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Y. Min et al.
induces a lower catalytic activity, when compared to other Ru-based systems already
reported, which is due to the poor accessibility to the Ru NP surface. PdNi bimetallic
NP over C 60 , C 60 -malonic acid, and C 60 -ethanediamine were also active for this reaction. Pd–6Ni–N–C 60 exhibited good catalytic performances for the reduction of the
nitro group and could be reused six times [83].
Pd NP embedded in a COF structure were successfully used as catalyst for the
reduction of 4-nitrophenol with NaBH 4 [88]. Pd NP encapsulated in a sacrificial MOF
were used to create a COF in a second-step reaction, which coated the Pd/MOF
species. The subsequent selective etching of the MOF allowed encapsulation of
multiple Pd NP inside the cavities of the COF. The reduction of 4-nitrophenol was
monitored by UV-vis absorption spectroscopy, the constant rate calculated to be
0.41 min
−1 . The catalytic performance of this catalyst was compared to other Pd
NP systems, which evidenced the superior catalytic activity of the encapsulated Pd
NP, and an effect of the shell thickness of the COF. The catalyst was characterized
by electron microscope techniques after the catalysis, which revealed no change.
Filtration and recycling tests (up to four cycles), together with the characterization after catalysis suggested that Pd NP are effectively protected from aggregation
and leaching by the COF shell. The successful synthesis of a thiol-modified COF
allowed the synthesis of Pd or Pt NP within the pores [89]. K 2 PtCl 4 or K 2 PdCl 4 were
first embedded in the thiol-modified COF and successively, the metallic salts were
reduced with NaBH 4 . Using this straightforward procedure, ultra-small NP (<2 nm)
of both metals were confined in the COF structure. Pt NP were successfully used
as catalyst in the reduction of 4-nitrophenol by NaBH 4 . The catalyst was reused
six times, displaying up to 90% of conversion in each cycle. TEM image shows
that the recycled catalyst does not undergo aggregation. Similarly, Pd NP within the
thiol-modified COF were used as catalyst in the Suzuki–Miyaura coupling reaction.
Excellent catalytic activities were also observed. The catalytic performances were
compared with Pd NP and with the [PdCl 2 (PPh 3 ) 2 ] complex, evidencing the positive
effect of the encapsulation, as lower activities were obtained with these latter systems.
The catalyst exhibited excellent stability and recyclability under the catalytic reaction
conditions, as evidenced by TEM analyses and recycling tests (up to five cycles).
In another example, chain-like aggregates of NiWO 4 were used as catalyst in the
reduction of ferricyanide to ferrocyanide in the presence of Na 2 S 2 O 3 under light
[131].
The electrocatalytic oxygen reduction reaction was used to confirm the controlled
arrangement of AuPt NP assemblies [127]. Peptide-coated single-walled carbon
nanotubes (SWCNT) were prepared, to further accommodate AuPt NP, synthesized
by reduction of HAuCl 4 and PtCl 6 with NaBH 4 in the presence of several peptidecoated SWCNT supports. The peptide-coated SWCNT supports connect efficiently
the conducting SWCNT with the electrocatalytically active NP. Engineering the
peptide allowed the efficient control of the distance between the bimetallic NP,
creating controlled assemblies. The electrochemical performances were governed
by the size and inter-particle distance, which was further endorsed by theoretical
calculations.
Y. Min et al.
induces a lower catalytic activity, when compared to other Ru-based systems already
reported, which is due to the poor accessibility to the Ru NP surface. PdNi bimetallic
NP over C 60 , C 60 -malonic acid, and C 60 -ethanediamine were also active for this reaction. Pd–6Ni–N–C 60 exhibited good catalytic performances for the reduction of the
nitro group and could be reused six times [83].
Pd NP embedded in a COF structure were successfully used as catalyst for the
reduction of 4-nitrophenol with NaBH 4 [88]. Pd NP encapsulated in a sacrificial MOF
were used to create a COF in a second-step reaction, which coated the Pd/MOF
species. The subsequent selective etching of the MOF allowed encapsulation of
multiple Pd NP inside the cavities of the COF. The reduction of 4-nitrophenol was
monitored by UV-vis absorption spectroscopy, the constant rate calculated to be
0.41 min
−1 . The catalytic performance of this catalyst was compared to other Pd
NP systems, which evidenced the superior catalytic activity of the encapsulated Pd
NP, and an effect of the shell thickness of the COF. The catalyst was characterized
by electron microscope techniques after the catalysis, which revealed no change.
Filtration and recycling tests (up to four cycles), together with the characterization after catalysis suggested that Pd NP are effectively protected from aggregation
and leaching by the COF shell. The successful synthesis of a thiol-modified COF
allowed the synthesis of Pd or Pt NP within the pores [89]. K 2 PtCl 4 or K 2 PdCl 4 were
first embedded in the thiol-modified COF and successively, the metallic salts were
reduced with NaBH 4 . Using this straightforward procedure, ultra-small NP (<2 nm)
of both metals were confined in the COF structure. Pt NP were successfully used
as catalyst in the reduction of 4-nitrophenol by NaBH 4 . The catalyst was reused
six times, displaying up to 90% of conversion in each cycle. TEM image shows
that the recycled catalyst does not undergo aggregation. Similarly, Pd NP within the
thiol-modified COF were used as catalyst in the Suzuki–Miyaura coupling reaction.
Excellent catalytic activities were also observed. The catalytic performances were
compared with Pd NP and with the [PdCl 2 (PPh 3 ) 2 ] complex, evidencing the positive
effect of the encapsulation, as lower activities were obtained with these latter systems.
The catalyst exhibited excellent stability and recyclability under the catalytic reaction
conditions, as evidenced by TEM analyses and recycling tests (up to five cycles).
In another example, chain-like aggregates of NiWO 4 were used as catalyst in the
reduction of ferricyanide to ferrocyanide in the presence of Na 2 S 2 O 3 under light
[131].
The electrocatalytic oxygen reduction reaction was used to confirm the controlled
arrangement of AuPt NP assemblies [127]. Peptide-coated single-walled carbon
nanotubes (SWCNT) were prepared, to further accommodate AuPt NP, synthesized
by reduction of HAuCl 4 and PtCl 6 with NaBH 4 in the presence of several peptidecoated SWCNT supports. The peptide-coated SWCNT supports connect efficiently
the conducting SWCNT with the electrocatalytically active NP. Engineering the
peptide allowed the efficient control of the distance between the bimetallic NP,
creating controlled assemblies. The electrochemical performances were governed
by the size and inter-particle distance, which was further endorsed by theoretical
calculations.