The Nature of Carbon Dioxide in Bare Ionic Liquids

The reaction between CO2 and chloroform in anion-functionalized ionic liquids with the formation of trichloroacetates

Here, 1,2,4-triazolide-based ionic liquids (ILs), N-ethyl-N,N-dimethyl-N-(2-methoxyethyl)ammonium 1,2,4-triazolide ([MOEN211][Triz]) and tetraethylammonium 1,2,4-triazolide ([N2222][Triz]), are used to capture CO2. The interaction results suggest that CO2 reacts with the anion [Triz]- to form carbamate species. Surprisingly, when deuterated chloroform (CDCl3) or chloroform (CHCl3) is added into the absorption system at room temperature, it is found that CO2 can react with not only the [Triz]- anion but also CDCl3 (or CHCl3) to form carbamate and trichloroacetate species, respectively. In other words, CO2 can easily react with cheap CHCl3 in the presence of [Triz]-based ILs to form valuable chemical trichloroacetate under ambient conditions. Moreover, the formation of trichloroacetate can also be detected in the systems containing imidazolide ([Im]-) and pyrazolide ([Pyr]-) ILs. The findings of this work may provide another useful route for carbon capture and utilization.

Amino Acid-Based Ionic Liquids-Aided CO2 Hydrogenation to Methanol

This study explored the use of amino acid-based ionic liquids to facilitate the conversion of carbon dioxide (CO2) into methanol through catalytic hydrogenation. Combining tetrabutylammonium L-argininate (TBA⋅Arg) with the ruthenium Ru-MACHO-BH complex allowed achieving significant yields of methanol under optimized conditions, with a turnover number (TON) up to 700. By systematically varying key reaction parameters, we demonstrated that the TBA⋅Arg ionic liquid promotes the efficient hydrogenation pathway leading to methanol formation, thus offering a sustainable approach to CO2 valorization. These findings underscore the potential of amino acid-based ionic liquids in catalyzing the transformation of CO2 into valuable chemicals, contributing to carbon mitigation efforts.

CO2 adsorption in natural deep eutectic solvents: insights from quantum mechanics and molecular dynamics

CO2 capture is an important process for mitigating CO2 emissions in the atmosphere. Recently, ionic liquids have been identified as possible systems for CO2 capture processes. Major drawbacks of such systems are mostly in the high cost of synthesis of such liquids and poor biodegradability. Natural deep eutectic solvents, a class of eutectic solvents using materials of natural origin, have been developed, which compared to ionic liquids are low-cost and more environmentally benign. However, very little is known on the details at a molecular level that govern the CO2 adsorption in these systems and what the limits are of the adsorption features. Elucidating such aspects would represent a step forward in the design and implementation of such promising systems in mitigating CO2 emissions. Herein, we report a computational study on the mechanisms and characteristics of CO2 adsorption in natural deep eutectic solvents containing arginine/glycerol mixtures. We establish details of the hydrogen bonding effects that drive the carbon dioxide capture in systems composed of L-arginine and glycerol using molecular dynamics and quantum mechanics simulations. Our findings indicate that, although both arginine and glycerol contain multiple atoms capable of acting as hydrogen bond donors and hydrogen bond acceptors, L-arginine primarily functions as the hydrogen bond acceptor while glycerol serves as the hydrogen bond donor in most interactions. Furthermore, both compounds contribute hydrogen bond donors that participate in CO2 binding. This study provides valuable insights into the behaviour of CO2 adsorption in natural deep eutectic solvents and enhances our understanding from the perspective of hydrogen bonding interactions.

A Green Chemo-Enzymatic Approach for CO2 Capture and Transformation into Bis(cyclic carbonate) Esters in Solvent-Free Media

