Carbon dioxide as carbon source: Activation via electrogenerated O2− in ionic liquids

Ionic Liquid-Catalyzed CO2 Conversion for Valuable Chemicals

CO2 is not only the main gas that causes the greenhouse effect but also a resource with abundant reserves, low price, and low toxicity. It is expected to become an important "carbon source" to replace oil and natural gas in the future. The efficient and clean resource utilization of CO2 has shown important scientific and economic value. Making full use of abundant CO2 resources is in line with the development direction of green chemistry and has attracted the attention of scientists. Environmentally friendly ionic liquids show unique advantages in the capture and conversion of CO2 due to their non-volatilization, designable structure, and good solubility, and show broad application prospects. The purpose of this paper is to discuss the research on the use of an ionic liquid as a catalyst to promote the synthesis of various value-added chemicals in CO2, hoping to make full use of CO2 resources while avoiding the defects of the traditional synthesis route, such as the use of highly toxic raw materials, complicated operation, or harsh reaction conditions. The purpose of this paper is to provide reference for the application and development of ionic liquids in CO2 capture and conversion.

Electrochemical synthesis and amidation of benzoin: benzamides from benzaldehydes

The benzoin condensation starting from benzaldehyde and the subsequent benzoin amidation to benzamide can be efficiently carried out under very mild conditions in an electrolysis cell. Among the advantages of using electrochemistry to generate our active reagents, the use of the easily dosed and non pollutant electron, instead of stoichiometric amounts of redox reagents or bases, usually renders the electrochemical methodology “greener” than classical organic reactions. Benzoin is obtained in good yield (85 %) carrying out the reaction in the room temperature ionic liquid BMIm-BF4. In this electrochemical reaction this liquid salt assumes the double role of solvent-supporting electrolyte system and precatalyst, yielding the corresponding N-heterocyclic carbene. The subsequent benzoin amidation is carried out by electrochemically generated superoxide anion, in the presence of an aliphatic primary or secondary amine. In this case the system superoxide/molecular oxygen acts as base and oxidant, yielding very good yields of benzamides (up to 89 %).

In Situ Electrosynthesis of Peroxydicarbonate Anion in Ionic Liquid Media Using Carbon Dioxide/Superoxide System

Climate engineering solutions with emphasis on CO₂ removal remain a global open challenge to balancing atmospheric CO₂ equilibrium levels. As a result, warnings of impending climate disasters are growing every day in urgency. Beyond ordinary CO₂ removal through natural CO₂ sinks such as oceans and forest vegetation, direct CO₂ conversion into valuable intermediaries is necessary. Here, a direct electrosynthesis of the peroxydicarbonate anion (C₂O₆^2-) was investigated by the reaction of CO₂ with the superoxide ion (O₂^·-), electrochemically generated from O₂ reduction in bis(trifluoromethylsulfonyl)imide [TFSI^-] anion derived ionic liquid (IL) media. This is the first time that the IL media were employed successfully for CO₂ conversion into C₂O₆^2-. Moreover, the charge transfer coefficient for the O₂^·- generation process in the ILs was less than 0.5, indicating that the process was irreversible. Voltammetry experiments coupled with global electrophilicity index analysis revealed that, when CO₂/O₂ was contacted simultaneously in the IL medium, O₂^·- was generated in situ first at a potential of approximately -1.0 V. Also, CO₂ was more susceptible to attack by O₂^·- before any possible interaction with the IL except for [PMIm⁺][TFSI^-]. This was because CO₂ has a higher global electrophilicity index (ω_CO2 = 0.489 eV) than those for the [EDMPAmm⁺][TFSI^-] and [MOEMMor⁺][TFSI^-]. By further COSMO-RS modeling, CO₂ absorption was proven feasible at the COSMO-surface of the [TFSI^-] IL-anion where the charge densities were σ = -1.100 and 1.1097 e/nm². Therefore, the susceptible competitiveness of either IL cations or CO₂ to the nucleophilic effects of O₂^·- was a function of their positive character as estimated by their electrophilicity indices. As determined by experimental attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and DFT-FTIR computation, the reaction yielded C₂O₆^2- in the ILs. Consequently, the presence of O=O symmetric stretching FTIR vibrational mode at ∼844 cm^-1 coupled with the disappearance of the oxidative cyclic voltammetry waves when sparging CO₂ and O₂ confirmed the presence of C₂O₆^2-. Moreover, based on DFT/B3LYP/6-31G, pure C₂O₆^2- has symmetric O=O stretching at ∼805 and ∼844 cm^-1 when it is in association with the IL-cation. This was the first spectroscopic observation of C₂O₆^2- in ILs, and the O=O symmetric stretching vibration has peculiarity for identifying C₂O₆^2- in ILs. This will open new doors to utilize CO₂ in industrial applications with the aid of reactive oxygen species.

Effect of protonation on the solvation structure of solute N-butylamine in an aprotic ionic liquid

Significant change in the solvation structure by protonation reaction in the ionic liquid [C₂mIm][TFSA].

Towards a sustainable electrochemical activation for recycling CO2: synthesis of bis-O-alkylcarbamates from aliphatic and benzyl diamines

Optimized conditions for carbamate synthesis with activated CO₂ are potentially applicable to sustainable large scale manufacturing of key polymeric resin precursors.

Superoxide Ion: Generation and Chemical Implications

Superoxide ion (O2(•-)) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2(•-) is rather scarce. In addition, numerous studies on O2(•-) were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2(•-) reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2(•-) so as to enable researchers to venture into future research. It comprises the main characteristics of O2(•-) followed by generation methods. The reaction types of O2(•-) are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2(•-) environmental chemistry is also discussed. The detection methods of O2(•-) are categorized and elaborated. Special attention is given to the feasibility of using ionic liquids as media for O2(•-), addressing the latest progress of generation and applications. The effect of electrodes on the O2(•-) electrochemical generation is reviewed. Finally, some remarks and future perspectives are concluded.