2D vertical heterostructure membranes for lanthanide separation

The design and synthesis of separation materials for lanthanides with extremely similar properties have always been a significant challenge. Here, a two-dimensional (2D) metal–organic framework (MOF) with crystal faces similar to the [002] of ZIF-8, which theory suggests should not be stable, is predicted and synthesized by solvent evaporation between graphene layers to prepare a 2D vertical heterostructure membrane. Theoretically, the pristine cluster of 2D MOFs contains one small and 1/4 large crown pores, and the small pores can selectively adsorb lanthanide elements, causing the selective penetration of lanthanide ions. Experimentally, the selectivity of lanthanide is obtained through the membrane with La3+/Yb3+ ≈55.79 and La3+/Ce3+ ≈6.02. The interlayer entrapment of graphene stabilizes the structure of the 2D MOF, and the intercalation of the 2D MOF expands and fixes the interlayer spacing of graphene oxide, improving the stability in strong acids, the selectivity, and the ion transmittance of the membrane.