Recent developments in carbon dioxide utilization for the production of organic chemicals

Photocatalytic CO2 reduction of Ag/Ag2S/Ti3C2T X heterojunctions with enhanced interfacial charge transfer

Photocatalytic reduction of CO2 to produce organic fuels is a promising strategy for addressing carbon reduction and energy scarcity. Transition metal carbides (Ti3C2T X ) are of particular interest due to their unique layered structures and excellent electrical conductivity. However, the practical application of Ti3C2T X is limited by the poor separation efficiency of photogenerated charge carriers and the low migration ability of photogenerated electrons. Herein, Ag/Ag2S/Ti3C2T X heterojunctions were synthesized by depositing Ag/Ag2S nanoparticles onto layered Ti3C2T X substrates using a combination of co-precipitation and photoreduction methods. Fluorescence spectra, UV diffuse reflection, and photoelectric chemical characterizations demonstrated that Ag/Ag2S/Ti3C2T X heterojunctions provided effective channels for the reverse and synergistic migration of electrons and holes, leading to improved spatial separation. Notably, the Ag component in the composite acts as an electron acceptor and reactive center, significantly enhancing the migration ability of photogenerated electrons. The total alcohol yield over Ag/Ag2S/Ti3C2T X (125.3 μmol gcatal. -1) was 5.1 times higher than that on Ag2S (24.7 μmol gcatal. -1) and 2.1 times higher than on Ti3C2T X (60.7 μmol gcatal. -1). This study offers valuable insights into designing efficient photocatalytic CO2 reduction catalysts.

Regulation of Ir Dopant in Mo Oxides by Flame Spray Pyrolysis for Efficient CO2 Hydrogenation

Mo carbide is recognized as one of the most promising catalysts for CO2 utilization via reverse water-gas shift (RWGS). However, the catalysts always suffered from low processing capacity, undesired products and deactivation. Herein, an Ir modified MoO3 synthesized by the flame spray pyrolysis (FSP) method exhibits higher reaction rate (63.0 gCO2 gcat -1 h-1) compared to the one made by traditional impregnation method (45.8 gCO2 gcat -1 h-1) over the RWGS reaction at 600 °C. The distinguishing feature between the two catalysts lies in the chemical state and space distribution of Ir species. Ir species predominated in the bulk phase of MoO3 during the quenching process of the FSP method and were mainly in the metallic states, which was revealed by X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) characterizations. In contrast, the Ir introduced via the impregnation method was mainly on the surface of MoO3 and in the oxidized state. The regulation of Ir dopant in MoO3 catalyst by different methods determines the carbonization process from MoO3 to Mo carbides and thus affects the catalytic performance over RWGS reaction. This work sheds light on the superiority of the FSP method in synthesizing Mo oxides with heteroatoms and further creating an efficient Mo-based catalyst for CO2 conversion.

CO2 fixation: cycloaddition of CO2 to epoxides using practical metal-free recyclable catalysts

The conversion of CO2 into valuable chemicals is a crucial field of research. Cyclic organic carbonates have attracted great interest because they can be prepared under mild conditions and because of their structural versatility which enables a large variety of applications. Therefore, there is a need for potent and yet practical catalysts for the cycloaddition of CO2 to cyclic carbonates that are able to combine availability, low cost and an adequate performance. We review here several recyclable catalytic systems that are readily available, easy to prepare, and inexpensive with an eye to the future development of more efficient practical catalysts through the provided guidelines.

Multi-criteria evaluation of carbon capture technologies in steel, cement, petrochemical, and fertilizer industries: Insights for emerging and developed countries

