Diffusion of H-2, 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

摘要

The diffusivity of H-2 and CO2 in the small pore Zr based metalorganic 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 H-2, and the corrected and transport diffusivities of CO2, as single components and binary mixture. H-2 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 H-2, partly a consequence of its greater kinetic radius, which renders it slower than H-2. In the context of a binary mixture, H-2 still diffuses faster between the two, although with a slightly lower self-diffusivity, while that of CO2 increases slightly. However, the difference in terms of order of magnitude is not altered and makes MIL-140A(Zr) a potential candidate for H-2/CO2 separation based on kinetics.