MS32-P06 Temperature-Dependent Supramolecular Isomerism of Lutetium-Aminoterephthalate Metal-Organic Frameworks: Synthesis, Crystallography and Physical Properties Alla Dikhtiarenko (KAUST Catalysis Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia) Pablo Serra-Crespo (Radiation and Isotopes for Health, Department of Radiation Science and Technology, Faculty of Applied Sciences, Technical University Delft,, Delft, Netherlands (Holland, Europe)) Sonia Castellanos (Advanced Research Center for Nanolithography, Amsterdam, Netherlands (Holland, Europe)) Alexey Pustovarenko (Chemical Engineering Department, Delft University of Technology, Delft, Netherlands (Holland, Europe)) Rafael Mendoza-Meroño (Departamento de Química Física y Analítica, Universidad de Oviedo, Oviedo, Spain) Santiago García-Granda (Departamento de Química Física y Analítica, Universidad de Oviedo, Oviedo, Spain) Jorge Gascon (KAUST Catalysis Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia)email:
Polymorphism or supramolecular isomerism is becoming an increasingly important subject in the field of crystal engineering, as it may facilitate the design of porous polymeric materials with targeted physical properties.[1] In this context, the unique properties of MOF polymorphs, displaying both different crystal structures and identical molecular composition, allow for the derivation of structure-property relationships solely based on structural parameters or topology of the polymeric network. There are various key factors governing the formation of MOFs’ polymorphic forms, including reaction time, temperature, concentration of precursors, pH, solvent, modulators, and so on. Although numerous individual factors[2] or their conjunction[3] affect the occurrence of polymorphic forms, temperature is the one of the most important variables. The study of polymorphism is not only important in producing novel materials with target properties but may also be helpful in developing a fundamental understanding of the factors influencing crystal growth, such as reaction temperature.
In this line, we present the investigation on the relationship between the crystal structures and gas adsorption / fluorescence properties of lutetium(III) 2-aminoterephthalate MOFs isomorph series. Three supramolecular isomers of lutetium metal-organic framework, {Lu2(H2O)4(ATA)3·4H2O}n (Lu-ATA@RT), {Lu2(H2O)2(C3H7NO)2(ATA)3}n (Lu-ATA@100) and {Lu2(C3H7NO)(ATA)3}n (Lu-ATA@150), have been obtained from the reaction of Lu(NO3)3·6H2O with 2-aminoterephthalic acid (ATA) at different temperatures. The resulting structures of Lu-ATA MOFs depend on the temperature applied during the synthesis, revealing a temperature-susceptible supramolecular isomerism. Single-crystal X-ray diffraction analyses suggest that new compounds with formula {Lu2(S)x(ATA)3}n (S = solvent: H2O, DMF) display different three-dimensional architectures which consist on dinuclear lutetium building units. The supramolecular isomer Lu-ATA@RT, formed at room temperature, has a pcu-net topology while its double interpenetrated analogue, Lu-ATA@100, assembles at 100 ºC under hydrothermal conditions. Hydrothermal synthesis at 150 ºC affords formation of the dense Lu-ATA@150 cage-like framework displaying a new hexagonal-packed net topology. All Lu-ATA isomeric phases are porous and display different gas-uptake behaviour towards carbon dioxide as a function of polymeric network arrangement. The luminescent properties of Lu-ATA frameworks in solid state as well as in suspension in the presence of different solvents reveal a solvent dependent emission.

[1] Aakeroy, C. B. et al. (2010). CrystEngComm, 12, 22-43.

[2] Jeong, S. et al. (2014). Chem. Mater., 26, 1711-1719.

[3] Konstas, K. et al. (2014). CrystEngComm, 16, 8937-8940.
Keywords: metal-organic frameworks, supramolecular isomerism, luminescence