This research addresses the global imperative to tackle climate change by evaluating different carbon capture technologies based on various criteria in hard-to-electrify sectors such as steel, cement, petrochemicals, and fertilizers, providing practical insights for policymakers engaged in the shift toward low-carbon industrial processes. The study employs a Multi-Criteria Decision-Making (MCDM) approach, specifically the Analytical Hierarchy Process (AHP), using a systematic and objective evaluation process, integrating rigorous pairwise comparisons using the Saaty scale through logical reasoning, along with eigenvalue calculations, resulting in a criteria and strategy ranking. In evaluating carbon capture technologies for heavy industry, external support (regulatory adherence, global collaboration, and financial incentives) is crucial for technology evaluation, which carries the highest weight (21.3 %). Technology maturity and reliability follow closely (17.4 %), emphasizing the importance of proven track records. Carbon capture efficiency and environmental and health impacts share a relatively high weight (13.7 %). Scalability and integration with existing infrastructure carry moderate weights (7.8 %). Energy requirements are less critical (6.7 %), while the cost-effectiveness criterion has a relatively low weight (3.9 %). Duration of operation and public acceptance and social impact also carry low weights (3.9 %), creating a balanced evaluation considering both technical and socio-economic factors. Post-combustion capture excels with a high score, making it suitable for emission reduction in hard-to-abate industries. Pre-combustion capture and oxy-fuel combustion have moderate scores, indicating balanced performance. Direct Air Capture faces challenges, resulting in a lower score, while carbon mineralization and biomass co-firing with carbon capture receive the lowest scores, suggesting potential limitations. We discuss the impact of climate change on carbon capture technologies, the influence of critical materials, the practical implications for Moroccan industries such as Lafarge Holcim (cement), OCP (phosphate mining and petrochemical processing), and Sonasid (steel), as well as for emerging and industrialized economies, including hydrogen, ammonia, and kerosene production from fossil fuels.

Fixation of CO2 with Epoxides Catalyzed by Pincer-Type Azo-Aromatic Complexes of Cobalt as Catalysts

Employing a series of azo-aromatic pincer-type cobalt(II) complexes, 1-5, and an imine-based cobalt complex, 6, a highly efficient catalytic protocol for the cycloaddition of CO2 with epoxides at low pressure of CO2 is reported. The electron-withdrawing group-substituted ligands containing complexes 2 and 4 were most efficient. The catalytic protocol with 2 involved a synergistic participation of an azo-aromatic catalyst (0.1 mol %) and tetra-butyl ammonium iodide (TBAI), a cocatalyst (0.2 mol %) at 90 °C temperature, and 1 bar CO2 pressure. A very good conversion, high turnover number, and reusability were observed. Complex 4 worked directly in the reaction, and its efficiency was similar to the efficiency of 2 and TBAI. As 2 was synthesized from a cheaper CoCl2, 2 showed to be more stable than 4; the combination of 2 and TBAI was used for a detailed study. The imine-based complex 6 was less efficient than the corresponding azo-aromatic complex 5. The catalytic protocol was versatile. It was also very effective for the full conversion of bis-epoxides to bis-carbonates at only 2 bar of CO2 pressure in 24 h. The reaction mechanism was investigated using various spectroscopic and computational studies.

Evolution of Copolymers of Epoxides and CO2: Catalysts, Monomers, Architectures, and Applications

The copolymerization of CO2 and epoxides presents a transformative approach to converting greenhouse gases into aliphatic polycarbonates (CO2-PCs), thereby reducing the polymer industry's dependence on fossil resources. Over the past 50 years, a wide array of metallic catalysts, both heterogeneous and homogeneous, have been developed to achieve precise control over polymer selectivity, sequence, regio-, and stereoselectivity. This review details the evolution of metal-based catalysts, with a particular focus on the emergence of organoborane catalysts, and explores how these catalysts effectively address kinetic and thermodynamic challenges in CO2/epoxides copoly2merization. Advances in the synthesis of CO2-PCs with varied sequence and chain architectures through diverse polymerization protocols are examined, alongside the applications of functional CO2-PCs produced by incorporating different epoxides. The review also underscores the contributions of computational techniques to our understanding of copolymerization mechanisms and highlights recent advances in the closed-loop chemical recycling of CO2-sourced polycarbonates. Finally, the industrialization efforts of CO2-PCs are discussed, offering readers a comprehensive understanding of the evolution and future potential of epoxide copolymerization with CO2.

