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Because of the growing demand for energy, oil extraction under complicated geological conditions is increasing. Herein, oil displacement by CO2 in wedge-shaped pores was investigated by molecular dynamics simulation. The results showed that, for both single and double wedge-shaped models, pore Ⅱ (pore size from 3 to 8 nm) exhibited a better CO2 flooding ability than pore Ⅰ (pore size from 8 to 3 nm). Compared with slit-shaped pores (3 and 8 nm), the overall oil displacement efficiency followed the sequence of 8 nm > double pore Ⅱ > single pore Ⅱ > 3 nm > double pore Ⅰ > single pore Ⅰ, which confirmed that the exits of the wedge-shaped pores had determinant effects on CO2 enhanced oil recovery over their entrances. "Oil/CO2 inter-pore migration" and "siphoning" phenomena occurred in wedge-shaped double pores by comparing the volumes of oil/CO2 and the center of mass. The results of the interaction and radial distribution function analyses indicate that the wide inlet and outlet had a larger CO2–oil contact surface, better phase miscibility, higher interaction, and faster displacement. These findings clarify the CO2 flooding mechanisms in wedge-shaped pores and provide a scientific basis for the practical applications of CO2 flooding. [ABSTRACT FROM AUTHOR]

Two-dimensional conjugated aromatic polymer with S/P substitutions demonstrated significant balance of H 2 permeance and selectivities over CO 2 /CO/N 2 /CH 4 via the effects of pore size and gas-membrane interaction. [Display omitted] • High cohesive energies confirm high structural stabilities of CAP-1S/CAP-1P. • CAP-1P exhibits almost complete H 2 selectivity with high H 2 permeance. • S/P substitution creates large pore sizes and strong gas-membrane interactions. • The interaction and pore size render efficient H 2 purification jointly. Based on two-dimensional conjugated aromatic polymer (2D-CAP), CAP-1S/CAP-1P monolayers were designed by substituting N with S/P atoms for H 2 purification. By using MD and DFT approaches, the H 2 purification performance and separation mechanisms of CAP-1S/CAP-1P membranes were investigated. Results showed that ultrahigh H 2 permeances of 3.546 × 10−5 and 2.593 × 10−4 mol m−2 s−1 Pa−1 were obtained in CAP-1S/CAP-1P, which were almost 104–105 times larger than the industrially acceptable standard. The selectivities of H 2 over CO 2 /CO/CH 4 /N 2 ranged from 5.719 × 1018 to 3.683 × 1039 in CAP-1S and 4.554 × 1013 to 2.153 × 1033 in CAP-1P. From a statistic viewpoint, the CAP-1S/CAP-1P membranes exhibited complete selectivities of H 2 over CO 2 /CO/CH 4 /N 2. The cohesive energies confirmed the high stabilities of CAP-1S/CAP-1P membranes. The minimum energy pathways, energy profiles, electron density, and charge density difference were analyzed to illustrate the significant impact of precise pore size on the H 2 separation performance. From a statistic mechanics view, the interaction between gases and CAP-1S/CAP-1P membranes indicated that the long-range Coulomb interactions dominated the gas diffusion processes. Results of this work highlighted CAP-1P as a promising H 2 separation membrane and elucidated the promotion mechanism by fine-tunning pore size and interaction between gases and membranes to balance the H 2 permeance and selectivity jointly. [ABSTRACT FROM AUTHOR]

By regulating the doping number of Li atoms in graphdiyne (GDY), the adsorption site of the structure is increased and the interaction between gas and skeleton is enhanced, thus creating a favorable environment for CO 2 adsorption. Li-GDYs have ultra-high CO 2 adsorption capacity and CO 2 /N 2 selectivity. [Display omitted] • Three structures with different Li doping types are screened. • Li-GDYs exhibit an ultra-high CO 2 adsorption capacity and CO 2 /N 2 selectivity. • Li doping has a more pronounced effect on enhancing the CO 2 − Li-GDYs interaction. • Gas distribution analyses demonstrate Li doping provides more adsorption sites. The development of CO 2 adsorbents with high adsorption and separation performances is important to solve severe environmental problems. Herein, two-dimensional graphdiyne acetylene rings doped with different concentrations of lithium atoms (1/2/6Li-GDYs) were introduced as potential adsorbents for CO 2 capture and separation by using Grand Canonical Monte Carlo and Density Functional Theory methods. According to the structure analysis, Li atoms could stably bind to GDY with a binding energy of 1.04 – 2.77 eV/atom; 1/2/6Li-GDYs had high cohesive energy of 7.02 – 7.54 eV/atom. Electronic structure analysis confirmed the large charge transfer and strong interaction between Li atoms and GDY. The pore physical properties of Li-GDYs indicated that the pore volume, porosity, and pore size provided a favorable environment for CO 2 adsorption. Among Li-GDYs, 2/6Li-GDYs exhibited an ultra-high CO 2 adsorption capacity of 11.91 mmol/g at 298 K and 100 kPa, and was superior to other metal-modified adsorbents. The CO 2 /N 2 selectivity in 1/2/6Li-GDYs reached ∼ 168, ∼311, and ∼ 1021 at 298 K and 100 kPa. Gas distribution analysis revealed a broad CO 2 distribution consisting of multilayer adsorption peaks around Li and adjacent C atoms, illustrating the significant effect of Li and Li-connected C atoms on CO 2 adsorption. Interaction analysis showed that Li doping enhanced the CO 2 -framework interaction more significantly than the N 2 -framework interaction, resulting in ultra-high CO 2 adsorption capacity and CO 2 /N 2 selectivity. The results of this work highlight 1/2/6Li-GDYs as ultrahigh-performance adsorbent materials for CO 2 adsorption and separation over N 2. [ABSTRACT FROM AUTHOR]

