Transformation of carbon dioxide

Modulating Carbon Dioxide Storage by Facile Synthesis of Nanoporous Pillared-Layered Metal-Organic Framework with Different Synthetic Routes

A Zn(II)-based paddle wheel pillared-layered metal-organic framework, [Zn₂ (DBrTPA)₂(DABCO)].(DMF)₂ (MUT-4), containing 1,4-diazabicyclo[2.2.2]octane (DABCO) and 2,5-dibromoterephthalic acid (DBrTPA) has been successfully synthesized with different synthetic methods, including solvothermal, sonochemical, and their mixing methods, some of which are energy-efficient, rapid, and room-temperature synthetic procedures. Structural characterization of MUT-4 with single-crystal X-ray crystallography showed that it crystallizes in the tetragonal I4₁/acd space group. MUT-4 has shown higher performance than known MOFs in the CO₂ adsorption such as UiO-66, UiO-66-NH₂, UiO-66-NO₂, PCN-66, ZIF-68, UiO-67, bio-MOF-11, MIL-101, MOF-177, ZIF-8, and ZIF-82. It has shown even better CO₂ adsorption performance in comparison to the previously reported DMOFs such as DMOF-1 and other DMOF analogues such as NO₂-DMOF-1, NH₂-DMOF-1, Br-DMOF-1, and Azo-DMOF-1. Furthermore, it has performed even better than modified known MOFs. Also, the carbon dioxide storage capacity of MUT-4 obtained using several different synthetic routes shows a significant difference. Thus, this study exhibited that CO₂ gas adsorption of MUT-4 could be modulated by optimizing its synthetic methods.

Sr[C2O5] is an Inorganic Pyrocarbonate Salt with [C2O5]2- Complex Anions

The synthesis of a novel type of carbonate, namely of the inorganic pyrocarbonate salt Sr[C₂O₅], which contains isolated [C₂O₅]^2--groups, significantly extends the crystal chemistry of inorganic carbonates beyond the established sp²- and sp³-carbonates. We synthesized Sr[C₂O₅] in a laser-heated diamond anvil cell by reacting Sr[CO₃] with CO₂. By single crystal synchrotron diffraction, Raman spectroscopy, and density functional theory (DFT) calculations, we show that it is a pyrocarbonate salt. Sr[C₂O₅] is the first member of a novel family of inorganic carbonates. We predict, based on DFT calculations, that further inorganic pyrocarbonates can be obtained and that these will be relevant to geoscience and may provide a better understanding of reactions converting CO₂ into useful inorganic compounds.

Visible-Light-Enabled Carboxylation of Benzyl Alcohol Derivatives with CO2 Using a Palladium/Iridium Dual Catalyst

A highly efficient carboxylation of benzyl alcohol derivatives with CO₂ using a palladium/iridium dual catalyst under visible-light irradiation was developed. A wide range of benzyl alcohol derivatives could be employed to provide benzylic carboxylic acids in moderate to high yields. Mechanistic studies indicated that the oxidative addition of benzyl alcohol derivatives was possibly the rate-determining-step. It was also found that a switchable site-selective carboxylation between benzylic C-O and aryl C-Cl moieties could be achieved simply by changing the palladium catalyst.

Organocatalytic selective coupling of episulfides with carbon disulfide for the synthesis of poly(trithiocarbonate)s and cyclic trithiocarbonates

Selective coupling of CS2 with episulfides affords perfectly alternating poly(trithiocarbonate)s or cyclic trithiocarbonates upon the onium salts used.

Nanomaterials and hybrid nanocomposites for CO2 capture and utilization: environmental and energy sustainability

Anthropogenic carbon dioxide (CO₂) emissions have dramatically increased since the industrial revolution, building up in the atmosphere and causing global warming. Sustainable CO₂ capture, utilization, and storage (CCUS) techniques are required, and materials and technologies for CO₂ capture, conversion, and utilization are of interest. Different CCUS methods such as adsorption, absorption, biochemical, and membrane methods are being developed. Besides, there has been a good advancement in CO₂ conversion into viable products, such as photoreduction of CO₂ using sunlight into hydrocarbon fuels, including methane and methanol, which is a promising method to use CO₂ as fuel feedstock using the advantages of solar energy. There are several methods and various materials used for CO₂ conversion. Also, efficient nanostructured catalysts are used for CO₂ photoreduction. This review discusses the sources of CO₂ emission, the strategies for minimizing CO₂ emissions, and CO₂ sequestration. In addition, the review highlights the technologies for CO₂ capture, separation, and storage. Two categories, non-conversion utilization (direct use) of CO₂ and conversion of CO₂ to chemicals and energy products, are used to classify different forms of CO₂ utilization. Direct utilization of CO₂ includes enhanced oil and gas recovery, welding, foaming, and propellants, and the use of supercritical CO₂ as a solvent. The conversion of CO₂ into chemicals and energy products via chemical processes and photosynthesis is a promising way to reduce CO₂ emissions and generate more economically valuable chemicals. Different catalytic systems, such as inorganics, organics, biological, and hybrid systems, are provided. Lastly, a summary and perspectives on this emerging research field are presented.