Reaction-induced unsaturated Mo oxycarbides afford highly active CO2 conversion catalysts

Sustainable CO2 conversion is crucial in curbing excess emissions. Molybdenum carbide catalysts have demonstrated excellent performances for catalytic CO2 conversion, but harsh carburization syntheses and poor stabilities make studies challenging. Here an unsaturated Mo oxide (Mo17O47) shows a high activity for the reverse water-gas shift reaction, without carburization pretreatments, and remains stable for 2,000 h at 600 °C. Flame spray pyrolysis synthesis and Ir promoter facilitate the formation of Mo17O47 and its in situ carburization during reaction. The reaction-induced cubic α-MoC with unsaturated Mo oxycarbide (MoOxCy) on the surface serves as the active sites that are crucial for catalysis. Mechanistic studies indicate that the C atom in CO2 inserts itself in the vacancy between two Mo atoms, and releases CO by taking another C atom from the oxycarbide to regenerate the vacancy, following a carbon cycle pathway. The design of Mo catalysts with unsaturated oxycarbide active sites affords new territory for high-temperature applications and provides alternative pathways for CO2 conversion.

Four-electron reduction of CO2: from formaldehyde and acetal synthesis to complex transformations

The expansive and dynamic field of the CO2 Reduction Reaction (CO2RR) seeks to harness CO2 as a sustainable carbon source or energy carrier. While significant progress has been made in two, six, and eight-electron reductions of CO2, the four-electron reduction remains understudied. This review fills this gap, comprehensively exploring CO2 reduction into formaldehyde (HCHO) or acetal-type compounds (EOCH2OE, with E = [Si], [B], [Zr], [U], [Y], [Nb], [Ta] or -R) using various CO2RR systems. These encompass (photo)electro-, bio-, and thermal reduction processes with diverse reductants. Formaldehyde, a versatile C1 product, is challenging to synthesize and isolate from the CO2RR. The review also discusses acetal compounds, emphasizing their significance as pathways to formaldehyde with distinct reactivity. Providing an overview of the state of four-electron CO2 reduction, this review highlights achievements, challenges, and the potential of the produced compounds - formaldehyde and acetals - as sustainable sources for valuable product synthesis, including chiral compounds.

DFT mechanistic study of the chemical fixation of CO2 by aziridine derivatives

Using density functional theory (DFT), we treat the reaction of coupling of CO2 with aziridine in gas phase, in the presence of water and of a green catalyst (NaBr). Computations show that, in gas phase, this ring-opening conversions to oxazolidinones initiates by coordinating a CO2 molecule to the nitrogen atom of the aziridine. Then, a nucleophilic interaction between one oxygen atom of the coordinated CO2 and the carbon atom of the aziridine occurs. For methyl substituted aziridine, two pathways are proposed leading either to 4-oxazolidinone or to 5-oxazolidinone. Besides, we show that the activation energy of this reaction reduces in aqueous solution, in the presence of a water molecule explicitly or NaBr catalyst. In addition, the corresponding reaction mechanisms and regioselectivity associated with this ring-opening conversions to oxazolidinones, in the presence of carbon dioxide are found to be influenced by solvent and catalyst. The present findings should allow better designing regioisomer oxazolidinones relevant for organic chemistry, medicinal and pharmacological applications.

Advances in Group VI Metal-Catalyzed Homogeneous Hydrogenation and Dehydrogenation Reactions

Transition metal-catalyzed homogeneous hydrogenation and dehydrogenation reactions for attaining plethora of organic scaffolds have evolved as a key domain of research in academia and industry. These protocols are atom-economic, greener, in line with the goal of sustainability, eventually pave the way for numerous novel environmentally benign methodologies. Appealing progress has been achieved in the realm of homogeneous catalysis utilizing noble metals. Owing to their high cost, less abundance along with toxicity issues led the scientific community to search for sustainable alternatives. In this context, earth- abundant base metals have gained substantial attention culminating enormous progress in recent years, predominantly with pincer-type complexes of nickel, cobalt, iron, and manganese. In this regard, group VI chromium, molybdenum and tungsten complexes have been overlooked and remain underdeveloped despite their earth-abundance and bio-compatibility. This review delineates a comprehensive overview in the arena of homogeneously catalysed (de)hydrogenation reactions using group VI base metals chromium, molybdenum, and tungsten till date. Various reactions have been described; hydrogenation, transfer hydrogenation, dehydrogenation, acceptorless dehydrogenative coupling, hydrogen auto transfer, along with their scope and brief mechanistic insights.

