Molecular Diffusion in a Flexible Mesoporous Metal-Organic Framework over the Course of Structural Contraction

In situ ¹H pulsed field gradient (PFG) NMR was used to investigate molecular diffusion of n-butane at 298 K during the negative gas adsorption (NGA) transition caused by contraction of the flexible metal-organic framework DUT-49(Cu). Supported by molecular dynamics simulations, it provided crucial insight to confined diffusion within a highly-flexible pore environment. The self-diffusion coefficients were derived from the experiment and compared with simulations, capturing the diffusion during n-butane adsorption and desorption. This complementary approach has yielded experimental characterization of molecular diffusion mechanisms during the unique process of NGA.