CO Insertion Research Articles

Melamine-based nitrogen-heterocyclic polymer networks as efficient platforms for CO2 adsorption and conversion

Constructing green and efficient porous material platforms for carbon dioxide (CO2) adsorption and chemical conversion can effectively solve a series of environmental problems caused by the greenhouse effect. Herein, four melamine-based polymer networks PANs (PAN-P, PAN-PY, PAN-PZ, and PAN-IM) with abundant N sites and hydrogen bond donor (HBD) groups were synthesized by simple polymerization. The chemical structure of PANs was determined by various characterizations, and then the CO2 uptake of PANs and their catalytic activity for the cycloaddition of CO2 with epoxides were investigated. Among them, PAN-P has the largest CO2 adsorption capacity, reaching values of 73.5 cm3/g at 273 K. Meanwhile, PAN-IM exhibits the best catalytic activity with 93 % yield and 99 % selectivity under metal-, halogen-, solvent-, and cocatalyst-free conditions (120 ◦C, 1.0 MPa CO2, 8 h), which mainly attribute to the multi-site synergistic activation of the imidazole heterocycle. In addition, PAN-IM also has satisfactory activity to various epoxides and exhibited good recyclability. Density functional theory (DFT) and FT-IR analysis were used to further reveal the interaction of PANs towards CO2 and epoxides. Finally, a possible mechanism was suggested, including activation of CO2 and epoxide, ring-opening of epoxide, insertion of CO2 and ring-closing to form cyclic carbonate. The research in this paper will provide a reference for the development of a green and efficient CO2 adsorption conversion platform.

Recent Advances in Nickel Catalyzed Carbonylative Reactionsviathe Insertion of Carbon Monoxide†

Comprehensive SummaryCarbonyl compounds have attracted considerable attention due to their extensive applications in drug discovery. Furthermore, they are important synthetic intermediates for the construction of carbon‐carbon and carbon‐heteroatom bonds. Transition‐metal‐catalyzed carbonylation via the insertion of CO is one of the most efficient and straightforward strategies to access carbonyl compounds. However, most of the transition‐metal‐catalyzed carbonylative reactions require expensive and toxic noble‐metal catalysts. Therefore, there is a growing demand for the exploration of nickel‐catalyzed carbonylative reactions via the insertion of CO due to the earth abundance and low cost of nickel. Compared with the well‐established palladium‐catalyzed carbonylative reactions, nickel‐catalyzed analogous transformations have been relatively underdeveloped. This is primarily because CO strongly binds to nickel, often resulting in catalyst poisoning. In recent years, some research groups have focused on using CO surrogates or NN2pincer nickel catalyst to circumvent the formation of Ni(CO)4. Nickel‐catalyzed carbonylation has been applied in the construction of carbonyl‐containing compounds, such as ketones, carboxylic acids, thioesters, acyl chloride and carboxamides.

Quantum chemistry and metadynamics study of kinetic routes to alanine formation by CO or CO2 insertions in E- or Z-ethanimine isomers

Quantum chemistry and metadynamics study of kinetic routes to alanine formation by CO or CO2 insertions in E- or Z-ethanimine isomers

Catalysis Conversion of Carbon Dioxide and Epoxides by Tetrahydroxydiboron To Prepare Cyclic Carbonates.

A binary catalytic system comprising tetrahydroxydiboron and tetrabutylammonium iodide (TBAI) was used to catalyze the cycloaddition of carbon dioxide (CO2) with epoxides. The tetrahydroxydiboron catalyst (9 mol %), in combination with the use of TBAI (13.5 mol %) as a nucleophile, is capable of catalyzing the cycloaddition of CO2 with various terminal epoxides under room temperature and a CO2 balloon. In addition, a range of internal epoxides, including sterically hindered bicyclic epoxides and vegetable oil-based epoxides, were suitable for the catalytic system, affording a series of cyclic carbonates in moderate to high yields. The tetrahydroxydiboron/TBAI cooperative catalytic mechanism was elucidated using Fourier transform infrared spectroscopy, nuclear magnetic resonance, and electrospray ionization-high-resolution mass spectrometry. Results reveal that the tetrahydroxydiboron catalyst exhibits dual effects, activating both CO2 and epoxides; initially, it underwent the insertion of CO2 to form a boron-CO2 adduct and subsequently activated the epoxides through interaction of the B-O bond.

