Enhanced separation of potassium ions by spontaneous K+-induced self-assembly of a novel metal-organic framework and excess specific cation-π interactions.

A novel metal-organic framework (MOF) was fabricated by spontaneous K(+)-induced supramolecular self-assembly with the embedded tripodal ligand units. When the 3D ligand was loaded onto Fe3O4@mSiO2 core-shell nanoparticles, it could effectively separate K(+) ions from a mixture of Na(+), K(+), Mg(2+), and Ca(2+) ions through nanoparticle-assisted MOF crystallization into a Fe3O4@mSiO2@MOF hybrid material. Excess potassium ions could be extracted because of the specific cation-π interaction between K(+) and the aromatic cavity of the MOF, leading to enhanced separation efficiency and suggesting a new application for MOFs.