The urgent need to mitigate anthropogenic CO₂ emissions has driven the development of energy-efficient carbon capture systems. This study investigated a [N₁₁₁₁][Triz]-H₂O hybrid solvent for CO₂ capture using integrated experimental and computational approaches. A multiscale methodology combining thermodynamic analysis, phase equilibrium measurements, and molecular dynamics (MD) simulations was employed to elucidate the absorption mechanisms and the composition-property relationships. The thermodynamic analysis, incorporating Henry's law, the non-random two-liquid (NRTL) model for activity coefficients, the Redlich-Kwong equation, and reaction equilibrium constraints, accurately predicted the gas-liquid equilibrium (GLE) behavior, achieving an R² of 99.1% and an average absolute relative deviation (AARD) of 7.76%. The [N₁₁₁₁][Triz]-H₂O hybrid solvent exhibits exceptional CO₂ absorption performance, with a capacity of 0.25 mol/mol (at 313.15 K and 0.025 MPa for w_IL = 80%), attributed to synergistic physical-chemical interactions. MD simulations reveal the dynamic CO₂ absorption process in [N₁₁₁₁][Triz]-H₂O hybrid solvents: CO₂ molecules preferentially accumulate at the gas-liquid interface before gradually diffusing into the bulk phase. Increasing the [N₁₁₁₁][Triz] content enhances CO₂ absorption capacity by providing more interaction sites, while water modulates interfacial behavior and diffusion kinetics. This research provides in-depth insights into the absorption behaviors of [N₁₁₁₁][Triz]-H₂O hybrid solvents for CO₂, offering theoretical support for the development of efficient CO₂ capture solvents and highlighting its potential for industrial implementation.

Emitting NH₃ into the atmosphere leads to significant air pollution, while NH₃ itself serves as an essential component for fertilizers and refrigerants in industry. Thus, recovering and reusing NH₃ is highly valuable. Ionic liquids (ILs) have shown great potential for NH₃ capture, where the accurate prediction of solubility is a critical point for selecting ILs and designing a separation process. This work combined the Ionic Fragment Contribution (IFC) strategy with machine learning (ML) to develop four models (IFC-ML) to predict NH₃ solubility in ILs. A dataset containing 785 solubility data points, covering 10 cations and 10 anions, was collected. From this dataset, the S1–S6 descriptors based on the IFC method were used as inputs for the ML models, together with temperature (T) and pressure (P). Among the models, the IFC-GBR model was recommended for predicting NH₃ solubility in ILs due to its higher coefficient of determination (R²) of 0.9945 and lower mean squared error (MSE) of 0.0003 than the others. Additionally, in comparison with previous conductor-like screening model for real solvents (COSMO-RS) and extreme learning machine (ELM) methods, the IFC-GBR (gradient boosting regressor) method showed a more accurate prediction of the NH₃ solubility in ILs over a wider range of temperatures and pressures, providing additional chemical insights into IL-NH₃ system that cations played a more important role for NH₃ solubility. These results highlighted the developed IFC-GBR model offered valuable insights for helping guide the process design of absorbing NH₃ through IL-based technology.

Ionic liquids (ILs) provide a promising way for efficient absorption and separation of ammonia (NH₃) due to their extremely low vapor pressures and adjustable structures. However, the understanding of absorption mechanisms especially in terms of theoretical insights is still not very clear, which is crucial for designing targeted ILs. In this work, a universal method that integrates density functional theory and molecular dynamic simulations was proposed to study the mechanisms of NH₃ absorption by protic ionic liquids (PILs). The results showed that the NH₃ absorption performance of the imidazolium-based PILs ([BIm][X], X= Tf₂N, SCN and NO₃) is determined by not only the hydrogen bonding between the N atom in NH₃ and the protic site (H–N³) on the cation but also the cation–anion interaction. With the increase in NH₃ absorption capacity, the hydrogen bonding between [BIm][Tf₂N] and NH₃ changed from orbital dominated to electrostatic dominated, so 3.0 mol NH₃ per mol IL at 313.15 K and 0.10 MPa was further proved as a threshold for NH₃ capacity of [BIm][Tf₂N] by the Gibbs free energy results, which agrees well with the experimental results. Furthermore, the anions of [BIm][X] could also compete with NH₃ for interaction with H-N³ of the cation, which weakens the interaction between the cation and NH₃ and then decreases the NH₃ absorption ability of PILs. This study provides further understanding on NH₃ absorption mechanisms with ILs, which will guide the design of novel functionalized ILs for NH₃ separation and recovery.

The chemical transformation of CO₂ and epoxides into cyclic carbonates has been receiving much attention and is one of the successful examples for CO₂ utilization as carbon resource. Many catalysts containing halide anions have been explored and exhibit excellent catalytic activity. However, halogen salt is generally toxic and corrosive to reactors. From a green chemistry perspective, it is more attractive to develop a halogen-free catalyst with excellent performance. Herein, a review of recent research progress of halogen-free catalysts in the cycloaddition of CO₂ and epoxide is presented. According to previous experimental and theoretical works, two possible strategies for achieving the halogen-free process were summarized. The relationship between catalytic activity and catalyst structure, the mechanism of CO₂ activation should be both studied deeply combined with experimental results and DFT calculation, which can guide the design of new catalysts and realize halogen-free process under mild reaction conditions.