A sustainable approach for CO2 capture and chemo-enzymatic transformation into bis(cyclic carbonate) esters from CO2, glycidol, and organic anhydrides under solvent-free conditions has been demonstrated. The chemo-enzymatic process is based on two consecutive catalytic steps, which can be executed through separated operations or within a one-pot combo system, taking advantage of the synergic effects that emerge from integrating ionic liquid (IL) technologies and biocatalysts. In a first step, lipase-catalyzed transesterification and esterification reactions of different diacyl donors (e.g., glutaric anhydride, succinic anhydride, dimethyl succinate, etc.) with glycidol in solvent-free under mild reaction conditions (70 °C, 6 h) produce the corresponding diglycidyl ester derivatives in up to 41% yield. By a second step, the synthesis of bis(cyclic carbonate) esters was carried out as a result of the cycloaddition reaction of CO2 (from an exhausted gas source, 15% CO2 purity) on these diglycidyl esters, catalyzed by the covalently attached 1-decyl-2-methylimidazolium IL (supported ionic liquid-like phase, SILLP), in solvent-free condition, leading up to 65% yield after 8 h at 45 °C and 1 MPa CO2 pressure. Both key elements of the reaction system (biocatalyst and SILLP) were successfully recovered and reused for at least 5 operational cycles. Finally, different metrics have been applied to assess the greenness of the solvent-free chemo-enzymatic synthesis of bis(cyclic carbonate) esters here reported.

Ionic Lignin Polymers for Controlled CO2 Capture, Release, and Conversion into High-Value Chemicals

In this study, an innovative and cost-effective ionic polymer for CO2 capture and utilization for the first time, using abundant and nonfood-based biomass lignin is reported. The modified ionic polymer synthesizes through the reaction of glycidyltrimethylammonium chloride with lignin under alkaline conditions to yield quaternary ammonium ionic functionality. Subsequently, the hydroxide-based pure ionic lignin polymer is employed for CO2 capture from both direct air and concentrated CO2 sources at room temperature and atmospheric pressure. Structural characterization of the polymers is accomplished through 1H, 13C, and 2D-heteronuclear single quantum coherence (HSQC) NMR, and FT-IR spectroscopy. The CO2 capture process is established through the formation of bicarbonate ions alongside the presence of CO2. The captured CO2 is precisely quantified by using inverse-gated proton decoupled 13C NMR with an internal standard (trioxane). Remarkably, the captured-CO2 amounts of ionic lignin polymer are 1.06 mmol g-1 (47 mg g-1) from concentrated-CO2 source and 0.60 mmol g-1 (26 mg g-1) from direct-air. The captured-CO2 in ionic lignin polymer is released in controlled manner and utilized in the synthesis of cyclic carbonate, showcasing the productive application of the captured carbon. Moreover, the fully controlled recovering of ionic lignin polymer achieves via repeated CO2 release ↔ CO2 capture.

Ionic Liquids in Metal, Photo-, Electro-, and (Bio) Catalysis

Ionic liquids (ILs) have unique physicochemical properties that make them advantageous for catalysis, such as low vapor pressure, non-flammability, high thermal and chemical stabilities, and the ability to enhance the activity and stability of (bio)catalysts. ILs can improve the efficiency, selectivity, and sustainability of bio(transformations) by acting as activators of enzymes, selectively dissolving substrates and products, and reducing toxicity. They can also be recycled and reused multiple times without losing their effectiveness. ILs based on imidazolium cation are preferred for structural organization aspects, with a semiorganized layer surrounding the catalyst. ILs act as a container, providing a confined space that allows modulation of electronic and geometric effects, miscibility of reactants and products, and residence time of species. ILs can stabilize ionic and radical species and control the catalytic activity of dynamic processes. Supported IL phase (SILP) derivatives and polymeric ILs (PILs) are good options for molecular engineering of greener catalytic processes. The major factors governing metal, photo-, electro-, and biocatalysts in ILs are discussed in detail based on the vast literature available over the past two and a half decades. Catalytic reactions, ranging from hydrogenation and cross-coupling to oxidations, promoted by homogeneous and heterogeneous catalysts in both single and multiphase conditions, are extensively reviewed and discussed considering the knowledge accumulated until now.

Formic acid stability in different solvents by DFT calculations

CONTEXT

New technologies have been developed toward the use of green energies. The production of formic acid (FA) from carbon dioxide (CO[Formula: see text]) hydrogenation with H[Formula: see text] is a sustainable process for H[Formula: see text] storage. However, the FA adduct stabilization is thermodynamically dependent on the type of solvent and thermodynamic conditions. The results suggest a wide range of dielectric permittivity values between the dimethyl sulfoxide (DMSO) and water solvents to stabilize the FA in the absence of base. The thermodynamics analysis and the infrared and charge density difference results show that the formation of the FA complex with H[Formula: see text]O is temperature dependent and has a major influence on aqueous solvents compared to the FA adduct with amine, in good agreement with the experiment. In these conditions, the stability thermodynamic of the FA molecule may be favorable at non-organic solvents and dielectric permittivity values closer to water. Therefore, a mixture of aqueous solvents with possible ionic composition could be used to increase the thermodynamic stability of H[Formula: see text] storage in CO[Formula: see text] conversion processes.

