Alkali Metal Ion-exchange in a Metal-Organic Framework Based on Lanthanum and 1,4-Phenylenebis(methylidyne)tetrakis(phosphonic acid)

The ion-exchange selectivity of four metal-organic frameworks (denoted as MLaL), formed by alkali metal ions (M⁺), La³⁺, and 1,4-phenylenebis(methylidyne)tetrakis(phosphonic acid) (L), was examined. Unusual selectivity for the alkali metal ions was observed, which did not follow the previously proposed mechanism that was explained based on the ion-size similarity in the framework. The changes in the crystal structures after ion-exchange reactions were observed by powder X-ray diffraction analysis. The change in the lattice energy in a mixed-metal framework is likely to be one of the significant parameters to affect ion-exchange selectivity.

Transmetalation in a Ce(III)-phosphoester Crystalline Coordination Polymer with an Exceptionally High Selectivity for Yb(III) and Lu(III)

A novel crystalline coordination polymer containing Ce³⁺ and bis(4-nitrophenyl) phosphate (L), CeL₃ , was synthesized and its unique transmetalation selectivities toward Yb³⁺ and Lu³⁺ in the lanthanide series were evaluated. The relatively large difference in transmetalation selectivity between the neighboring Tm³⁺ and Yb³⁺ species is noteworthy because the reactivities of heavy lanthanides are generally considerably similar. The structural strain of the polymeric framework is likely responsible for this unusual trend. Powder X-ray diffraction analysis indicated that, in the cases of only Yb³⁺ and Lu³⁺ , large differences in their ionic sizes compared to that of Ce³⁺ in the parent framework may induce a structural strain after solid solution formation, while cleavage of the relatively weak Ce-O bond allows the formation of new Yb-O and Lu-O bonds with the incoming Yb³⁺ and Lu³⁺ , respectively. Structural phase transitions likely caused by the heterogeneous nucleation of the Yb- (or Lu-) type phase were also observed.

Intralanthanide Separation on Layered Titanium(IV) Organophosphate Materials via a Selective Transmetalation Process

The lanthanides (Ln) are an essential part of many advanced technologies. Our societal transformation toward renewable energy drives their ever-growing demand. The similar chemical properties of the Ln pose fundamental difficulties in separating them from each other, yet high purity elements are crucial for specific applications. Here, we propose an intralanthanide separation method utilizing a group of titanium(IV) butyl phosphate coordination polymers as solid-phase extractants. These materials are characterized, and they contain layered structures directed by the hydrophobic interaction of the alkyl chains. The selective Ln uptake results from the transmetalation reaction (framework metal cation exchange), where the titanium(IV) serves as sacrificial coordination centers. The "tetrad effect" is observed from a dilute Ln³⁺ mixture. However, smaller Ln³⁺ ions are preferentially extracted in competitive binary separation models between adjacent Ln pairs. The intralanthanide ion-exchange selectivity arises synergistically from the coordination and steric strain preferences, both of which follow the reversed Ln contraction order. A one-step aqueous separation of neodymium (Nd) and dysprosium (Dy) is quantitatively achievable by simply controlling the solution pH in a batch mode, translating into a separation factor of greater than 2000 and 99.1% molar purity of Dy in the solid phase. Coordination polymers provide a versatile platform for further exploring selective Ln separation processes via the transmetalation process.

Fabrication of a monolithic cryogel from the cyclohexane organogel of a coordination polymer based on a phosphoester

A monolithic coordination polymer ([Sm(dehp)₃]) has been successfully prepared through the lyophilization of a cyclohexane organogel.

Coordination polymers based on a glycine-derivative ligand

The combination of a glycine-derivative supramolecular salt with lanthanide(iii) chloride hydrates under hydrothermal conditions (120 °C, 48 h) produced a family of isotypical materials formulated as [Ln(bodt)(Hbodt)].

Environmentally friendly separation of dysprosium and neodymium by fractional precipitation of coordination polymers

Dy is exclusively precipitated as a coordination polymer from a Nd–Dy mixture.