Molecular Dynamics Simulation of the Adsorption and Diffusion of C₈ Aromatic Isomers in MIL-47(V)

The separation of C₈ aromatic isomers (oX: o-xylene, pX: p-xylene, mX: m-xylene, and EB: ethylbenzene) remains an enormous challenge in industrial production due to their similar molecular structures and physical properties. Porous materials with suitable pore structures and selective recognition sites to discriminate the slight structural differences of isomers are imminently needed. In this paper, MIL-47(V) with a three-dimensional (3D) grid structure of 10.5 × 10.5 Ų and a one-dimensional (1D) diamond channel was selected as the adsorbent. However, the mechanism of the adsorption and separation of C₈ aromatic isomers in porous materials still needs to be understood. Given the importance of C₈ aromatic isomers' confinement in MIL-47(V) for adsorption and diffusion applications, it is important to understand C₈ aromatic isomers' behavior in MIL-47(V). Here, we demonstrated from a simulation perspective that metal-organic frameworks MIL-47(V) with one-dimensional (1D) diamond channels can identify C₈ aromatic isomers. Molecular dynamics (MD) simulations have shown that organic ligands with guest response sites of MIL-47(V) can effectively distinguish between C₈ aromatic isomers by adaptation to the shape of a specific isomer. MIL-47(V) has high adsorption and an excellent separation sequence between C₈ aromatic isomers: oX > pX ≈ mX > EB. Significant differences exist in π-π superposition interactions between C₈ aromatic isomers and between C₈ aromatic isomers and the skeletons. This phenomenon is mainly caused by the unique pore structure and guest response characteristics of MIL-47(V). This work is identified as a supplementary instruction to experimental research and is expected to provide profound insights into research on developing C₈ aromatic isomers' adsorption and separation and theoretical support.