Simulation of Adsorption and Separation Behavior of Elemental Gases on Lanthanide-Based Nd-MOF

Abstract

In this work, we use molecular dynamics (MD) method to calculate the monomeric and competitive absorption behavior of six nuclear-industrial elemental gases: H₂, N₂, I₂, Ar, Kr, Xe in the lanthanide-based MOF (Nd-MOF: {[Ln₂(IDA)₃]⋅(H₂O)₂}_n (Ln = Nd; H₂IDA = iminodiacetic acid). Subsequently, the density functional theory (DFT) is employed to calculate the electronic density difference of MOF systems for different gases and adsorption sites. Furthermore, the thermodynamic stability of MOF materials is analyzed by integrating DFT combined MD. The result shows that the MOF system has a higher absorptive selectivity to the inert elemental gases, while the absorptions of I₂ are very weak, due to molecular sieve effect. The channel structure of Nd-MOF exhibits different characteristics depending on the composition of the adsorption sites, and both types of channels have deeper adsorption potential wells for inert gases. Moreover, we note that the lattice remains stable under working conditions (250–400 K), and is prone to thermal decomposition at 700 K with the saturation of heat capacity. The Nd-MOF system is expected for the adsorption and separation of mixed-elemental gases and the purification of I₂.