaction mechanism on a molecular level, we have developed metal complexes, metal salts, inorganic/organic salts, ionic liquids, as well as nitrogen rich and porous materials as efficient catalysts for CO2 reductive conversions. The goal of this personal account is to summarize the catalytic processes of CO2 reductive conversion that have been developed in the past 7 years: 1) For the reductive functionalization of CO2, the major challenge lies in accurately adjusting reaction parameters (such as pressure) to achieve high catalytic efficiency and the product selectivity; 2) For photocatalytic or electrocatalytic reduction of CO2, how to suppress competitive hydrogen evolution reactions and improve catalyst stability are key points that requires continuous attention.

Highly Selective On‐Surface Dehydrogenative Aromatization of n‐Hexyl to Phenyl Substituents

Dehydrogenative aromatization of alkyl substituents represents a powerful approach to aryl‐substituted functional molecules. However, the inertness of alkyl groups and the need for harsh reaction conditions accompanied by low product selectivity hamper its widespread applications. Here, we demonstrate the highly selective on‐surface thermal aromatization of n‐hexyl substituents on polycyclic aromatic hydrocarbons (PAHs) to their phenyl‐substituted analogues under mild conditions. After depositing two representative precursor molecules, n‐hexyl‐substituted hexaphenylbenzene (HPB‐Hex) and bianthryl octacarboxylic tetraimide (BATI‐Hex), onto a pre‐heated Au(111) substrate, dehydroaromatization of the peripheral n‐hexyl groups into phenyl rings occurs, following the planarization of hexaphenylbenzene and bianthryl core. This process involves sequential intramolecular C‐C bond rotations, dehydrogenation, and cyclodehydrogenation reactions, yielding phenyl‐substituted hexabenzocoronene (HBC‐Ph) and bisanthene octacarboxylic tetraimides (BSTI‐Ph). The reaction sequences were monitored using scanning tunneling microscopy (STM) and bond‐resolved non‐contact atomic force microscopy (nc‐AFM), offering structural proof of both intermediates and final products. These experimental techniques were complemented by density functional theory (DFT) simulations, which facilitated the detection of crucial steps in the conversion of n‐hexyl to phenyl groups. Moreover, the effect of alkyl aromatization on the electronic properties of the newly formed aromatic hydrocarbons was elucidated using scanning tunneling spectroscopy (STS).

Highly Selective On‐Surface Dehydrogenative Aromatization of n‐Hexyl to Phenyl Substituents

Dehydrogenative aromatization of alkyl substituents represents a powerful approach to aryl‐substituted functional molecules. However, the inertness of alkyl groups and the need for harsh reaction conditions accompanied by low product selectivity hamper its widespread applications. Here, we demonstrate the highly selective on‐surface thermal aromatization of n‐hexyl substituents on polycyclic aromatic hydrocarbons (PAHs) to their phenyl‐substituted analogues under mild conditions. After depositing two representative precursor molecules, n‐hexyl‐substituted hexaphenylbenzene (HPB‐Hex) and bianthryl octacarboxylic tetraimide (BATI‐Hex), onto a pre‐heated Au(111) substrate, dehydroaromatization of the peripheral n‐hexyl groups into phenyl rings occurs, following the planarization of hexaphenylbenzene and bianthryl core. This process involves sequential intramolecular C‐C bond rotations, dehydrogenation, and cyclodehydrogenation reactions, yielding phenyl‐substituted hexabenzocoronene (HBC‐Ph) and bisanthene octacarboxylic tetraimides (BSTI‐Ph). The reaction sequences were monitored using scanning tunneling microscopy (STM) and bond‐resolved non‐contact atomic force microscopy (nc‐AFM), offering structural proof of both intermediates and final products. These experimental techniques were complemented by density functional theory (DFT) simulations, which facilitated the detection of crucial steps in the conversion of n‐hexyl to phenyl groups. Moreover, the effect of alkyl aromatization on the electronic properties of the newly formed aromatic hydrocarbons was elucidated using scanning tunneling spectroscopy (STS).

Ionomer and Membrane Designs for Low-temperature CO2 and CO Electrolysis.

