Temperature-Dependent Supramolecular Isomerism of Lutetium-Aminoterephthalate Metal-Organic Frameworks: Synthesis, Crystallography, and Physical Properties

Abstract

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 metal-organic frameworks 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 of 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 °C under hydrothermal conditions. Hydrothermal synthesis at 150 °C 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 behavior toward carbon dioxide as a function of polymeric network arrangement. The luminescent properties of Lu-ATA frameworks in the solid state as well as in suspension in the presence of different solvents reveal a solvent-dependent emission.