CYCLOMAT

Over the past decade, carbon materials have attracted a great deal of attention in a wide range of applications of technological importance. Thus in catalysis, a growing interest has emerged for the synthesis by nano-replication technique, owing to the attractive characteristics of the resulting materials, i.e. high surface areas, narrow pore size distributions, controlled pore shapes and volumes. Generally, its principle involves the preparation of the silica template and filling of the silica pores with an appropriate carbon precursor followed by its carbonization and removal of the silica framework. The aim of the project CYCLOMAT lies within this framework and deals with the synthesis by nano-replication of metal carbon catalysts, in which metallic nanoparticles of gold or platinum will be embedded onto the surface of ordered mesoporous carbons. Two metals will retain our attention, i.e. gold and platinum. However, the most characteristic aspect of our project will be based on the use of cyclodextrins as promoting agents. Cyclodextrins are water soluble cyclic oligosaccharides formed of n glucopyranose units exhibiting a hydrophobic internal cavity that can host a large variety of molecules and a hydrophilic exterior surface thanks to the presence of a large number of hydroxyl groups. In the present case, the cyclodextrins will be used with a threefold purpose: i) as carbon sources to stabilize the carbon architecture ii) as metal complexing agents (in the form of host-guest complexes or supramolecular adducts) to stabilize the metal precursors and iii) as polyhydroxylated molecules favoring the dispersions of the cyclodextrin-metal complexes on the silica walls. We believe that our proposal will contribute to provide a new generation of tolerant and robust catalysts with a minimum of agglomeration and metal leaching. Through this self-assembly approach, it is also expected that, during catalysis, the chemical transformations will occur in confined media (pores), where the restricted molecular organization can lead to higher activities and selectivities. To validate our concept, we have chosen the aqueous-phase catalytic oxidation of 5-hydroxy-2-methylfurfural (HMF) as a model reaction. This reaction constitutes a real strategic challenge to replace key petroleum-based building blocks, by opening an access to the formation of 2,5-furandicarboxylic acid, which is a potential substitute of terephthalic acid and may be used as polymer precursor. In parallel, the synthesis and characterization of control carbon-based catalysts prepared by nanoparticles deposition and by conventional methods will also be realized for comparison. The performances of these control catalysts will be studied in the same reaction, namely the catalytic oxidation of HMF. This aspect will be crucial to evaluate the true effectiveness of the nano-replicated catalysts synthesized from cyclodextrins. Finally, the topics developed during this three-year program fits with the P2N AAP 2011 (axe thématique 1: synthèse et fabrication de nanomatériaux et chimie en milieu confine). In the framework of the this project, we propose to gather the scientific skills of two well known laboratories to reach our objectives: i) the UCCS (Prof. E. MONFLIER and Prof. A. PONCHEL) which will bring their background in the utilization of cyclodextrins for the production of nano-sized metal particles and nano-replicated materials, ii) the IRCELYON (Dr. C. PINEL and Dr. M. BESSON) specialized in the design of oxidation processes in water catalyzed by carbon-supported metals