ИСТИНА

The study comprehensively investigated a new structural type of lanthanide-organic frameworks [(CH3)2NH2]2[Ln2(bdc)4(DMF)2](H2O)2 called LMSU-1 (Lomonosov Moscow State University). The existence of the LMSU-1 structural type from La to Er has been established according to the low-temperature SCXRD experiment. The Ln-LMSU-1 consists of binuclear centrosymmetric anionic structural blocks [Ln2(bdc)4]2-, connected by terephthalate linkers, the packaging voids contain guests such as water and dimethylformamide molecules, and dimethylammonium cations [1]. The lanthanide contraction has a noticeable impact on the linker structural function, leading to a division within the framework family into La-type (CN(Ln) = 9) and Dy-type (CN(Ln) = 8). To investigate structural stability of the LMSU-1 family, we have performed a charge density analysis for all known Ln-MSU-1 according to Bader’s “Atoms in Molecule” (AIM) theory. Using VT-PXRD (Variable Temperature PXRD), we uncovered that even a subtle change in the structural function of the linker significantly influences the thermal behavior of the framework (Figure 1). For La-type frameworks, the elimination of guest molecules occurs in two successive isothermal stages, leading to the formation of stable intermediate forms. Conversely, the thermal behavior of Dy-type frameworks is entirely different, as the detachment of guest molecules is prolonged. For instance, for Dy-LMSU-1, the detachment process continues from 140 to 250°C. In addition, it was found that the greater the lanthanide compression, the lower the temperature at which large guest molecules are eliminated. Furthermore, we researched the luminescent properties of the EuxTb1-x-LMSU-1. During the study, a remarkable change in the luminescence signal was observed as the framework underwent structural transformations upon heating, which could pave the way for using the luminescent signal in structural studies. Additionally, these frameworks show great potential for luminescent thermometry.