Brightly Luminescent (Tb x Lu 1-x ) 2 bdc 3 ·nH 2 O MOFs: Effect of Synthesis Conditions on Structure and Luminescent Properties.

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 x Lu 1-x ) 2 bdc 3 ·nH 2 O MOFs (bdc = 1,4-benzenedicarboxylate) containing more than 30 at. % of Tb 3+ , only one crystalline phase was formed: Ln 2 bdc 3 ·4H 2 O. At lower Tb 3+ concentrations, MOFs crystallized as the mixture of Ln 2 bdc 3 ·4H 2 O and Ln 2 bdc 3 ·10H 2 O (diluted solutions) or Ln 2 bdc 3 (concentrated solutions). All synthesized samples that contained Tb 3+ ions demonstrated bright green luminescence upon excitation into the 1 ππ* excited state of terephthalate ions. The photoluminescence quantum yields (PLQY) of the compounds corresponding to the Ln 2 bdc 3 crystalline phase were significantly larger than for Ln 2 bdc 3 ·4H 2 O and Ln 2 bdc 3 ·10H 2 O phases due to absence of quenching from water molecules possessing high-energy O-H vibrational modes. One of the synthesized materials, namely, (Tb 0.1 Lu 0.9 ) 2 bdc 3 ·1.4H 2 O, had one of the highest PLQY among Tb-based MOFs, 95%.