Aqueous biphasic catalysis with Metal NanoParticles at Core-Crosslinked Micelle nanoreactors – MNPatCCM

Metal nanoparticles (MNPs) are well-established tools in catalysis, providing higher activities than both bulk surfaces and molecular catalysts in several reactions, specifically hydrogenations. However, there is a lack of mechanistic understanding as well as tools allowing predicting value and guidance toward further optimisation. One of the challenges in nanocatalysis is to have highly active, selective, robust (long lifetime) and recyclable catalysts. The synthesis of stable MNP dispersions from homogeneous solutions requires a stabiliser, often an organic ligand or a polymer. A recently developped concept that advantageously combines “homogeneous” reaction conditions with a “heterogeneous” catalyst recovery is the embedding of the MNPs in the hydrophobic cores of amphiphilic core-cross linked polymer micelles (CCMs), which form stable aqueous dispersions and act as individual catalytic nanoreactors in an aqueous biphasic catalysis protocol. Migration of the reactants and products across the core-cross linked polymer micelle hydrophilic shell is facile. The catalytic transformation occurs within the “homogeneous” core-cross linked polymer micelle core and the product/catalyst separation is accomplished by simple phase decantation. The MNPatCCM project aims at optimising the performance of catalytic CCM-type nanoreactors made of metal (rhodium, nickel) nanoparticles anchored to ligand-functionalized cores of core-crosslinked polymer micelles for hydrogenation and hydrogenolysis/hydrodeoxygenation reactions. The anchoring ligands in core-crosslinked polymer micelles will be introduced using polymerizable versions of the molecular stabilizers previously investigated in organic colloidal dispersions. The effect of added bases will be investigated in order to determine the relevance of integrating such a promoter in the core-crosslinked polymer micelles structure for guiding the hydrogenation activation and, consequently, the improvement of catalytic performance. The activities and selectivities obtained with the metal nanoparticles dispersed in an organic medium will help the design of novel core-crosslinked polymer micelles based on core engineering for aqueous biphasic hydrogenations and hydrogenolysis/hydrodeoxygenations, with particular attention to recycling and sustainability concerns (increasing the efficiency of the use of metals, of particular for noble metal Rh). After improving the catalytic performance of rhodium-loaded catalytic nanoreactors, the synthesis strategy will be extended to the development of similar systems embedding nanoparticles of a first-row abundant metal, namely nickel. This will allow addressing a key concern in catalysis, namely to replace noble metals by less critical ones, in terms of abundance and cost. The substrate screening and condition optimisation will take advantage of methods adapted to determine the relevance of the best catalysts at the industrial scale. The ultimate goal will be to perform economic analysis and life cycle assessment for the most promising catalytic reactions with substrates of industrial interest.