Diffusion of H2, CO2, and Their Mixtures in the Porous Zirconium Based Metal–Organic Framework MIL-140A(Zr): Combination of Quasi-Elastic Neutron Scattering Measurements and Molecular Dynamics Simulations

Abstract

The diffusivity of H2 and CO2 in the small pore Zr based metal–organic framework (MOF) MIL-140A(Zr) has been evaluated using a combination of quasi-elastic neutron scattering measurements and molecular dynamics simulations. These two techniques were used to determine the self-diffusivities of H2, and the corrected and transport diffusivities of CO2, as single components and binary mixture. H2 was shown to be the faster of the two gases to diffuse through the narrow triangular channel of MIL-140A(Zr), its self-diffusivity value being 1 order of magnitude higher than that of CO2, at the same temperature. In this case, although no specific interaction sites are present, the CO2 interacts more strongly with the pore wall than H2, partly a consequence of its greater kinetic radius, which renders it slower than H2. In the context of a binary mixture, H2 still diffuses faster between the two, although with a slightly lower self-diffusivity, while that of CO2 increases slightly. However, the difference in terms o...