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Despite extensive research into developing efficient and environmentally friendly catalysts for converting CO2 over the last decade, the search for a robust and cost‐effective catalytic system is ongoing. This study describes developing and applying a new catalytic system using inexpensive ferrate and zincate anions immobilized on easily available commercial ion exchange resins (IER) to produce cyclic carbonates from CO2 with high efficiency and low cost. Two polystyrene‐based anion exchange resins, AmberlystTM A26‐Cl (A26‐Cl) and AmberliteTM IRA‐400‐Cl (IRA400‐Cl), were compared. The results demonstrated the catalysts' remarkable activity under mild conditions and demonstrated the synergistic effect between the polystyrene support and the active ammonium metallates, presenting a scalable, eco‐friendly method for cyclic carbonate production using waste CO2. A Design of Experiment (DoE) approach was implemented to optimize the catalytic cycloaddition of CO2. The reaction scale‐up to produce a 5 g batch of propylene oxide and conducting recycling tests demonstrated that the catalyst retained its activity over four cycles. The research also explored the use of various epoxides and found that terminal epoxides produced very good yields. In summary, this study introduces a cost‐effective, scalable method for converting CO2 into valuable cyclic carbonates, leveraging the synergistic effects of polystyrene supports and active ammonium metallates. [ABSTRACT FROM AUTHOR]

CO 2 methanation is considered as a promising reaction in the context of mitigating climate change by reducing CO 2 emissions and providing a renewable source of methane fuel. The CeNiO 3 and LaNiO 3 perovskite catalysts were synthesized using the sol-gel method. The effect of perovskite structure on the catalytic activity was studied. The results were compared with Ce-supported and La-supported Ni catalysts (Ni/CeO 2 & Ni/La 2 O 3). Different methods including XRD, N 2 adsorption-desorption, H 2 -TPR, FE-SEM, and CO 2 -TPD, were employed for the characterization of the catalysts. The perovskite catalysts are more active than the corresponding supported catalysts. Among all prepared catalysts CeNiO 3 perovskite catalyst showed highest activity 80% conversion and 98% selectivity at 300 °C. Weak basicity, high active metal reducibility and the synergy between Ni and Ce due to perovskite structure are the responsible factors for high activity of CeNiO 3 catalyst. The CeNiO 3 catalyst showed excellent stability for CO 2 methanation during 24 h of time on study with different GHSVs. The effect of calcination temperature was also studied on CeNiO 3 catalyst at 650, 750 and 850 °C temperatures. Raman spectra concluded that the oxygen vacancy sites increased with rise of calcination temperature from 650 to 750 °C and decreased with further increase in temperature. The CeNiO 3 calcined at 750 °C (CeNiO 3 -750) showed highest activity among all other catalysts. The increased activity is due to increased oxygen vacancies which ensures that Ni nanoparticles are highly dispersed. [Display omitted] • CeNiO 3 & LaNiO 3 perovskites were prepared successfully by sol-gel method. • Ni/CeO 2 & Ni/La 2 O 3 catalysts prepared by wet impregnation method for comparison studies. • CeNiO 3 perovskite showed the highest activity for CO 2 methanation at 300 °C. • The effect of calcination temperature of CeNiO 3 on CO 2 methanation was examined. • Rising calcination temperature from 750 to 850 °C lowered CeNiO 3 oxygen vacancies. [ABSTRACT FROM AUTHOR]

Cyclic organic carbonates are defined as key compounds for a sustainable chemical economy. Their synthesis from CO2 under mild conditions is a useful way to valorise this greenhouse gas as carbon source. Even if a wide range of catalysts were described to promote the carbon dioxide cycloaddition into epoxides, only few ones concern enzymatic systems. The zinc–l‐histidine active site of carbonic anhydrase inspired the present work, pointing out that the imidazole moiety of the amino acid ligand has a crucial role. An extensive study was undertaken to establish the structure–activity relationship of imidazole derivatives, zinc salts, and their respective catalytic activity in the CO2 cycloaddition reaction. The effect of aromatic, alkyl, or iodine substituents and their position in N‐heterocycles were highlighted. A synergic effect was noted when combining imidazole compounds with zinc salts. The optimization of reaction conditions emphasised the in situ ZnI2–1‐methylimidazole catalytic system, which is selective toward cyclic styrene carbonates and efficient under solvent‐free mild conditions (50 °C, atmospheric CO2 pressure). Once reusing tests confirmed the catalytic system robustness, the reaction scope was enlarged to several epoxides resulting in 84%–99% yields of their corresponding cyclic carbonates. [ABSTRACT FROM AUTHOR]

This study introduces a metal-free binary catalytic system for coupling CO2 with cyclohexane oxide (CHO) under mild conditions, allowing for tunable product selectivity. Using trans-cyclohexane diol (trans-CHD) and phosphazene superbase (P4) as catalysts, the system selectively produces cyclic carbonates and oligocarbonates at 1 bar CO2 pressure and 80 °C. By adjusting the catalyst ratio, varying proportions of cis-cyclohexane carbonate (cis-CHC), trans-cyclohexane carbonate (trans-CHC), and oligocarbonate are achieved, with 51 mol% CHO conversion and respective selectivities of 36%, 31%, and 33%. The catalytic efficiency and precise control of product outcomes underscore this system's potential. [ABSTRACT FROM AUTHOR]

The thermodynamically and kinetically sluggish electrocatalytic C−N coupling from CO2 and NO3− is inert to initially take place while typically occurring after CO2 protonation, which severely dwindles urea efficiency and carbon atom economy. Herein, we report a single O‐philic adsorption strategy to facilitate initial C−N coupling of *OCO and subsequent protonation over dual‐metal hetero‐single‐atoms in N2−Fe−(N−B)2−Cu−N2 coordination mode (FeN4/B2CuN2@NC), which greatly inhibits the formation of C‐containing byproducts and facilitates urea electrosynthesis in an unprecedented C‐selectivity of 97.1 % with urea yield of 2072.5 μg h−1 mgcat.−1 and 71.9 % Faradaic efficiency, outperforming state‐of‐the‐art electrodes. The carbon‐directed antibonding interaction with Cu−B is elaborated to benefit single O‐philic adsorption of CO2 rather than conventional C‐end or bridging O,O‐end adsorption modes, which can accelerate the kinetics of initiated C−N coupling and protonation. Theoretical results indicate that the O‐monodentate adsorption pathway benefits the thermodynamics of the C−N coupling of *OCO with *NO2 and the protonation rate‐determining step, which markedly inhibits CO2 direct protonation. This oriented strategy of manipulating reactant adsorption patterns to initiate a specific step is universal to moderate oxophilic transition metals and offers a kinetic‐enhanced path for multiple conversion processes. [ABSTRACT FROM AUTHOR]

The construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long‐standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO2‐to‐CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso‐tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br2] (2,2′‐bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non‐sacrificial electrodes. The reaction can be directly scaled up to gram‐scale and operates effectively at a CO2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO2 reduction is key in the formation of the [Ni(bpy)(CO)2], which is proposed as the catalytic intermediate responsible for the C−C bond formation in the carbonylation steps. [ABSTRACT FROM AUTHOR]

The construction of carbonyl compounds via carbonylation reactions using safe CO sources remains a long‐standing challenge to synthetic chemists. Herein, we propose a catalyst cascade Scheme in which CO2 is used as a CO surrogate in the carbonylation of benzyl chlorides. Our approach is based on the cooperation between two coexisting catalytic cycles: the CO2‐to‐CO electroreduction cycle promoted by [Fe(TPP)Cl] (TPP=meso‐tetraphenylporphyrin) and an electrochemical carbonylation cycle catalyzed by [Ni(bpy)Br2] (2,2′‐bipyridine). As a proof of concept, this protocol allows for the synthesis of symmetric ketones from good to excellent yields in an undivided cell with non‐sacrificial electrodes. The reaction can be directly scaled up to gram‐scale and operates effectively at a CO2 concentration of 10 %, demonstrating its robustness. Our mechanistic studies based on cyclic voltammetry, IR spectroelectrochemistry and Density Functional Theory calculations suggest a synergistic effect between the two catalysts. The CO produced from CO2 reduction is key in the formation of the [Ni(bpy)(CO)2], which is proposed as the catalytic intermediate responsible for the C−C bond formation in the carbonylation steps. [ABSTRACT FROM AUTHOR]

