Copolymerization Of Carbon Dioxide Research Articles

Highly Selective and Productive Synthesis of a Carbon Dioxide-Based Copolymer upon Zwitterionic Growth

This work discloses a zwitterionic approach for selective copolymerization of carbon dioxide (CO₂) and propylene oxide (PO), producing poly(propylene carbonate) (PPC), a biodegradable polymer with broad applications. Small-molecule catalysts composed of triethylamine (TEA) and trialkyl boranes are effective for CO₂/PO copolymerization with an alternating degree of >99% and a productivity of 171 g PPC/g catalyst. A diamine N,N,N′,N′-tetraethyl ethylenediamine (TEED) paired with trialkyl borane exhibited improved activity and productivity (up to 216 g PPC/g catalyst). By adjusting the Lewis acid–base pair, the PPC selectivity can be regulated to 99%. In addition, PPCs have medium regioregularity with a head-to-tail diad content of 80–82% and number-average molecular weights of up to 56.0 kg/mol with narrow polydispersity (below 1.2). The overall catalytic performance of these readily available simple molecules is better than that of previously reported organic catalysts for CO₂/PO copolymerization. Successive insertion of PO and CO₂ into the Lewis pair leads to the formation of an end-to-end zwitterion featuring a TEB-masked anion and an onium cation, which is highly selective to the alternating copolymerization, as demonstrated by quantum mechanical calculations.

Alternating Copolymerization of Carbon Dioxide with Epoxides Using Highly Active Dinuclear Nickel Complexes: Catalysis and Kinetics.

A novel series of well-defined dicarboxylate dinuclear nickel complexes containing benzotriazole based 1,3-diamine-bisphenolate (1,3-DiBTP) ligands were readily synthesized through a one-pot procedure, which were highly active single-component catalysts for copolymerization of CO2 and epoxides. X-ray structural determination of dinickel complexes 1-11 indicates that the DiBTP ligand acted as a N,O,N,N,O,N-hexadentate framework to chelate two nickel atoms, and two carboxylates are nonequivalently coordinated. The best benzoate-bonded dinickel catalyst 6 displayed the effective activity for both high-pressure and 1 atm CO2-copolymerization of cyclohexene oxide (CHO) in a controllable manner. Noteworthily, a high turnover frequency up to 9600 h-1 could be reached at 140 °C and a CO2 pressure of 20.7 bar utilizing a low catalyst loading of 0.01 mol %, and the same copolymerization conditions were capable of producing narrowly dispersed poly(cyclohexene carbonate) (PCHC) having >99% polycarbonate selectivity. In addition to CO2/CHO copolymerization, 4-vinyl-1,2-cyclohexene oxide or cyclopentene oxide was also applied to efficiently copolymerize CO2 under conditions of 80 °C and 20.7 bar initial CO2 pressure. Kinetic studies of CO2/CHO copolymerization catalyzed by 6 were investigated. Such polymerization revealed first-order dependence for both catalyst 6 and CHO concentrations, and the activation energy for PCHC generation by 6 is 57.69 kJ mol-1. A possible polymerization mechanism for CO2-copolymerization of CHO was proposed based on kinetics and structural studies of the obtained polycarbonates.

Conceptual design, environmental, and economic evaluation of direct copolymerization process of carbon dioxide and 1,4-butanediol

The routes to convert CO2 into environmentally benign materials have attracted wide attentions. In this work, an emerging process to produce poly(butylene carbonate) (or PBC) from direct copolymerization of carbon dioxide and 1,4-butanediol is firstly simulated with analyses on the CO2 emission ratio (CO2-e, in kg-CO2/kg-PBC) and yearly unit manufacturing cost of product (YUMC, in USD/kg). In order to address the issues associated with large amount of solvents used in the lab scale, two proposed scenarios including the reduction of solvent amount, and heat integration by vapor recompression cycle (VRC) were simulated. It is found that CO2-e is reduced by 82.0% (from 30.06 to 5.42) when the solvent amount is reduced to 10%, and another 19.9% reduction in CO2-e (to 4.34) when applying the VRC. YUMCs are reduced by ca. 68% for both proposed scenarios (from 5.62 to ca. 1.8). The findings reported in this study may prove informative for developing CO2 conversion technologies from lab scale to industrial scale.