Vapor-phase ethanol carbonylation over Ni supported on activated carbon: Influence of the textural properties and oxygen-containing groups

The performance of ethanol carbonylation for Ni supported on different activated carbons varies considerably. The physicochemical properties of Ni catalysts supported on different activated carbons have been investigated in detail by a series of characterization studies. Catalysts with less oxygen-containing groups and smaller pore size are demonstrated to be more effective for vapor-phase ethanol carbonylation, with higher ethanol conversion and selectivity of propionate and ethyl propionate. However, there is no clear correlation between the carbonylation activity and the initial Ni nanoparticles size of the fresh catalysts due to the re-dispersion of the Ni nanoparticles by the ethane iodide interaction during the reaction. It is also proved that the deactivation of the catalyst may be caused by the loss of the active component Ni and the deposition of oxygen-containing carbon species. ​In situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS) showed that ethane iodide is essential for the ethanol carbonylation reaction and that carbonylation intermediates (C2H5CO-Ni-I) are formed only in the presence of ethane iodide. The mechanism of the ethanol carbonylation reaction was proposed, showing that the carbonylation of CO insertion and the elimination of ethylene production in the intermediate are competing reactions. This work has implications for the design of highly efficient alcohol carbonylation catalysts.

Construction of covalent organic framework functionalized with carbene dual active sites for enhancing CO2 carboxylation conversion

It is challenging to drive the integral insertion of linear CO2 with thermodynamic stability and kinetic inertness as carboxylation reagents into C-H, O-H, and other chemical bonds. The known strategies mainly focus on unilaterally activating substrates as nucleophilic reagents, and the CO2 insertion process has to overcome high reaction energy barriers. Herein, this work reports copper carbene NHC-CuCl and CO2 adduct NHC-CO2 as dual active sites are introduced into the porous crystal covalent organic framework to effectively drive the simultaneous activation of substrate and CO2. The catalyst COF@NHC-CuCl/CO2 exhibited high space–time yield (STY = 71.9 h−1 at 40 °C and 36.7 h−1 at 25 °C, ambient pressure) in the carboxylative coupling of propargylic alcohols, which is superior to most of the cutting-edge heterogeneous catalysts. Experimental data and density functional theory calculation revealed that the carboxylation reaction involving NHC-CO2 and ordinary CO2 source follows different reaction mechanisms. The free energy barrier of the CO2 insertion process (TS:35.9 kcal/mol → 17.4 kcal/mol) is effectively reduced by NHC modulation of the CO2 bond energy parameters to facilitate the reaction. Due to the unique structural design, COF@NHC-CuCl/CO2 exhibited outstanding diffusion mass transfer, catalytic diversity and reusability. This work proposes a novel construction strategy of heterogeneous dual activation catalyst to provide a sustainable solution for efficiently producing value-added chemicals from CO2 under mild conditions.

Structure-Activity relationship and reaction mechanisms of the Cu/PSAC-Nx catalysts in the oxidation carbonylation of ethanol to diethyl carbonate

Cu catalysts supported on nitrogen-doped carbon with ultra-high specific surface area (2726 m2⋅g−1) derived from peanut shells (PSAC-Nx) were fabricated and investigated in the oxidative carbonylation of ethanol to diethyl carbonate (DEC). The Cu/PSAC-Nx catalysts exhibited superior catalytic performance with a maximum STYDEC of 3371 mg·g−1·h−1, attributed to the higher surface Cu0 and Cu+ concentration. Both Cu0 and Cu+ acted as the active species that accelerated the activation of ethanol molecules and promoted the insertion of CO, respectively, in the DEC synthesis. Among the four by-products, diethoxyethane preferred to be generated at higher temperatures or extended reaction time, while acetaldehyde and ethyl acetate tended to be produced at the Cu2+ species and ethyl formate was inclined to be created at a higher oxygen fraction. This work provided theoretical and experimental guidance for the rational design of efficient catalysts and the optimization of reaction conditions for the ethanol oxidative carbonylation to DEC.

