Europium and Terbium Benzene-1,2,4,5-Tetracarboxylates: Synthesis Peculiarities, Crystal Structures, and Luminescent Thermometry up to 400 °C

In this study, we successfully obtained for the first time a luminescent organic-based thermometer that exhibits high reproducibility, stability, and functionality up to 400 °C. Our approach involved the selection of novel highly emissive and thermally stable MOFs KEu(btec)(H2O) and dehydrated KTb(btec), btec = benzene-1,2,4,5-tetracarboxylate, along with the highly thermally stable copolyimide P84 = 80% methylphenylene-diamine + 20% methylene as the matrix; luminescence lifetime was selected as a temperature-dependent parameter due to its versatility in diverse environmental conditions. Synthesis peculiarities were studied for various lanthanide benzene-1,2,4,5-tetracarboxylates, and the crystal structures of KEu(btec)(H2O) and KTb(btec) were determined by Rietveld refinement from powder X-ray diffraction data.