Li-decorated graphdiyne for ultrahigh-performance CO2 capture and separation over N2

The development of CO2 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 CO2 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; 1/2/6LiGDYs 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 CO2 adsorption. Among Li-GDYs, 2/6Li-GDYs exhibited an ultra-high CO2 adsorption capacity of 11.91 mmol/g at 298 K and 100 kPa, and was superior to other metal-modified adsorbents. The CO2/N2 selectivity in 1/2/6Li-GDYs reached 168,-311, and 1021 at 298 K and 100 kPa. Gas distribution analysis revealed a broad CO2 distribution consisting of multilayer adsorption peaks around Li and adjacent C atoms, illustrating the significant effect of Li and Li-connected C atoms on CO2 adsorption. Interaction analysis showed that Li doping enhanced the CO2- framework interaction more significantly than the N2-framework interaction, resulting in ultra-high CO2 adsorption capacity and CO2/N2 selectivity. The results of this work highlight 1/2/6Li-GDYs as ultrahigh performance adsorbent materials for CO2 adsorption and separation over N2.