[Display omitted] • Oxygen vacancy and isolated Ti3+ embed into interface of a Z-scheme heterojunction. • Calcination precisely regulated oxygen vacancy and isolated Ti3+ in the interface. • The interface showed superior photocatalytic CO 2 reduction activity to reported ones. • The interfacial modification greatly promoted CO 2 activation and reduction activity. Exploring the real force that drives the separation of Coulomb-bound electron-hole pairs in the interface of heterojunction photocatalysts can establish a clear mechanism for efficient solar energy conversion efficiency. Herein, the formation of oxygen vacancy (Ov) and isolated Ti3+ was precisely regulated at the interface of g-C 3 N 4 /TiO 2 Z-scheme heterojunction (g-C 3 N 4 /Ov-Ti3+-TiO 2) by optimizing the opening degree of the calcination system, showing excellent production rate of CO and CH 4 from CO 2 photoreduction under visible light. This photocatalytic system also exhibited prominent stability. Combining theoretical calculation and characterization, the introduction of Ov and isolated Ti3+ on the interface could construct a charge transfer channel to break the forbidden transition of n → π*, improving the separation process of photoexcited electron-hole pairs. The photoexcited electrons weakened the covalent interaction of C O bonds to promote the activation of adsorbed inert CO 2 molecules, significantly reducing the energy barrier of the rate-limiting step during CO 2 reduction. This work demonstrates the great application potential of reasonably regulating heterojunction interface for efficient photocatalytic CO 2 reduction. [ABSTRACT FROM AUTHOR]

Research has focused on the threat of global warming-induced climate change to modern human civilization. Carbon dioxide (CO2) is a primary greenhouse gas that causes global warming. Current efforts have focused on using CO2 as a raw source for producing value-added chemicals. Among the different CO2 conversion processes, the Sabatier process, also known as "CO2 methanation," is an effective approach, particularly if H2 is generated by renewable energy sources. In this process, methane (CH4) and water (H2O) are produced from CO2 and H2 using different transition-metal-based catalysts. Although numerous studies have been conducted to assess the significance of CO2 methanation, quantitative analysis of the publication trends in this research field is still lacking. This review presents the global research landscape of CO2 methanation over the last 20 years (2000–2022). The Web of Science (WoS) database was used to extract 1657 publications, and the VOSviewer software was used for bibliometric investigations. Bibliometric analysis revealed that 77.53% of the papers were published within the past 5 years (2018–2022). The International journal of hydrogen energy is leading journal publishing research articles about CO2 methanation followed by Applied Catalysis B. This study conducted a statistical analysis on the influence of leading countries, institutions, journals, authors, and top keywords in the field of CO2 methanation. Additionally, future research directions and findings of the most cited publications are discussed. Because the CO2 methanation reaction requires a highly stable and active catalyst, a brief introduction and major challenges of these catalysts are also reviewed. We hope that bibliometric findings will help scholars to understand this field of research more effectively and comprehensively. [ABSTRACT FROM AUTHOR]

Background: Industrial biomanufacturing of value-added products using CO2 as a carbon source is considered more sustainable, cost-effective and resource-efficient than using common carbohydrate feedstocks. Cupriavidus necator H16 is a representative H2-oxidizing lithoautotrophic bacterium that can be utilized to valorize CO2 into valuable chemicals and has recently gained much attention as a promising platform host for versatile C1-based biomanufacturing. Since this microbial platform is genetically tractable and has a high-flux carbon storage pathway, it has been engineered to produce a variety of valuable compounds from renewable carbon sources. In this study, the bacterium was engineered to produce resveratrol autotrophically using an artificial phenylpropanoid pathway. Results: The heterologous genes involved in the resveratrol biosynthetic pathway—tyrosine ammonia lyase (TAL), 4-coumaroyl CoA ligase (4CL), and stilbene synthase (STS) —were implemented in C. necator H16. The overexpression of acetyl-CoA carboxylase (ACC), disruption of the PHB synthetic pathway, and an increase in the copy number of STS genes enhanced resveratrol production. In particular, the increased copies of VvSTS derived from Vitis vinifera resulted a 2-fold improvement in resveratrol synthesis from fructose. The final engineered CR-5 strain produced 1.9 mg/L of resveratrol from CO2 and tyrosine via lithoautotrophic fermentation. Conclusions: To the best of our knowledge, this study is the first to describe the valorization of CO2 into polyphenolic compounds by engineering a phenylpropanoid pathway using the lithoautotrophic bacterium C. necator H16, demonstrating the potential of this strain a platform for sustainable chemical production. [ABSTRACT FROM AUTHOR]

Zinc(II) Schiff base complexes with different substituents at 5, 5' positions have been synthesized to study the effect of the electronic environment of the metal towards the cycloaddition reaction between CO2 and epoxide. The complexes have been characterized by FT‐IR, XPS, NMR, electronic spectroscopy, LC–MS, and TGA. We have used density functional theory to study the electronic structure of the Zn(II) complexes and modelled the electronic spectra and the mechanism of catalysis. Results obtained from DFT and LC–MS indicate the dimeric structures for all the complexes except ZnL4. The monomeric ZnL4 has the strongest electron withdrawing group, i. e. −NO2 at 5, 5' positions along with two labile water molecules attached to the Zn center. The dimeric complexes exhibit good to moderate yield for cycloaddition reaction to styrene carbonate under solvent‐free conditions and a relatively low reaction temperature of 80 °C, with CO2 pressure of ~1 atm. The best yield has been achieved by ZnL4. Different rate‐determining steps are captured by the DFT studies for dimeric and monomeric complexes. Without taking any preventing measure of dimerization by attaching the bulky tBu groups, relatively lesser catalytic amounts of all the complexes have shown yields of cyclic carbonate between 53–74 %, depending on the nature of the substituent present. [ABSTRACT FROM AUTHOR]

This paper deals with the proposition of a kinetic model for the direct synthesis of DME via CO2 hydrogenation in view of the necessary optimization of the catalytic system, reactor design, and process strategy. Despite the fact that DME synthesis is typically treated as a mere combination of two separated catalytic steps (i.e., methanol synthesis and methanol dehydration), the model analysis is now proposed by taking into account the improvements related to the process running over a hybrid catalyst in a rational integration of the two catalytic steps, with boundary conditions properly assumed from the thermodynamics of direct DME synthesis. Specifically, the CO2 activation step at the metal–oxide interface in the presence of ZrO2 has been described for the first time through the introduction of an ad hoc mechanism based on solid assumptions from inherent studies in the literature. The kinetic modeling was investigated in a tubular fixed-bed reactor operating from 200 to 260 °C between 1 and 50 bar as a function of a gas hourly space velocity ranging from 2500 to 60,000 NL/kgcat/h, in a stoichiometric CO2/H2 feed mixture of 1:3 v/v. A well-detailed elementary mechanism was used to predict the CO2 conversion rate and identify the key reaction pathways, starting with the analysis of the implicated reactions and corresponding kinetic mechanisms and expressions, and finally estimating the main parameters based on an appropriate modeling of test conditions. [ABSTRACT FROM AUTHOR]

Using carbon dioxide as a feedstock for synthesizing organic molecules with added value can contribute to a more sustainable chemical industry since CO2 is an abundant, inexpensive, and nontoxic renewable carbon resource. In this regard, the synthesis of cyclic carbonates and related organic compounds from CO2 as building blocks has been widely studied, and less attention has been paid to their stereocontrolled process. Therefore, this review focuses on the recent development of enantioselective catalysts for the CO2-mediated formation of chiral organic carbonates. [ABSTRACT FROM AUTHOR]

Gas-fed reactors for CO2 reduction processes are a solid technology to mitigate CO2 accumulation in the atmosphere. However, since it is necessary to feed them with a pure CO2 stream, a highly energy-demanding process is required to separate CO2 from the flue gasses. Recently introduced bicarbonate zero-gap flow reactors are a valid solution to integrate carbon capture and valorization, with them being able to convert the CO2 capture medium (i.e., the bicarbonate solution) into added-value chemicals, such as CO, thus avoiding this expensive separation process. We report here a study on the influence of the electrode structure on the performance of a bicarbonate reactor in terms of Faradaic efficiency, activity, and CO2 utilization. In particular, the effect of catalyst mass loading and electrode permeability on bicarbonate electrolysis was investigated by exploiting three commercial carbon supports, and the results obtained were deepened via electrochemical impedance spectroscopy, which is introduced for the first time in the field of bicarbonate electrolyzers. As an outcome of the study, a novel low-loaded silver-based electrode fabricated via the sputtering deposition technique is proposed. The silver mass loading was optimized by increasing it from 116 μg/cm2 to 565 μg/cm2, thereby obtaining an important enhancement in selectivity (from 55% to 77%) and activity, while a further rise to 1.13 mg/cm2 did not provide significant improvements. The tremendous effect of the electrode permeability on activity and proficiency in releasing CO2 from the bicarbonate solution was shown. Hence, an increase in electrode permeability doubled the activity and boosted the production of in situ CO2 by 40%. The optimized Ag-electrode provided Faradaic efficiencies for CO close to 80% at a cell voltage of 3 V and under ambient conditions, with silver loading of 565 μg/cm2, the lowest value ever reported in the literature so far. [ABSTRACT FROM AUTHOR]

