Innovative CVD growth of Metal-Organic Frameworks thin films
Published : 13 December 2016
Metal Organic Frameworks (MOFs) are periodic hybrid organic-inorganic crystalline materials issued form the periodic assembly of inorganic metallic nodes with polytopic organic bridging ligands. Among these materials, some identified structures have emerged which display nano-sized permanent microporosity coupled to a very large thermal and chemical stability. These materials have several potential applications (sensors, catalysts, insulators, battery electrolytes, materials for optoelectronic and non-linear optics). In particular, their very large specific surface areas (> 7000 m²/g, among the largest recorded for any materials) make them very uniquely adequate for applications in gas-separation or sensing.
These materials are generally synthetized via solution methods, which complicate the growth of performing thin films. Very recently, the first reports of Chemical Vapor Deposition (CVD) and/or Molecular Layer Deposition (MLD) routes have appeared. These breakthroughs pave the way to applications in micro- and nanotechnologies.
The work proposed herein aims at developing a CVD and/or MLD-based route for MOFs to be used for gas-sensing applications. Firstly, the gas-phase MOF growth through surface organometallic chemical approaches will be undertaken. In particular we will investigate the effect of varying surface pretreatment and post-synthesis activation routes on the growth parameters and on the final porosity of the materials. This task will include fine structural characterization of the grown MOF thin films (by X-ray diffraction, electronic microscopy), their chemical composition (by XPS, FTIR, ToF-SIMS) and porosity (by ellipso-porosimetry and GISAXS). The next task will focus on the development of sensitive microporous layers to allow the detection of small molecules (CH4, NOX, …). The most performing materials will be characterized under gas atmosphere firstly on simple sensors (on Quartz microbalance) and then in integrating devices (pre-concentrators).