The tunable effect of the second metal site on the hydroformylation of propylene over Rh-M-BTC (M= Fe, Ru, Mn, Rh, Pt, Pd, Re, Cu, Ni)

Hydroformylation is one of the most important homogeneous reactions in industry. Cu-BTC, as a kind of MOFs material with coordinate unsaturated metal sites, has strong interaction with adsorption molecules and is widely used in adsorption and catalytic research fields. The open metal sites in it can be adjusted according to the demand. In this work, Rh-BTC was selected as the catalyst for the hydroformylation of propylene. In order to regulate the electronic properties of Rh metal center, eight Rh-M-BTC materials (M= Fe, Ru, Mn, Rh, Pt, Pd, Re, Cu, Ni) were investigated. The Mulliken charge of Rh-M metal nodes and the reaction energy barrier of the key steps of propylene hydroformylation on Rh-M-BTC were calculated, including the step of propylene insertion, CO insertion, and aldehyde formation. The results showed that on Rh-Pd-BTC, the energy barrier difference between linear and branched path for the regional decisive step propylene insertion step is the lowest, only 0.04 eV. The reaction energy barrier of the linear path for CO insertion is only half of that of the branched path. The linear path has obvious advantages. Therefore, Rh-Pd-BTC was suggested as the most suitable model studied in the work for hydroformylation of propylene.

Incorporating of Cobalt into UiO-67 Metal–Organic Framework for Catalysis CO2 Transformations: An Efficient Bi-functional Approach for CO2 Insertion and Photocatalytic Reduction

Incorporating of Cobalt into UiO-67 Metal–Organic Framework for Catalysis CO2 Transformations: An Efficient Bi-functional Approach for CO2 Insertion and Photocatalytic Reduction

Engineering the Coordination Environment of Single‐Rh‐Site with N and S Atoms for Efficient Methanol Carbonylation

The local coordination environment of central active sites plays a critical role in tuning the catalytic properties of heterogeneous single‐metal‐site catalysts (HSMSCs). However, carbon supports with inert surface properties provide weak interaction with the active sites, which hamper the effective modulation of the coordination structure of HSMSCs. Herein, this work shows that introducing N and S atoms into carbon support can modify the coordination environment of single‐Rh‐site and effectively improves the catalytic activity for the methanol carbonylation reaction. The synthesized Rh/AC‐NS with single‐Rh‐site exhibits a high methanol conversion of 88% and a stable acetyl production rate of 2812 h−1, in contrast with 1285 h−1 of Rh/AC without N‐ and S‐ functional groups, and meanwhile remarkably higher than those of Rh/AC‐N and Rh/AC‐S with only N‐ or S‐ functional group under the same mild reaction conditions. As revealed by the experimental result and density functional theory (DFT) calculations, the special combination of N‐ and S‐ functional groups offers favorable coordination configuration and also beneficial electronic structure for facilitated CH3I oxidative addition and CO insertion steps of single‐Rh‐site. This work offers new opportunities for rationally tuning the coordination structure of HSMSCs for heterogeneous catalysis.

A Review of Theoretical Studies on Carbon Monoxide Hydrogenation via Fischer-Tropsch Synthesis over Transition Metals.

The increasing demand for clean fuels and sustainable products has attracted much interest in the development of active and selective catalysts for CO conversion to desirable products. This review maps the theoretical progress of the different facets of most commercial catalysts, including Co, Fe, Ni, Rh, and Ru. All relevant elementary steps involving CO dissociation and hydrogenation and their dependence on surface structure, surface coverage, temperature, and pressure are considered. The dominant Fischer-Tropsch synthesis mechanism is also explored, including the sensitivity to the structure of H-assisted CO dissociation and direct CO dissociation. Low-coordinated step sites are shown to enhance catalytic activity and suppress methane formation. The hydrogen adsorption and CO dissociation mechanisms are highly dependent on the surface coverage, in which hydrogen adsorption increases, and the CO insertion mechanism becomes more favorable at high coverages. It is revealed that the chain-growth probability and product selectivity are affected by the type of catalyst and its structure as well as the applied temperature and pressure.

