title: Metal-organic framework luminescence in the yellow gap by codoping of the homoleptic imidazolate ∞(3)[Ba(Im)2] with divalent europium.
abstract: The rare case of a metal-triggered broad-band yellow emitter among inorganic-organic hybrid materials was achieved by in situ codoping of the novel imidazolate metal-organic framework ∞(3)[Ba(Im)2] with divalent europium. The emission maximum of this dense framework is in the center of the yellow gap of primary light-emitting diode phosphors. Up to 20% Eu2+ can be added to replace Ba2+ as connectivity centers without causing observable phase segregation. High-resolution energy-dispersive X-ray spectroscopy showed that incorporation of even 30% Eu2+ is possible on an atomic level, with 2-10% Eu2+ giving the peak quantum efficiency (QE = 0.32). The yellow emission can be triggered by two processes: direct excitation of Eu2+ and an antenna effect of the imidazolate linkers. The emission is fully europium-centered, involving 5d → 4f transitions, and depends on the imidazolate surroundings of the metal ions. The framework can be obtained by a solvent-free in situ approach starting from barium metal, europium metal, and a melt of imidazole in a redox reaction. Better homogeneity for the distribution of the luminescence centers was achieved by utilizing the hydrides BaH2 and EuH2 instead of the metals.
authors.affiliation: Institut für Anorganische Chemie, Universität Würzburg, Würzburg, Germany.
authors.forename: Jens-Christoph
authors.initials: JC
authors.lastname: Rybak
authors.forename: Michael
authors.initials: M
authors.lastname: Hailmann
authors.forename: Philipp R
authors.initials: PR
authors.lastname: Matthes
authors.forename: Alexander
authors.initials: A
authors.lastname: Zurawski
authors.forename: Jörn
authors.initials: J
authors.lastname: Nitsch
authors.forename: Andreas
authors.initials: A
authors.lastname: Steffen
authors.forename: Joachim G
authors.initials: JG
authors.lastname: Heck
authors.forename: Claus
authors.initials: C
authors.lastname: Feldmann
authors.forename: Stefan
authors.initials: S
authors.lastname: Götzendörfer
authors.forename: Jürgen
authors.initials: J
authors.lastname: Meinhardt
authors.forename: Gerhard
authors.initials: G
authors.lastname: Sextl
authors.forename: Holger
authors.initials: H
authors.lastname: Kohlmann
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: Sedlmaier
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Schnick
authors.forename: Klaus
authors.initials: K
authors.lastname: Müller-Buschbaum
mesh_terms: D001464:Barium / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005063:Europium / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D049449:Luminescence; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D007093:Imidazoles; D009942:Organometallic Compounds; D001464:Barium; D005063:Europium