Anthropogenic carbon dioxide (CO₂) emissions have dramatically increased since the industrial revolution, building up in the atmosphere and causing global warming.

Group 6 transition metal-based molecular complexes for sustainable catalytic CO2 activation

CO2 activation is one of the key steps towards CO2 mitigation. In this context, the group 6 transition metal-based molecular catalysts can lead the way.

Recent advancements in visible-light-driven carboxylation with carbon dioxide

Carbon dioxide as a classic C1 source has long been investigated in organic synthetic chemistry. Diverse catalytic methods for CO2 activation were reported in the past several decades. In this...

Strategic design of a bifunctional Ag(i)-grafted NHC-MOF for efficient chemical fixation of CO2 from a dilute gas under ambient conditions

Facile grafting of catalytically active Ag(i) into CO2-philic NHC-MOF for simultaneous capture and conversion of CO2 from dilute gas to value-added α-alkylidene cyclic carbonate and oxazolidinones under mild conditions is demonstrated.

Catalyst-free CO2 Hydrogenation with BH3NH3 in Water: DFT Mechanistic Insights

Extensive DFT calculations show that BH3NH3 may transfer dihydrogen to CO2 rather than HCO3- in water over a barrier of 25.9 kcal/mol, followed by faster hydride transfer from borate anions...

Controllable methylenation with ethylene glycol as the methylene source: bridging enaminones and synthesis of tetrahydropyrimidines

Controllable methylenation using renewable ethylene glycol as the methylene source has been developed for the introduction of one or two methylene building blocks.

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.

Facile synthesis, structure and properties of CO2-sourced poly(thioether-co-carbonate)s containing acetyl pendants via thio-ene click polymerization

Synthetic transformation of CO2 into di- and trivinyl carbonates allows for photo-initiated thio-ene polymerization leading to sequence controlled poly(thioether-carbonate)s.

Photocatalytic activation and utilization of CO2 for N-formylation of amines promoted by a zinc(ii) phthalocyanine grafted on g-carbon nitride hybrid

Photochemical conversion of various amines to N-formamides using CO2 under ambient conditions with a hybrid photocatalyst composed of zinc phthalocyanine grafted to g-carbon nitride in high to excellent yields has been described.

Challenges and recent advancements in the transformation of CO2 into carboxylic acids: straightforward assembly with homogeneous 3d metals

Transformation of carbon dioxide (CO2) into valuable organic carboxylic acids is essential for maintaining sustainability. In this review, such CO2 thermo-, photo- and electrochemical transformations under 3d-transition metal catalysis are described from 2017 until 2022.

Photocatalytic synthesis of tetra-substituted furans promoted by carbon dioxide

A CO2-promoted transition metal-free photocatalytic synthesis of tetra-substituted furan derivatives from 1,3-diketones as the only starting material.

Carboxylation of terminal alkynes with CO2 catalyzed by imidazolium-bridged bis(phenolato) rare-earth metal complexes

An imidazolium-bridged bis(phenolato) yttrium complex shows excellent catalytic reactivity in the direct carboxylation of terminal alkynes and further one-pot three-component esterification.

Ru Nanoparticle Functionalized Silica Nanotubes as a Catalyst for CO2 Hydrogenation Reaction

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The catalytic display of supported heterogeneous catalysts is essentially reliant on their constitutive elements, including active species and supports. Accordingly, the scheme and development of active catalysts with synergistically enhanced outcomes between active sites and supports are of high importance. A simple NaBH4 reduction method was used to synthesize cylindrical amine-functionalized silica nanotubes supported Ru catalyst (ASNT@Ru catalyst), including amine functionality. The physicochemical properties of the material were analyzed by various analytical methods such as SEM-TEM analysis, N2 physisorption, ICP-OES, XPS, etc., and all the data were found in good agreement with each other. Amine-free SNT support using the calcination process was also synthesized to examine the effect of amine in ASNT support on the uniform Ru dispersion. Taking advantage of the fundamental physical and chemical properties of ASNT support and well-distributed Ru NPs, the ASNT@Ru catalyst was utilized for CO2 hydrogenation reaction, which gave excellent catalytic activity/ stability in terms of a good quantity of the formic. Catalysts recycling was recorded five times, and formic acid was obtained in good quantity.