Co(III)/Alkali-Metal(I) Heterodinuclear Catalysts for the Ring-Opening Copolymerization of CO2 and Propylene Oxide.

The ring-opening copolymerization of carbon dioxide and propene oxide is a useful means to valorize waste into commercially attractive poly(propylene carbonate) (PPC) polyols. The reaction is limited by low catalytic activities, poor tolerance to a large excess of chain transfer agent, and tendency to form byproducts. Here, a series of new catalysts are reported that comprise heterodinuclear Co(III)/M(I) macrocyclic complexes (where M(I) = Group 1 metal). These catalysts show highly efficient production of PPC polyols, outstanding yields (turnover numbers), quantitative carbon dioxide uptake (>99%), and high selectivity for polyol formation (>95%). The most active, a Co(III)/K(I) complex, shows a turnover frequency of 800 h–1 at low catalyst loading (0.025 mol %, 70 °C, 30 bar CO2). The copolymerizations are well controlled and produce hydroxyl telechelic PPC with predictable molar masses and narrow dispersity (Đ < 1.15). The polymerization kinetics show a second order rate law, first order in both propylene oxide and catalyst concentrations, and zeroth order in CO2 pressure. An Eyring analysis, examining the effect of temperature on the propagation rate coefficient (kp), reveals the transition state barrier for polycarbonate formation: ΔG‡ = +92.6 ± 2.5 kJ mol–1. The Co(III)/K(I) catalyst is also highly active and selective in copolymerizations of other epoxides with carbon dioxide.

Catalysis and kinetics for alternating copolymerization of carbon dioxide with epoxides using dinuclear nickel catalysts of pyrazolyl based diamine-bisphenolate ligands

The synthesis of structurally well-characterized dinuclear nickel complexes bearing a new type of pyrazolyl based diamine-bisphenolate ligand was reported for the first time. Catalysis towards nickel-catalyzed copolymerization of CO2 with cyclohexene oxide (CHO) by these newly prepared bimetallic complexes was systematically investigated. Particularly, dinickel complex 4 supporting 2-nitrophenoxide coligands was demonstrated to effectively catalyze CO2-copolymerization of CHO, 4-vinyl-1,2-cyclohexene oxide or cyclopentene oxide, generating the corresponding CO2-based polycarbonates with >99% carbonate linkages under optimal conditions. Kinetic studies of CO2/CHO copolymerization revealed that such copolymerization catalysis is first-order in dinickel complex 4 and second-order in CHO concentration.

A Novel [OSSO]-Type Chromium(III) Complex as a Versatile Catalyst for Copolymerization of Carbon Dioxide with Epoxides.

A new chromium(III) complex, bearing a bis-thioether-diphenolate [OSSO]-type ligand, was found to be an efficient catalyst in the copolymerization of CO2 and epoxides to achieve poly(propylene carbonate), poly(cyclohexene carbonate), poly(hexene carbonate) and poly(styrene carbonate), as well as poly(propylene carbonate)(cyclohexene carbonate) and poly(propylene carbonate)(hexene carbonate) terpolymers.

Ti(IV)-Tris(phenolate) Catalyst Systems for the Ring-Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide.

Titanium(IV) complexes of amino-tris(phenolate) ligands (LTiX, X = chloride, isopropoxide) together with bis(triphenylphosphine)iminium chloride (PPNCl) are active catalyst systems for the ring-opening copolymerization of carbon dioxide and cyclohexene oxide. They show moderate activity, with turnover frequency values of ∼60 h–1 (0.02 mol % of catalyst, 80 °C, 40 bar of CO2) and high selectivity (carbonate linkages >90%), but their absolute performances are lower than those of the most active Ti(IV) catalyst systems. The reactions proceed with linear evolution of polycarbonate (PCHC) molar mass with epoxide conversion, consistent with controlled polymerizations, and evolve bimodal molar mass distributions of PCHC (up to Mn = 42 kg mol–1). The stoichiometric reaction between [LTiOiPr] and tetraphenylphosphonium chloride, PPh4Cl, allows isolation of the putative catalytic intermediate [LTi(OiPr)Cl]−, which is characterized using single-crystal X-ray diffraction techniques. The anionic titanium complex [LTi(OR)Cl]− is proposed as a model for the propagating alkoxide intermediates in the catalytic cycle.

