Oriented UiO-67 Metal-Organic Framework Membrane with Fast and Selective Lithium-Ion Transport

Metal-organic frameworks (MOFs) membranes with high pore density and tunable pore size down to the subnanoscale exhibit great potential in ion separation when appropriately designed and prepared. By a washing-assisted secondary growing method, a well intergrown UiO-67 membrane with preferential growth along the [022] direction was synthesized on a polyvinylpyrrolidone (PVP)-modified AAO substrate. Because of the oriented growth of UiO-67 nanocrystals, highly interconnected ion-transporting channels are created throughout the UiO-67/AAO membrane capable of achieving an ultrahigh Li+ permeance of 27.01 molm(-2) h(-1) as well as very decent Li+/Mg2+ selectivity of up to 159.4. Molecular dynamics simulations reveal that the high selectivity is associated with the large disparity of the transport energy barrier between Li+ and Mg2+, which is caused by different extents of ion dehydration in unique bimodal and oriented membrane channels.

Automated summary

Metal-organic frameworks (MOFs) membranes have great potential in ion separation, with UiO-67 membranes synthesized using a washing-assisted secondary growing method showing high Li+ permeance and excellent Li+/Mg2+ selectivity. The high selectivity is associated with the difference in ion dehydration between Li+ and Mg2+ in the membrane channels.