Owing to residual biomass availability, the share of advanced biofuels produced from secondary biomass is forecasted to increase and significantly contribute towards achieving net-zero emissions. The current work investigates bio-methanol production through a new process configuration designed to improve the environmental performance when compared to the state-of-the art technologies (Base Case). The environmental evaluation is conducted according to the Life Cycle Assessment (LCA) methodology. ReCiPe was employed as an impact assessment method with the aid of GaBi software. Depending on the plant geographical location, wooden biomass and exhausted olive pomace were evaluated as biomass sources. A scenario analysis targeting different energy sources was performed as well. The outcome of the environmental evaluation highlights a better performance in eight of a total of nine impact categories studied in the wooden biomass scenarios compared to the exhausted olive pomace. Moreover, two of the CONVERGE technology cases were compared against the Base Case. As the results show, CONVERGE technology registers a lower score in at least six of the impact categories studied. Concerning the total CO2 emissions, CONVERGE exhibits a better performance compared to the Base Case, if the additional amount of CO2 is either stored, sold as a by-product or vented into the atmosphere. [ABSTRACT FROM AUTHOR]

• For the first time, the direct carboxylation mechanism of phenol at ZrO 2 is elucidated • The reaction proceeds rather through an Eley Rideal than a Langmuir-Hinshelwood mechanism. • The monoclinic phase is more reactive than the tetragonal one, hence attesting the geometry effect ZrO 2 catalytic properties. • This work is expected to serve as a base for future work related to aromatics carboxylation at metal oxide surfaces. In the present context of environmental concerns, sustainable solutions must be proposed to dispose of waste CO 2 , a well-known greenhouse gas. Among the various emerging projects, upgrading CO 2 molecule into high-value added chemicals appears to be very promising. More particularly, the carboxylation of aromatic compounds to (di-) acid aromatic monomers is of great interest for the high performance polymer industry. Focusing on the direct phenol carboxylation to para -hydroxybenzoic acid as a model reaction, the reactivity of ZrO 2 was investigated in this paper, this material being recently reported in various experimental works for its catalytic efficiency. For the first time, we established the phenol carboxylation mechanism at the surface of a metal oxide material, showing that the reaction can only proceed through an Eley-Rideal mechanism. In this mechanism, CO 2 is strongly chemisorbed at the surface, whereas phenol is physisorbed close to the CO 2 adsorbate. Besides, while the monoclinic and the tetragonal phases often coexist in ZrO 2 particles, we demonstrated that only the monoclinic geometry exhibits a substantial activity. However, the selectivity remains a major challenge, the ortho - isomer being the most abundant product, as in the original Kolbe-Schmitt method. While most of the processes generally reported in literature for the direct carboxylation of phenol are achieved in liquid media, a very few theoretical knowledge is available to describe such a process at solid surfaces. Therefore, we expect the present manuscript to be a pioneer work, aiming at providing a better understanding of metal oxide surface reactivity, paving the road to the rational design of efficient solid catalysts for aromatics carboxylation reactions. While a multistep process (Langmuir-Hinshelwood mechanism) is often proposed in heterogeneous catalysis, at ZrO2 surface the direct carboxylation of aromatics can only proceed via a single step process (Eley-Rideal mechanism). [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 -to-PHB conversion with co-culture of acetogenic and PHB-accumulative bacteria. • Applied voltage boosts intercell PHB content by 7.14-fold, which is optimal at 2.5 V. • Functionalized cathode with PEDOT:PSS boost acetate and PHB production 1.5 times. • Significant increase in CO 2 -utilizing electrotrophs: Acetobacterium, Clostridium. • Relative abundance PHB-biosynthesizing bacteria increased 4- to 14-fold. This study proposes an novel single-stage microbial electrosynthesis system (MES) that bioelectrochemically converts CO 2 into poly(3-hydroxybutyrate) (PHB). This innovative approach utilizes a symbiotic co-culture of electroactive acetogenic bacteria and PHB-accumulating bacteria within a single reactor, bypassing the need for separate acetate production and extraction. Systematic optimization of key operational parameters, including applied voltage, carbon source, and cathode material, was conducted to maximize PHB production. Results demonstrate that using a voltage of 2.5 V yielded a 7.14-fold increase in PHB content compared to open circuit conditions. Furthermore, functionalizing the cathode with a conductive and hydrophilic PEDOT: PSS polymer coating significantly enhanced the system's performance, resulting in a 1.5-fold increase in both acetate and PHB production compared to unmodified carbon felt electrodes. The long-term stability and effectiveness of the co-culture system were validated through comprehensive microbial and metagenomic analyses. Results revealed a significant enrichment of CO 2 -utilizing electrotrophs within the cathode biofilm, including Acetobacterium and Clostridium. Concurrently, a 4 to 14-fold increase in the relative abundance of PHB-biosynthesizing bacteria, such as Pseudomonas , Rhodobacter and Caulobacter was observed in the planktonic phase. This study offers a promising pathway towards a circular bioeconomy by enabling the valorization of CO 2 into valuable bio-based products via single-stage MES, utilizing a symbiotic co-culture. [ABSTRACT FROM AUTHOR]

The exfoliation of graphite to graphene is one of the main methods of graphene production. In this paper, we provide an overview of the main molten salt methods for the exfoliation of graphite to graphene, including thermal and electrochemical exfoliation of graphite in molten salt. The fundamental mechanism of these methods is discussed in detail, along with the characterization techniques and instruments used to analyze the produced graphene. Additionally, the principles of eutectic salt mixtures, which play a crucial role in the exfoliation process, are discussed. The utilization of graphene-based materials in catalysis, particularly in the CO 2 and biomass valorization to produce sustainable fuels and chemicals, has been reviewed. The molten salt method is a simple and efficient way to produce graphene-based materials by using a molten salt medium to exfoliate the graphite. The purpose of this study is to provide a comprehensive overview of the current state of knowledge regarding the use of molten salt for the exfoliation of graphite to graphene, including their benefits and limitations. • Molten Salt methods for synthesis of graphene-based material are discussed. • Various setups, salts, atmospheres, and operational conditions are summarized. • Methods for the characterization of C-based products are highlighted. • The catalytic role of graphene-based material in CO 2 valorization is emphasized. • The role of Molten Salt method in biomass and waste valorization is highlighted. [ABSTRACT FROM AUTHOR]

Herein, a direct, metal‐free, and site‐selective electrochemical C−H carboxylation of arenes by reductive activation using CO2 as the economic and abundant carboxylic source was reported. The electrocarboxylation was carried out in an operationally simple manner with high chemo‐ and regioselectivity, setting the stage for the challenging site‐selective C−H carboxylation of unactivated (hetero)arenes. The robust nature of the electrochemical strategy was reflected by a broad scope of substrates with excellent atom economy and unique selectivity. Notably, the direct and selective C−H carboxylation of various challenging arenes worked well in this approach, including electron‐deficient naphthalenes, pyridines, simple phenyl derivatives, and substituted quinolines. The method benefits from being externally catalyst‐free, metal‐free and base‐free, which makes it extremely attractive for potential applications. [ABSTRACT FROM AUTHOR]

Herein, a direct, metal‐free, and site‐selective electrochemical C−H carboxylation of arenes by reductive activation using CO2 as the economic and abundant carboxylic source was reported. The electrocarboxylation was carried out in an operationally simple manner with high chemo‐ and regioselectivity, setting the stage for the challenging site‐selective C−H carboxylation of unactivated (hetero)arenes. The robust nature of the electrochemical strategy was reflected by a broad scope of substrates with excellent atom economy and unique selectivity. Notably, the direct and selective C−H carboxylation of various challenging arenes worked well in this approach, including electron‐deficient naphthalenes, pyridines, simple phenyl derivatives, and substituted quinolines. The method benefits from being externally catalyst‐free, metal‐free and base‐free, which makes it extremely attractive for potential applications. [ABSTRACT FROM AUTHOR]

