Heterometallic Europium(III)-Lutetium(III) Terephthalates as Bright Luminescent Antenna MOFs

A new series of luminescent heterometallic europium(III)-lutetium(III) terephthalate metal-organic frameworks, namely (EuxLu1-x)(2)bdc(3)center dot nH(2)O, was synthesized using a direct reaction in a water solution. At the Eu3+ concentration of 1-40 at %, the MOFs were formed as a binary mixture of the (EuxLu1-x)(2)bdc(3) and (EuxLu1-x)(2)bdc(3)center dot 4H(2)O crystalline phases, where the Ln(2)bdc(3)center dot 4H(2)O crystalline phase was enriched by europium(III) ions. At an Eu3+ concentration of more than 40 at %, only one crystalline phase was formed: (EuxLu1-x)(2)bdc(3)center dot 4H(2)O. All MOFs containing Eu3+ exhibited sensitization of bright Eu3+-centered luminescence upon the 280 nm excitation into a (1)pi pi* excited state of the terephthalate ion. The fine structure of the emission spectra of Eu3+ 5D0-F-7(J) (J = 0-4) significantly depended on the Eu3+ concentration. The luminescence quantum yield of Eu3+ was significantly larger for Eu-Lu terephthalates containing a low concentration of Eu3+ due to the absence of Eu-Eu energy migration and the presence of the Ln(2)bdc(3) crystalline phase with a significantly smaller nonradiative decay rate compared to the Ln(2)bdc(3)center dot 4H(2)O.

Automated summary

A new series of luminescent heterometallic europium(III)-lutetium(III) terephthalate metal-organic frameworks were synthesized, and the luminescence properties were found to be significantly influenced by the Eu/Lu ratio and Eu3+ concentration.