Biodegradable polycarbonates from lignocellulose based 4-pentenoic acid and carbon dioxide

The production of biodegradable polycarbonate by copolymerizing CO₂ with epoxides has emerged as an effective method to utilize CO₂ in response to growing concerns about CO₂ emissions and plastic pollution. Previous studies have mainly focused on the preparation of CO₂-based polycarbonates from petrochemical-derived propylene oxide (PO) or cyclohexene oxide (CHO). However, to reduce dependence on fossil fuels, the development of 100% bio-based polymers has gained attention in polymer synthesis. Herein, we reported the synthesis of glycidyl 4-pentenoate (GPA) from lignocellulose based 4-pentenoic acid (4-PA), which was further copolymerized with CO₂ using a binary catalyst SalenCoCl/PPNCl to produce bio-based polycarbonates with vinyl side chains and molecular weights up to 17.1 kg/mol. Introducing a third monomer, PO, allows for the synthesis of the GPA/PO/CO₂ terpolymer, and the glass transition temperature (T _g) of the terpolymer can be adjusted from 2°C to 19°C by controlling the molar feeding ratio of GPA to PO from 7:3 to 3:7. Additionally, post-modification of the vinyl side chains enables the production of functional polycarbonates, providing a novel approach to the preparation of bio-based materials with diverse side chains and functions.

CO2 Decomposition in Microwave Discharge Created in Liquid Hydrocarbon

The task of CO2 decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO2 is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H2, C2H2, C2H4, CH4, CO2, and CO. No oxygen was found in the products. The mechanisms of CO2 decomposition in the discharge are considered. The formation of H2 occurs simultaneously with the decomposition of CO2 in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh.

Supercritical fluid-assisted modification combined with the resynthesis of SmCoO3 as an effective tool to enhance the long-term performance of SmCoO3-derived catalysts for the dry reforming of methane to syngas

The dry reforming of methane to syngas (DRM) is of increasing significance concerning, first, the production of raw materials for commercial organic/petrochemical syntheses and for hydrogen energetic, and, second, the utilization of two most harmful greenhouse gases. Herein, new SmCoO₃-based DRM catalysts derived from heterometallic precursors and operated without preliminary reduction are reported. For the first time, the effect of supercritical fluids-assisted modification of the SmCoO₃-derived catalysts combined with the re-oxidation of spent catalysts to SmCoO₃ onto its long-term performance was studied. In particular, the modification of heterometallic precursors by supercritical antisolvent precipitation (SAS) considerably decreases coke formation upon the exploitation of the derived SmCoO₃ sample. Moreover, the re-oxidation of the corresponding spent catalysts followed by pre-heating under N₂ affords catalysts that stably provide syngas yields of 88-95% for at least 41 h at 900 °C. The achieved yields are among the highest ones currently reported for DRM catalysts derived from both LnMO₃ perovskites and related oxides. The origins of such good performance are discussed. Given the simplicity and availability of all the applied methods and chemicals, this result opens prospects for exploiting SAS in the design of efficient DRM catalysts.

Tunable and recyclable polyesters from CO2 and butadiene

Carbon dioxide is inexpensive and abundant, and its prevalence as waste makes it attractive as a sustainable chemical feedstock. Although there are examples of copolymerizations of CO₂ with high-energy monomers, the direct copolymerization of CO₂ with olefins has not been reported. Here an alternative route to functionalizable, recyclable polyesters derived from CO₂, butadiene and hydrogen via an intermediary lactone, 3-ethyl-6-vinyltetrahydro-2H-pyran-2-one, is described. Catalytic ring-opening polymerization of the lactone by 1,5,7-triazabicyclo[4.4.0]dec-5-ene yields polyesters with molar masses up to 13.6 kg mol^-1 and pendent vinyl side chains that can undergo post-polymerization functionalization. The polymer has a low ceiling temperature of 138 °C, allowing for facile chemical recycling, and is inherently biodegradable under aerobic aqueous conditions (OECD-301B protocol). These results show that a well-defined polyester can be derived from CO₂, olefins and hydrogen, expanding access to new polymer feedstocks that were once considered unfeasible.