Synthesis of benzothienofuranones and dihydrobenzothienopyranones by palladium iodide-catalyzed carbonylative double cyclization

3-(2-(Methylthio)phenyl)prop-2-yn-1-ols have been successfully converted in one synthetic step into benzo[4,5]thieno[2,3-c]furan-1-ones by a PdI2/KI-catalyzed oxidative carbonylative double cyclization process, performed in MeCN under relative mild conditions (1–10 mol % PdI2, 7 equiv of KI, 80 °C, 60 atm of a 4:1 mixture CO–air). The process takes place through an ordered sequence of steps, involving 5-endo-dig S-cyclization, iodide-promoted demethylation of the ensuing sulfonium salt, CO insertion, a second cyclization (possibly, through the formation of a palladacycle intermediate followed by reductive elimination), and Pd(0) reoxidation by oxygen (from air) used as external benign oxidant. Under similar conditions, 4-(2-(methylthio)phenyl)but-3-yn-1-ols, bearing a butynol moiety ortho to the methylthio group, led to a mixture of double cyclization and dicarbonylation products, however, by slightly tuning the reaction conditions, dihydrobenzo[4,5]thieno[3,2-c]pyran-1-ones could be selectively obtained with no formation of the dicarbonylated byproduct. The structures of four representative products, including two tetracyclic derivatives, have been confirmed by XRD analysis.

Metal Effect on Cationic [Cp2MH]+ (M = Group 4 and 5)-Mediated CO2 Hydrogenation in the Gas Phase.

Effective CO2 hydrogenation has recently attracted quite some attention for producing more valuable chemical oxygenates (such as methanol, formate) in mild conditions. However, the influence of the metal center on the CO2 activation remains unclear. First, electrospray ionization mass spectrometry (ESI-MS) was employed to explore the direct CO2 hydrogenation to formic acid mediated by [Cp2MH]+ (M = Zr, Hf) in the gas phase at room temperature. The key formate intermediate [Cp2M(O2CH)]+ (M = Zr, Hf) was confirmed by traveling wave ion mobility spectrometry (TWIMS). Second, to gain insights into the metal effect, the CO2 hydrogenation process involving Group 4 (i.e., Ti, Zr, Hf) transition metals was calculated along with Group 5 (i.e., V, Nb, Ta) by density functional theory (DFT) methods. The CO2 insertion process was found to be the rate-limiting step. For [Cp2TiH]+, [Cp2ZrH]+, [Cp2HfH]+, [Cp2VH]+, [Cp2NbH]+, and [Cp2TaH]+, the barriers are +7.7, +6.5, +5.9, +9.2, +8.0, and +6.3 kcal/mol, respectively. [Cp2HfH]+-mediated CO2 hydrogenation occurs the most rapidly, as revealed by MS. According to the orbital analysis on the CO2 insertion transition state, the electron-deficient metal center resulting in a low-lying lowest unoccupied molecular orbital (LUMO) could interact more favorably with the π bond of deformed CO2, which was also consistent with the natural bond orbital (NBO) results. Last but not the least, NBO charges on the metal centers were found to correlate linearly well with the CO2 insertion barriers rather than hydride affinity. Thus, the reactivity of different metal hydride complexes with CO2 to produce a formate could be estimated by the NBO charge on metals. Our findings might provide a series of candidates for the catalyst as well as guidance for catalyst design in mild CO2 hydrogenation.

