267
(ACNa) which is known to strongly interact with β-cyclodextrin. A decrease of the
conversion was observed in the presence of ACNa in comparison with the catalytic
test made without ACNa. Indeed, the adsorption of 4-nitrophenol onto Pd nanoparticle surface could be enhanced by the complexation of 4-nitrophenol with
β-cyclodextrin. The recyclability of this catalytic system was also studied, and it
was reused during seven successive catalytic runs without any loss of activity and
increase of the mean diameter of the Pd nanoparticles. Moreover, these Pd nanoparticles revealed to be active in the hydrogenation of a wide variety of nitroarenes and
also in the Suzuki-Miyaura coupling reaction.
Palladium nanoparticles were immobilized on cyclodextrin-modified
poly(amidoamine)s (PAAs) by a chemical reduction of Pd(OAc) 2 in dimethylsulfoxide (Zhang et al. 2019). FTIR data confirmed the presence of the polymer and the
cyclodextrin structures in the material. Scanning electron microscopy image showed
that the Pd nanoparticles were uniformly dispersed onto the PAAs-cyclodextrin
with a globular radius of 10 nm. The catalytic activity of these supported Pd
nanoparticles was evaluated in the Suzuki reaction in aqueous medium. The temperature and the nature of the base were studied for the optimization of the reaction
between the phenylboronic acid and 4-bromoethoxybenzene. The catalyst showed
good activities which is probably due to the cyclodextrin moiety which ensured a
good dispersion of the heterogeneous catalyst in water. The beneficial effect of the
cyclodextrin through inhibitive experiments using adamantane was confirmed by an
activity decrease. The study was then extended to a variety of aryl halides, and the
cross-coupling products were obtained from moderate to excellent yields. The catalytic system could finally be recycled by maintaining activity after six successive runs.
The development of nanofibers has received an increasing interest since several
years. This kind of material could be considered for the development of heterogeneous catalysts by the deposition or the incorporation of metal nanoparticles onto
and into the nanofibers. The group of Uyar is a precursor in this field. Indeed, in
2019, they reported the incorporation of Ag nanoparticles into nanofibers made
from the electrospinning of hydroxypropyl-β-cyclodextrin solution containing Ag
nanoparticles (Celebioglu et al. 2019b). In this case, Ag nanoparticles were synthesized before the electrospinning step using hydroxypropyl-β-cyclodextrin as reducing agent of silver metal precursor in an alkaline solution. Hydroxypropyl-β-cyclodextrin
was also used for the production of the nanofiber mats. The catalytic nanofibers
were prepared starting from a dimethylformamide solution or an aqueous solution.
Ag nanoparticles were homogeneously dispersed onto the nanofiber mats, and the
mean diameter of Ag nanoparticles increased when the nanofibers were prepared in
dimethylformamide instead of aqueous solutions and when the amount of silver
increased in the nanofiber mats from 1 wt. % to 2 wt. %. Indeed, the mean size of
Ag nanoparticles in the fiber matrix produced from dimethylformamide increased
from 3.5 nm to 4.8 nm for, respectively, 1 wt. % and 2 wt. % of Ag loading. And the
mean size of Ag nanoparticles in the fiber matrix produced from aqueous solutions
increased from 1.9 nm to 2.3 nm for, respectively, 1 wt. % and 2 wt. %. The same
tendency was observed for the mean diameter of the electrospun nanofibers. The
5 Metal Nanoparticles and Cyclodextrins for Catalytic Applications
(ACNa) which is known to strongly interact with β-cyclodextrin. A decrease of the
conversion was observed in the presence of ACNa in comparison with the catalytic
test made without ACNa. Indeed, the adsorption of 4-nitrophenol onto Pd nanoparticle surface could be enhanced by the complexation of 4-nitrophenol with
β-cyclodextrin. The recyclability of this catalytic system was also studied, and it
was reused during seven successive catalytic runs without any loss of activity and
increase of the mean diameter of the Pd nanoparticles. Moreover, these Pd nanoparticles revealed to be active in the hydrogenation of a wide variety of nitroarenes and
also in the Suzuki-Miyaura coupling reaction.
Palladium nanoparticles were immobilized on cyclodextrin-modified
poly(amidoamine)s (PAAs) by a chemical reduction of Pd(OAc) 2 in dimethylsulfoxide (Zhang et al. 2019). FTIR data confirmed the presence of the polymer and the
cyclodextrin structures in the material. Scanning electron microscopy image showed
that the Pd nanoparticles were uniformly dispersed onto the PAAs-cyclodextrin
with a globular radius of 10 nm. The catalytic activity of these supported Pd
nanoparticles was evaluated in the Suzuki reaction in aqueous medium. The temperature and the nature of the base were studied for the optimization of the reaction
between the phenylboronic acid and 4-bromoethoxybenzene. The catalyst showed
good activities which is probably due to the cyclodextrin moiety which ensured a
good dispersion of the heterogeneous catalyst in water. The beneficial effect of the
cyclodextrin through inhibitive experiments using adamantane was confirmed by an
activity decrease. The study was then extended to a variety of aryl halides, and the
cross-coupling products were obtained from moderate to excellent yields. The catalytic system could finally be recycled by maintaining activity after six successive runs.
The development of nanofibers has received an increasing interest since several
years. This kind of material could be considered for the development of heterogeneous catalysts by the deposition or the incorporation of metal nanoparticles onto
and into the nanofibers. The group of Uyar is a precursor in this field. Indeed, in
2019, they reported the incorporation of Ag nanoparticles into nanofibers made
from the electrospinning of hydroxypropyl-β-cyclodextrin solution containing Ag
nanoparticles (Celebioglu et al. 2019b). In this case, Ag nanoparticles were synthesized before the electrospinning step using hydroxypropyl-β-cyclodextrin as reducing agent of silver metal precursor in an alkaline solution. Hydroxypropyl-β-cyclodextrin
was also used for the production of the nanofiber mats. The catalytic nanofibers
were prepared starting from a dimethylformamide solution or an aqueous solution.
Ag nanoparticles were homogeneously dispersed onto the nanofiber mats, and the
mean diameter of Ag nanoparticles increased when the nanofibers were prepared in
dimethylformamide instead of aqueous solutions and when the amount of silver
increased in the nanofiber mats from 1 wt. % to 2 wt. %. Indeed, the mean size of
Ag nanoparticles in the fiber matrix produced from dimethylformamide increased
from 3.5 nm to 4.8 nm for, respectively, 1 wt. % and 2 wt. % of Ag loading. And the
mean size of Ag nanoparticles in the fiber matrix produced from aqueous solutions
increased from 1.9 nm to 2.3 nm for, respectively, 1 wt. % and 2 wt. %. The same
tendency was observed for the mean diameter of the electrospun nanofibers. The
5 Metal Nanoparticles and Cyclodextrins for Catalytic Applications