METHODS

Using the Quantum ESPRESSO package, density functional theory (DFT) calculations were performed with periodic boundary conditions, and the electronic wave functions were expanded in plane waves. For the exchange-correlation functional, we use the vdW-DF functional with the inclusion of van der Waals (vdW) forces. Electron-ion interactions are treated by the projector augmented wave (PAW) method with pseudopotentials available in the PSlibrary repository. The wave functions and the electronic densities were expanded employing accurate cut-off energies of 6.80[Formula: see text]10[Formula: see text] and 5.44[Formula: see text]10[Formula: see text] eV, respectively. The electronic density was computed from the wave functions calculated at the [Formula: see text]-point in the first Brillouin-zone. Each structural optimization was minimized according to the Broyden-Fletcher-Goldfarb-Shanno (BFGS) algorithm, with force and energy convergence criteria of 25 meV[Formula: see text]Å[Formula: see text] and 1.36 meV, respectively. The electrostatic solvation effects were performed by the [Formula: see text] package with the Self-Consistent Continuum Solvation (SCCS) approach.

Direct Air Capture and Integrated Conversion of Carbon Dioxide into Cyclic Carbonates with Basic Organic Salts

Direct air capture and integrated conversion is a very attractive strategy to reduce CO₂ concentration in the atmosphere. However, the existing capturing processes are technologically challenging due to the costs of the processes and the low concentration of CO₂. The efficient valorization of the CO₂ captured could help overcome many techno-economic limitations. Here, we present a novel economical methodology for direct air capture and conversion that is able to efficiently convert CO₂ from the air into cyclic carbonates. The new approach employs commercially available basic ionic liquids, works without the need for sophisticated and expensive co-catalysts or sorbents and under mild reaction conditions. The CO₂ from atmospheric air was efficiently captured by IL solution (0.98 molCO₂/mol_IL) and, subsequently, completely converted into cyclic carbonates using epoxides or halohydrins potentially derived from biomass as substrates. A mechanism of conversion was evaluated, which helped to identify relevant reaction intermediates based on halohydrins, and consequently, a 100% selectivity was obtained using the new methodology.

Functionalized Ionic Liquids for CO2 Capture under Ambient Pressure

Ionic liquids (ILs) have been widely explored as alternative solvents for carbon dioxide (CO2) capture and utilization. However, most of these processes are under pressures significantly higher than atmospheric level, which not only levies additional equipment and operation costs, but also makes the large-scale CO2 capture and conversion less practical. In this study, we rationally designed glycol ether-functionalized imidazolium, phosphonium and ammonium ILs containing acetate (OAc-) or Tf2N- anions, and found these task-specific ILs could solubilize up to 0.55 mol CO2 per mole of IL (or 5.9 wt% CO2) at room temperature and atmospheric pressure. Although acetate anions enabled a better capture of CO2, Tf2N- anions are more compatible with alcohol dehydrogenase (ADH), which is a key enzyme involved in the cascade enzymatic conversion of CO2 to methanol. Our promising results indicate the possibility of CO2 capture under ambient pressure and its enzymatic conversion to valuable commodity.

Dipole-Bound State, Photodetachment Spectroscopy, and Resonant Photoelectron Imaging of Cryogenically-Cooled 2-Cyanopyrrolide