Highly active bimetallic nickel catalysts for alternating copolymerization of carbon dioxide with epoxides

Catalyst 1 was reported for the first time to be effective for nickel-catalyzed CO2/CHO copolymerization at 1 atm CO2 pressure.

Direct copolymerization of carbon dioxide and 1,4-butanediol enhanced by ceria nanorod catalyst

Direct copolymerization of CO2 and 1,4-butanediol to yield poly(butylene carbonate) oligomers has been recently realized using CeO2 as a catalyst and 2-cyanopyridine as a dehydrating agent. In this study, CeO2 nanorod and nanocube were synthesized, characterized, and compared their catalytic activities with commercial CeO2 nanoparticle and submicronparticle. Reaction testing reveals that CeO2 nanorod exhibits a much higher yield of polycarbonate oligomer than other CeO2 catalysts. Surface characterizations indicate that CeO2 nanorod displays a significantly higher CO2 uptake and stronger interactions with CO2, properties that could be beneficial to activate stable CO2 molecule. In-situ infrared spectroscopy suggests that bidentate carbonate, i.e., CO2 adsorbs over the CeO2 surface with an oxygen atom and an oxygen vacancy coordinated with a cerium atom, is the key intermediate associated with the observed catalytic activities. These results manifest the importance of surface oxygen vacancy of CeO2 for activating CO2 to proceed non-reductive conversion.

Co-catalyst and Metal-free CO2 Fixation into Cyclic Carbonates: COPs to the Rescue

The non-redox fixation of CO2 in cyclic and polymeric carbonates is regarded as one of the most promising technologies for small-scale CO2 utilization. Yet, most heterogeneous catalysts reported to date require the use of co-catalysts, harsh reaction conditions, and non-base metals. In this issue of Chem, Yavuz and coworkers report the one-step synthesis of a new covalent organic polymer that circumvents these issues.

Synthesis, structures, and thermal properties of terpolymers of propylene oxide, carbon dioxide, and cyclohexene oxide

High molecular weight block terpolymers with different contents of polypropylene carbonate and cyclohexene carbonate units in the polymer chain were synthesized by the copolymerization of carbon dioxide, propylene oxide, and cyclohexene oxide. Zinc adipate was used as a catalyst. The terpolymerization products were characterized by 1H and 13C NMR spectroscopy, IR spectroscopy, GPC, DSC, and DMA methods. The influence of the reaction conditions on the composition, microstructure, and molecular-weight and thermal characteristics was studied.

Nickel-catalyzed copolymerization of carbon dioxide with internal epoxides by di-nuclear bis(benzotriazole iminophenolate) complexes

We report the synthesis of structurally well-characterized di-nuclear nickel bis(benzotriazole iminophenolate) (BiIBTP) complexes containing diverse mono- or bi-dentate monoanionic coligands for the utilization of copolymerization of carbon dioxide (CO2) with internal epoxides. The molecular structures of complexes 1–3 can be ascribed to bimetallic nickel(II) species containing a hexadentate BiIBTP main ligand and two homo-coligands of pentafluorobenzoate, pentafluorophenolate or chloride, whereas 4 and 5 are BiIBTP-ligated di-nickel chloride analogues mixed with carboxylate coligands. Di-nickel complexes 1 and 3 supported by O2CC6F5 and Cl coligands were demonstrated to be efficient catalysts for alternating copolymerization of CO2 with cyclohexene oxide (CHO) to afford CO2-based poly(cyclohexene carbonate)s (PCHCs) with >99% carbonate repeated units. Particularly, di-Ni di-chloride complex 3 was capable of giving high activity with a turnover frequency of 688 h−1 for such copolymerization under the optimal conditions. Interestingly, di-Ni catalyst 1 enables us to produce the low molecular weight di-hydroxyl end-capped PCHCs with unimodal molecular weight distributions while commercially available CHO without further purification was used as the epoxide monomer. In addition to CO2-CHO copolymerization, bimetallic complex 1 was also found to effectively copolymerize CO2 with cyclopentene oxide, generating highly alternating poly(cyclopentene carbonate)s with molecular weights in a broad range. Kinetic studies of CO2/CHO copolymerization catalyzed by 1 were investigated using 1H NMR spectroscopy and revealed the first-order dependence for both catalyst 1 and CHO concentrations.

