221
support, is the choice of the stabilizing agent which ensures the good dispersion of
the active phase with the desired particle size. Taking into account this, the need to
develop more eco-friendly metal nanoparticle synthesis without harmful solvents,
the use of water-soluble capping agents has grown since the beginning of the
twenty-first century. Ammonium salts, phosphanes, dendrimers, polymers, or oligosaccharides are generally found in the literature and show interesting results in
terms of catalytic activity and stability. Among these capping agents, cyclodextrins
are interesting candidates in the field of nanocatalysis due to their low cost, nontoxicity, high capacity to interact with metal ions, and the possibility to form inclusion complexes with reactants in order to bring them close to the active site.
According to a bibliographic survey up to 2020 involving cyclodextrin, catalysis,
and metal nanoparticles as keywords, a huge number of publications have been
found. Therefore, we decided to restrict our study to the cases where cyclodextrins
are present during the catalytic process using metal nanoparticles, either in solventdispersed form or immobilized on a support, as active phase. This means that the
works dealing with cyclodextrin-assisted syntheses of supported metal nanoparticles including a calcination/carbonization step or a washing step to remove the
cyclodextrin have not been considered here.
This chapter is divided into two distinct parts. In the first part, we focus on the
publications concerning the solvent-dispersed nanoparticles. Several parameters
such as the size of the cavity, the functionalization of the cyclodextrin rims, and the
presence of co-stabilizers (surfactants, phosphanes, or polymers) or cyclodextrinbased polymers have been studied to get stable, active, and recyclable nanoheterogeneous catalysts. Cyclodextrins can be either added during the nanoparticle
synthesis or after the metal nanoparticle synthesis and can consequently play the
role of mass transfer agent to bring the substrate in the vicinity of the active species
and improve the activity and/or the selectivity. The second part is dedicated to catalysts with nanoparticles immobilized onto and/or into a support matrix in the presence of cyclodextrins. In this case, different strategies are discussed for the synthesis
of heterogeneous catalysts consisting of nanoparticles immobilized on a support,
such as inorganic supports, carbonaceous materials, or polymers, in the presence of
cyclodextrins either non-covalently grafted or covalently grafted on the supports.
Nanoparticles can be synthesized (i) before their adsorption/incorporation onto or
into the support or (ii) in the presence of the support and also of the cyclodextrins.
It should be noticed that the structure of the cyclodextrin remains intact whatever
the strategy. Consequently, in line with the first part, the relationships between the
supramolecular structures and their activities are discussed, and the different roles
of the cyclodextrin are further underlined.
5 Metal Nanoparticles and Cyclodextrins for Catalytic Applications
support, is the choice of the stabilizing agent which ensures the good dispersion of
the active phase with the desired particle size. Taking into account this, the need to
develop more eco-friendly metal nanoparticle synthesis without harmful solvents,
the use of water-soluble capping agents has grown since the beginning of the
twenty-first century. Ammonium salts, phosphanes, dendrimers, polymers, or oligosaccharides are generally found in the literature and show interesting results in
terms of catalytic activity and stability. Among these capping agents, cyclodextrins
are interesting candidates in the field of nanocatalysis due to their low cost, nontoxicity, high capacity to interact with metal ions, and the possibility to form inclusion complexes with reactants in order to bring them close to the active site.
According to a bibliographic survey up to 2020 involving cyclodextrin, catalysis,
and metal nanoparticles as keywords, a huge number of publications have been
found. Therefore, we decided to restrict our study to the cases where cyclodextrins
are present during the catalytic process using metal nanoparticles, either in solventdispersed form or immobilized on a support, as active phase. This means that the
works dealing with cyclodextrin-assisted syntheses of supported metal nanoparticles including a calcination/carbonization step or a washing step to remove the
cyclodextrin have not been considered here.
This chapter is divided into two distinct parts. In the first part, we focus on the
publications concerning the solvent-dispersed nanoparticles. Several parameters
such as the size of the cavity, the functionalization of the cyclodextrin rims, and the
presence of co-stabilizers (surfactants, phosphanes, or polymers) or cyclodextrinbased polymers have been studied to get stable, active, and recyclable nanoheterogeneous catalysts. Cyclodextrins can be either added during the nanoparticle
synthesis or after the metal nanoparticle synthesis and can consequently play the
role of mass transfer agent to bring the substrate in the vicinity of the active species
and improve the activity and/or the selectivity. The second part is dedicated to catalysts with nanoparticles immobilized onto and/or into a support matrix in the presence of cyclodextrins. In this case, different strategies are discussed for the synthesis
of heterogeneous catalysts consisting of nanoparticles immobilized on a support,
such as inorganic supports, carbonaceous materials, or polymers, in the presence of
cyclodextrins either non-covalently grafted or covalently grafted on the supports.
Nanoparticles can be synthesized (i) before their adsorption/incorporation onto or
into the support or (ii) in the presence of the support and also of the cyclodextrins.
It should be noticed that the structure of the cyclodextrin remains intact whatever
the strategy. Consequently, in line with the first part, the relationships between the
supramolecular structures and their activities are discussed, and the different roles
of the cyclodextrin are further underlined.
5 Metal Nanoparticles and Cyclodextrins for Catalytic Applications