Cerium oxide nanoparticles (CON) are gaining considerable interest as an attractive and essential catalytic material in the chemical process of environmental and energy industry. The synthesis of ultra-small CON remains challenging task for their industrial scale implementation. Herein, we report a novel and sustainable method for synthesizing CeO2 nanoparticles under direct sunlight with Tryptophan and Tyrosine as UV light active capping agents. Different properties of synthesized CON such as crystalline structures, morphology, phase, and size were examined by SEM, HR-TEM, XRD, Raman Spectroscopy and UV–Vis Spectroscopy. Further, XPS analysis was carried out for the determination of surface composition of CON synthesized under direct sunlight. CON synthesized using Tryptophan and Tyrosine shows higher Ce3+ species on the surface due to high UV absorption. Further, CON has showed excellent catalytic activity for the synthesis of dimethyl carbonate from transesterification of ethylene carbonate with methanol due to increased Ce3+ species. CON synthesized using tryptophan showed an excellent yield of 58.54% in the transesterification of ethylene carbonate at 140 °C in 3 h. [ABSTRACT FROM AUTHOR]

Capnophilic lactic fermentation (CLF) is an anaplerotic pathway exclusively identified in the anaerobic hyperthermophilic bacterium Thermotoga neapolitana, a member of the order Thermotogales. The CO2-activated pathway enables non-competitive synthesis of hydrogen and L-lactic acid at high yields, making it an economically attractive process for bioenergy production. In this work, we discovered and characterized CLF in Thermotoga sp. strain RQ7, a naturally competent strain, opening a new avenue for molecular investigation of the pathway. Evaluation of the fermentation products and expression analyses of key CLF-genes by RT-PCR revealed similar CLF-phenotypes between T. neapolitana and T. sp. strain RQ7, which were absent in the non-CLF-performing strain T. maritima. Key CLF enzymes, such as PFOR, HYD, LDH, RNF, and NFN, are up-regulated in the two CLF strains. Another important finding is the up-regulation of V-ATPase, which couples ATP hydrolysis to proton transport across the membranes, in the two CLF-performing strains. The fact that V-ATPase is absent in T. maritima suggested that this enzyme plays a key role in maintaining the necessary proton gradient to support high demand of reducing equivalents for simultaneous hydrogen and lactic acid synthesis in CLF. [ABSTRACT FROM AUTHOR]

CO 2 -assisted ethane dehydrogenation (CO 2 -ODHE) is a promising carbon atom economy process for upgrading CO 2 to CO in tandem with C 2 H 6 to C 2 H 4 conversion. Iron oxide-based materials are selective for on purpose ethylene production through CO 2 -ODHE. The feed admission mode was found to play an important role on catalytic performance. Alternating C 2 H 6 (reduction step) and CO 2 (oxidation step) feedstock to a fixed bed reactor (chemical looping concept, CO 2 -ODHE-CL) attained constant ethane and CO 2 conversion per step at 600 °C, equal to ∼17.6 %, while C 2 H 4 selectivity during the reduction step was ∼75 %. The lattice oxygen mobility is a descriptor for the materials used during the CO 2 -ODHE-CL, since low mobility resulted in an increased C-H bond scission selectivity, i.e., C 2 H 4 production, during the reduction step. Temperature programmed 18O 2 isotope exchange experiments, along with temperature programmed H 2 – reduction, were employed to exemplify the latter statement, investigating the lattice oxygen reactivity of the examined materials and the mechanism through which the lattice oxygen is reacting. X-ray techniques (X-ray Diffraction, X-ray Raman Scattering Spectrometry, X-ray Absorption Spectrometry) along with structural modeling demonstrated that the formation of a spinel like arrangement between Mg and Fe, stabilized lattice oxygen and thus minimized the undesired C-C bond scission during the C 2 H 6 step of CO 2 -ODHE-CL. [Display omitted] • Iron oxide-based materials have high selectivity for C 2 H 4 during CO 2 -ODHE-CL. • The oxygen mobility is crucial for the materials performance during CO 2 -ODHE-CL. • The increaseof Mg atoms in tetrahedral positions for Fe onepot-800,4 h suggests a spinel arrangement among Mg, Fe and O. • The spinel arrangement stabilizes the lattice oxygen minimizing the C-C bond scission. [ABSTRACT FROM AUTHOR]

[Display omitted] • Process development with Clostridium carboxidivorans in elevated-pressure reactor. • Definition of crucial gas feeding strategies influencing the product metabolism. • Unprecedented hexanol carbon selectivity (60%) • Highest hexanol titer (3.7 gL−1) and productivity (0.9 gg CDW −1d−1) from H 2 and CO 2. • Enhanced caproate production (1.6 gL−1) from Clostridium carboxidivorans. To successfully scale-up the production of bio-based building blocks through CO 2 and H 2 -based gas fermentation, it is crucial to deeply understand and control the microbial catalyst response to the bioreactor environment. This study investigates the effects of key process parameters, such as CO 2 and H 2 partial pressures, gas feeding strategies, and mixture composition, on the production pathways of an evolved Clostridium carboxidivorans strain. The ultimate goal is to optimize 1-hexanol production in elevated-pressure stirred-tank reactors. Continuous gas feeding enhanced acetogenic and solventogenic metabolisms, while gas-limited conditions promoted chain elongation to caproic acid. An optimized process, combining an initial gas-limited step followed by a continuous gas phase, increased 1-hexanol production, achieving a maximum biomass-specific productivity of 0.9 g g CDW −1 day−1. In-situ product extraction improved 1-hexanol carbon selectivity to an unprecedented 60 %. These findings demonstrate the potential of CO 2 and H 2 -fed fermentation to produce high-value chemicals other than ethanol and acetate. [ABSTRACT FROM AUTHOR]

[Display omitted] • First model of low temperature Martian CO 2 -H 2 O electrolyzer for C 1 ,C 2 products. • Model works across pH, 230–300 K and reaction extent of 0 %–100 %. • CO, HCHO, CH 3 OH, CH 4 , C 2 H 4 , & C 2 H 5 OH shown to be viable under Mars conditions. • Earth CO 2 RR catalysts/electrolyzers work for Mars ISRU with minimal modification. The long-term, crewed exploration of Mars is a priority for both national and private space entities. Given economical constraints on the mass sent off-world from Earth, in situ resource utilization (ISRU) through ultra-low temperature CO 2 -H 2 O electrolyzer technology that is fed using the Martian atmosphere's CO 2 (∼95 %) and the subsurface Martian water cycle (enabled by perchlorate salts that depress the Martian brine's freezing point to < 213 K) has been proposed as a pathway towards fuel and chemical feedstock. Herein we applied a validated, computationally frugal electrolyzer model to a Martian CO 2 -H 2 O electrolyzer and examined its viability. Through a judicious combination of catalysts, such electrolyzers could produce O 2 , CO, HCHO, CH 3 OH, CH 4 , C 2 H 4 , and C 2 H 5 OH even at ambient Martian temperatures (∼237 K). Our modeling herein shows the theoretical production of these key resources in acidic electrolyzers to be at a scalable rate of 0.052 – 1.13 g per cm2 per day of CO, 0.0004 – 0.086 g per cm2 per day of CH 3 OH, 0.001–0.048 g per cm2 per day of CH 4 , 0.0164 – 0.171 g per cm2 per day of C 2 H 4 , 0.008 – 0.0125 g per cm2 per day of C 2 H 5 OH. A range of catalyst candidates were examined for product selectivity, energy efficiency and throughput. Ambient temperature CO 2 -H 2 O electrolysis is shown to be an energy efficient approach to chemical feedstocks needed for the sustained exploration of Mars and beyond. This model can inform future astronaut life support device development for NASA and other space faring entities. [ABSTRACT FROM AUTHOR]

[Display omitted] • Synthesis of new tetradentate bis(N -heterocyclic carbene)-bis(phenolate) ligands L. • Synthesis of a new Cr(III) complex: [Cr(H 2 L)(acac) 2 ]Br. • Synthesis of a new Fe(III) complex: [Fe(H 2 L)(acac) 2 ]Br. • Synthesis of two new Ni(II) complexes: [NiL]. • [Fe(H 2 L)(acac) 2 ]Br is a good catalyst in the CO 2 cycloaddition with epoxides. In the frame of a coordination chemistry study on hybrid bis(N -heterocyclic carbene)-bis(phenolate) ligands (L), the synthesis of novel Fe(III), Cr(III) and Ni(II) complexes is reported. The Fe(III) and Cr(III) complexes are obtained starting from their acetylacetonates [M(acac) 3 ] (M = Fe or Cr, acac = acetylacetonate), and are characterized by a general formula [M(acac) 2 (H 2 L)]Br (2 , M = Fe and 3 , M = Cr), in which only the phenolate donors of the ligand are coordinated to the metal center. Differently, the Ni(II) complexes are prepared starting from Ni(OAc) 2 ·4H 2 O or NiCl 2 ·6H 2 O, and the corresponding products are characterized by the general formula [NiLx] (4 , x = 1 and 5 , x = 2), in which both the N -heterocyclic carbene and the phenolate donors of the ligand are coordinated to the metal center. The synthesized compounds were characterized by means of elemental analysis, ESI-MS and in the case of [Fe(acac) 2 (H 2 L) ]Br single crystal XRD. Complexes 2 – 5 were used in homogeneous catalysis, in the cycloaddition reaction between CO 2 and epoxides. The Fe(III) complex 2 , [Fe(acac) 2 (H 2 L) ]Br , outperformed the other catalysts prepared in the frame of this study, showing a good activity under mild reaction conditions (i.e. p CO2 = 1 bar) and in the absence of co-catalysts. [ABSTRACT FROM AUTHOR]