Co-Ni Cyanide Bi-Metal Catalysts: Copolymerization of Carbon Dioxide with Propylene Oxide and Chain Transfer Agents

Synthesis of copolymers from carbon dioxide (CO2) and epoxides is an important research direction as such processes utilize the abundant greenhouse gas and deliver useful products. Specifically, cooligomers of CO2 and propylene oxide (PO) with a non-alternating structure can be used for polyurethane preparation. They are synthesized by employing Zn-Co cyanide catalysts. The application of alternative metal cyanide complexes is interesting from scientific and practical points of view. The purpose of this work was to study the copolymerization of CO2 and PO in the presence of Co-Ni cyanide catalysts and chain transfer agents (CTAs) in order to obtain low molecular weight products. Three Co-Ni catalysts with different contents of complexing agents were synthesized, characterized by several analytical methods and applied for this reaction. The complex without complexing agents was chosen for detailed investigation. 1,6-Hexanediol proved to be a more preferred CTA than poly(propylene glycol) and adipic acid. An oligo(ethercarbonate) (Mn = 2560, PDI = 2.5, CO2 = 20 mol.%) capped with OH groups was synthesized with relatively high productivity (1320 gPO+CO2/gcat in 24 h) and characterized by matrix-assisted laser desorption/ionization (MALDI) MS and NMR methods. The main chain transfer routes during the cooligomerization were suggested on the basis of the research results.

Copolymerization of carbon dioxide and propylene oxide catalyzed by two kinds of bifunctional salen‐cobalt(III) complexes bearing four quaternary ammonium salts

AbstractTwo new bifunctional salen‐cobalt(III) complexes were synthesized, which consist of salicylaldehyde bearing four quaternary ammonium salts and two different diamines. The copolymerization results indicated that decreasing temperature is advantageous for both the complexes. Of both the diamines, the complex 9 with o‐diaminobenzene has a higher catalytic effect compared to complex 6 with 1,2‐diaminocyclohexane. The catalytic effect of complex 9 is over 3.5 times than that of complex 6 at a temperature of 30°C. The research of PCO2 on the copolymerization revealed that the first‐rank pressure was at 2 MPa for the two complexes. The highest turnover number are under conditions of T = 30°C, PCO2 = 2 MPa, and t = 24 hr. Differential scanning calorimeter curves indicated that poly(propylene carbonate) (PPC) by complex 9 has the highest Tg of 54.2°C. DTGA curves showed that there were two thermal degradation peaks, the first is for the ester bond, and the second is for the C–C bond.

Kinetics of Ternary Copolymerization of Carbon Dioxide with Propylene Oxide, Butene Oxide, and Cyclohexene Oxide

The kinetics of ternary copolymerization of СО2 with epoxides, namely, propylene oxide, butene oxide, and cyclohexene oxide, carried out in the presence of a binary catalytic system is studied for the first time. The rates of reactions are determined by measuring СО2 uptake in the course of time. Dependences of the rate of reaction on the composition of epoxides in a medium are determined for the copolymerizations of СО2 with butene oxide–propylene oxide, СО2 with cyclohexene oxide–propylene oxide, and СО2 with cyclohexene oxide–butene oxide. The relationship between reactivity ratios in the insertion of various epoxides into the copolymers is ascertained. The glass transition temperature of the ternary copolymers is controlled by their composition; it varies in the range of 9.3–122.3°С.

Catalytic Chain Transfer Copolymerization of Propylene Oxide and CO2 using Zinc Glutarate Catalyst.

Oligo and poly(propylene ether carbonate)‐polyols with molecular weights from 0.8 to over 50 kg/mol and with 60–92 mol % carbonate linkages were synthesized by chain transfer copolymerization of carbon dioxide (CO2) and propylene oxide (PO) mediated by zinc glutarate. Online‐monitoring of the polymerization revealed that the CTA controlled copolymerization has an induction time which is resulting from reversible catalyst deactivation by the CTA. Latter is neutralized after the first monomer additions. The outcome of the chain transfer reaction is a function of the carbonate content, i. e. CO2 pressure, most likely on account of differences in mobility (diffusion) of the various polymers. Melt viscosities of poly(ether carbonate)diols with a carbonate content between 60 and 92 mol % are reported as function of the molecular weight, showing that the mobility is higher when the ether content is higher. The procedure of PO/CO2 catalytic chain copolymerization allows tailoring the glass temperature and viscosity.

