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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]