Interpreting of the carbon dioxide adsorption on high surface area zeolitic imidazolate Framework-8 (ZIF-8) nanoparticles using a statistical physics model

Abstract

The objective of this paper was to study CO2 adsorption on the extremely porous ZIF-8 (Zn(mIm)2 with mIm = 2-methylimidazolate). The ZIF-8 was characterized via X-ray diffraction, scanning electron microscopy, TGA analysis and N2 adsorption-desorption isotherms. The adsorption isotherms were generated at different temperatures, namely, 273 K, 298 K, 323 K, and 353 K. Based on the experimental result, a new model was simulated and interpreted using a multilayer model with saturation. The physicochemical parameters that described the CO2 adsorption process were determined by physical statistical formalism. The characteristic parameters of the CO2 adsorption isotherm such as the number of carbon dioxide molecules per site (nCO2), the receptor site densities (DZIF-8), and the energetic parameters (ΔE1a, ΔE2a) were investigated. In addition, the thermodynamic functions that governed the adsorption process such as the internal energy (Eint), entropy (Sad) and Gibbs free energy (Gad) were determined by a statistical physics model. Thus, the results showed that CO2 adsorption on ZIF-8 was spontaneous and exothermic in nature.