Constructing multiple active sites in iron oxide catalysts for improving carbonylation reactions

Surface engineering is a promising strategy to improve the catalytic activities of heterogeneous catalysts. Nevertheless, few studies have been devoted to investigate the catalytic behavior differences of the multiple metal active sites triggered by the surface imperfections on catalysis. Herein, oxygen vacancies induced Fe2O3 catalyst are demonstrated with different Fe sites around one oxygen vacancy and exhibited significant catalytic performance for the carbonylation of various aryl halides and amines/alcohols with CO. The developed catalytic system displays excellent activity, selectivity, and reusability for the synthesis of carbonylated chemicals, including drugs and chiral molecules, via aminocarbonylation and alkoxycarbonylation. Combined characterizations disclose the formation of oxygen vacancies. Control experiments and density functional theory calculations demonstrate the selective combination of the three Fe sites is vital to improve the catalytic performance by catalyzing the elemental steps of PhI activation, CO insertion and C-N/C-O coupling respectively, endowing combinatorial sites catalyst for multistep reactions.

Cellulose nanofibers (CNF) supported (Salen)Cr(III) composite as an efficient heterogeneous catalyst for CO2 cycloaddition

For the simultaneous attainment of the utilization of renewable biomass resources and the mitigation of greenhouse effects, it is very promising to develop a green, recyclable, and highly efficient heterogeneous catalyst for the synthesis of cyclic carbonates by CO2 cycloaddition reaction with epoxides. Herein, novel cellulose nanofibers (CNF) supported (Salen)Cr(Ⅲ) complex was effectively synthesized for the aforementioned reaction. The cellulose nanofibers (CNF) were firstly modified with (3-aminopropyl) triethoxysilane (APTES), and then its Schiff base with salicylaldehyde was synthesized, which further subjected to coordination treatment with chromium chloride to form a novel heterogeneous catalyst, labelled as CNF-(Salen)Cr(Ⅲ). The catalytic performance of the catalysts shown that CNF-(Salen)Cr(Ⅲ) and co-catalyst TBAB can synergistically catalyze the cycloaddition of CO2 with epichlorohydrin (ECH) at mild reaction conditions, and the yield of chloropropene carbonate (CPC) reached up to 97.8% with high selectivity. The CNF-(Salen)Cr(Ⅲ) complex maintained high catalytic activity after six cycles of repeated runs and has acceptable catalytic effect on other series of epoxies. Based on density functional theory (DFT) calculations, a reaction mechanism including adsorption activation of epoxides, epoxides ring opening, CO2 insertion, and the formation of cyclic carbonate, was proposed for the CNF-(Salen)Cr(Ⅲ) complex catalyzed cycloaddition of CO2 with epoxides.

A Cavity-Shaped Gold(I) Fragment Enables CO2 Insertion into Au-OH and Au-NH Bonds.

A cavity-shaped linear gold(I) hydroxide complex acts as a platform to access unusual gold monomeric species. Notably, this sterically crowded gold fragment enables the trapping of CO2 via insertion into Au-OH and Au-NH bonds to form unprecedented monomeric gold(I) carbonate and carbamate complexes. In addition, we succeeded in the identification of the first gold(I) terminal hydride bearing a phosphine ligand. The basic nature of the Au(I)-hydroxide moiety is also explored through the reactivity toward other molecules containing acidic protons such as trifluoromethanesulfonic acid and terminal alkynes.

Dinitrogen Functionalization with Carbon Dioxide and Carbon Disulfide Giving Symmetric and Unsymmetric Hydrazido Complexes

AbstractHere we show that a tridentate bis(aryloxide)anilide‐ligated titanium/potassium scaffold promotes functionalization of coordinated N2 with CO2 and CS2 through formation of N−C bonds. Treatment of a naphthalene complex with N2 gave an end‐on bridging dinitrogen complex featuring a [Ti2K2N2] core. The dinitrogen complex underwent insertion of CO2 into each Ti−NN bond to afford an N,N′‐dicarboxylated hydrazido complex. Stepwise nitrogen‐carbon bond formation at coordinated N2 proceeded to afford an unsymmetric hydrazido complex upon sequentially treating the dinitrogen complex with CS2 and CO2. Addition of Me3SiCl to the dicarboxylated hydrazido complex resulted in partial silylation of the carboxylate groups but did not lead to removal of the functionalized N2 unit from the metal centers. However, reduction of the dicarboxylated hydrazido complex with potassium naphthalenide afforded an oxo‐bridged dinuclear complex along with release of free potassium cyanate.