Silver-Catalyzed Carbon Dioxide Fixation on Alkynylindoles

A silver-catalyzed carbon dioxide fixation reaction into 2-alkynylindole derivatives was developed to afford tricyclic indoles. Carbon dioxide was selectively fixed on the N atom of the indole, and only 6-endo-dig cyclization proceeded under mild reaction conditions. Carboxylation on C3 of the indole was not observed. This method was applicable for a variety of 2-alkynylindoles, and the corresponding products were obtained in high yields without the production of side products.

Cyclic Carbonate Synthesis from Epoxides and CO2 Catalyzed by Aluminum-Salen Complexes Bearing a nido-C2B9 Carborane Ligand

The active and well-designed Schiff base ligands are considered "privileged ligands". The so-called salen ligands, i.e., the tetradentate [O, N, N, O] bis-Schiff base ligands, have also found broad applications in many homogeneous catalytic reactions. Modification of the salen ligands has concentrated on altering the substituents in the phenolate rings and variations in the diamine backbones. Herein, o-carborane-supported salen ligands (2) were designed and prepared. A series of aluminum-salen complexes (3·(sol)₂), which were supported by the nido-C₂B₉ carborane anions, were synthesized. These Al(III) complexes showed high activities (TOF up to 1500 h^-1) in catalyzing the cycloaddition of epoxides and CO₂ at atmospheric pressure and near room temperature. Complexes 3·(sol)₂ are one of the rare examples of Al-based catalysts capable of promoting cycloaddition at 1 bar pressure of CO₂. Density functional theory (DFT) studies combined with the catalytic results reveal that the catalytic cycles occur on two axial sites of the Al(III) center.

Synthesis, characterization and application of oxovanadium(iv) complexes with [NNO] donor ligands: X-ray structures of their corresponding dioxovanadium(v) complexes

Two oxovanadium(iv) complexes ligated by [NNO] donor ligands have been synthesized and characterized by ESI-HRMS, elemental (CHN) analysis and spectroscopic (UV-Vis, IR and EPR) techniques. Block shaped brown crystals from the methanolic solutions of these oxovanadium(iv) complexes were obtained during the crystallization process. Crystallographic structures of the resulting crystals revealed that the original oxovanadium(iv) complexes have been transformed into new dioxovanadium(v) complexes with concomitant oxidation of VIV to VV. The original oxovanadium(iv) complexes have been identified to be an efficient catalyst for the CO2 cycloaddition reaction with epoxides resulting up to 100% cyclic carbonate products. The geometries of oxovanadium(iv) complexes are optimized by the density functional theory (DFT) calculations at the uB3LYP/6-31G**/LANL2DZ level of theory. The geometry and structural parameters of optimized structures of oxovanadium(iv) complexes are in excellent agreement with the parameters of X-ray structures of their dioxovanadium(v) counterparts. Further, TD-DFT and Spin Density Plots for the oxovanadium(iv) complexes are performed in order to get more insights about their electronic absorption and EPR spectroscopies, respectively.

Catalytic reduction of carbon dioxide by a zinc hydride compound, [Tptm]ZnH, and conversion to the methanol level

The zinc hydride compound, [Tptm]ZnH, may achieve the reduction of CO₂ by (RO)₃SiH (R = Me, Et) to the methanol oxidation level, (MeO)_xSi(OR)_4-x, via the formate species, HCO₂Si(OR)₃. However, because insertion of CO₂ into the Zn-H bond is more facile than insertion of HCO₂Si(OR)₃, conversion of HCO₂Si(OR)₃ to the methanol level only occurs to a significant extent in the absence of CO₂.

Novel porous organic polymers functionalized by metalloporphyrin and phosphonium salts for the efficient synergistic catalysis of CO2 conversion under mild conditions

Metalloporphyrin- and phosphonium-functionalized porous organic polymers (POPs) were fabricated successfully via a post-synthesis modification strategy, which were demonstrated to be efficient heterogeneous catalysts for CO2 conversion.

Interfacial band bending induced charge-transfer regulation over Ag@ZIF-8@g-C3N4 to boost photocatalytic CO2 reduction into syngas

The use of the AZC-10 heterostructure enables excellent syngas production rates of 4076.4 μmol gcatalyst−1 h−1 and 3326.55 μmol gcatalyst−1 h−1 for CO and H2, respectively, much higher than other reported photocatalysts.

