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MOlecular Loading and SURface anchoring of Metal-Organic Frameworks: a training and career development action

Final Report Summary - MOLSURMOF (MOlecular Loading and SURface anchoring of Metal-Organic Frameworks: a training and career development action)

The main goal of the MOL-SURMOF project granted in the frame of the Marie Curie IEF Action, was the investigation of the electronic properties of metal-organic frameworks anchored to solid surfaces (SURMOFs) before and after their loading with organic electro-active molecules (MOL) to shed light on the charge transport mechanism of these materials, such surface anchored hybrid metal/organic structures that bear a huge potential in electronic devices.
Metal-organic frameworks (MOFs), crystalline and porous materials based on the coordination of metal ions and organic linkers, have been extensively studied but mainly for gas storage, separation and catalysis applications. In the last couple of years, however, they have been attracting much attention as potential candidates for novel electronic devices, thanks to their tailorable chemistry, crystallinity and porosity. Nevertheless, a thorough experimental characterization of the electrical transport properties and charge transport mechanism of these materials has so far been rather problematic due to the challenges in their processing as robust, crystalline and oriented thin films. In fact, from the point of view of setting up an experiment to measure electrochemical properties, either conductivity or impedance, for example, powder MOFs might present a challenge. Indeed, these types of experiments need the robust anchoring of the species under study, to an electrode. The electrode fabrication can therefore be considered as the main limitation for the widespread use of this application. Within this context, the approach proposed in the frame of this proposal, i.e the use of surface anchored metal-organic frameworks (SURMOFs) and molecularly loaded SURMOFs (MOL-SURMOFs) grown on template surfaces by means of the stepwise liquid phase epitaxy (LPE) method, represents a huge step forward in this field and contributed to reinforce a completely new field of applications for these materials. Indeed, SURMOFs and MOL-SURMOFs can themselves be used as robust solid electrodes and hence integrated in electrochemical cells or Hg-based tunneling junctions. By following these two experimental approaches, it has indeed been possible to measure the electrical properties and to elucidate the charge transport mechanism of these novel materials.
We believe that the knowledge of the factors influencing the charge transport mechanism in SURMOF films, both as pristine and after incorporation of a guest molecule, paves the way towards the exploitation of their predicted and foreseen large potential for applications in electronic devices. To the best of our knowledge this is the first study of this kind and as such it will with no doubts substantially promote the understanding of electric transport properties of MOFs (one manuscript submitted and one in preparation).
Additionally, in the frame of this project, cyclic voltammetry was shown to be the method of choice for the investigation of the film quality of SURMOFs and MOL-SURMOFs but also of surface anchored purely organic gels (SURGELS) and purely organic membranes (two published manuscripts).

Additional information can be found in the attached document.