• Co-Salen complexes containing different groups and bearing potassium iodide (KI) complexed with crown ether (K@SCs) were prepared. • Salen derivative organic polymer as heterogeneous catalyst for CO 2 cycloaddition reaction. • Alkali metal halides and Lewis acids have good synergistic effects in catalytic reactions. Metallosalen presents very important applications in both homogenous and heterogeneous catalysis. Correspondingly, porous polymeric metallosalen combined with the performance of organometallics and heterogeneous polymers possess potential in CO 2 fixation reactions. Herein, a family collection of K@SCs were conceived and obtained by combining cobalt-salen complexes with different groups and diaminobenzene-18-crown-6 complexed with KI, which allows multiphase catalytic immobilization of CO 2 to epoxides. Catalyst K@SC-3 can fix CO 2 into a variety of substituted epoxides in >90% yields to the corresponding cyclic carbonates in co-catalyst-free and solvent-free conditions. Furthermore, K@SC-3 can be recovered and reused at least six times by simple centrifugal separation, demonstrating superior stability. The kinetics experiments were also carried out at varied temperatures catalyzed by K@SC-3. It is concluded that a first-order equation of epoxide was proved and the activation energy was calculated to be 27.13 KJ/mol. [Display omitted] [ABSTRACT FROM AUTHOR]

By regulating the doping site and concentration of Li atoms in β1-Graphyne, more charges accumulate on the surrounding C atoms and the gas-framework interaction increase, thus creating a favorable environment for CO 2 adsorption and an ultra-high CO 2 adsorption capacity and CO 2 /N 2 selectivity in Li-β1-GYs. [Display omitted] • Li-β1-GYs exhibit an ultra-high CO 2 adsorption capacity and CO 2 /N 2 selectivity. • Li doping has a more pronounced effect on enhancing the CO 2 −Li-β1-GYs interaction. • Gas distribution analyses demonstrate Li doping provides more adsorption sites. The selective CO 2 adsorption is of great significance to many energy and environment-related processes. Herein, CO 2 /N 2 adsorption and separation in Li-doped 2D graphyne allotrope (β1-GY) were studied by using grand canonical Monte Carlo simulation and density(GCMC) functional theory approaches(DFT). The results showed that Li atoms were stably combined with β1-GY and the binding energy was −2.85−−3.60 eV, which ensured the structural stability of Li-doped β 1 -graphyne (Li-β1-GY) for CO 2 /N 2 adsorption and separation. Different Li doping types were evaluated, and five Li-β1-GY structures were screened, including the a, b, c, ac, and bc structures. Li doping provided more adsorption sites and improved the CO 2 adsorption performance. Among all Li-β1-GYs, the ac structure showed the best CO 2 adsorption performance. The CO 2 adsorption capacity of ac structure reached 11.10 mmol−1 g−1 at 298 K and 100 kPa, which was higher than the well-known metal–organic framework Mg-MOF-74 (∼8.60 mmol−1 g−1) under the same condition. At 298 K and 100 kPa, the CO 2 /N 2 selectivity reached 354. The gas distribution confirmed that CO 2 was adsorbed around the Li and C atoms and demonstrated the significant improvement of C atoms around Li atoms on the CO 2 adsorption. The interaction analyses showed that Li doping enhanced the CO 2 -framework interaction more distinctively than the N 2 -framework interaction, leading to an ultra-high CO 2 adsorption capacity and CO 2 /N 2 selectivity. Results of this work highlighted Li-β1-GYs as promising materials for CO 2 /N 2 adsorption and separation. [ABSTRACT FROM AUTHOR]

• CO 2 absorption in MEA + H 2 O + Ethanol is explained by zwitterion mechanism with rate-limiting of deprotonation. • Water accelerates reactions by participating in the deprotonation of MEA-zwitterion and changing the solvation environment. • An improved kinetic model based on zwitterion mechanism was proposed with an average absolute relative difference of 6.73%. The kinetics of CO 2 absorption in ethanolamine (MEA) + H 2 O + ethanol systems was investigated using stopped-flow apparatus. The first-order reaction rate constant (k 0) values were tested with varying H 2 O and MEA concentrations. Transiting from the aqueous to non-aqueous solvents, the k 0 decreases and the reaction order for MEA shifts from 1.05 to 1.88. The zwitterion mechanism with the rate-limiting step of deprotonation was used to explore the role of water and its effect. Results showed that water could impact reactions through direct involvement and changing solvation environment. An improved kinetic model based on the zwitterion mechanism was obtained to indicate the quantitative influence of H 2 O concentration on the reaction kinetics of MEA + H 2 O + ethanol systems. The predicted values from the model well agreed to the experimental data with the average absolute relative difference of 6.73%. This study highlights the important effects of water on the reaction kinetics of CO 2 absorption into water-lean amine solutions. [ABSTRACT FROM AUTHOR]