Dinitrogen Functionalization with Carbon Dioxide and Carbon Disulfide Giving Symmetric and Unsymmetric Hydrazido Complexes.

Here we show that a tridentate bis(aryloxide)anilide-ligated titanium/potassium scaffold promotes functionalization of coordinated N2 with CO2 and CS2 through formation of N-C bonds. Treatment of a naphthalene complex with N2 gave an end-on bridging dinitrogen complex featuring a [Ti2 K2 N2 ] core. The dinitrogen complex underwent insertion of CO2 into each Ti-NN bond to afford an N,N'-dicarboxylated hydrazido complex. Stepwise nitrogen-carbon bond formation at coordinated N2 proceeded to afford an unsymmetric hydrazido complex upon sequentially treating the dinitrogen complex with CS2 and CO2 . Addition of Me3 SiCl to the dicarboxylated hydrazido complex resulted in partial silylation of the carboxylate groups but did not lead to removal of the functionalized N2 unit from the metal centers. However, reduction of the dicarboxylated hydrazido complex with potassium naphthalenide afforded an oxo-bridged dinuclear complex along with release of free potassium cyanate.

Single-Crystal to Single-Crystal Transformations: Stepwise CO2 Insertions into Bridging Hydrides of [(NHC)CuH]2 Complexes.

Mechanistic studies of substrate insertion into dimeric [(NHC)CuH]2 (NHC=N-heterocyclic carbene) complexes with two bridging hydrides have been shown to require dimer dissociation to generate transient, highly reactive (NHC)Cu-H monomers in solution. Using single-crystal to single-crystal (SC-SC) transformations, we discovered a new pathway of stepwise insertion of CO2 into [(NHC)CuH]2 without complete dissociation of the dimer. The first CO2 insertion into dimeric [(IPr*OMe)CuH]2 (IPr*OMe=N,N'-bis(2,6-bis(diphenylmethyl)-4-methoxy-phenyl)imidazole-2-ylidene) produced a dicopper formate hydride [(IPr*OMe)Cu]2 (μ-1,3-O2 CH)(μ-H). A second CO2 insertion produced a dicopper bis(formate), [(IPr*OMe)Cu]2 (μ-1,3-O2 CH)(μ-1,1-O2 CH), containing two different bonding modes of the bridging formate. These dicopper formate complexes are inaccessible from solution reactions since the dicopper core cleanly ruptures to monomeric complexes when dissolved in a solvent.

Single‐Crystal to Single‐Crystal Transformations: Stepwise CO2 Insertions into Bridging Hydrides of [(NHC)CuH]2 Complexes

AbstractMechanistic studies of substrate insertion into dimeric [(NHC)CuH]2 (NHC=N‐heterocyclic carbene) complexes with two bridging hydrides have been shown to require dimer dissociation to generate transient, highly reactive (NHC)Cu−H monomers in solution. Using single‐crystal to single‐crystal (SC‐SC) transformations, we discovered a new pathway of stepwise insertion of CO2 into [(NHC)CuH]2 without complete dissociation of the dimer. The first CO2 insertion into dimeric [(IPr*OMe)CuH]2 (IPr*OMe=N,N′‐bis(2,6‐bis(diphenylmethyl)‐4‐methoxy‐phenyl)imidazole‐2‐ylidene) produced a dicopper formate hydride [(IPr*OMe)Cu]2(μ‐1,3‐O2CH)(μ‐H). A second CO2 insertion produced a dicopper bis(formate), [(IPr*OMe)Cu]2(μ‐1,3‐O2CH)(μ‐1,1‐O2CH), containing two different bonding modes of the bridging formate. These dicopper formate complexes are inaccessible from solution reactions since the dicopper core cleanly ruptures to monomeric complexes when dissolved in a solvent.