Simulation study on the impregnation of ZIF-8 with Pd nanoparticle, fullerene C60, and metallofullerene Sc3C2@C80 guests: Analyzing guest effectiveness for enhancing CO2 uptake capacity

Abstract

Today, it is accepted that CO₂ from the burning of fossil fuels plays a major role in global warming. Therefore, in recent years, to reduce the CO₂ concentration in the atmosphere, the synthesis and design of porous materials such as ZIFs have attracted the attention of many researchers. Improving the adsorption capacity of the synthesized ZIFs is very necessary to make them suitable for industrial applications. For this purpose, various strategies such as modification of linkers, catenation, introduction of open-metal sites and impregnation with fullerene and metallic nanoparticles have been proposed and investigated. In this study, using Grand Canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations, the effect of ZIF-8 impregnation with different guest molecules such as Pd nanoparticles, C₆₀ fullerene and Sc₃C₂@C₈₀ metallofullerene on CO₂ adsorption capacity has been investigated and the performance of the guest molecules are compared. The simulation results show that the pristine ZIF-8 has three special adsorption sites I, II and III in its structure. While increasing the concentration of guest molecules (i.e. the number of 1 and 3 guest molecules) in ZIF-8 by creating a new and more active IV site and thus increasing the number of adsorption sites from 3 to 4, increases the CO₂ adsorption capacity. While higher concentrations of guest molecules (i.e. 6 and 9 guest molecules) decrease the CO₂ adsorption capacity by blocking the pores of ZIF-8 and reducing the pore volume and surface area. The simulation results also show that the role of guest molecules in increasing gas adsorption capacity can be determined as the trend of Sc₃C₂@C₈₀ > C₆₀ ≥ Pd. The simulation results show that despite having a lower gas adsorption capacity, Pd nanoparticles have stronger interactions with CO₂ molecules and cause stronger CO₂ gas adsorption. In this study, the role of guest molecules in increasing the strength of interaction with CO₂ gas was determined as Pd > Sc₃C₂@C₈₀ > C₆₀. The results of this study provide a new and broad view of the impregnation phenomenon of ZIFs as well as the function of different guest molecules in the impregnation phenomenon. It is expected that the results of this study can help researchers in this field to choose the appropriate guest molecule in the impregnation phenomenon in order to improve the gas adsorption capacity.