Nowadays, sustainable and renewable energy production is a global priority. Over the past decade, several Power-to-X (PtX) technologies have been proposed to store and convert the surplus of renewable energies into chemical bonds of chemicals produced by different processes. CO2 is a major contributor to climate change, yet it is also an undervalued source of carbon that could be recycled and represents an opportunity to generate renewable energy. In this context, PtX technologies would allow for CO2 valorization into renewable fuels while reducing greenhouse gas (GHG) emissions. With this work we want to provide an up-to-date overview of biomethanation as a PtX technology by considering the biological aspects and the main parameters affecting its application and scalability at an industrial level. Particular attention will be paid to the concept of CO2-streams valorization and to the integration of the process with renewable energies. Aspects related to new promising technologies such as in situ, ex situ, hybrid biomethanation and the concept of underground methanation will be discussed, also in connection with recent application cases. Furthermore, the technical and economic feasibility will be critically analyzed to highlight current options and limitations for implementing a sustainable process. [ABSTRACT FROM AUTHOR]

This study investigated immobilization (without binders and high-temperature heating) of highly active CO2 methanation catalyst particles, prepared by the polygonal barrel-sputtering method, onto porous Al2O3 plates. The catalyst particles were fixed uniformly and firmly on the plates and retained their high CO2 methanation performance. [ABSTRACT FROM AUTHOR]

Concerns over the massive increase in CO2 emissions induced by overconsumption of fossil fuels have driven the rapid development of CO2 valorization techniques. Carbon capture and utilization (CCU) technology, which emerged as a promising strategy to relieve increasing environmental concerns and create more carbon feedstocks simultaneously, hold great promise to close the anthropogenic chemical carbon cycle. Herein, recent breakthroughs related to the two predominant techniques involved in returning CO2 into a useful state, namely CO2 capture and CO2 conversion are systematically overviewed. Initially, CO2 capture principles, recent advances, as well as future challenges of state‐of‐the‐art absorbents/adsorbents and membrane separation technology are summarized. Furthermore, innovative catalysts related to the CO2 conversion technologies (including thermo‐driven CO2 hydrogenation, photo‐and electrochemical CO2 reduction, and enzymatic CO2 conversion) are discussed, emphasis is focused on the catalytic performance, design principles, and economic efficiency. Finally, a perspective regarding the future research opportunities toward CCU technologies is provided. This review aims to stimulate innovation and accelerate interdisciplinary integrations toward CCU related technologies via a discussion of fundamental mechanisms, recent breakthroughs, current associated difficulties as well as future directions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigation on heterogeneous catalysts for valorizing CO 2 to valuable chemicals. • Formulation of active sites to address challenges in C-C coupling utilizing CO 2. • Mechanistic details in heterogeneous catalysis of CO 2 -ethylene direct coupling. • Insights into the structure–activity relationship and the water-promoting effect. • Guidelines for mimicking molecular catalysts to design heterogeneous catalysts. Direct coupling of CO 2 and ethylene (hereinafter DCCE) to acrylic acid is valuable for valorizing CO 2 to manufacture acrylate-derived products. However, previous studies in DCCE have been limited on molecular catalysts with challenges in improving catalytic performance. In this work, we employed density functional theory calculations and ab initio molecular dynamics simulations to investigate the heterogeneous catalysis of DCCE over atomically dispersed metal centers at nitrogen-doped zigzag edge of graphene. Based on competitive adsorption and structural stability, Mo, Cr, V, Ru, and Ni active sites are chosen to explore the reaction kinetics. We find that the activation barriers are determined by the charge redistribution at transition states, which explains the trend of activity for the C-C coupling and the hydrogen transfer, two key steps in DCCE. Furthermore, we show that the intramolecular hydrogen transfer (rate-limiting step) is hindered due to the lack of local coordinate at the active sites. We thus propose to use co-adsorbed water as a "proton-exchanger" following a water-assisted route, and show that the activation barriers are reduced over all metal centers. Particularly, water promotes the hydrogen transfer over metals with strong CO 2 -ethylene co-activation and facile C-C coupling kinetics, which could be considered promising for DCCE. In both mechanisms, the stability of metallactone intermediate can be used to predict the catalytic activity. It is anticipated that the insights from this work can provide guidelines for mimicking well-defined multifunctional active sites in molecular catalysts to design heterogeneous catalysts for such C-C coupling, which advances catalytic utilization of CO 2. [ABSTRACT FROM AUTHOR]

NiII and MnIII Schiff base complexes (Salophen‐Ni and Salophen‐MnCl) bearing a pending carboxylic group were prepared and characterized. Both complexes were grafted onto a mesoporous amino‐functionalized SBA‐15 silica, by formation of an amide function between the propylamine groups of the support and the carboxylic acid functions of the salophen ligand (corresponding respective to 1.30 wt.% of Ni and 1.06 wt.% of Mn). The co‐catalytic behaviour of the free and grafted complexes was then evaluated in the CO2 cycloaddition reaction onto styrene oxide, using tetra‐butylammonium bromide (n−Bu4NBr) as the main catalyst. In homogeneous conditions, the MnIII Schiff base complex and the NiII one, to a lesser extent, behave as efficient co‐catalysts for this reaction (styrene conversion of 100 % and 65 % respectively after 3 h at 120 °C, under 15 bars of CO2). Upon immobilization at the surface of the amino‐functionalized SBA‐15, we showed that the co‐catalytic activity of the less efficient one, i. e. Ni2+ salophen complex, could be enhanced (reaching a full conversion after 7 h), hence highlighting a potential synergistic effect between the unused amine functions of the support and the Ni2+ salophen co‐catalyst. Both salophen complexes were successfully re‐used in homogeneous conditions or after their immobilization without any appreciable loss of activity. This work is only a first step towards a completely heterogeneous catalytic system, in which the tetraalkylammonium halide catalyst and the metal‐salophen co‐catalyst will both be covalently anchored on the same support. [ABSTRACT FROM AUTHOR]

Methanol production through CO2 hydrogenation was investigated in a series of fixed‐bed reactors. Staging of the reactor into several smaller reactors is considered to enhance methanol production, in addition to maximizing a measure of annual profit. The degrees of freedom of the reactor system are the number of stages, the cooling medium temperature, the heat transfer area, and the volume of the stages. Depending on the objective function (OF) criteria, staging of the reactor increases the OF values to various extents. When the objective is to maximize the methanol production, the OF of a three‐stage reactor system with an inlet H2/CO2 ratio of 2 is 2.61 % higher than in the single‐stage configuration. Staging of the reactor also increases the synthesis gas conversion to methanol. However, if maximizing the annual profit is the objective, the profitability of the two‐stage configuration is 2.05 % greater than in the case with one reactor, due to the higher methanol production of the staged reaction system. [ABSTRACT FROM AUTHOR]

