Adsorption and Diffusion of Benzene in Mg-MOF-74 with Open Metal Sites

We performed molecular simulations to investigate the adsorption and diffusion of benzene in metal–organic framework Mg-MOF-74. At 300 K and 20 Pa, the saturated loading of benzene reaches 8.2 mmol/g, almost twice of (12,12) single-walled carbon nanotube with a similar pore size, and 93% of the benzene molecules in Mg-MOF-74 can desorb at 390 K. The energy analysis indicates that the van der Waals contribution still dominates 70–80% of the total fluid–wall interaction energy compared with the Coulombic contribution. We further analyzed the structure of benzene confined in Mg-MOF-74 by the molecular snapshots, pair correlation functions, orientational order parameters, and local density profiles. It is found that low temperature and high pressure make the structure of adsorbed benzene more similar to that of the liquid benzene. Moreover, the benzene molecules in the contact adsorption layer lie flat on the surface of adsorbent, whereas those molecules near the pore center have no particular orientations. D...