Taking the Third Route for Construction of POMOFs: The First Use of Carboxylate-Functionalized Mn$^{III}$Anderson-Evans POM-Hybrid Linkers and Lanthanide Nodes

The purpose of the present contribution is to illustrate how to design and grow crystals of POMOFs based on POM-hybrid linkers with lanthanide ions as nodes. Thus, the Mn$^{III}$-centered Anderson–Evans polyoxometalate (Mn-A-E-POM) was functionalized with 4-(((1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)amino)methyl)benzoic acid (H$_{4}^{-}$L) to afford the hybrid inorganic–organic POM [N(n-C$_{4}$H$_{9}$)$_{4}$]$_{4}$[(MnMo$_{6}$O$_{18}$)(HL)(L)] (1), which in turn reacts with lanthanide salts and yields two three-dimensional frameworks with the general formulas Ln(DMF)$_{6}$Ln(DMF)$_{5}$Ln$_{3}$(DMF)$_{10}$[(MnMo$_{6}$O$_{18}$)(L)$_{2}$]$_{3}$·xDMF (2; Ln = La–Nd) and [Ln(DMF)4(H2O)]2[Ln3(DMF)6][(MnMo6O18)(L)2]3·xDMF (3; Ln = Y, Sm–Lu). The differentiation in these two families results from the lanthanide contraction. The crystallization process is crucial for obtaining these two families in a bulk pure phase. Family 2 can be obtained by stirring, while for family 3 the less energy demanding layering method proved to be the most efficient pathway. Notably, the change in the ionic radii causes a change in space group (from P2$_{1}$ (family 2) to P2$_{1}$/c (family 3); however, the topology of the frameworks is unaffected.