recyclability. After five successive catalytic runs, it presented similar values of
activity and selectivity (>90%). Somewhat later, the same group studied how the
hydrogen doping into MoO 3 nanorods modulate the metal-support interactions and
enhance the chemoselectivity of supported Ir NPs in the hydrogenation of furfural to
furfuryl alcohol [115]. Through a controlled hydrogen doping by varying the
reduction temperature, the contents of low-valence Mo species (Mo5+ and Mo4+)
and Ir
0 /Ir
δ+ ratios on the surface were adjusted to obtain the most efficient catalyst. In
particular, Ir/H-MoO x reduced at 400
C showed the best activity (TOF: 4.62 min
À1 )
and selectivity (> 99%) in the hydrogenation of furfural to furfuryl alcohol in mild
conditions (30
C and 20 bar H 2 ). These works highlight the importance of supports
in MNP catalysis, which can modify the electronic properties of the metal centres
and therefore enhance the nanoparticle catalytic behaviour.
6.2.4 Ir NPs Supported on Magnetic NPs
The immobilisation of MNPs on magnetic responsive supports, such as Fe 3 O 4 ,
MnFe 2 O 4 or CoFe 2 O 4 , facilitates the catalysts recovery and the separation of the
products after catalysis. In 2012, Rossi et al. reported the generation of Ir NPs by H 2
reduction of IrCl 3 on a magnetic support based on Fe 3 O 4 NPs covered by an aminomodified silica shell [116]. The resulting magnetically recoverable catalyst,
Fe 3 O 4 @SiO 2 -NH 2 -Ir
0 (Fig. 15b), exhibited a remarkable activity in the hydrogenation of alkenes (e.g. TOF: 6,000 h
À1 in the hydrogenation of cyclohexene to
cyclohexane). It was observed that the functionalisation of the silica shell with
amino groups was crucial for the stability of the catalyst. The surface amino group
improves the metal-support interactions and enhance the recyclability of the catalyst.
With the help of an external magnet, the catalyst was recovered and reused up to six
times without any loss of activity. Moreover, the amino groups on SiO 2 surface
promote the metal adsorption during the synthesis and minimises the metal leaching
during the catalysis (Fig. 15a). Again, this work emphasised the importance of the
support on MNP catalysis, which plays a crucial role in the stability and recyclability
of the catalyst.
6.2.5 Ir NPs Supported on MgO
MgO is a well-known high surface area support widely used in heterogeneous
catalysis. Like other basic supports, MgO is capable to modify the catalytic properties of MNPs. Another efficient way to modify the MNP reactivity is through the use
of additives. For example, Tomishige et al. presented Ir NPs supported on MgO and
modified with Fe cations as effective heterogeneous catalyst for the selective hydrogenation of α,β-unsaturated ketones [117]. In particular, Fe cation-modified Ir/MgO
produced the corresponding α,β-unsaturated secondary alcohol with a high activity
(initial TOF ¼ 12 min
À1 ) and selectivity (up to 90%). The catalyst was obtained in
situ by mixing Ir/MgO and the Fe cation precursor [Ir/MgO
+
Fe(NO 3 ) 3 ]. Kinetic
432
L. M. Martínez-Prieto et al.
activity and selectivity (>90%). Somewhat later, the same group studied how the
hydrogen doping into MoO 3 nanorods modulate the metal-support interactions and
enhance the chemoselectivity of supported Ir NPs in the hydrogenation of furfural to
furfuryl alcohol [115]. Through a controlled hydrogen doping by varying the
reduction temperature, the contents of low-valence Mo species (Mo5+ and Mo4+)
and Ir
0 /Ir
δ+ ratios on the surface were adjusted to obtain the most efficient catalyst. In
particular, Ir/H-MoO x reduced at 400
C showed the best activity (TOF: 4.62 min
À1 )
and selectivity (> 99%) in the hydrogenation of furfural to furfuryl alcohol in mild
conditions (30
C and 20 bar H 2 ). These works highlight the importance of supports
in MNP catalysis, which can modify the electronic properties of the metal centres
and therefore enhance the nanoparticle catalytic behaviour.
6.2.4 Ir NPs Supported on Magnetic NPs
The immobilisation of MNPs on magnetic responsive supports, such as Fe 3 O 4 ,
MnFe 2 O 4 or CoFe 2 O 4 , facilitates the catalysts recovery and the separation of the
products after catalysis. In 2012, Rossi et al. reported the generation of Ir NPs by H 2
reduction of IrCl 3 on a magnetic support based on Fe 3 O 4 NPs covered by an aminomodified silica shell [116]. The resulting magnetically recoverable catalyst,
Fe 3 O 4 @SiO 2 -NH 2 -Ir
0 (Fig. 15b), exhibited a remarkable activity in the hydrogenation of alkenes (e.g. TOF: 6,000 h
À1 in the hydrogenation of cyclohexene to
cyclohexane). It was observed that the functionalisation of the silica shell with
amino groups was crucial for the stability of the catalyst. The surface amino group
improves the metal-support interactions and enhance the recyclability of the catalyst.
With the help of an external magnet, the catalyst was recovered and reused up to six
times without any loss of activity. Moreover, the amino groups on SiO 2 surface
promote the metal adsorption during the synthesis and minimises the metal leaching
during the catalysis (Fig. 15a). Again, this work emphasised the importance of the
support on MNP catalysis, which plays a crucial role in the stability and recyclability
of the catalyst.
6.2.5 Ir NPs Supported on MgO
MgO is a well-known high surface area support widely used in heterogeneous
catalysis. Like other basic supports, MgO is capable to modify the catalytic properties of MNPs. Another efficient way to modify the MNP reactivity is through the use
of additives. For example, Tomishige et al. presented Ir NPs supported on MgO and
modified with Fe cations as effective heterogeneous catalyst for the selective hydrogenation of α,β-unsaturated ketones [117]. In particular, Fe cation-modified Ir/MgO
produced the corresponding α,β-unsaturated secondary alcohol with a high activity
(initial TOF ¼ 12 min
À1 ) and selectivity (up to 90%). The catalyst was obtained in
situ by mixing Ir/MgO and the Fe cation precursor [Ir/MgO
+
Fe(NO 3 ) 3 ]. Kinetic
432
L. M. Martínez-Prieto et al.