Rare-Earth Multivariate Metal-Organic Frameworks: Cationic Radius Biased Compositional Control and Property Tuning.

The synthesis of a multivariate metal-organic framework (MTV-MOF) family, [Ln(DNNDI)1.5]n (UoB-116), is reported (DNNDI: N,N'-bis(dinicotinate)-1,4,5,8-naphthalenetetracarboxydiimide). UoB-116(Ln) is formed by 15 different metals (Ln = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), all of which were shown to be isoreticular. The uniformity of the framework structure facilitated the synthesis of MTV-MOFs with 2, 4, 12, 15, or 16 (including In(III)) different metals. Single crystal structures of each unimetallic MOFs and MTV-MOFs with 12 or 16 metals were determined, confirming the isoreticular nature of this family of MOFs. Energy Dispersive X-ray (EDX) analysis confirmed distribution of each metal throughout crystals of the MTV-MOFs and compositional analysis indicated increased concentration of lanthanides with smaller cationic radius. A protocol was developed to control relative composition in bimetallic systems, UoB-116(La1-xLux) and UoB-116(Dy1-xLax) (x = 0-1). In the case of UoB-116(Dy1-xLax) it is shown that the porosity, magnetism and UV-visible properties can be tuned through metal cation composition.