Tunable luminescence modulation and warm light emission of Zn-MOF (4,4′-bipyridyl and zinc acetate) doped with Eu3+ and Tb3+

Herein, we describe the synthesis and doping of Zn-MOF (4,4'-bipyridyl and zinc acetate), crystallographic structure, optical properties of heteronuclear coordination polymers with emission in the visible (Eu3+/Tb3+ and Zn-MOF). The MOF presents a linear structure in the form of a nanotube. Density functional theory (DFT) and time dependent-DFT calculations were performed on the ground and excited states of Zn-MOF to provide insight of geometries, frontier molecular orbitals, and singlet and triplet state energies of the polymer. The metal-organic framework was doped with Eu3+ or Tb3+ in different proportions (Eu0.5-nTbn@Zn-MOF, when n = 0.00, 0.05, 0.10, 0.15, ..., 0.5). The doped Zn-MOFs exhibit the typical red and green emission corresponding to Eu3+ and Tb3+ ions, respectively, energy transfer from MOF to metal ions takes place (antenna effect). It is noteworthy that the emission color of the lanthanides doped Zn-MOFs changes from red to orange-yellow-green depending on the proportion between Eu3+ and Tb3+. These compounds presented a tau ranging from 1.29 to 1.62 and 1.06-1.56 ms for Eu3+ and Tb3+, respectively, and the corresponding absolute quantum yields values range from 38 to 61%.