Luminescent, heterometallic terbium(III)–lutetium(III) terephthalate metal-organic frameworks (MOFs) were synthesized via direct reaction between aqueous solutions of disodium terephthalate and nitrates of corresponding lanthanides by using two methods: synthesis from diluted and concentrated solutions. For (Tb_xLu_1−x)₂bdc₃·nH₂O MOFs (bdc = 1,4-benzenedicarboxylate) containing more than 30 at. % of Tb³⁺, only one crystalline phase was formed: Ln₂bdc₃·4H₂O. At lower Tb³⁺ concentrations, MOFs crystallized as the mixture of Ln₂bdc₃·4H₂O and Ln₂bdc₃·10H₂O (diluted solutions) or Ln₂bdc₃ (concentrated solutions). All synthesized samples that contained Tb³⁺ ions demonstrated bright green luminescence upon excitation into the ¹ππ* excited state of terephthalate ions. The photoluminescence quantum yields (PLQY) of the compounds corresponding to the Ln₂bdc₃ crystalline phase were significantly larger than for Ln₂bdc₃·4H₂O and Ln₂bdc₃·10H₂O phases due to absence of quenching from water molecules possessing high-energy O-H vibrational modes. One of the synthesized materials, namely, (Tb_0.1Lu_0.9)₂bdc₃·1.4H₂O, had one of the highest PLQY among Tb-based MOFs, 95%.

New heterometallic antenna terephthalate MOFs, namely, (Eu_xM_1−x)₂bdc₃·4H₂O (M = Y, La, Gd) (x = 0.001–1), were synthesized by a one-step method from aqueous solutions. The resulting compounds are isomorphic to each other; the crystalline phase corresponds to Ln₂bdc₃∙4H₂O. Upon 300 nm excitation to the singlet excited state of terephthalate ions, all compounds exhibit a bright red emission corresponding to the of ⁵D₀–⁷F_J (J = 0–4) f-f transitions of Eu³⁺ ions. The Eu(III) concentration dependence of the photophysical properties was carefully studied. We revealed that Gd-doping results in photoluminescence enhancement due to the heavy atom effect. To quantitatively compare the antenna effect among different compounds, we proposed the new approach, where the quantum yield of the ⁵D₀ formation is used to characterize the efficiency of energy transfer from the ligand antenna to the Eu³⁺ emitter.

The structural features and luminescent properties of heterometallic Tb–Gd, Tb–La, and Tb–Y terephthalate metal–organic frameworks, namely (Tb_xM_1−x)₂(1,4-bdc)₃∙4H₂O (M = Gd, La, Y), were studied in detail in a wide concentration range (x = 0.001–1). The crystalline phase of synthesized compounds corresponds to Ln₂(1,4-bdc)₃·4H₂O. The lifetime of ⁵D₄ decreased with increased Tb³⁺ concentration, but PLQY depends non-linearly on the Tb³⁺ concentration. The 50% substitution of Tb³⁺ for Y³⁺, Gd³⁺, or La³⁺ ions result in the significant enhancement of photoluminescence quantum yield, up to 1.6 times. The morphology, thermal stability, and vibrational structure of the selected homo- and bi-metallic materials is reported as well.

A series of novel heterometallic rare-earth chloroterephthalate metal–organic frameworks with the general formula (Tb_xGd_1−x)₂(Cl-1,4-bdc)₃·5H₂O (x = 0–1) were synthesized via direct precipitation from aqueous solutions. The structural and photophysical properties of these compounds were studied in detail. All compounds exhibit bright luminescence upon UV excitation into the ligand absorption band due to an efficient antenna effect. The photoluminescence quantum yield shows a non-monotonic dependence on the concentration of the terbium ion with a maximum value of 71% achieved for the compound containing equal molar fractions of the lanthanide ions. The (Tb_0.5Gd_0.5)₂(Cl-1,4-bdc)₃·5H₂O sample was evaluatedfor its utility in both qualitative and quantitative analysis of selected metal ions and in latent fingerprint development. It was shown to enable the detection of Cr(III), Fe(III), and Cu(II) ions through luminescence quenching, with the emission intensity being concentration-dependent. This behaviour highlights the compound’s potential as a basis for analytical protocols and materials aimed at the quantitative determination of these metal ions.