Carboxylation of Alkenes and Alkynes Using CO2 as a Reagent: An Overview

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CO2 fixation reactions are of paramount interest both from economical and environmental perspectives. As an abundant, non-toxic, and renewable C1 feedstock, CO2 can be utilized for the synthesis of fuels and commodity chemicals under elevated reaction conditions. The major challenge in the CO2 utilization reactions is its chemical inertness due to high thermodynamic stability and kinetic barrier. The carboxylation of unsaturated hydrocarbons with CO2 is an important transformation as it forms high-value reaction products having industrial as well as medicinal importance. This mini-review is mainly focused on the recent developments in the homogeneously and heterogeneously catalyzed carboxylation of alkenes and alkynes by using carbon dioxide as a reagent. We have highlighted various types of carboxylation reactions of alkenes and alkynes involving different catalytic systems, which comprise mainly C-H bond activation, hydrocarboxylation, carbocarboxylation, heterocarboxylation, and ring-closing carboxylation, including visible-light assisted synthesis processes. The mechanistic pathways of these carboxylation reactions have been described. Moreover, challenges and future perspectives of these carboxylation reactions are discussed.

Ligand and solvent effects on CO2 insertion into group 10 metal alkyl bonds

The insertion of carbon dioxide into metal element σ-bonds is an important elementary step in many catalytic reactions for carbon dioxide valorization. Here, the insertion of carbon dioxide into a family of group 10 alkyl complexes of the type (^RPBP)M(CH₃) (^RPBP = B(NCH₂PR₂)₂C₆H₄⁻; R = Cy or ^tBu; M = Ni or Pd) to generate κ¹-acetate complexes of the form (^RPBP)M{OC(O)CH₃} is investigated. This involved the preparation and characterization of a number of new complexes supported by the unusual ^RPBP ligand, which features a central boryl donor that exerts a strong trans-influence, and the identification of a new decomposition pathway that results in C–B bond formation. In contrast to other group 10 methyl complexes supported by pincer ligands, carbon dioxide insertion into (^RPBP)M(CH₃) is facile and occurs at room temperature because of the high trans-influence of the boryl donor. Given the mild conditions for carbon dioxide insertion, we perform a rare kinetic study on carbon dioxide insertion into a late-transition metal alkyl species using (^tBuPBP)Pd(CH₃). These studies demonstrate that the Dimroth–Reichardt parameter for a solvent correlates with the rate of carbon dioxide insertion and that Lewis acids do not promote insertion. DFT calculations indicate that insertion into (^tBuPBP)M(CH₃) (M = Ni or Pd) proceeds via an S_E2 mechanism and we compare the reaction pathway for carbon dioxide insertion into group 10 methyl complexes with insertion into group 10 hydrides. Overall, this work provides fundamental insight that will be valuable for the development of improved and new catalysts for carbon dioxide utilization.

The kinetics of carbon dioxide insertion into a pincer-supported palladium methyl complex are studied. The complex inserts carbon dioxide at room temperature, and we explore both solvent and Lewis acid effects on carbon dioxide insertion.

Zn(II)-Functionalized COF as a Recyclable Catalyst for the Sustainable Synthesis of Cyclic Carbonates and Cyclic Carbamates from Atmospheric CO2

A simple covalent organic framework (COF) bearing β-ketoenamine units as a potential heterogeneous ligand for ZnII-catalyzed fixation and transformation of CO2 into value-added chemicals is reported. Catalytic investigations convincingly demonstrated...

Polyamine-functionalized imidazolyl poly(ionic liquid)s for the efficient conversion of CO2 into cyclic carbonates

The synergistic effect of polyamine groups and nucleophile (Br−) significantly improved the catalytic performance of N4-PIL-2, which can convert epoxides into cyclic carbonates with excellent yields and selectivity under ambient pressure.