Carboxylation of sodium arylsulfinates with CO2 over mesoporous K-Cu-20TiO2

A mesoporous ternary metal oxide (K-Cu-20TiO₂) from a simple sol–gel method was prepared to catalyze heterogeneously the carboxylation reaction of various sodium arylsulfinates under atmospheric carbon dioxide. The catalyst showed excellent selectivity and good functional group tolerance to carboxylation recycle. The oxidation state of active copper(i) by characterization using FTIR, XRD, TG, XPS and TEM techniques proved to be efficacious to conduct atom economical reactions.

A mesoporous ternary metal oxide (K-Cu-20TiO₂) from a simple sol–gel method was prepared to catalyze heterogeneously the carboxylation reaction of various sodium arylsulfinates under atmospheric carbon dioxide.

CO2 Cleavage Reaction Driven by Alkylidyne Complexes of Group 6 Metals and Uranium: A Density Functional Theory Study on Energetics, Reaction Mechanism, and Structural/Bonding Properties

Designing novel catalysts is essential for the efficient conversion of metal alkylidyne into metal oxo ketene complexes in the presence of CO₂, which to some extent resolves the environmental concerns of the ever-increasing carbon emission. In this regard, a series of metal alkylidyne complexes, [b-ONO]M≡CCH₃(THF)₂ ([b-ONO] = {(C₆H₄[C(CF₃)₂O])₂N}^3-; M = Cr, Mo, W, and U), have been comprehensively studied by relativistic density functional theory calculations. The calculated thermodynamics and kinetics unravel that the tungsten complex is capable of catalyzing the CO₂ cleavage reaction, agreeing with the experimental findings for its analogue. Interestingly, the uranium complex shows superior catalytic performance because of the associated considerably lower energy barrier and larger reaction rate constant. The M≡C moiety in the complexes turns out to be the active site for the [2 + 2] cyclic addition. In contrast, complexes of Cr and Mo could not offer good catalytic performance. Along the reaction coordinate, the M-C (M = Cr, Mo, W, and U) bond regularly transforms from triple to double to single bonds; concomitantly, the newly formed M-O in the product is identified to have a triple-bond character. The catalytic reactions have been extensively explained and addressed by geometric/electronic structures and bonding analyses.

Recent Advances in the Catalytic Applications of Lanthanide-Oxo Clusters

Lanthanide-oxo/hydroxo clusters (LOCs) in this mini-review refer to polynuclear complexes featuring a polyhedral metal-oxo/hydroxo cluster core of lanthanide ions exclusively or with coexisting 3d metal ions. We summarize herein the recent works using this unique family of cluster complexes for catalysis; this aspect of research stands in stark contrast to their extensively studied synthetic and structural chemistry as well as the much-researched magnetic properties. Following a brief introduction of the synthetic strategies for these clusters, pertinent results from available literature reports are surveyed and discussed according to the types of catalyzed reactions. Particular attention was paid to the selection of a cluster catalyst for a specific type of reactions as well as the corresponding reaction mechanism. To the end, the advantages and challenges in utilizing LOCs as multifunctional catalysts are summarized, and possible future research directions are proposed.

Visible-Light Photoredox-Catalyzed Dicarbofunctionalization of Styrenes with Oxime Esters and CO2: Multicomponent Reactions toward Cyanocarboxylic Acids and γ-Keto Acids

A photoredox-catalyzed dicarbofunctionalization of styrenes with oxime esters and CO₂ has been achieved. Notably, a series of four-, five-, or six-membered cyclic ketone oximes worked well to furnish a wide range of ε-, ζ-, and η-cyanocarboxylic acids in good yields. Furthermore, a series of γ-keto acids also could be obtained by employing acyclic ketone oxime esters as the carbonyl radical precursor. It provides convergent access to diverse biologically important cyanocarboxylic and γ-keto acids.

