Adsorption and Diffusion of Light Gases in ZIF-68 and ZIF-70: A Simulation Study

作者：Rankin Rees B; Liu Jinchen; Kulkarni Anant D; Johnson J Karl^*

来源：Journal of Physical Chemistry C, 2009, 113(39): 16906-16914.

DOI：10.1021/jp903735m

We have computed the adsorption and diffusion of CO(2), N(2), CH(4), and H(2) in zeolitic imidazolate framework (ZIF) materials ZIF-68 and ZIF-70 from atomistic simulations. These simulations were performed using geometries obtained from density functional theory (DFT) optimization of the experimental crystal structure of ZIF-68 and on four structures of ZIF-70, one based on the experimental crystal structure and three having different imidazole/nitroimidazole substitution ratios. The framework charges for charge-quadrupole interaction (CQI) terms in our simulations were parametrized with charges obtained from Bader charge decomposition (periodic DFT calculations) and ChelpG charges (Cluster DFT calculations). The adsorption and diffusion of the quadrupolar fluids can be dramatically different when using the Bader and ChelpG charges. Agreement between simulations and experiments for the N(2) adsorption isotherms in ZIF-68 and 70 is very good when CQI terms are included. In contrast, simulations overpredict the amount of CO(2) adsorbed at 298 K compared with experiments.

• 出版日期2009-10-1