Li-decorated β1-graphyne for high-performance CO₂ capture and separation over N₂

The selective CO₂ adsorption is of great significance to many energy and environment-related processes. Herein, CO₂/N₂ 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 β1-graphyne (Li-β1-GY) for CO₂/N₂ 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 CO₂ adsorption performance. Among all Li-β1-GYs, the ac structure showed the best CO2 adsorption performance. The CO₂ 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 CO₂/N₂ selectivity reached 354. The gas distribution confirmed that CO₂ was adsorbed around the Li and C atoms and demonstrated the significant improvement of C atoms around Li atoms on the CO₂ adsorption. The interaction analyses showed that Li doping enhanced the CO₂-framework interaction more distinctively than the N₂-framework interaction, leading to an ultra-high CO₂ adsorption capacity and CO₂/N₂ selectivity. Results of this work highlighted Li-β1-GYs as promising materials for CO₂/N₂ adsorption and separation.