• Mn-promoted Ni catalysts on silica-modified alumina (SA) prepared. • Increasing Mn/Ni ratio yields more active and stable methanation catalysts. • Ni/SA methanation performance promoted by MnO at 1 bar and 20 bar. • Mn addition improves Ni reducibility and dispersion, CO 2 adsorption and activation. • Mn present as MnO clusters on Ni active phase in reduced catalysts. The viability of the Power-to-Gas (PtG) concept is strongly dependent on the development of highly active and stable methanation catalysts obtained from cheap and abundant elements. In this paper, the promotional effect of MnO on Ni catalysts supported on silica-modified γ-Al 2 O 3 (SA) was investigated in CO 2 and CO methanation on catalysts with Mn/Ni atomic ratios between 0 and 0.25. Significantly higher methanation rates and CH 4 selectivities were obtained for Mn-promoted compositions compared to Ni-only catalysts. The optimal NiMn/SA (Mn/Ni = 0.25) catalyst exhibited improved stability compared with unpromoted Ni/SA at 20 bar. The nature of the catalyst precursor and active catalyst was studied with STEM-EDX, XPS, and X-ray absorption spectroscopy (XAS). Evidence of a mixed Ni-Mn oxide in the catalyst precursor was obtained by EXAFS. EXAFS measurements revealed that the reduced catalyst consisted of metallic Ni particles and small oxidic Mn2+ species. Moreover, Mn addition improved the Ni dispersion and enhanced the Ni2+ reducibility by weakening the interaction between the Ni-oxide precursor and the support. A mechanistic study involving IR spectroscopy and steady-state isotopic (13CO 2) transient kinetic analysis (SSITKA) showed that the presence of Mn enhanced CO 2 adsorption and activation. [ABSTRACT FROM AUTHOR]

In the context of CO2 valorisation, the reverse water–gas shift reaction (RWGS) is gathering momentum since it represents a direct route for CO2 reduction to CO. The endothermic nature of the reaction posses a challenge when it comes to process energy demand making necessary the design of effective low-temperature RWGS catalysts. Herein, multicomponent Cs-promoted Cu, Ni and Pt catalysts supported on TiO2 have been studied in the low-temperature RWGS. Cs resulted an efficient promoter affecting the redox properties of the different catalysts and favouring a strong metal-support interaction effect thus modulating the catalytic behaviour of the different systems. Positive impact of Cs is shown over the different catalysts and overall, it greatly benefits CO selectivity. For instance, Cs incorporation over Ni/TiO2 catalysts increased CO selectivity from 0 to almost 50%. Pt-based catalysts present the best activity/selectivity balance although CuCs/TiO2 catalyst present comparable catalytic activity to Pt-studied systems reaching commendable activity and CO selectivity levels, being an economically appealing alternative for this process. [ABSTRACT FROM AUTHOR]

Sodium fluoride is the most efficient catalyst to deprotonate and carboxylate methanol. [Display omitted] • Sodium fluoride decreases the activation barrier down to 18 kJ/mol. • Carbon dioxide promotes deprotonation by colliding with methanol. • The acidic medium emerges after the dimethyl carbonate formation. • Up to 21 % yields of dimethyl carbonate were attained. Carbon dioxide (CO 2) in the atmosphere of the Earth represents an abundant and largely free source of carbon, which remains heavily underestimated nowadays. The disbalance between the emission and utilization of CO 2 puts the sustainable development of humanity at risk because of its possible correlation with global climate change. The valorization of CO 2 is an important strategy to attend to the above-mentioned challenges. CO 2 can be converted to dimethyl carbonate by grafting to methanol (CH 3 OH) in the presence of the catalyst. The presently known catalytic solutions require high temperatures and pressures to be employed. Herein, we report sodium fluoride as a new catalyst offering an unprecedentedly low activation barrier, 23 kJ/mol, for the carboxylation of CH 3 OH. The fluoride anion coordinates the hydroxyl hydrogen of CH 3 OH thanks to forming a very strong H-bond. Upon the collision with CO 2 , the proton detaches, and CO 2 grafts to CH 3 O* while becoming the carboxyl group. The reaction finishes by methylating CH 3 OC(O)O– via the methyl radical originating from another CH 3 OH molecule (esterification stage). The hydrogen fluoride molecule is an intermediate in this reaction providing the proton and fostering esterification. The subsequent in-lab experiments showed that much milder conditions can be used to synthesize DMC out of CH 3 OH. Under 80 °C and 40 bar, we obtained an outstanding DMC yield of 21.1 %. However, the synthesis was also possible at lower temperatures giving DMC yields of 16.3 % at 65 °C, 14.7 % at 55 °C, and 10.8 % at 25 °C. The unprecedented possibility to obtain a non-negligible production of an organic carbonate at room temperature represents a cornerstone advance in the field of CO 2 valorization and promises huge energy savings. Given the current global amount of the yearly prepared DMC amounting to over one million tons and the demand for this chemical by emerging chemical technologies, the achieved result is deemed to be of paramount importance. The exemplified catalytic mechanism is also interesting in the context of other syntheses, in which a low-energetic production of the methoxy moieties is a cornerstone. [ABSTRACT FROM AUTHOR]

One dimensional silica-based nanotubes represent an innovative and promising morphology in the context of heterogeneous catalysis. Here these nanostructures were prepared for the first time as bifunctional materials, with hafnium or tin atoms inserted as single sites in the silica structure and imidazolium moieties anchored at the surface. The low dimensional solids thus present both acid sites owing to the presence of metal cations in tetrahedral coordination (co-catalyst) and nucleophilic species coming from the counterion of the imidazolium moieties (catalyst). The design of the catalysts consisted of two main steps. The Hf- or Sn-doped silica solids were initially prepared using a straightforward sol-gel method including a pH adjustment step allowing a quantitative insertion of the metal cations in the silica framework. These materials were post-functionalized with imidazolium moieties. The solids were extensively characterized thus confirming the presence of well-defined and open tubular structure, high specific surface area, successful insertion of Hf and Sn in the silica framework, and a correct functionalization with imidazolium salts. The different catalysts were tested in the valorization of CO 2 with styrene oxide to give the corresponding cyclic carbonate. The bifunctional solids were stable and recyclable. The versatility of the best catalyst, represented by the Hf-based material, was confirmed using different epoxides. Finally, by tuning the reaction conditions or changing the imidazolium salt, a further boost of the catalytic performances was achieved. [Display omitted] • A series of novel 1D silica-based nanotubes were prepared for the first time as bifunctional catalysts. • A synergistic activation enhancing the overall catalytic performances was disclosed. • The structure-activity correlation allows highlighting the combined effect of Brønsted and Lewis acid sites. • Hf-doped SiO 2 nanotubes were particularly efficient for the synthesis of glycidol carbonate. • The novel structures were highly active and versatile in CO 2 conversion, stable and reusable. [ABSTRACT FROM AUTHOR]

• Multi-functional catalysis offers intriguing possibilities for CO 2 valorization. • Ca incorporation onto ZSM-5 creates multiple Lewis acidic species. • Brønsted-Lewis acid synergy in Ca-ZSM-5 increases light olefin yield from CO 2. Utilization of multi-functional catalysis is fast becoming the method of choice to boost the production of valuable chemicals from CO 2. Here, we present a possible route to increase selectivity to light olefins by modifying the acidity of the zeolitic component of a multi-functional catalyst. This is carried out via incorporation of Ca on the zeolite ZSM-5 by incipient wetness impregnation. This incorporation, while straightforward, leads to reduced Brønsted acidity and the formation of multiple Lewis acidic species inside the zeolite. NMR investigations point towards incorporation of CO/ketene into the zeolite leading to the creation of surface acetate species, which augments the production of light olefins. Additionally, the suppression of oligomerization due to the reduction of Brønsted acid sites also produces more light olefins at the expense of longer chain hydrocarbons. [ABSTRACT FROM AUTHOR]

The process of methanol synthesis based on the hydrogenation of CO2 was investigated over binary Cu/ZnO catalyst materials, prepared by applying a novel electroless plating fabrication method. The activity of the produced catalytic samples was determined at temperature range between 200 and 300 °C and the feedstock conversion data were supplemented with a detailed microstructure analysis using high-resolution transmission electron microscopy (HRTEM), X-ray powder diffraction (XRD) and Cu and Zn K-edge, X-ray absorption near-edge structure (XANES) measurements and extended X-ray absorption fine-structure (EXAFS) measurements. It was confirmed that the disorder in the Cu crystallites created unique geometrical situations, which acted as the additional reactive centres for the adsorption of the reactant molecule species. Copper and zinc structural synergy (spill-over) was also demonstrated as being crucial for the carbon dioxide's activation. EXAFS and XANES results provide strong evidence for surface alloying between copper and zinc and thus the present results demonstrate new approach applicable for explaining metal-support interactions.Graphical Abstract: [ABSTRACT FROM AUTHOR]

Abstract In this study the influence of metal dispersion, spinel formation, and surface properties of binary and ternary catalysts (CuO CeO 2 , ZnO CeO 2 , CuO ZnO CeO 2 , and CuO ZnO Al 2 O 3) was evaluated. The catalysts prepared by polyol method using polyethylene glycol as a solvent have been tested in the CO 2 hydrogenation to methanol performed at atmospheric pressure. The catalysts prepared by polyol method presented improved properties in terms of metal oxide dispersion, morphology (i.e. sponge-like shape for the CeO 2 -containing catalysts), and a large variety of metal and metal oxide species on the surface. Moreover, the CuO ZnO CeO 2 and CuO ZnO Al 2 O 3 catalysts exhibited a higher activity and selectivity in the methanol synthesis by CO 2 hydrogenation than those displayed by catalysts prepared by more conventional methods. [ABSTRACT FROM AUTHOR]