A Novel One-Pot Synthesis of Poly(Propylene Carbonate) Containing Cross-Linked Networks by Copolymerization of Carbon Dioxide, Propylene Oxide, Maleic Anhydride, and Furfuryl Glycidyl Ether.

The thermoplastic poly(propylene carbonate) (PPC) containing cross-linked networks was one-pot synthesized by copolymerization of carbon dioxide, propylene oxide (PO), maleic anhydride (MA), and furfuryl glycidyl ether (FGE). The copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements. The thermal and dimensional stability of the copolymers were improved. When the MA and FGE load increased from 1 mol% to 4 mol% of PO, the copolymers contained the gel contents of 11.0%–26.1% and their yields were about double that of the PPC. The 5% weight-loss degradation temperatures (Td,-5%) and the maximum weight-loss degradation temperatures (Td,max) increased from 149.7–271.3 °C and from 282.6–288.6 °C, respectively, corresponding to 217.1 °C and 239.0 °C of PPC. Additionally, the hot-set elongation tests showed that the copolymers exhibited elasticity and dimensional stability with the minimum permanent deformation of 6.5% which was far less than that of PPC of 157.2%, while the tensile strengths were a little lower than that of PPC because of the following two conflicting factors, cross-links and flexibility of the units formed by the introduced third monomers, MA and FGE. In brief, we provide a novel method of one-pot synthesis of PPC containing cross-linked networks. According to this idea, the properties would be more extensively regulated by changing the cross-linkable monomers.

Supplementary File: A Novel One-Pot Synthesis of Poly(PropyleneCarbonate) Containing Cross-Linked Networks by Copolymerization of Carbon Dioxide, Propylene Oxide, Maleic Anhydride, and Furfuryl Glycidyl Ether

Supplementary File: A Novel One-Pot Synthesis of Poly(PropyleneCarbonate) Containing Cross-Linked Networks by Copolymerization of Carbon Dioxide, Propylene Oxide, Maleic Anhydride, and Furfuryl Glycidyl Ether

Transition metal complexes with pyrazine amine ligand: Preparation, structure and carbon dioxide copolymerization behavior

Three complexes [Fe(L)2](ClO4)2 (1)、[Ni(L)2](ClO4)2 (2) and [Co(L)2](ClO4)2 (3) were synthesized by the reaction of N,N’-(4-methylpyridin-2-yl)pyrazine-2,6-diamine (L) with Fe(ClO4)2·6H2O, (Ni(ClO4)2·6H2O or Co(ClO4)2·6H2O) at room temperature, respectively. They were characterized by elemental analysis, IR spectroscopy and single crystal X-ray diffraction. The catalytic behavior of the complexes for the synthesis of propylene carbonate from propylene oxide and carbon dioxide were studied. The results show that all of them showed excellent catalytic activities with TOF as high as 2104 h-1, 2824 h-1 and 2605 h-1, respectively. Complex 2 that exhibit higher catalytic activity was taken to explore the influence of time, pressure and temperature to optimize the reaction condition in detail.

Carboxylate Salts as Ideal Initiators for the Metal-Free Copolymerization of CO2 with Epoxides: Synthesis of Well-Defined Polycarbonates Diols and Polyols

Tetrabutylammonium carbonate (TBAC) which is obtained by treating CO2 with tetrabutylammonium hydroxide is shown to perform as an ideal difunctional initiator for the copolymerization of carbon dioxide (CO2) and propylene oxide (PO) in the presence of triethylborane (TEB). In this system, CO2 thus serves as the initiating moiety of its own copolymerization with epoxides when used in the form of a carbonate salt. Based on this remarkable result, mono-, tri-, and tetrafunctional ammonium carboxylate initiators and also other difunctional carboxylate initiators were synthesized and used for the synthesis of well-defined ω-hydroxyl-polycarbonates with linear and star structures. Well-defined telechelics, three- and four-armed star samples of molar mass varying from 1 kg/mol to 10 kg/mol, with around 95% carbonate content, were successfully synthesized. The structure of the obtained polycarbonate ω-polyols were characterized by 1H NMR, MALDI-TOF, and GPC. The terminal hydroxyl functionality of polycarbonate diol was further used for polycondensation with diisocyanates to afford polyurethanes. Finally, taking TBAC as an example, the recyclability of this ammonium-based initiator is demonstrated for the preparation of polycarbonate diols.