Color tuning and white light emission by codoping in isostructural homochiral lanthanide metal-organic frameworks.

Four lanthanide-based homochiral metal-organic frameworks (Ln-HMOFs), {[Ln 2 (HL) 2 (H 2 O) 4 ]·2Cl·5H 2 O} n [Ln = Gd (1), Eu (2), Tb (3) and Dy (4)], have been synthesized through solvothermal reactions of chiral ligand ( S )-5-(((1-carboxyethyl)amino)methyl)isophthalic acid (H 3 L) with corresponding LnCl 3 ·6H 2 O. They are binodal (3,6)-connected frameworks with kgd nets based on binuclear cluster units and zwitterionic (HL) 2- linkers. Considering the isostructuralism of these Ln-HMOFs as well as the blue emission of compound 1 and the strong typical Eu 3+ and Tb 3+ emissions of compounds 2 and 3, single-phase mixed-lanthanide HMOFs have been prepared by doping of Ln 3+ into the Ln-HMOFs to modulate light-emitting color. Interestingly, the bimetallic doped Eu/Tb-HMOFs [(Eu x Tb 1- x ) 2 (HL) 2 (H 2 O) 4 ]·2Cl·5H 2 O display a fluent change of light-emitting color among green, yellow, orange, orange-red, and red by adjusting the doping concentration of Eu 3+ ions into the Tb-HMOF. Very importantly, the trimetallic doped Eu/Gd/Tb-HMOF [(Eu 0.1388 Gd 0.6108 Tb 0.2504 ) 2 (HL) 2 (H 2 O) 4 ]·2Cl·5H 2 O emits white light upon excitation at 355 nm, whose emission can also be switched between different colors when excited with different ultraviolet light. Furthermore, the fluorescence response of Tb-HMOF to various usual metal ions, and especially fluorescent sensing behaviours to Fe 3+ , Cr 3+ and Al 3+ have been preliminarily investigated.