Metal-organic frameworks for application in photochemical sensing
Metal-organic frameworks (MOFs) are one-, two- or three-dimensional matrices of metal ions and organic ligands. Synthesis of MOFs has traditionally been a lengthy and energy-intensive process. Furthermore, attempts to capture small molecules or nanoparticles inside the MOF structure have generally been unsuccessful.
Researchers at the University of Oxford have developed a synthetic protocol, which can access optochemically responsive MOFs containing a range of light-emitting guest species. This rapid, simple and high-yielding process have been used to synthesise functional MOFs, capable of detecting volatile organic compounds (VOCs) via tuneable photonics-based sensing.
Metal-organic frameworks (MOFs) are crystalline hybrid materials with pores formed between the organic ligand “struts” and the metal ion or clusters “vertices”. These nanoscale voids vary in size and functionality depending on the metal/ligand system employed. If these holes in the MOF could be filled with functional guest molecules, forming a tuneable host/guest system, this could impart unusual physical and chemical properties on this emerging class of material.
Welcoming the guests
Researchers at the University of Oxford have developed a high-yielding synthetic approach, which facilitates the inclusion of a variety of functional guest molecules into the MOF structure. This one-pot self-assembly methodology simply requires mixing the correct ratios of metal ions, organic ligands and functional molecules to yield a supramolecular hybrid material comprising functionalised 2D nanosheets. For example, incorporation of luminescent zinc-quinolate complexes (ZnQ) in this fashion results in a solvent-sensitive, luminescent, host/guest system.
Sensing volatile organic compounds (VOCs)
Exposure of the Zn-based hybrid material to liquid or gaseous organic compounds results in a dramatic change in its optical properties easily detectable in UV light (See Image). Even in the solid state, the emission wavelength changes upon exposure to two different polar solvents. This pattern is observed for fast detection of a vast range of VOCs, both polar and non-polar. We believe that these materials could be applied to photochemical sensors for VOCs.
The main advantages of the Oxford technology are:
- Facile, high-yielding and patent protected synthetic methodology
- Could be used to include a range of functional molecules
- Inclusion of ZnQ provides a route to engineer reversible photochemical VOC sensors
- Material structure, properties and durability have been extensively characterised
- Material can be deployed in solid-state in the form of 2D nanosheets, thin films, polymer-MOF nanocomposites (fibres/membranes), or simply in solution state.
Oxford University Innovation Ltd. has filed a patent covering this technology and is now seeking an appropriate commercialisation partner.
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