A highly stable and white-light-emitting Eu(iii) MOF

Abstract

A long π-conjugated organic ligand 2-(2,4-disulfophenyl)imidazo(4,5-f)(1,10)-phenanthroline (H₃sfpip) featuring blue-green emission was used to construct Eu(III) MOFs to obtain a target white-light-emitting LnMOF with no dopant atom in its structure. Two complexes, [Eu(H₂O)₂(OH)(Hsfpip)]·H₂O (1) and [Eu(H₂O)(oa)_0.5(Hsfpip)]·2H₂O (2), were successfully synthesized under similar hydrothermal reaction conditions. The absence or presence of an ancillary ligand such as oxalic acid (oa) showed direct influence on the coordination mode of the Hsfpip linker and in the final topology of the polymeric structure. Complex 1 displays an unstable 2D polymeric structure and weak red luminescence from Eu³⁺ due to the quenching effect of high-energy O–H oscillators around the inner coordination sphere of the metal center, whereas the introduction of an ancillary ligand such as oxalic acid results in a tight-bonding 3D polymeric structure and an intense white light emission from complex 2. Moreover, due to the skeleton rigidity and robustness of complex 2, the white light emission can be improved via a heating process.