Green Carbon Science: Efficient Carbon Resource Processing, Utilization, and Recycling Towards Carbon Neutrality

Green carbon science is defined as "Study and optimization of the transformation of carbon containing compounds and the relevant processes involved in the entire carbon cycle from carbon resource processing, carbon energy utilization, and carbon recycling to use carbon resources efficiently and minimize the net CO2 emission." [1] Green carbon science is related closely to carbon neutrality, and the relevant fields have developed quickly in the last decade. In this Minireview, we proposed the concept of carbon energy index, and the recent progresses in petroleum refining, production of liquid fuels, chemicals, and materials using coal, methane, CO2, biomass, and waste plastics are highlighted in combination with green carbon science, and an outlook for these important fields is provided in the final section.

A DFT-design of single component bifunctional organocatalysts for the carbon dioxide/propylene oxide coupling reaction

The aim of this work is to develop single-component bifunctional organic catalysts capable of effective coupling reactions between CO2 and propylene epoxide (PO) under mild conditions using density functional theory (DFT) calculations. The dual functionalities of the target catalysts come from their inclusion of a hydroxyl-containing electrophile and the nucleophilicity of iodide ion. In this respect, a series of hydroxyl-functionalized quaternary onium-based ionic liquids were studied using M062X-D3/def2-TZVP//M062X-D3/def2-SVPP model chemistry. The design of catalysts was based on tailoring two structural factors; the first one is the onium center of pnictogens (N, P, As, Sb and Bi), and the second one is the number of hydrogen bond donor groups (n = 1-3). The proposed catalysts were examined by investigation of their catalytic mechanisms to afford the cyclic carbonate. Additionally, the highest active transition state, along with the potential energy difference, was examined using non-covalent interaction (NCI) analysis. Also, the activation strain model (ASM) was used to explain the kinetic behavior of PO activation. The findings showed that the ring-opening step of PO is always the critical step of the reaction. Among the suggested catalysts, the results indicated that the dihydroxyl ammonium-based catalyst (2OH-NI) is a good choice for this catalysis under mild and solvent-free conditions.

Sequential Selective C-H and C(sp3 )-+ P Bond Functionalizations: An Entry to Bioactive Arylated Scaffolds

Organophosphonium salts containing C(sp³ )-⁺ P bonds are among the most utilized reagents in organic synthesis for constructing C-C double bonds. However, their use as C-selective electrophilic groups is rare. Here, we explore an efficient and general transition-metal-free method for sequential chemo- and regioselective C-H and C(sp³ )-⁺ P bond functionalizations. In the present study, C-H alkylation resulting in the synthesis of benzhydryl triarylphosphonium salts was achieved by one-pot, four-component cross-coupling reactions of simple and commercially available starting materials. The utility of the resulting phosphonium salt building blocks was demonstrated by the chemoselective post-functionalization of benzylic C(sp³ )-⁺ PPh₃ groups to achieve aminations, thiolations, and arylations. In this way, benzhydrylamines, benzhydrylthioethers, and triarylmethanes, structural motifs that are present in many pharmaceuticals and agrochemicals, are readily accessed. These include the synthesis of two anticancer agents from simple materials in only two to three steps. Additionally, a protocol for late-stage functionalization of bioactive drugs has been developed using benzhydrylphosphonium salts. This new approach should provide novel transformations for application in both academic and pharmaceutical research.

Selective Reduction of CO2 to a Tantalum Formate Complex and Release of Methyl Formate from the Tantalum(V) Center

A cyclometalated NHC-coordinated hydrido tantalum alkoxide was found to selectively react with CO₂ to afford the genuine tantalum formate (NHC)(HCOO)Ta(OR_F)₃ with OR_F = OC(CF₃)₂CH₃. In the solid state, the presence of a κ²-O,O-formate moiety was established by single-crystal X-ray diffraction and ATR-IR spectroscopy, while NMR experiments and DFT modeling studies suggest that the κ¹-O-coordination mode is preferred in solution. Despite the accessibility of the latter κ¹-O-formate in solution, no over-reduction to a dinuclear methylene diolate was observed. Upon treatment with MeOTf, the κ¹-O-formate was methylated selectively, which led to the formation of a tantalum triflate complex along with methyl formate. This is a rare example in which a value-added oxygen-containing organic product (here HCOOMe) is released from an oxophilic early transition metal (here Ta^V).

