Quantitative Predictions of Molecular Diffusion in Binary Mixed-Linker Zeolitic Imidazolate Frameworks Using Molecular Simulations

Experimental studies have shown that adsorbate diffusion in zeolitic imidazolate frameworks (ZIFs) can be tuned by incorporating two different imidazolate linkers in the ZIF crystals. We demonstrate for the first time that atomistic simulations are capable of quantitatively predicting self-diffusion in binary mixed-linker ZIFs. Diffusion coefficients of various adsorbates for which prior experimental data exist are predicted in ZIF-8-90, ZIF-8/SALEM-2 materials composed of imidazolate and 2-methylimidazolate linkers in the cubic SOD topology, and ZIF-7-90 materials over a composition range that is known experimentally to be in the SOD topology. A combination of conventional and biased molecular dynamics simulations as well as a previously developed lattice-diffusion model allows us to access the full range of diffusion time scales for adsorbates such as small hydrocarbons, alcohols, benzene, and water.