Selective Conversion of CO2 into Cyclic Carbonate on Atom Level Catalysts

The conversion of carbon dioxide (CO₂) into organic carbonates under ambient temperatures and pressures with high conversion and selectivity still faces a great challenge. The zerovalent atomic catalysts (ACs), featuring accurate structure and valence states, provide a new and accurate model system for catalysis. Herein we developed a general preadsorption-reduction strategy to synthesize zerovalent cobalt AC on graphdiyne (Co⁰/GDY). The Co⁰/GDY ACs were used for efficient and selective CO₂ fixation. We were surprised to find that Co⁰/GDY ACs reached nearly 100% conversion at 80 °C and 1 atm in CO₂ fixation and with a significantly high turnover frequency (TOF) of 3024.8 h^-1, which is almost several orders larger than that of benchmarked catalysts. Such high conversion and selectivity represent the advantages of emerging catalysts.

Accessing Divergent Main-Chain-Functionalized Polyethylenes via Copolymerization of Ethylene with a CO2/Butadiene-Derived Lactone

Carbon dioxide (CO₂) has been used as a sustainable comonomer in the synthesis of different functional polymers including polycarbonates, polyurea, and polyurethane. Until today, despite the great interest, little success has been made for incorporating CO₂ into the most widely used polyethylene materials. Herein, we report the incorporation of CO₂ to polyethylenes through the copolymerization of ethylene with a CO₂/butadiene-derived lactone, 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVP). Two-types of main-chain-functionalized polyethylenes can be synthesized through different copolymerization strategies. Palladium-catalyzed coordination/insertion copolymerization furnished polyethylenes bearing unsaturated lactones, while radical copolymerization afforded polyethylenes bearing bicyclic lactones. Modification of the polyethylene chains was successfully accomplished through Michael addition or aminolysis. This highly versatile copolymerization protocol provides access to a diverse range of polyethylene materials made from ethylene, CO₂, and 1,3-butadiene.

Anchoring Ag(I) into Nitro-Functionalized Metal-Organic Frameworks: Effectively Catalyzing Cycloaddition of CO2 with Propargylic Alcohols under Mild Conditions

Carboxylative cyclization of propargylic alcohols with CO₂ is significant in synthetic chemistry, but harsh conditions are often needed according to reported results. Herein, a new stable nitro-functionalized metal-organic framework (MOF) of {[Co₃(L)₂(bpy)₄(H₂O)₂]·DMF·H₂O·bpy}_n (1) was fabricated through the solvothermal reaction, which exhibited excellent stability in acid and basic solutions. Owing to the porous structure, unsaturated metal sites, and uncoordinated 4,4'-bpy ligands, 1 can serve as an excellent platform for catalytic applications. Hence, Ag(I) ions were incorporated in 1 through a postsynthetic method, and the as-synthesized Ag-1 catalyst with low metal loading (0.64 mol %) displayed excellent catalytic performance in the chemical fixation of CO₂ with alkynols under room temperature and atmospheric pressure. The results of ¹H NMR analyses further confirmed that Ag-1 can efficiently activate hydroxyl groups and promote the reaction. Moreover, the turnover frequency (TOF) of the Ag-1 catalyst can reach 262 h^-1 in a short period of time, which is a high TOF value among the state-of-the-art MOF-based catalysts for catalyzing cycloaddition of CO₂ with propargylic alcohols.

Distinct chemical fixation of CO2 enabled by exotic gold nanoclusters

Atomically precise metal nanoclusters, especially the metal nanoclusters with an exotic core structure, have given rise to a great deal of interest in catalysis, attributing to their well-defined structures at the atomic level and consequently unique electronic properties. Herein, the catalytic performances of three gold nanoclusters, such as Au₃₈S₂(S-Adm)₂₀ with a body-centered cubic (bcc) kernel structure, Au₃₀(S-Adm)₁₈ with a hexagonal close-packed (hcp) core structure, and Au₂₁(S-Adm)₁₅ with a face-centered cubic (fcc) kernel structure, were attempted for the CO₂ cycloaddition with epoxides toward cyclic carbonates. Due to the excess positive charge with a strong Lewis acidity and large chemical adsorption capacity, the bcc-Au₃₈S₂(S-Adm)₂₀ nanocluster outperformed the hcp-Au₃₀(S-Adm)₁₈ and fcc-Au₂₁(S-Adm)₁₅ nanoclusters. Additionally, the synergistic effect between the gold nanocluster and co-catalyst played a crucial role in CO₂ cycloaddition.