Small-angle Neutron Scattering Study of Electrosorption of Ions in Nanopores of a Conductive Metal-Organic Framework*

Insights into the molecular mechanisms of transport and adsorption of electrolyte ions in porous materials under applied potentials are essential to develop next generation of materials for energy storage, water purification and desalination etc.. Here we present a small-angle neutron scattering (SANS) characterization of ion electrosorption in a conductive Metal-Organic Framework (MOF) electrode by taking advantage of neutron’s sensitivity on light elements and isotopes. The method tracks the arrangements of not only ions adsorbed in the micropores, also those adsorbed on the outer surface of cylindrical protrusions that the electrode is composed of under working conditions. The scattering results reveal that the solvent molecules can access most nanopores of the MOF electrode without applying potential. The changes in scattering intensity when potentials are applied suggests the ion rearrangement in the micropores following different mechanisms depending on the electrode polarization. These observations shed new insights on ion electrosorption in electrode materials.