Adsorption energy and diffusion barrier of methanol in Ni₂(4,4'-bipyridine)₃(NO₃)₄ were investigated using molecular mechanics and molecular dynamics method. The results indicated that each Ni₂(4,4'-bipyridine)₃(NO₃)₄ unit can adsorb 4 methanol molecules and the structure was optimized for the uptake of 2 methanol molecules. The framework structure underwent obvious deformation when the loading was above 2, which resulted in methanol adsorption isotherm step. The calculated diffusion barrier (35.94 kJ•mol^－1) accorded with the experiment well. It could be concluded that structure deformation strongly affected the adsorption and diffusion characteristic of adsorbate in flexible metal-organic frameworks (MOFs).

Key words: molecular simulation, methanol, MOFs, adsorption energy, diffusion barrier