Accessing Organonitrogen Compounds via C-N Coupling in Electrocatalytic CO2 Reduction

Given the limited product variety of electrocatalytic CO₂ reduction reactions solely from CO₂ and H₂O as the reactants, it is desirable to expand the product scope by introducing additional reactants that provide elemental diversity. The integration of inorganic heteroatom-containing reactants into electrocatalytic CO₂ reduction could, in principle, enable the sustainable synthesis of valuable products, such as organonitrogen compounds, which have widespread applications but typically rely on NH₃ derived from the energy-intensive and fossil-fuel-dependent Haber-Bosch process for their industrial-scale production. In this Perspective, research progress toward building C-N bonds in N-integrated electrocatalytic CO₂ reduction is highlighted, and the electrosyntheses of urea, acetamides, and amines are examined from the standpoints of reactivity, catalyst structure, and, most fundamentally, mechanism. Mechanistic discussions of C-N coupling in these advances are emphasized and critically evaluated, with the aim of directing future investigations on improving the product yield and broadening the product scope of N-integrated electrocatalytic CO₂ reduction.

Electrochemical Reductive N-Methylation with CO2 Enabled by a Molecular Catalyst

The development of benign methylation reactions utilizing CO₂ as a one-carbon building block would enable a more sustainable chemical industry. Electrochemical CO₂ reduction has been extensively studied, but its application for reductive methylation reactions remains out of the scope of current electrocatalysis. Here, we report the first electrochemical reductive N-methylation reaction with CO₂ and demonstrate its compatibility with amines, hydroxylamines, and hydrazine. Catalyzed by cobalt phthalocyanine molecules supported on carbon nanotubes, the N-methylation reaction proceeds in aqueous media via the chemical condensation of an electrophilic carbon intermediate, proposed to be adsorbed or near-electrode formaldehyde formed from the four-electron reduction of CO₂, with nucleophilic nitrogenous reactants and subsequent reduction. By comparing various amines, we discover that the nucleophilicity of the amine reactant is a descriptor for the C-N coupling efficacy. We extend the scope of the reaction to be compatible with cheap and abundant nitro-compounds by developing a cascade reduction process in which CO₂ and nitro-compounds are reduced concurrently to yield N-methylamines with high monomethylation selectivity via the overall transfer of 12 electrons and 12 protons.

Reaction of potassium phosphide KP(iPr)Ter with chalcogens, heteroallenes and an acyl chloride

The reactivity of the secondary phosphide KP(iPr)Ter (1) (Ter = 2,6-bis-(2,4,6-trimethylphenyl)phenyl) toward small molecules is reported. Phosphide 1 displays distinct nucleophilic character and reacts selectively with chalcogens (S₈, Se_x), heteroallenes (CO₂, nPrNCS), and an acyl chloride (AdCOCl) to give the corresponding dichalcogenophosphinates (2a, 3), phosphanyl formate (5), thiocarbamoylphosphane (6a), or acylphosphane (7a), respectively. Furthermore the follow-up chemistry of these products was investigated. 2a was converted to a PSPS ligand (2b) which forms a Au(I) complex (2c) with (Me₂S)AuCl. Likewise, a gold complex of 7a was prepared. All species were isolated and fully characterized.

Liquid “Syngas” Based on Supercritical Water and Graphite Oxide/TiO2 Composite as Catalyst for CO2 to Organic Conversion

The conversion of carbon monoxide into organic substances is one of the top topics of modern science due to the development of industry and the climate changes caused by it on the one hand, and the possibility of obtaining an economic effect on the other, as it could allow for partial recovery of fuels. A problem in this regard has always been the low solubility of CO2 in water, which eliminated the possibility of easy converting carbon dioxide into the liquid. The development of research on water critical states revealed the fact that water in a subcritical state has a much higher ability to dissolve gases. And this effect was used to obtain the "liquid synthesis gas" model presented in this paper. Equally important was the selection of an appropriate catalyst that would increase the efficiency of the conversion process by generating hydrogen in the system under the influence of cold plasma. In this work we present the studies of transformation of CO2 dissolved in supercritical water using partially reduced graphite oxide—nanometric titania composite (RGO-TiO2) as catalyst, due to the ability of RGO to generate hydrogen in the water environment (water splitting) under the influence of various physical factors, especially cold plasma. The RGO catalyst was stabilized with titanium oxide to obtain higher activity at lower RGO concentrations in the system. Therefore, research on conversions was preceded by a thorough analysis of CO2 solubility in supercritical water, as well as an analysis of the structural, morphological, and spectroscopic properties of the catalyst.

Graphic Abstract

General scheme of cold plasma reactor.