Conducting two dimensional metal organic frameworks

The aim of the work in this project is to develop ultra high vacuum synthesis routes for two dimensional metal organic framework materials used in gas sensing. The sensing technology will be easily miniaturised and provide lightweight mobile or networked molecular detection of chemicals in the vapour phase. The sensors will be cheap, light, and not require much power. Ultimately such gas sensors could be incorporated into mobile devices to provide constant monitoring of gasses hazardous to health. The main project focus is to synthesise on a surface 2D conducting metal organic frameworks (MOFs) and characterise them using scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy. Conductive 2D MOF networks are recently discovered materials, resulting from square planar complexation of late transition metals and some simple polyaromatic hydrocarbon ligands. The MOFs will also be grown on insulating substrates and used for high sensitivity gas sensing. A correlation can then be drawn between the quality of the film structure with its use for chemiresistive sensing of volatile organic compounds. If grown as percolation networks, then the MOF sensors will provide orders of magnitude increased sensitivity relative to thin film sensors made from the same materials.

This project falls within the EPSRC Physical Sciences research area.

The aims are:
- To grow 2D MOFs in an ultra-high vacuum environment and to characterise the resultant materials using scanning tunnelling microscopy, X-ray photoelectron spectroscopy, electrical conductivity measurements, X-ray diffraction, and Raman spectroscopy.
- To use high resolution STM images to distinguish between the metal complex centres in mixed-metal MOFs, for example to distinguish between Ni and Co metal centres.
- To create 2D MOF percolation networks by depositing sub-monolayers on electrically insulating substrates decorated with interdigitated noble metal electrodes, and to evaluate these through dc resistance and lock-in techniques.
- To use the percolation networks for gas phase sensing of volatile organic compounds such as C3H8 and common hazardous gasses including CO and NH3. This will include establishing the limit of detection of the networks.