This review discusses the importance of mitigating CO 2 emissions by valorizing CO 2 through high-pressure catalytic processes. It focuses on various key processes, including CO 2 methanation, reverse water-gas shift, methane dry reforming, methanol, and dimethyl ether synthesis, emphasizing pros and cons of high-pressure operation. CO 2 methanation, methanol synthesis, and dimethyl ether synthesis reactions are thermodynamically favored under high-pressure conditions. However, in the case of methane dry reforming and reverse water-gas shift, applying high pressure, results in decreased selectivity toward desired products and an increase in coke production, which can be detrimental to both the catalyst and the reaction system. Nevertheless, high-pressure utilization proves industrially advantageous for cost reduction when these processes are integrated with Fischer-Tropsch or methanol synthesis units. This review also compiles recent advances in heterogeneous catalysts design for high-pressure applications. By examining the impact of pressure on CO 2 valorization and the state of the art, this work contributes to improving scientific understanding and optimizing these processes for sustainable CO 2 management, as well as addressing challenges in high-pressure CO 2 valorization that are crucial for industrial scaling-up. This includes the development of cost-effective and robust reactor materials and the development of low-cost catalysts that yield improved selectivity and long-term stability under realistic working environments. [Display omitted] [ABSTRACT FROM AUTHOR]

The research in advanced materials for effective CO 2 capture and conversion is an imperative duty for the next years. In this sense MOF materials are being intensively tested for this purpose. Herein, seven different copper-based MOF materials with different functional organic groups in their linkers have been assessed to comprehend some structural features that influence the CO 2 transformation via cycloaddition reaction with epoxides: Cu-URJC-1 (tetrazole group), Cu-URJC-8 (primary amine group), Cu-MOF-74 (hydroxyl group), JUC-62 (azo group), PCN-16 (triple bond group), HNUST-1 (amide group) and HKUST-1. When epichlorohydrin was used as a substrate, Cu-URJC-8 produced the best epoxide conversion (90%) and selectivity to cyclic carbonate (>99%), despite showing a modest surface area. This result can be explained by the higher basicity of primary amines than other basic functional organic groups of the MOFs. However, when styrene oxide was used as substrate, Cu-URJC-1 led to the best reaction results with a conversion and selectivity toward cyclic carbonate of 60 and 86%, respectively. This result was achieved because this material presents the synergic effect of having in its flexible structure 12 Å channels, that favors the styrene oxide diffusion, and a great number of basic nitrogen atoms, which can increase the reactivity of carbon dioxide. In summary, the presence of nitrogen atoms in the organic linker increases the CO 2 conversion by promoting the reactivity of this molecule. [Display omitted] • Seven copper-MOFs have been tested in the CO2 cycloaddition reaction with epoxides. • Qst of CO2 adsorption is higher for nitrogen-containing structures. • Cu-URJC-8 attained the highest yield to cyclic carbonates. • Lewis basic groups in the MOF linker is a relevant factor on epoxide conversion. [ABSTRACT FROM AUTHOR]

Methane dry reforming (MDR) is a very appealing process to bring back waste CO 2 into the chemical production chain. Operating in chemical looping (CL) conditions allows to reduce deactivation by coke deposition and facilitates the use of concentrating solar energy to power this reaction. Perovskites have successfully applied as oxygen carriers for chemical looping, and those of the family La 1−x Sr x FeO 3 having lower Sr content have showed high activity and cycling stability for MDR. To further enhance the performance of these oxygen carriers, in this work we evaluate the impact of dispersing Ni in low concentration (<1 mol %) on the performance of La 0.9 Sr 0.1 FeO 3 for CL-MDR. Simple impregnation allows to distribute evenly the metal, which according to XPS is present as Ni2+ in the fresh material. CH 4 -TPR reveal that NiO x species are firstly reduced at around 650 ºC and they shift the onset of methane partial oxidation to lower temperatures with regards to the unmodified perovskite. However, during isothermal CL tests at 850 ºC, the presence of Ni does not modify much the syngas production during the methane reforming stage, although the H 2 /CO ratio increases with the presence of this metal. This indicates an increment in the contribution of methane cracking. In contrast, when feeding CO 2, the generation of CO is greatly enhanced by the incorporation of Ni, particularly at a loading of 0.4 mol %, while higher metal concentration are slightly less effective. Higher CO generation is attributed to the promotion of reverse Boudouard reaction, which can remove the coke previously deposited in the methane reforming stage. Accordingly, the Ni/ La 0.9 Sr 0.1 FeO 3 presents stable activity during several consecutive cycles. [Display omitted] • Low concentration of Ni (<1 mol %) was incorporated by wet impregnation on La 0.9 Sr 0.1 FeO 3. • Ni/ La 0.9 Sr 0.1 FeO 3 samples present high activity for chemical looping methane dry reforming at 850 ºC. • The presence of Ni does not increase substantially the activity for methane partial oxidation but increase the H 2 /CO ratio. • In contrast, Ni remarkably promote CO formation during the CO 2 stages with regards to the unloaded perovskite. • Stable activity is observed during 5 cycles due to the efficient coke removal by reverse Boudouard reaction. [ABSTRACT FROM AUTHOR]

Highlights • Power supply interruption affects the performance of the system for a reduced period of time. • MES showed to be recovered after power supply interruption. • Longer off periods did not result in longer recovery times. • MES system proved to be ready for real-field application powered with renewable energy. • The cathodic biofilm was dominated by bioelectrochemically active acetogenic bacteria. Abstract Microbial electrosynthesis (MES) allow CO 2 capture and utilization for the electricity-driven bioproduction of organics such as acetic acid. Such systems can be coupled to any renewable electricity supply, especially those derived from solar and wind energy. However, fluctuations or even absence of electricity may cause damages or changes in the microbial community, and/or affect the performance and robustness of MES. Therefore, the transformation of gaseous CO 2 into organic products in a MES was assessed continuously during 120 days of operation. Time-increasing power outages, from 4 h to 64 h, were applied in order to evaluate the effects of electric energy (current) absence on microbial community, organics formation, production rates and product accumulation. Acetic acid was the main product observed before and after the power outages. A maximum titer and production rate of 6965 mg L−1 and 516.2 mg L−1 d−1 (35.8 g m−2 d−1) of acetic acid were observed, respectively. During the absence of power supply, it was observed that acetic acid is oxidized back to CO 2 which suggests microbial activity and/or pathway reversal. However, the electro-autotrophic activity recovered after the power gaps, and acetic acid production was restored after reconnecting the energy supply, reaching a current density of −25 A m−2. The microbial community of the biofilm responsible for this behavior was characterized by means of high-throughput sequencing, revealing that Clostridium , Desulfovibrio and Sporomusa accounted for 93% of the total community attached onto the cathodic biofilm. Such resilience of electrotrophic microorganisms reinforces the opportunity to couple bioelectrochemical systems to renewable energy, overcoming the eventual electrical power fluctuations. [ABSTRACT FROM AUTHOR]

A novel gas-phase electrocatalytic system based on a low-temperature proton exchange membrane (Sterion) was developed for the gas-phase electrocatalytic conversion of CO2 to liquid fuels. This system achieved gas-phase electrocatalytic reduction of CO2 at low temperatures (below 90 °C) over a Cu cathode by using water electrolysis-derived protons generated in-situ on an IrO2 anode. Three Cu-based cathodes with varying metal particle sizes were prepared by supporting this metal on an activated carbon at three loadings (50, 20, and 10 wt %; 50% Cu-AC, 20% Cu-AC, and 10% Cu-AC, respectively). The cathodes were characterized by N2 adsorption-desorption, temperature-programmed reduction (TPR), and X-ray diffraction (XRD) and their performance towards the electrocatalytic conversion of CO2 was subsequently studied. The membrane electrode assembly (MEA) containing the cathode with the largest Cu particle size (50% Cu-AC, 40 nm) showed the highest CO2 electrocatalytic activity per mole of Cu, with methyl formate being the main product. This higher electrocatalytic activity was attributed to the lower Cu-CO bonding strength over large Cu particles. Different product distributions were obtained over 20% Cu-AC and 10% Cu-AC, with acetaldehyde and methanol being the main reaction products, respectively. The CO2 consumption rate increased with the applied current and reaction temperature. [ABSTRACT FROM AUTHOR]

