Tuneable fluorescent MOF gels
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Fluorescent gels made from metal organic frameworks can be tuned to emit almost any colour of light, by carefully selecting the metal ion used.
Metal organic frameworks (MOFs) are materials made from a network of metal ions connected by organic ligands. By choosing the metal ion and the ligand carefully, scientists can tune their properties and behaviour.
Xue-Bo Yin and his team from Nankai University in China have used MOFs to create a series of gels that can be tuned to emit different colours of light.
The MOFs are made from different lanthanide cations, linked together by a ligand called 5-boronoisophthalic acid (or 5-bop), and they have a ribbon-like structure. These nanoribbons in turn tangle together to create gels. Materials made from a continuous MOF structure are normally quite rigid, but the tangle of ribbons forms a softer gel.
When a UV laser of a single wavelength is shined on the gel, it emits fluorescence in a range of colours. The colour depends on the choice of lanthanide cations. The way it works is that the 5-bop ligand absorbs the energy from the laser and transmits this energy through the gel to the lanthanide cations. Depending on which cations are used, the gels emits fluorescence in a range of colours. In some gels there is just one type of cation, whereas in others there are more than one 鈥� and their ratio determines the colour of light emitted.
Dr Yin says that the materials could be used to make coloured LEDs. 鈥淟ight-emitting diodes (LEDs) are the next generation of lighting system by virtue of their environmental friendliness, high efficiency, and long lifetime. White-emitting LED devices can be prepared by coating the MOF gels onto UV lamp. The shape of the MOF gels is variable, so LEDs with different shape and colour may be achieved for extensive applications in the near future.鈥�
This article is free to read in our open access, flagship journal Chemical Science: Fei Chen et al., Chem. Sci., 2019, Advance Article. . You can access all of our ChemSci Picks in this .