Development and applications of efficient and recyclable nanosized catalysts
The project concerns the research for eco-compatible chemical processes for the synthesis of organic compounds, intermediates and targets in health industry and material sciences. This search is nowadays inevitable since - even if highly active catalysts are currently available to promote chemical reactions giving rise to these molecules – their scale-up is optimal only if the catalyst can be first separated from the reaction mixture and next reused. Therefore, numerous supports (polymers, dendrimers, silica, nanoparticles…), often nano-sized and on which catalysts can be grafted, were developed. They offer the opportunity to recover the latter via different techniques such as nanofiltrations, precipitation and subsequent filtration, or magnetic decantation. In this project, the processes developed involve two types of supports: dendrimers (arborescent polymers obtained via an iterative process and displaying a perfectly defined structure) and nanoparticles (NPs).
Supports more particularly studied involve phosphorous dendrimers (know-how Toulouse), and magnetic carbon-coated cobalt (or Fe) nanoparticles (know-how Regensburg). The association of these two supports was also studied in one case.
Catalysts grafted involve transition metals, rare earth metals (Sc, Y and lanthanides) or organic molecules (organocatalysts) which all allow to promote many chemical reactions giving rise to key compounds overall the life sciences or also materials preparation. In some cases, grafting strategies involves «click chemistry« and are therefore in phase with sustainable development. Non-covalent grafting of catalysts by p-stacking also constitutes an originality of this project.
Activities, selectivities and recyclabilities of the nano-sized catalysts prepared were evaluated in several reactions (Suzuki coupling, acylation, hydroxycarbonylation, polymerization…). We have also studied the influence of the nature of the support on the catalytic performances and dendrimers have been found to enhance the activity in several cases («dendritric effect«).
Lastly, dendritic catalysts were recovered by precipitation/filtration while magnetic NPs were separated from the reaction media with a magnet.
Catalysts supported onto dendrimers or magnetic nanoparticles are able to efficiently promote key reactions in organic chemistry and can be recycled until sixteen times without loss of activity. Another striking and unexpected result is that the use of a dendritic support allows to avoid metal residues in the product formed. This property is of great concern for the preparation of drugs. The association of both supports while grafting a pyrene-tagged dendron onto a magnetic graphene-coated cobalt NP via p-stacking also permitted to develop a very active and original catalyst which could be recycled twelve times with a magnet.
Numerous publications were accepted (see part E), often in journal with very high impact factors (Angewandte Chemie International Edition), thus illustrating the success of the researches and also the very wide interest for the topic.
The immobilization of organo- and metal catalysts on dendrimers and nanoparticles towards the development of sustainable chemical processes is proposed in this collaborative project. The groups involved are investigating a number of different catalytic processes that form the basis of the joint efforts envisaged here. The focus of this collaborative project is on evaluating supports with globular structures (dendrimers, nanoparticles) to arrive at catalysts that can be employed in continuous setups using nanofiltration techniques. Applying these techniques catalytic transformations aiming at the conversion of furans, i.e. renewable resources, to arenes and coupling reactions of arenes will be investigated. Moreover the use of safe arylating agents (triarylbismuths), and “green” Lewis acids ( Rare Earth triflates) will be investigated in reactions of industrial interest.
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
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Beginning and duration of the scientific project: - 0 Months