Low-temperature electroreduction of CO2 and CO (CO(2)RR) into valuable chemicals and fuels offers a promising pathway to reduce greenhouse gas emissions and achieve carbon neutrality. Today's low-temperature CO(2)RR technology relies on the use of ionomers, polymers with ionized groups, primarily as catalyst layer (CL) additives. In the meantime, ionomers can assemble into ion-exchange membranes (IEMs), serving as important components of electrolyzers. According to the ion-exchange functions, ionomer additives are classified as cation-exchange ionomers (CEIs) and anion-exchange ionomers (AEIs); similarly, IEMs are divided into cation-exchange membranes (CEMs) and anion-exchange membranes (AEMs), as well as the multilayer polymer electrolytes (MPEs). Recent studies show that ionomer additives can regulate the catalytic microenvironment and thereby enhance performance towards desired products. This Review discusses the roles of ionomer additives and IEMs in CO2 and CO reduction reactions, highlighting the latest mechanistic insights and performance advances. It outlines challenges in designing ionomer additives and IEMs to improve product selectivity, energy efficiency (EE), and operational lifetime of CO(2)RR electrolyzers, while also providing perspectives on future research directions. The aim is to connect the current status of ionomer and membrane development with performance metrics analysis, offering insights for the advancement of commercially relevant low-temperature CO(2)RR electrolyzers.

Organoiodine Catalysed Intramolecular C−N Bond Oxidative Coupling for the Synthesis of 3‐Monosubstituted Oxindoles

AbstractAn efficient organoiodine‐catalysed intramolecular direct C−N bond oxidative coupling reaction is presented. Structurally diverse 3‐(mono)substituted oxindoles were rapidly obtained in a complex oxidative system in up to 87 % yield. Various N‐alkoxy‐2‐phenylpropanamides were well‐tolerated. This study showed that the electronic effects on the aromatic ring of reactants have a crucial effect on the selectivity (C−N/C−O) of cyclisation products. In addition, gram‐scale synthesis and late‐stage modification of 3‐(mono)substituted oxindole derivatives revealed the practical application of this transformation.

Circular Economy and Chemical Conversion for Polyester Wastes.

Polyester waste in the environment threatens public health and environmental ecosystems. Chemical recycling of polyester waste offers a dual solution to ensure resource sustainability and ecological restoration. This minireview highlights the traditional recycling methods and novel recycling strategies of polyester plastics. The conventional strategy includes pyrolysis, carbonation, and solvolysis of polyesters for degradation and recycling. Furthermore, the review delves into exploring emerging technologies including hydrogenolysis, electrocatalysis, photothermal, photoreforming, and enzymatic for upcycling polyesters. It emphasizes the selectivity of products during the polyester conversion process and elucidates conversion pathways. More importantly, the separation and purification of the products, the life cycle assessment, and the economic analysis of the overall recycling process are essential for evaluating the environmental and economic viability of chemical recycling of waste polyester plastics. Finally, the review offers perspective into the future challenges and developments of chemical recycling in the polyester economy.

Mechanistic insight into accelerating of light olefin products by surface OH* group on the Fe5C2 catalyst

The conversion of CO2 into high-value-added chemicals via the Fischer-Tropsch Synthesis (FTS) reaction has gathered a lot of attention. The surface oxygenation environment is a significant factor affecting performance of the catalyst. In this work, spin-polarized density-functional theory calculations have been used to investigate the OH* modulation mechanism on CO2 hydrogenation to generate C1 and C2 species. On the pure Fe5C2(510) surface, CH4 is formed through the hydrogenation of dissociated carbon by CO2 activation. At low OH* coverage, the C–C coupling reactions are dramatically promoted compared to methane formation. In addition, CO2 hydrogenation reactions are facilitated by the OH* species, indicating a high activatity and C2+ selectivity. At high OH* coverage, C2 products preferentially form through the CsH2-CdH2* intermediates, contributing to the high selectivity of light olefin products. The results demonstrate that maintaining the surface environment with OH* could be an indispensable measure to obtain the target product in the iron-based CO2 Fischer-Tropsch synthesis system.

Investigation of highly efficient CO2 hydrogenation at ambient conditions using dielectric barrier discharge plasma

The increasing utilization of CO2 for synthesizing high-value fuels or essential chemicals is a potentially effective approach to mitigating global warming and climate change. Compared to thermal catalytic CO2 conversion under hash operating conditions (400∼500°C, 10 MPa), non-thermal plasma can overcome kinetic barriers and trigger reactions beyond thermal equilibrium at ambient temperature and pressure. In this study, the effects of operating conditions (discharge frequency, input power, and gas flow rate) and geometrical parameters (discharge length, discharge gap, and dielectric materials) have been extensively analyzed using typical cylindrical dielectric barrier discharge (DBD) plasma. The discharge characteristics changed by operating conditions (including waveforms of applied voltage and current) are compared, indicating higher applied voltage and lower gas flow rate can strengthen the filamentary discharges. The results demonstrate CO2 conversion rate increases with the increase of applied voltage and the decrease of CO2/H2 ratio, achieving its maximum value of 43.0% at 20 mL/min. The highest energy efficiency of 3771.9 μg/kJ for CO generation is obtained at the applied voltage of 5.5 kV and gas flow rate of 40 mL/min, respectively. Besides, the constructure of plasma reactor also impacts the performance of CO2 conversion. On the one hand, the discharge gap has a significant role in the variation of CO2 conversion and product selectivity, which is attributed to the electric field density and corresponding electron-induced reaction. On the other hand, the circulating water-cooling jacket was used to find out the influence of reaction temperature, which switched the product from CO to CH4. This work will pave the way for a sustainable alternative towards future CO2 conversion and utilization.

Biofilm mass transfer and thermodynamic constraints shape biofilm in trickle bed reactor syngas biomethanation

Syngas (H2, CO2, CO) produced thermochemically from lignocellulosic biomass is an underexploited source for resource recovery and valorisation through its biological conversion for the production of a wide range of chemicals and fuels. Syngas biomethanation is one such promising bioconversion pathway, displaying interesting features such as high conversion efficiency and product selectivity, as methane is the sole product of the process. The biological conversion of syngas to high purity biomethane is still typically associated with a number of challenges related to the syngas composition, CO toxicity, and gas–liquid mass transfer limitations. In this work, the syngas biomethanation process carried out in trickle bed reactors was investigated at its boundary conditions to explore the limits of the process, focusing on syngas composition and mass-transfer conditions potentially limiting process performance. The process was found to be robust when exposed to CO excess, but highly sensitive to H2 excess, which caused severe inhibition even under small amounts of excess H2. This implies that biomethane purity comparable to natural gas can be achieved by addition of renewable H2, but this requires precise control to avoid process failure. Modulating the liquid recirculation rate and gas residence time allowed for a maximum methane productivity of 9.8 ± 0.5 mmol CH4 h−1 Lreactor−1 with full conversion of H2 and CO at a gas residence time of 1 h. Nevertheless, increasing the gas–liquid mass transfer with increasing liquid recirculation rate did not lead to increased methane productivity, which suggested additional rate-limiting bottlenecks in the process. Careful investigation of other factors potentially limiting the process led to the conclusion that diffusive transport of syngas components in the biofilm was the main bottleneck of the process. This diffusive limitation leads to a scenario of severe substrate scarcity in the biofilm phase that conditions the thermodynamic feasibility of the different biochemical reactions involved in syngas biomethanation. In turn, these thermodynamic constraints were found to drive the stratification of microbial groups and sequential consumption of syngas components along the height of the reactor

A kinetic study of nonthermal plasma pyrolysis of methane: Insights into hydrogen and carbon material production

Nonthermal plasma-assisted methane pyrolysis has emerged as a promising approach for hydrogen production under mild conditions while simultaneously yielding valuable carbon materials. Herein, we develop a plasma chemical kinetic model to elucidate the underlying reaction mechanisms involved in methane pyrolysis to hydrogen and solid carbon within a gliding arc (GA) reactor. A zero-dimensional (0D) chemical kinetics model was developed to simulate the plasma chemistry during the GA-based methane pyrolysis process, incorporating reactions involving electrons, excited species, ions, and heavy species. The model accurately predicted methane conversion and product selectivity in agreement with the experimental data. A strong correlation between hydrogen production and methane conversion was observed, primarily driven by the reaction CH4 + H → CH3 + H2, contributing 44.2% to hydrogen formation and 37.7% to methane depletion. Electron impact collisions with hydrocarbons play a secondary role, accounting for 31.1% of H2 formation. This work provides a detailed investigation into the mechanism of solid carbon formation in GA-assisted methane pyrolysis. Most of the solid carbon originates from the electron impact dissociation of C2H2 through reactions e + C2H2 → e + C2 + H2/2H and subsequent C2 condensation. C2 radicals are highlighted as the major contributors to solid carbon formation, accounting for 95.0% of the total carbon yield, which might be due to the relatively low C–H dissociation energy in C2H2. This kinetic study offers a comprehensive understanding of the mechanisms behind H2 and solid carbon formation during GA-assisted methane pyrolysis.

Selective Electrochemical CO2 Reduction to Ethylene and Multi-carbon Products on Oxide-derived Porous CuO Micro-cages

The electrochemical reduction of CO2 (CO2RR) presents a dual benefit: it helps mitigate environmental pollution while producing valuable multi-carbon (C2+) chemicals and storing renewable energy in chemical fuels. However, there is an urgent need for efficient electrocatalysts that can selectively increase the production of ethylene and C2+ products for the wide-scale implementation of CO2RR. Herein, we have facilely synthesized porous micro-caged oxide-derived copper oxide (OD-Cu MC) using a one-pot hydrothermal approach followed by air-annealing at 350 °C. The resulting electrocatalyst exhibited excellent performance for ethylene (C2H4) production, achieving a faradaic efficiency (FE) of 44.8 % for C2H4 and cumulative FE of 73.1 % for C2+ products at current density (ID) of 300 mA cm−2. At an ID of 400 mA cm−2, OD-Cu MC demonstrated a turnover frequency (TOF) of 0.012 s−1 for ethylene, which is 7.8 times higher than the TOF observed for commercially available copper oxide (CuO-CM). Moreover, at an ID of 300 mA cm−2, OD-Cu MC achieved a single-pass CO2 conversion (SPCC) of 35.2 % and a half-cell energy efficiency of 15.6 % for C2+ products. The catalyst also showed good stability, maintaining its performance for over 4 h at an ID of 200 mA cm−2. This straightforward synthesis approach opens new avenues for enhancing C2+ product selectivity in CO2RR.

Boosting light olefin production from pyrolysis of low-density polyethylene: A two-stage catalytic process

The increasing production of waste plastics poses significant environmental and health risks. Low-density polyethylene (LDPE), a major component of plastic waste, is a high-quality feedstock for pyrolysis due to its high carbon and hydrogen content. Traditional pyrolysis methods, such as thermal cracking and one-step catalytic pyrolysis, have limitations in yield and selectivity of valuable products like light olefins. This study introduces a two-stage catalytic pyrolysis (TSCP) process aimed at enhancing the production of light olefins from LDPE. In the first stage, LDPE undergoes pyrolysis with MCM-41 catalyst, yielding a substantial number of liquid products and a minor portion of light olefins. The second stage utilizes Mg-ZSM-5 catalyst to further crack the high-temperature volatile matter into light olefins. The optimal conditions identified were 450 °C in the first stage and 500 °C in the second stage, achieving a maximum light olefin yield of 45.80 wt% and a low reaction temperature, decreasing the energy consumption. Additionally, the MCM-41 catalyst demonstrates excellent regeneration performance, with only a slight decrease in liquid yield after nine cycles. The Mg-ZSM-5 catalyst maintains high stability, with light olefin yield remaining at 83.60 % of the initial yield after 48 h of operation.

Hexagonal boron nitride fibers as ideal catalytic support to experimentally measure the distinct activity of Pt nanoparticles in CO2 hydrogenation

Catalytic studies aim to design new catalysts to eliminate unwanted by-products and obtain 100 % selectivity for the preferred target product without losing activity. For this purpose, understanding the role of each component building up the catalyst is essential. However, determining the intrinsic catalytic activity of pure metals, especially precious metals in the CO2 hydrogenation reaction under ambient conditions is complex. This is because the catalyst supports used thus far always influence the catalytic process either directly or indirectly due to interface formation that modifies the electronic and morphological structure of the metals. Even SiO2, regarded as inert shows some activity owing to the hydroxyl groups on its surface. In this work, we propose chemically inert and defect-free hexagonal boron-nitride fibers (BNF) synthesized via a co-precipitation method with wide band gap and robust covalent bonds as an uncommon reference catalyst support to evaluate the catalytic activity of size-controlled Pt nanoparticles (4.7 ± 0.6 nm) in the hydrogenation of CO2. The fibers alone show no catalytic activity; however, Pt/BNF exhibited low but notable activity of 377 nmol/g at 400 °C and the catalyst can achieve nearly 100 % CO selectivity. X-ray photoelectron spectroscopy, transmission electron microscopy, and diffuse reflectance infrared Fourier transform spectroscopy measurements were used to indicate that hexagonal boron-nitride affects neither the metal nanoparticles nor the reaction itself; the measured catalytic activity stems from the activity of Pt deposites without the effect of the support, as they were alone. CO vibration spectroscopy studies suggest that due to the lack of substrate-metal interaction, Pt nanoparticles adopt an ideal spherical structure, resulting in several low coordination sites capable of CO2 conversion. Thus, BNF is proposed in the present article to be used as a reference catalyst support material. It can be efficiently used in investigations involving the proposed metal and reaction or under varying conditions with different metal nanoparticles and reaction systems.

Boosting multi-carbon products selectivity of carbon dioxide reduction via bifunctional cyclodextrin-modification on copper/copper(I) oxide electrocatalysts

Electrochemical carbon dioxide reduction to multi-carbon (C2+) products presents a significant opportunity for converting greenhouse gases into valuable fuels and feedstocks. The development of highly active and stable catalysts remains a critical challenge. In this study, we report the design and synthesis of cyclodextrin-modified Cu/Cu2O electrocatalysts, which exhibit remarkable efficiency in driving the CO2 electroreduction process towards C2+ products. Our optimized catalyst achieves a C2+ Faradaic efficiency exceeding 50 % at a high current density of over 200 mA cm−2. Experimental findings, supported by density functional theory (DFT) calculations, reveal that cyclodextrin plays a dual role in stabilizing Cu+ and increasing the surface density of hydroxyl radicals. This dual function greatly benefits for enhancing *CO intermediate adsorption and promotes *CHO formation, thereby facilitating the crucial dimerization step for the formation of C2+ products. This work provides valuable insights into the development of highly active and selective electrocatalysts by carefully tuning the local catalytic environment, potentially opening new avenues for functionalizing electrocatalysts for future research in this area.

Altering preferential product selectivity in electrocatalytic CO2 reduction over fluorine-modified CuIn bimetallic materials

Integrating carbon dioxide (CO2)-derived renewable technologies into the petrochemical industry presents a promising avenue for carbon neutrality. The renewable-energy-powered electrochemical CO2 reduction (eCO2R) process, particularly over Cu-based electrocatalysts, is a valuable asset for our decarbonization efforts to avoid climate consequences. Intending to enhance process efficiency, this work is a distinctive case study emphasizing the need to develop electrocatalysts in conjunction with adjusting operating conditions. A representative case is presented using fluorine-modified CuIn bimetallic electrocatalysts with tunable In/Cu ratios, demonstrating how to alter selectivity preferences based on reactor configuration: Our optimized catalyst system led to the highest faradaic efficiency (FE) for C2+ products of 68 % and the highest C1 FE of 80 % using gas diffusion electrodes (GDE)- and H-cell-type based electrolyzer, respectively. Moreover, the controllable In/Cu ratio and the degree of fluoride doping played a pivotal role in governing the physicochemical properties of the bimetallic electrocatalysts and their eCO2R performance. Diverse characterization tools offered systematic insights into the relationships between catalyst structure and properties, reactor configuration, electrolyte, and performance, aiming to enhance the Technology Readiness Level of the eCO2R process.

Fluorine-regulated Cu catalyst boosts electrochemical reduction of CO2 towards ethylene production

Electrochemical reduction of carbon dioxide (CO2RR) into value-added multi-carbon (C2) products utilizing renewable energy is a promising way to reduce carbon emission and achieve carbon neutrality. However, rational design of catalysts towards high C2 products selectivity remains a formidable task. Herein, fluorine modified copper catalyst was synthesised by thermal anneal in the presence of ammonium fluoride and sequential annealing in argon atmosphere. The charge distribution and coordination environment on copper surface were adjusted by doped fluorine atoms, which enables the formation of key intermediates and their sequential evolution into ethylene. The catalyst achieves a remarkable Faradaic efficiency (FE) of 40.6 % for eCO2RR to ethylene and remains stable over 13 hours. Density functional theory calculations indicates that the excellent CO2RR performance can be attributed to the suppressed hydrogen evolution on fluorine-doped copper catalyst. Our work brings a potential modification strategy of Cu-based catalyst for electrolytic CO2-to-C2 pathway.

Advancements in Inverse-Electron-Demand Diels–Alder Cycloaddition of 2-Pyrones: Mechanisms, Methodologies

The Diels-Alder (DA) cycloaddition is well-known for its effectiveness in synthesizing natural products and multifunctional materials. This article specifically explores the inverse-electron-demand Diels-Alder (IEDDA) cycloaddition involving 2-pyrones, which display ambiphilic properties due to their unique electronic characteristics. We investigate the mechanisms underlying IEDDA, with a focus on how electron-donating and electron-withdrawing substituents influence reactivity and product selectivity. Various methodologies are reviewed, encompassing non-catalytic and catalytic approaches. Special attention is given to advancements in microwave-assisted techniques and high-pressure conditions, which enhance both reaction efficiency and selectivity. Additionally, the synthesis of chiral bridged bicyclic lactones from substituted 2-pyrones is examined, illustrating their versatility in organic synthesis. This review underscores the significance of IEDDA cycloaddition in pioneering new synthetic routes for building complex molecular structures.