Valence-bound anions with polar neutral cores can have diffuse dipole-bound excited states just below the electron detachment threshold. Because of the similarity in geometry and vibrational frequencies between the dipole-bound states (DBSs) and the corresponding neutrals, DBSs have been exploited as intermediate states to conduct resonant photoelectron spectroscopy (PES), resulting in highly non-Franck-Condon photoelectron spectra via vibrational autodetachment and providing much richer vibrational information than conventional PES. Here, we report a photodetachment and high-resolution photoelectron imaging study of the 2-cyanopyrrolide anion, cooled in a cryogenic ion trap. The electron affinity of the 2-cyanopyrrolyl radical is measured to be 3.0981 ± 0.0006 eV (24 988 ± 5 cm^-1). A DBS is observed for 2-cyanopyrrolide at 240 cm^-1 below its detachment threshold using photodetachment spectroscopy. Twenty-three above-threshold vibrational resonances (Feshbach resonances) of the DBS are observed. Resonant PES is conducted at each Feshbach resonance, yielding a wealth of vibrational information about the 2-cyanopyrrolyl radical. Resonant two-photon PES confirms the s-like dipole-bound orbital and reveals a relatively long lifetime of the bound zero-point level of the DBS. Fundamental frequencies for 19 vibrational modes (out of a total of 24) are obtained for the cyanopyrrolyl radical, including six out-of-plane modes. The current work provides important spectroscopic information about 2-cyanopyrrolyl, which should be valuable for the study of this radical in combustion or astronomical environments.

Synergism between iron porphyrin and dicationic ionic liquids: tandem CO2 electroreduction–carbonylation reactions

We report a simple procedure that drastically reduces the E(Fei/Fe0) and E0cat of the FeIIITPP·Cl catalyst via a synergetic effect with the imidazolium dications of the IL electrolyte, and its application in tandem carbonylations.

The Influence of Hydrogen Bond Donors on the CO2 Absorption Mechanism by the Bio-Phenol-Based Deep Eutectic Solvents

Recently, deep eutectic solvents (DESs), a new type of solvent, have been studied widely for CO₂ capture. In this work, the anion-functionalized deep eutectic solvents composed of phenol-based ionic liquids (ILs) and hydrogen bond donors (HBDs) ethylene glycol (EG) or 4-methylimidazole (4CH₃-Im) were synthesized for CO₂ capture. The phenol-based ILs used in this study were prepared from bio-derived phenols carvacrol (Car) and thymol (Thy). The CO₂ absorption capacities of the DESs were determined. The absorption mechanisms by the DESs were also studied using nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR), and mass spectroscopy. Interestingly, the results indicated that CO₂ reacted with both the phenolic anions and EG, generating the phenol-based carbonates and the EG-based carbonates, when CO₂ interacted with the DESs formed by the ILs and EG. However, CO₂ only reacted with the phenolic anions when the DESs formed by the ILs and 4CH₃-Im. The results indicated that the HBDs impacted greatly on the CO₂ absorption mechanism, suggesting the mechanism can be tuned by changing the HBDs, and the different reaction pathways may be due to the steric hinderance differences of the functional groups of the HBDs.

Acid Catalysis with Alkane/Water Microdroplets in Ionic Liquids

Ionic liquids are composed of an organic cation and a highly delocalized perfluorinated anion, which remain tight to each other and neutral across the extended liquid framework. Here we show that n-alkanes in millimolar amounts enable a sufficient ion charge separation to release the innate acidity of the ionic liquid and catalyze the industrially relevant alkylation of phenol, after generating homogeneous, self-stabilized, and surfactant-free microdroplets (1-5 μm). This extremely mild and simple protocol circumvents any external additive or potential ionic liquid degradation and can be extended to water, which spontaneously generates microdroplets (ca. 3 μm) and catalyzes Brönsted rather than Lewis acid reactions. These results open new avenues not only in the use of ionic liquids as acid catalysts/solvents but also in the preparation of surfactant-free, well-defined ionic liquid microemulsions.

A depth-suitable and water-stable trap for CO2 capture

In terms of CO₂ capture and storage (CCS), it is highly desired to substitute of high efficiency process for the applied one which is far from the ideal one. Physical processes cannot capture CO₂ effectively, meanwhile CO₂ desorption is energy-intensive in chemical processes. Herein, a depth-suitable and water-stable trap for CO₂ capture was discovered. Carboxylates can react with polybasic acid roots by forming united hydrogen bonds. Carboxylate ionic liquid (IL) aqueous solutions can absorb one equimolar CO₂ chemically under ambient pressure, and its CO₂ desorption is easy, similar to that in physical absorption/desorption processes. When used as aqueous solutions, carboxylate ILs can replace alkanolamines directly in the applied CCS process, and the efficiency is enhanced significantly due to the low regenerating temperature. CO₂ (or polybasic acids) can be used as a polarity switch for ILs and surfactants. A new method for producing carboxylate ILs is also proposed.

Carboxylates can react with carbonic acid and form two united hydrogen bonds, which is depth-suitable for CO₂ capture.