Search

[Display omitted] Excessive CO 2 emissions have contributed to global environmental issues, driving the development of CO 2 capture adsorbents. Among various candidates, metal–organic frameworks (MOFs) are considered the most promising due to their unique microporous structure. Herein, a series of partially interpenetrated MOFs named UPC-XX were built to investigate the continuous enhancement in CO 2 capture performance via synergistic effects from functional group, pore size, and steric-hindrance using theoretical calculations. It's showed that the introduction of functional groups improved the structure polarity and created more adsorption sites, thus, enhanced CO 2 capture capacity. The pore size modification augments the exposure of adsorption sites to mitigate the negative impact of pore space and surface area reduction caused by the introduction of functional groups, thereby further increasing the CO 2 capture capacity. The steric-hindrance effect optimized the adsorption sites distribution, which hasn't been considered in the previous two regulation strategies, thus, further increased the CO 2 capture capacity. The results underscore UPC-MOFs as outstanding adsorbent materials, among the UPC-MOFs, UPC-OSO 3 -steric exhibited the highest CO 2 capture capacity of 12.69 mmol/g with selectivities of 1142.41 (CO 2 over N 2) and 507.42 (CO 2 over CH 4) at 1.0 bar, 298 K. And the synergistic effect mechanisms of functional group, structure size, and steric hindrance were elucidated through theoretical calculations analyzing pore characteristics, gas distribution, isosteric heat, and van der Waals/Coulomb interactions. [ABSTRACT FROM AUTHOR]

The CO 2 capture and separation performance is enhanced by the improved structural polarity and additional adsorption sites created by anchoring alkali metal Li/Na/K. And the increase shows a positive correlation with AM concentration. Specially, UPC-6Li presents the best CO 2 capture capacity of 221.64 cm3 cm−3, along with the CO 2 over N 2 /CH 4 selectivity of 308/206, among UPC-AMs. [Display omitted] • CO 2 capture and separation performance were evaluated in 2D-COFs anchored by different concentration alkali metal (Li, Na, and K). • UPC-6Li exhibited the best CO 2 capture capacity of 221.64 cm3 cm−3 and CO 2 over N 2 /CH 4 selectivity of 308/206. • Improved structural polarity and additional metal adsorption sites are the main reasons for optimized performance. The development of advanced adsorbents with high CO 2 capture and separation performances is essential for decreasing atmospheric CO 2 concentration. Herein, grand canonical Monte Carlo and density functional theory were employed to investigate the adsorption and separation properties of CO 2 , N 2 , and CH 4 in 2D covalent organic framework (COFs) anchored by alkali metal (AMs) Li, Na, and K (UPC-nAMs, n = 3 or 6) at 298 K and 0–1.0 bar. The anchoring of AMs formed favorable adsorption sites, endowing UPC-nAMs with better CO 2 capture and separation performances. This effect was more evident with an increase in Li/Na/K concentration. The CO 2 adsorption capacity of UPC-6Li/Na/K was ∼ 221.64, 188.28, and 140.50 cm3 cm−3. The smaller atomic size of Li occupied less adsorption space, resulting in the highest CO 2 capture capacity of 221.64 cm3 cm−3 with selectivity of 308/206 over N 2 /CH 4 in UPC-6Li at 298 K and 1.0 bar. Structural stability, pore characteristics, isothermal adsorption heat, van der Waals and Coulomb interactions, gas distribution density, adsorption configuration, and gas radial distribution function were analyzed to identify the intrinsic mechanism of anchoring Li/Na/K to improve CO 2 capture and separation performances. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are emerging adsorbent materials for CO2 capture and separation due to their tunable pore size, periodic permutation, and chemical thermal stability. Herein, four functionalized 3D COF‐300s (COF‐300‐X, X = –SO3H, –NO2, –OH, and –NH2) for CO2 adsorption and separation are studied by using density functional theory and grand canonical Monte Carlo simulation. The results show that four functionalized COF‐300s could create a feasible environment for CO2 adsorption with high accessible surface area, suitable pore size, and high porosity. The CO2 adsorption capacity in COF‐300s could be significantly improved by functionalization. In comparison, the best performing COF‐300‐SO3H shows a superior CO2 adsorption capacity of 6.23 mmol g−1 and a high CO2/N2 selectivity of 393 at 298 K and 100 kPa. The adsorption heat and interaction analyses demonstrate that the CO2 affinity in COF‐300s is enhanced by the introduction of polar functional groups, which renders great CO2 adsorption and separation performances. The gas distribution shows that the adsorption sites are concentrated near the functional groups and the distribution of CO2 in COF‐300‐SO3H has a characteristic of multilayer adsorptions. This work highlights COF‐300‐SO3H as an outperforming adsorbent candidate for CO2 capture and separation. [ABSTRACT FROM AUTHOR]

Understanding the internal mechanism of CO2 adsorption and separation of COF adsorbent materials is of great significance for high-efficiency carbon capture and storage (CCS). Herein, polyarylether-based covalent organic frameworks (PAE-COFs) structures with functionalized –CN, –COOH, and –C(NH2)NOH groups were evaluated for CO2 adsorption and separation over N2 by using grand canonical Monte Carlo (GCMC) simulation and density functional theory (DFT). Our calculation results showed that the adsorption and separation performance of CO2 in COF frameworks was related to the physical characteristics of pores, the types of gas molecules, and the interaction between COFs and gas molecules. JUC-505 modified by –CN functional group provided a feasible microporous environment with moderate specific surface area and porosity, presenting a high CO2 adsorption capacity of 5.14 mmol/g at 273 K and 1 bar. The PAE-COFs structures had good CO2/N2 separation performance, in which the CO2/N2 selectivity of JUC-505-COOH reached up to 90 at 273 K and 1 bar. Interactions analysis showed that the van der Waals and Coulomb interactions between CO2 and the framework were significantly stronger than those between N2 and the framework. Therefore, CO2 had a higher adsorption heat, which led to the larger adsorption capacity and the high selectivity of CO2 over N2. The gas radial distribution functions and 2D density distribution displayed that the CO2 adsorption corresponded to a multi-layer adsorption in frameworks, leading to the high performances of PAE-COFs for CO2 capture and separation. [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]

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]