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

作者：Xu, Shengyu; Wei, Shuxian; Wang, Lu; Liu, Sen; Wang, Maohuai^*; Liu, Siyuan; Wang, Zhaojie; Yang, Tianfang^*; Lu, Xiaoqing^*

来源：Applied Surface Science, 2022, 605: 154724.

DOI：10.1016/j.apsusc.2022.154724

• Graphyne
• Li doping
• Gas-framework interaction
• CO2/N-2 adsorption and separation

The selective CO2 adsorption is of great significance to many energy and environment-related processes. Herein, CO2/N-2 adsorption and separation in Li-doped 2D graphyne allotrope (beta 1-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 beta 1-GY and the binding energy was -2.85--3.60 eV, which ensured the structural stability of Li-doped beta 1-graphyne (Li-beta 1-GY) for CO2/N-2 adsorption and separation. Different Li doping types were evaluated, and five Li-beta 1-GY structures were screened, including the a, b, c, ac, and be structures. Li doping provided more adsorption sites and improved the CO2 adsorption performance. Among all Li-beta 1-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 (similar to 8.60 mmol(-1) g(-1)) under the same condition. At 298 K and 100 kPa, the CO2/N-2 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 N-2-framework interaction, leading to an ultra-high CO2 adsorption capacity and CO2/N-2 selectivity. Results of this work highlighted Li-beta 1-GYs as promising materials for CO2/N-2 adsorption and separation.