Observation of single-file diffusion in a MOF

The translational and rotational dynamics of neopentane adsorbed in the one-dimensional channels of MIL-47(V) has been studied by quasi-elastic neutron scattering. The rotational motion of neopentane is well-described by the rotational diffusion model, with a correlation time of 41 ps at 300 K. The translational motion of the molecule has been fitted by several models: isotropic diffusion, normal 1D and single-file diffusion. It is found that the observed line shapes can only be reproduced by the single-file diffusion model. The single-file mobility factor, F, is (8 + 1) x 10(-14) m(2) s(-1/2) at 300 K. This is the first observation of this unusual diffusion behaviour in a MOF.