This work aimed to establish the feasibility to conduct in liquid phase the photocatalyzed conversion of CO2 to formic acid, typically conducted in stirred tank reactors, in a multiphase capillary reactor (inner diameter: 3 × 10−3 m), at 298 K in a 0.5M NaOH solution under Taylor-flow, which favors mass transfer (gas and liquid velocity: 0.05 and 0.08 m/s). The effect of (i) type of catalyst (Cu/TiO2 and TiO2), (ii) catalyst loading (0–1.0 g/L), (iii) catalyst addition mode (Cu/TiO2 in slurry or immobilized onto the capillary wall), (iv) radiation wavelength (254 nm, 365 nm and visible light), was studied. The synthesized catalysts exhibited anatase phase and the Cu content was 3.75% w/w. The specific surface area of Cu/TiO2 and TiO2 was 242.2 and 121.5 m2/g, respectively. The established band-gap was 2.54 eV for Cu/TiO2 and 3.24 eV for TiO2. Cu2+ and Ti4+ were the species on the catalyst surface. The assessed system allows the CO2 utilization by its transformation at short reaction times into formic acid (quantified by HPLC), an attractive molecule for hydrogen storage. The maximum formic acid production rate was 4033 μmol gcat−1 h−1 when the reaction was photocatalyzed by 1 g/L of Cu/TiO2 using 254 nm radiation and it was 3233 μmol gcat−1 h−1 with 365 nm and 0.5 g/L of catalyst loading. The use of a capillary reactor also eliminates catalyst separation, by catalyst immobilization onto the inner capillary wall. This led to a formic acid production rate of 946 μmol gcat−1 h−1. The catalyst was also active under visible light. [ABSTRACT FROM AUTHOR]

[Display omitted] • Coke deposition in SAPO-34 is responsible for the deactivation of In 2 O 3 -ZrO 2 /SAPO-34. • Coke forms from methanol/DME in the reaction medium. • H 2 O concentration in the medium is key for attenuating deactivation. On account of the superior performance of In 2 O 3 -ZrO 2 /SAPO-34 tandem catalyst in the direct synthesis of olefins from CO, CO 2 and CO/CO 2 mixture by hydrogenation, it is interesting to establish the conditions to avoid its deactivation due to the rapid coke deposition on SAPO-34. The co-feeding of H 2 O and/or methanol together with H 2 + CO 2 /CO was studied in a packed bed reactor at: 400 °C, 30 bar; CO 2 /CO x in the feed, 0–1; H 2 /CO x in the feed, 1–3; and space time of 5 g cat h mol C −1, quantifying the evolution with time on stream (up to 16 h) of CO 2 and CO x conversions and olefin, paraffin and CH 4 yields. The effects of the co-feeding on coke content and its nature were determined by temperature programmed oxidation (TPO) analyses of the spent catalyst. The results highlighted the complex effect of the concentration of H 2 O and oxygenates (methanol/dimethyl ether (DME)) on the deactivation of SAPO-34 and on the products yields in the pseudo-steady state of the catalyst. Co-feeding H 2 O lessens coke deactivation, however, high H 2 O concentration leads to attenuate the acidity of SAPO-34, limiting the performance of the tandem catalyst (mainly in the CO 2 conversion). Oxygenates co-feeding concentration limit value lies on its favoring effect for coke formation. In addition to this effect, the favorable attenuation of coke deactivation by the high H 2 concentration (studied in runs with H 2 /CO x ratio in the feed in the 1–3 range) plays a key role in the viability of the process, leading to a pseudo-steady catalyst state in which the activity is constant. The proven effect of H 2 O and methanol concentrations will be useful for establishing new catalysts and reaction conditions at which their presence in the reactor will attenuate deactivation. [ABSTRACT FROM AUTHOR]

• The role of membrane engineering for more sustainable industrial cycles is reported. • Membrane crystallizers improvement by operating conditions and membrane material. • Multifunctional membrane reactor for the direct conversion of CO2 and H2 to DME. • Exergy analyses to minimize the exergy destruction of desalination plants. • New metrics to assess the role of membrane operations in Process Intensification. The fast growing of membrane systems in industrial applications suggests the dissemination of last results, particularly in the areas of strategic interest. In this contribution, the role of membrane engineering for more sustainable industrial cycles, following the Process Intensification strategy, is reported. The development of Membrane Crystallizers (MCr) with specific focus on their application to the treatment of brines is presented, together with the use of molecular dynamic simulation to help in the selection of the most appropriate membrane material. The potential of membrane reactors for CO 2 valorization through new designs is also highlighted. Moreover, tools like exergy analyses and new metrics to compare the performance of membrane operations to conventional ones in the logic of Process Intensification are discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

• The large-scale synthesis of single atomic (Co, Fe, and Ni)-N-C catalyst reported. • HRTEM confirmed presence of single atomic M-Nx moieties in the catalysts. • The performance of Ni-N-C is superior to Co-N-C and Fe-N-C based on FE to CO. • The highest CO FE of 80% and TOF of 57,379 h −1 are achieved during CO 2 RR. Here, we report a facile approach for synthesizing M –N–C catalysts (M = Co, Fe, Ni) at a commercial scale without employing organic solvents. Our characterization efforts indicate that single atomic catalysts with high surface areas were successfully obtained. Electrochemical measurements demonstrate that, among the three synthesized catalysts, Ni–N–C exhibits the highest performance in the electrochemical CO 2 reduction reaction (CO 2 RR) to carbon monoxide (CO), affording 80% Faradaic efficiency (FE) of CO production at –0.49 V RHE with a turnover frequency (TOF) of 57,379 h–1. Large-scale synthesis coupled with high performance allows moving forward with the practical implementation of M –N–C catalysts for industrially relevant CO 2 RR. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • CO 2 valorization via electrified CO 2 reforming of methane and reverse water–gas shift. • eRWGS ensures specific energy demands as low as 0.7 kWh/Nm3 CO2 for CO 2 valorization. • Joule-heated Rh/Al 2 O 3 washcoated SiSiC foams demonstrate excellent stability over 75 h. • A new path for low carbon chemical synthesis utilizing captured CO 2 and excess renewable electricity. The growing environmental concerns have driven catalytic CO 2 valorization as a forward-looking solution to mitigate the carbon footprint of valuable chemical products. CO 2 conversion processes into synthesis gas, such as CO 2 reforming of methane (CRM) or reverse water–gas shift (RWGS), may have a strategic role for the future sustainable production of chemicals and energy carriers. However, fuel combustion to supply the heat of the associated endothermic reactions would result in unwanted CO 2 emissions, frustrating the overall objective. Electrification of the endothermic processes may represent the technological solution to such an issue. Here we report a promising approach for the direct electrification of the CO 2 reforming of methane (eCRM) and reverse water–gas shift (eRWGS) processes in washcoated structured reactors. We employ catalytically activated open-cell foams that provide optimal heat and mass transfer properties and serve as Joule heating substrates for the catalytic conversion of CO 2 via reaction with methane or hydrogen. The proposed reactor system with Joule-heated Rh/Al 2 O 3 -coated foam exhibited excellent catalytic and electrical stability for more than 75 h, operating up to 800 °C and approaching equilibrium conversion at high space velocity, i.e., GHSV of 600 and 100 kNl/kg cat /h for eRWGS and eCRM, respectively. Such a reactor concept has potential to ensure remarkably low specific energy demand for CO 2 valorization. Assuming an optimized process configuration approx. 0.7 kWh/Nm3 CO2 is calculated for eRWGS. By replacing fuel combustion with Joule heating driven by renewable electricity, the electrified CO 2 valorization processes provide an important approach for dealing with the intermittent nature of renewable sources by storing the energy in chemicals with a low carbon footprint. [ABSTRACT FROM AUTHOR]

A direct metal-free, base-free, and site-selective electrochemical C-H carboxylation of arenes by reductive activation using CO SB 2 sb as an economic and abundant carboxyl source was developed. C-H Carboxylation, CO2 Valorization, Carbon Dioxide, Electroreduction, Selectivity Keywords: C-H Carboxylation; CO2 Valorization; Carbon Dioxide; Electroreduction; Selectivity EN C-H Carboxylation CO2 Valorization Carbon Dioxide Electroreduction Selectivity 1 1 1 01/11/23 20230116 NES 230116 B A site-selective electrochemical b C-H carboxylation of arenes with CO SB 2 sb is reported by Youai Qiu and co-workers in their Research Article (e202214710). [Extracted from the article]