Study of the Butane Diffusion in Metal Organic Framework Materials by PFG NMR Experiments

1. Introduction The presence of organic part in the new class of hybrid solids imparts an important chemical versatility to these materials compared to "classical" solids. The architecture of Metal Organic Frameworks (MOF) may lead to open structures with 1D (chains), 2D (layers) or 3D dimensionality developing very large surface areas (above 1000 m 2 /g) [1]. Some MOFs possess a structural originality: the frameworks are flexible and movements larger than 10 Å can be generated in response of external stimuli (temperature, adsorption of guest molecules). It is therefore interesting to explore the diffusion properties of these materials. The present work reports the study by Pulsed Field Gradient (PFG) NMR of the diffusion of butane in two hybrid solids, named MIL-53 (Ga)and MIL-103 (La), MIL standing for "Institut Lavoisier Materials". The structure of MIL-53 and MIL-103 consists of chains of octahedral metal ions (Ga, La, respectively) connected by organic linkers (benzene dicarboxylate, benzene tribenzoate, respectively) forming 1D channels with 8.6 Ǻ and 10 Ǻ pore diameter, respectively [2,3].