FULL PAPER
DOI: 10.1002/asia.201300668
Core Cross-Linked Micelle-Based Nanoreactors for Efficient Photocatalysis
[
a]
[a]
[b]
[b]
Min Zheng, Zaicheng Sun,* Zhigang Xie,* and Xiabin Jing
Abstract: Stable nanoscale cross-linked
polymer micelles containing Ru com-
plexes (Ru-CMs) were prepared from
stability in common solvents. The Ru-
CMs showed photocatalytic activity
and selectivity in the oxidation of sul-
fides that were as high as those of the
well-known [Ru AHCTUNGERTNNUNG( bpy) ACHTUNGTRNENU(G PF ) ] complex,
3 6 2
because the micelles were swollen in
the methanol–sulfide mixture. More-
over, because of the nanoscale size of
the particles and their high stability,
the Ru-CM photocatalysts can be read-
ily recovered by ultrafiltration and
reused without loss of photocatalytic
activity. This work highlights the poten-
tial of using cross-linked micelles as
a platform for developing highly effi-
cient heterogeneous photocatalysts for
a number of important organic trans-
formations.
monomethoxy
block-poly(l-lysine) (MPEG-PLys) and
(bpy) Ru(fmbpy)](PF ) (bpy=bipyri-
ACHTUNGTRENNUNG[ poly(ethylene glycol)]-
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
[
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
A
C
H
T
U
N
G
T
R
E
N
N
U
N
G
2
6 2
dine, fmbpy=5-formy-5’-methyl-2,2’-bi-
pyridine). To stabilize the micelles, bi-
functional glutaraldehyde was used as
a cross-linker to react with the free
amino groups of the PLys block. After
that, the Ru-CMs showed very good
Keywords: micelles · nanoreactors ·
oxidation · photocatalysts · ruthe-
nium
Introduction
by trace amounts of heavy metals but also reduces process-
[3]
ing and waste disposal costs in large-scale production. Or-
ganometallic catalysts loaded on hard frameworks such as
Sunlight can be considered as a sustainable and renewable
energy source for thermal and electrical energy (photovolta-
ic cells). Besides that, photocatalytic organic reactions
driven by visible light are gaining interest from organic
chemists, because of their mild conditions for substrate acti-
vation and the potential to mediate thermodynamically
[4]
mesoporous silica and zeolites are extensively employed.
However, the low dispersibility of inorganic catalysts in an
organic reaction mixture often causes a low conversion rate
of the reaction owing to the heterogeneous interface be-
tween the reactant and the catalyst.
[
1]
uphill reactions by harvesting energy from sunlight. Sever-
Block copolymers (BCPs) can self-assemble into various
kinds of nanoscale aggregates such as spheres, cylinders, and
vesicles by varying the BCP composition, solvent, concentra-
2
3
+
al metal complexes, including Ru
dine) and [Ir
bpy=4,4’-di-tert-butyl-2,2’-bipyridine), have been used as
A
H
U
G
R
N
N
(bpy)
(bpy=2,2’-bipyri-
ACHTUNGTRENNUNG( ppy) ACHTUNGTRENNUNG( dtb-bpy)] (ppy=2-phenylpyridine, dtb-
2
+
[5]
tion, and temperature. Of the aggregates, BCP micelles
[
2]
[6]
photocatalysts for a number of organic transforms. These
photocatalysts display high catalytic activity and selectivity
for many organic reactions as a result of the homogeneous
reaction environment. However, the catalysts are prepared
from precious metals, and as such, the recovery and reuse of
the catalysts are essential and critical for their wide use in
chemical industries. Great effort has been made to develop
reusable heterogeneous photocatalytic systems based on Ru
complexes. The reuse of such heterogeneous photocatalysts
not only eliminates contamination of the organic products
have great potential for use in targeted drug delivery,
[7]
nanoreactors for inorganic materials, mesoporous nano-
[8]
[9]
structured templates, and hybrid composite materials.
However, the dynamic instability of BCP micelles can
hinder their use in such applications. Although the critical
micelle concentration (CMC) of polymer micelles is much
lower than that of small-molecule surfactants, BCP micelles
are still susceptible to disassembly under high dilution con-
[5b]
ditions. A change in the solvent, an increase in tempera-
ture, mechanical stress, and shear force can also lead to
rapid disassembly of BCP micelles. These considerations
have motivated important breakthroughs in the stabilization
of BCP micelles through cross-linking of either their corona
[
a] Dr. M. Zheng, Prof. Dr. Z. Sun
State Key Laboratory of Luminescence and Applications
Changchun Institute of Optics, Fine Mechanics and Physics, CAS
[10]
or cores.
By interchain bonding, cross-linked micelles
3
888 East Nanuhu Road, Changchun, Jilin 130033 (P. R. China)
(CMs) are stable, self-assembled nanostructures that can be
used under harsh conditions. A wide variety of micelle
cross-linking methodologies have been developed, including
E-mail: sunzc@ciomp.ac.cn
[
b] Prof. Dr. Z. Xie, Prof. Dr. X. Jing
State Key Laboratory of Polymer Physics and Chemistry
Changchun Institute of Applied Chemistry, CAS
5
[11]
radical-induced bond formation, photoinduced cycloaddi-
[
12]
[13]
tions,
siloxane condensation,
the use of bifunctional
625 Renmin Street, Changchun Jilin 130022 (P. R. China)
[14]
[10]
cross-linking agents, and many others. CMs can serve as
ideal nanoreactors to incorporate molecular catalytic mod-
ules into highly stable, recyclable, and reusable heterogene-
E-mail: xiez@ciac.jl.cn
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201300668.
Chem. Asian J. 2013, 8, 2807 – 2812
2807
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim