Merging of the photocatalysis and copper catalysis in metal-organic frameworks for oxidative C-C bond formation

Article abstract of DOI:10.1039/c4sc02362e

The direct formation of new C-C bonds through photocatalytic oxidative coupling from low reactive sp³ C-H bonds using environmentally benign and cheap oxygen as oxidant is an important area in sustainable chemistry. By incorporating the photore

Full text of DOI:10.1039/c4sc02362e

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DOI: 10.1039/C4SC02362E
EDGE ARTICLE
Merging of the Photocatalysis and Copper Catalysis in Metal-Organic
Frameworks for Oxidative C–C Bond Formation
a
a
a
a
b
a
Dongying Shi, Cheng He, Bo Qi, Cong Chen, Jingyang Niu and Chunying Duan*
Received (in XXX, XXX) Xth XXXXXXXXX 20XX, Accepted Xth XXXXXXXXX 20XX
5
DOI: 10.1039/b000000x
3
The direct formation of new C–C bonds through photocatalytic oxidative coupling from low reactive sp
C–H bonds using environmentally benign and cheap oxygen as oxidant is an important area on
5
–
sustainable chemistry. By incorporating the photoredox catalyst [SiW O Ru(H O)] into the pores of
1
1
39
2
the Cu-based metal–organic frameworks, a new approach for merging Cu-catalysis/Ru-photocatalysis
II
1
0
within one single MOF was achieved. The direct Cu –O–W(Ru) bridges made the two metal catalyses
being synergetic, enabling the application on the catalysis of the oxidative coupling C–C bond formation
from acetophenones and N-phenyl-tetrahydroisoquinoline in excellent conversion and size-selectivity.
The method takes advantage of visible light photoredox catalysis to generate iminium ion intermediate
from N-phenyl-tetrahydroisoquinoline under mild conditions and the easy combination with Cu-catalyzed
activation of nucleophiles. Control catalytic experiments using the similar Cu-based sheets but with the
photoredox catalytic anions imbedded was also displayed for comparison.
1
5
1
0
Introduction
MOF. The combining of photocatalysis with the metal ions or
organocatalysis was expected to be a promising approach to
The direct formation of new C–C bonds through oxidative
coupling reactions from the lower active sp C–H bonds using
oxygen as oxidant is an important area on sustainable chemistry.
11
5
0
create synergistic catalysts.
3
1
2
2
3
3
4
4
0
5
0
5
0
5
Among the reported promising examples, the oxidative activation
of the C–H bonds adjacent to nitrogen atom in tertiary amines
represents a powerful strategy, giving valuable, highly reactive
2
iminium ion intermediates for further functionalization. Recent
investigations also revealed that the visible light photoredox
3
catalysis was a promising approach to such reaction sequences
with respect to the development of new sustainable and green
synthetic methods. It was also postulated that the combination of
the photocatalysis and the metal catalysis within a dual catalytic
transformation is attractive to circumvent the potential side
reactions relative to the highly active intermediates those exist in
4
the photocatalysis. The special hurdles need to be overcome
Scheme 1. Synthetic procedure for the 3D CR–BPY1 MOF that is
composed of wavy-like Cu–BPY sheets and [SiW11O40Ru] anions
showing the combination of the dual catalytic units and channels for
chemical transformations.
include the careful adaptation and the fine tuning of the reaction
7
–
5
rates of the two catalytic cycles, beside the appropriate choice of
6
the metal catalysis and photocatalysis.
5
5
Metal–organic frameworks are hybrid solids with the infinite
network structures built from organic bridging ligands and
inorganic connecting nodes. Besides the potential applications in
By incorporating a ruthenium(III) substituted polyoxometalate
5
–
[
SiW O Ru(H O)]
within the pores of the copper(II)-
11 39
2
7
bipyridine MOFs, herein, we reported a new approach to merge
the visible light photocatalytic aerobic oxidation and copper(II)
catalytic coupling reaction within one MOF (Scheme 1). We
envisioned that the ruthenium-containing fragments possibly
worked as oxidative photocatalyst to generate the iminium ion
many diverse areas, MOFs are ideally suited for catalytic
conversions, since they can impose size and shape selective
8
6
0
restriction through readily fine-tuned channels or pores,
providing precise knowledge about the pore structure, the nature
9
and distribution of catalytically active sites. In comparison to the
1
2
from N-phenyl-tetrahydroisoquinolines, whereas the Cu-based
heterogeneous catalytic systems that have been examined earlier,
the design flexibility and framework tenability resulting from the
huge variations of metal nodes and organic linkers allow the
introduction of more than two independent catalyses in one single
MOF potentially activated the nucleophiles, like they have been
1
3
6
5
recognized in the oxidative C–C bond coupling.
This journal is © The Royal Society of Chemistry [year]
[journal], [year], [vol], 00–00 | 1

Chemical Science
Page 2 of 9
1
6
Results and discussion
in various catalytic oxidation processes of organic substrates,
4
0
such kinds of MOFs potentially allow the combination of
Synthesis and characterizations of CR–BPY1
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photocatalysis and MOF-based heterogeneous catalysis to
DOI: 10.1039/C4SC02362E
Solvothermal reaction of 4,4′-bipyridine (BPY), Cu(NO ) ·3H O
achieve synthetically useful organic transformation. Moreover,
the directly bridging of the copper and ruthenium by Cu –O–
3
2
2
II
and K [SiW O Ru(H O)]·10H O gave CR–BPY1 in a yield of
5
11 39
2
2
5
0
5
0
52%. Elemental analyses and powder X-ray analysis indicated the
pure phase of its bulk sample. Single-crystal structural analysis 45 catalysis between photocatalyst and metal catalyst.
W(Ru) provided a promising way to achieve the synergistic
revealed that CR–BPY1 crystallized in a space group P42 m.
The confocal fluorescence microscopy technology has attracted
much attention in biological imaging. It may provide a way to
analyse relatively thick porous materials, because it offers the
1
Two crystallographically independent copper(II) ions are
connected by BPY ligands and μ
produce a 2D wavy-like Cu–BPY sheets (Fig. S5, ESI†). The
Cu(2) atom adopted a six-coordinate octahedral geometry with 50 assessment of guest-accessible volume in MOFs can be reliably
2
-water bridges alternatively to
1
7
1
1
2
advantage of increased penetration depth ( > 500 mm). The
four nitrogen atoms from four BPY ligands positioned in the
equatorial plane and two water molecules occupied the axial
positions. The Cu(1) atom displayed a five-coordinate square
done by using confocal fluorescence microscopy with a tool-box
of dyes with a wide range of sizes. It would be applicable to any
porous materials, whose single-crystal structures are not available,
1
8
pyramidal geometry with two μ -water groups and two nitrogen
or non-crystalline materials. Dye uptake investigation was
2
atoms of BPY ligands positioned in the basal plane, and a 55 carried out by soaking CR–BPY1 in a methanol solution of 2′,7′-
5
–
terminal oxygen atom of the depronated [SiW11
O
39Ru(H
2
O)]
dichlorofluorescein. It gave the quantum uptake equivalent to 5%
1
9
polyoxoanion occupied the vertex position. The ruthenium atom
of the MOF weight (Fig. S11, ESI†). The confocal laser
scanning microscopy exhibited strong green fluorescence (λex
488 nm) assignable to the emission of the fluorescein dye (Fig. 2),
the metal atoms adjacent to the heteroatom allows the 60 confirming the successful uptake of the dye molecules inside the
disordered in the twelve equivalent positions within a depronated
=
5
– 14
[SiW O Ru(H O)] . The availability of vacant d-orbitals on
1
1
39
2
1
5
20
polyoxometalate matrix to function as a π-acceptor ligand.
crystals of the MOF.
Furthermore, the rather uniform
distribution of the dye molecules throughout the crystal suggested
that the dyes penetrated deeply into the crystal rather than staying
external surface. Without guest water molecules, the effective
free volume of CR–BPY1 was estimated to be 29.0 % by
6
5
2
1
PLATON software.
Fig. 2 Confocal images of empty (a, c) and soaked (b, d) 2′,7′-
dichlorofluorescein dye. Brightfield images (a, b) and confocal images (c,
d) detected at λem = 510 – 610 nm, exited by λex ＝ 488 nm through a
7
0
4
05/488 nm filter. (e) The 3D reconstruction of the soaked 2′,7′-
dichlorofluorescein dye (b). Three images at the end of axes in (e)
exemplify the X, Y and Z-axis projections of the soaked dye.
Fig. 1 Crystal structure of CR–BPY1 with the 3D framework generated
CR–BPY1 exhibited an absorption band centered at 398 nm in
2
5
by the covalently linking of the wavy-like 2D sheets (drawn in stick-ball
7
5
the solid state UV-vis absorption spectrum (Fig. S1, ESI†),
5
–
II
model) and the [SiW11
O39Ru(H
2
O)] (drawn in polyhedron) by Cu –O–
5– 22
2
assignable to the transitions of [SiW11O39Ru(H O)] . Upon
W(Ru) bridges, showing the interpenetration of two symmetric frameworks.
excitation at this band, CR–BPY1 didn’t exhibit any obvious
emission, however, progressive addition of the N-phenyl-
While these copper atoms were connected by the BPY ligands
to form two-dimension square grid at first. Adjacent sheets were
tetrahydroisoquinoline into the dichloromethane suspension of
5
–
II
3
0
connected together using the depronated [SiW11
O
39Ru(H
2
O)]
80 CR–BPY1 up to 0.50 mM caused the appearance of the Ru -
II
23
polyoxoanion by Cu –O–W(Ru) bridges to generate a 3D frame-
work. Two symmetric-related frameworks further interpenetrated
each other perpendicularly to consolidate the robust structure (Fig.
relative emission band at about 422 nm (Fig. 3a). The results
suggested that CR–BPY1 oxidized N-phenyl-tetrahydroiso-
II
24
quinoline to form the Ru species and the iminium intermediate.
Electrospray ionization mass spectrometry of the CH Cl
Å. To the best of our knowledge, CR–BPY1 represents the first 85 suspension containing N-phenyl-tetrahydroisoquinoline and CR–
1
), in which the opening of the pores was reduced to 10.0 Å × 5.3
2
2
3
5
example of MOFs which are comprised of ruthenium substituted
BPY1 after 3 hours irradiation in the light exhibited an intense
peak at m/z = 208. This peak was assignable to the relative imine
ion, confirming that CR–BPY1 oxidized N-phenyl-tetrahydroiso-
5
–
polyoxometalate [SiW O Ru(H O)] . As the noble metal
1
1
39
2
substituted polyoxometalates exhibited excellent photoreactivity
2
| Journal Name, [year], [vol], 00–00
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Page 3 of 9
Chemical Science
II
quinoline to form the Ru species and the iminium intermediate
Fig. S13, ESI†). The electron paramagnetic resonance (EPR) of
well-defined size were really helpful for the catalytic reactions,
but the size of the crystals did not dominate the catalVyieswisAdrtiicrleecOtlnyli.ne
Table 1 Controlled trials for the C–C coupli Dn gO I r: e1 a0 c. t1 i 0o 3n 9 /o Cf 4 NS C- p 0h 2e 3n 6y 2l -E
(
II
CR–BPY1 exhibited the characteristic signal of Cu with g =
.14 (Fig. 3c). Solid state electrochemical measurements (Fig. 3d)
exhibited a broad redox band centred at –186 mV (vs SCE)
relative to the overlap of the Cu /Cu and Ru /Ru redox couples.
The potentials were comparable to these Cu and Ru -containing
catalysts, enabled CR–BPY1 to prompt the oxidative coupling
of N-phenyl-tetrahydroisoquinoline with nucleophiles under light.
It seems that CR–BPY1 adsorbed the N-phenyl-tetrahydroiso-
quinoline in its pores and activated the substrate to form iminium
intermediate.
4
5
2
tetrahydroisoquinoline and nitromethane.
5
II
I
III
II
II
III
2
5
26
a
b
Entry
Catalysts
CR–BPY1
CR–BPY2
Cu(NO ·3H
Conversion (%)
1
0
1
2
3
4
5
6
7
90
46
3
)
2
2
O
39
K
5
5
[SiW11
[SiW11
O
39Ru(H
39Ru(H
2
O)]
25
K
O
2
O)], Cu(NO
3
)
2 2
·3H O
42
no catalyst
CR–BPY1, no light
20
<10
a
Reaction conditions: N-phenyl-tetrahydroisoquinoline (0.25 mmol), 1
mol% catalyst, 2.0 mL nitromethane, 18 W fluorescent lamp at room
b
5
0
temperature. The conversions after irradiation 24 hours were determined
1
by H NMR of crude products.
Control experiments for the C–C coupling reaction of N-
phenyl-tetrahydroisoquinoline and nitromethane were tested and
summarized in Table 1. Almost no conversion was observed when
the reaction was conducted in the dark (entry 7), while a very slow
background reaction was observed in the absence of catalyst
5
6
6
5
0
5
(
entry 6), which demonstrated that both the light and the
photocatalyst are required for efficient conversion to the coupling
products. In addition, using the same equiv of copper(II) salts
or/and K [SiW O Ru(H O)] as catalysts, respectively gives
5
11 39
2
conversions of 39%, 25% and 42% in homogeneous fashion
(entry 3–5). These results suggested that the direct connection of
Fig. 3 (a) Family of emission spectra of CR–BPY1 (0.1% in weight) in
1
2
5
0
2 2
CH Cl suspension upon addition of N-phenyl-tetrahydroisoquinoline up
7–
to 0.50 mM, excitation at 362 nm. (b) The luminescence intensities of
CR–BPY1 and CR–BPY2 upon addition of the same amount of N-
phenyl-tetrahydroisoquinoline up to 0.50 mM at room temperature in
copper(II) ions to [SiW O Ru] anions not only enabled the dual
11
40
catalysts to individually activate N-phenyl-tetrahydroisoquinoline
and nitromethane, but also enforced the proximity between the
potential intermediates i.e. the iminium ion and nucleophile,
CH
phenyl-tetrahydroisoquinoline and nitromethane as the coupling partners.
c) EPR spectra of CR–BPY1 (g = 2.1438) and CR–BPY2 (g = 2.1320) in
solid state at 77K, respectively. (d) Solid state cyclic voltammetry of CR–
2 2
Cl ; The catalytic activities of CR–BPY1 and CR–BPY2 using N-
2
8
(
avoiding the unwanted side reactions or reverse reactions.
–
1
BPY1 and CR–BPY2, respectively, scan rate: 50 mV·s .
Catalysis details of CR–BPY1
2
3
3
4
5
0
5
0
The catalysis was examined initially using N-phenyl-tetrahydro-
isoquinoline and nitromethane as the coupling partners, along
with a common fluorescent lamp (18 W) as the light source. The
resulting reaction gave a yield of 90% after 24 hours irradiation.
The removal of CR–BPY1 by filtration after 18 hours shut down
the reaction, and the filtrate afforded only 12% additional
conversion for another 18 hours at the same reaction conditions.
1
Fig. 4 H NMR in DCl/DMSO and solid state IR spectra of the desolvated
CR–BPY1 (a) and (c), respectively, and of the desolvated CR–BPY1
impregnated in a dichloromethane solution of acetophenone (b) and (d),
respectively, showing the absorbency and activation of substrate in the
MOF. The blue and red triangle represented the signals of acetophenone
in the NMR and IR spectra, respectively.
The observation suggested that CR–BPY1 was
a true
7
7
8
0
5
0
2
7
heterogeneous catalyst. Solids of CR–BPY1 could be isolated
from the reaction suspension by simple filtration alone and reused
at least three times with moderated loss of activity (from 90% to
8
2% of yield after three cycles). The index of XRD patterns of
CR–BPY1 filtrated off from the reaction mixture suggested the
maintenance of the crystallinity (Fig. S14, ESI†). With the size of
the microcrystals reduced to 2 µm by grinding CR–BPY1 crystals
for 20 mins, the time of the reaction giving the same conversion
to that of the as-synthesized materials was reduced by about 10%
Although several examples of photocatalysts and metal copper
catalysts have been reported to prompt the oxidative coupling C–
C bond formation, CR–BPY1 represents the new example of the
heterogeneous bimetal catalyst that merge the copper catalyst and
the ruthenium(III) substituted polyoxometalate catalyst within
one single material. The high modularity of the systems allows an
(
Fig. S15, ESI†). It seems that the MOFs-based particles having
This journal is © The Royal Society of Chemistry [year]
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Chemical Science
Page 4 of 9
easy adaption of the concept of dual catalysis, and represents an
between photocatalyst and metal catalyst. Importantly, in contrast
example of combining dual catalysis to achieve synthetically
useful organic transformation. In this case, our catalytic systems
to the smooth reactions of substrates 1–3, the C–C coupling
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reaction in the presence of bulky ketone (1-(3',5'-di-tert-butyl
DOI: 10.1039/C4SC02362E
were extended with other pronucleophiles, i.e. substituted
acetophenones. As shown in Fig. 4, H NMR of desolvated CR– 45 under the same reaction conditions (Table 2, entry 4). The
[1,1'-biphenyl]-4-yl)-ethanone) 4, gave less than 10% conversion
1
5
0
5
BPY1 solids immersed in a dichloromethane solution of
acetophenone exhibited that CR–BPY1 could adsorb about 2
equiv of acetophenone per copper(II) moiety. IR spectrum of
CR–BPY1 impregnated with a dichloromethane solution of
negligible adsorption by immersing CR–BPY1 into a dioxane
solution of substrate 4, coupled with the fact that the size of
substrate 4 was larger than that of the channels, revealed that 4
31
was too large to be adsorbed in the channels. Furthermore, it is
–
1
1
acetophenone revealed a C=O stretching vibration at 1679 cm . 50 suggested that the synergistic catalytic coupling reaction indeed
–
1
The red shift from 1685 cm (free acetophenone) suggested the
adsorption and the activation of the acetophenone in the channels
of the MOFs. It is hypothesized that the interactions between the
copper ions in CR–BPY1 and the C=O groups of acetophenone
occurred in the channels of the MOF, not on the external surface.
Synthesis and catalytic characterizations of CR–BPY2
To further investigate the synergistic interactions between the
2
9
5–
1
possibly gave an active nucleophile.
inorganic copper and [SiW11
O
39Ru(H
2
O)] anion, a reference
5
6
6
7
7
5
0
5
0
5
compound CR–BPY2 was assembled using the same starting
components but different synthetic conditions (hierarchical
diffusion). CR–BPY2 was synthesized by a diffusion method in a
test tube by laying a solution of 4,4′-bipyridine in acetonitrile
onto the solution of K [SiW O Ru(H O)]·10H O and
Table 2 Photocatalytic oxidative C–C coupling reactions of N-phenyl-
tetrahydroisoquinoline and substituted acetophenones.
a
5
11 39
2
2
3 2 2
Cu(NO ) ⋅3H O in water for several days in a yield of 59%.
Elemental analyses and powder X-ray analysis indicated the pure
phase of its bulk sample. Single-crystal structural analysis
revealed that CR–BPY2 crystallized in the orthorhombic lattice
with a space group Pccn. Two crystallographically independent
copper(II) ions connected four BPY bridges alternatively to
produce a 2D sheet (Fig. 5), which were further stacked
paralleled along the crystallographic a axis to form the 3D
5
–
structure with [SiW O Ru(H O)] imbedded (Fig. S8, ESI†).
1
1
39
2
The copper(II) ions resided in an octahedral geometries with the
equatorial plane which was defined by four nitrogen atoms of
BPY ligands, and the axial positions were occupied by two water
molecules (Fig. S7, ESI†). Without guest water molecules, the
effective free volume of CR–BPY2 was also estimated to be 33.9
%
by PLATON software, which is quite large than that of CR–
BPY1. These results suggested that the pore of CR–BPY2 is
larger enough to adsorbe the substrates. Since
O)] polyoxoanions were imbibed in the
5
–
[
SiW11O39Ru(H
2
a
2
0
Reaction conditions: N-phenyl-tetrahydroisoquinoline (0.25 mmol), 1
channels, it is thus an excellent reference for investigating the
catalytic activity on the same coupling reaction.
mol% catalyst, 18 W fluorescent lamp, 20 mol% L-proline in 2.0 mL of
b
1
1
,4-dioxane. The conversions were determined by H NMR spectroscopy
of crude products.
The reactions were carried out in the presence of a common
2
5
used secondary amine, L-proline, as an organic co-catalyst to
3
0
activate the ketones. In case of the acetophenone as reactant
with a fluorescent lamp (18 W) as the light source; the catalytic
reaction gave a yield of 72%. Control experiments demonstrated
that the use of K [SiW O Ru(H O)] or copper(II) salts as
5
11 39
2
3
3
4
0
5
0
catalysts, only gave less than 25% of the conversions,
respectively. The results indicated the significant contribution of
cooperative effects of the individual parts within one single MOF.
From the mechanistic point of view, the ruthenium(III) of the
5
–
polyoxometalate [SiW O Ru(H O)] interacted with N-phenyl-
1
1
39
2
tetrahydroisoquinoline to form iminium ions, whereas the copper
atoms coordinated to the acetophenones weakly to form the enol
intermediate that worked as active nucleophile for the oxidative
coupling C–C bond formation. At the same time, the presence of
copper ions could enhance the activation of N-phenyl-
tetrahydroisoquinoline, benefiting the synergistic catalysis
80
Fig. 5 Crystal structure of CR–BPY2 showing the stacking pattern of the
grid-like sheets with [SiW11O39Ru(H O)] imbedded. The atoms of
2
copper, tungsten, carbon, nitrogen and oxygen were drawn in cyan, green,
gray, dark blue and red, respectively.
5
–
85
CR–BPY2 also exhibited an absorption band centered at 398
4
| Journal Name, [year], [vol], 00–00
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Page 5 of 9
Chemical Science
nm in the solid state UV-vis absorption spectrum. Upon
General methods and materials
excitation at this band, CR–BPY2 didn’t exhibit obvious
emission, however, progressive addition of the N-phenyl-
tetrahydroisoquinoline into the dichloromethane suspension of
All chemicals were of reagent grade quality obtained from
commercial sources and used without fDurOthI:e1r0.1p0u3r9if/iCc4aStiCo0n2.36H2E
NMR was measured on a Varian INOVA-400 spectrometer with
6 3
chemical shifts reported as ppm (in DMSO-d or CDCl , TMS as
View Article Online
1
6
6
7
7
8
0
5
0
5
0
II
5
0
5
0
5
0
5
CR–BPY2 up to 0.50 mM caused the appearance of the Ru -
relative emission band at about 422 nm, suggesting that CR–
internal standard). The elemental analyses (EA) of C, H and N
were performed on a Vario EL III elemental analyzer. Inductively
coupled plasma (ICP) analyses were performed on a NexION
300D spectrometer. The powder XRD diffractograms were
obtained on a Riguku D/MAX-2400 X-ray diffractometer with
Cu sealed tube (λ = 1.54178 Å). IR spectra were recorded as KBr
pellets on a NEXUS instrument. Solid UV-Vis spectra were
recorded on a U-4100 spectrometer. Liquid UV-Vis spectra were
performed on a TU-1900 spectrophotometer. Solid fluorescent
spectra were measured on a JASCO FP-6500 instrument. The
excitation and emission slits were both 3 nm wide. Solid state
cyclic voltammograms were measured on a Zahner PP211
II
BPY2 oxidized N-phenyl-tetrahydroisoquinoline to form the Ru
species. The EPR of CR–BPY2 exhibited the characteristic signal
II
32
of Cu (g = 2.13). The quite sharper peak manner than that of
II
1
1
2
2
3
3
CR–BPY1 might be one of the indicator for that the isolated Cu
ions in CR–BPY2. No metal-metal interactions were found
II
corresponding to the Cu ions in CR–BPY2. Solid state
electrochemical measurements exhibited two redox peaks
II
I
III
II
corresponding to the Cu /Cu and Ru /Ru redox couples, with
the redox potential calculated at 75 mV and 84 mV (vs SCE). The
potentials enabled CR–BPY2 to prompt the oxidative coupling of
N-phenyl-tetrahydroisoquinoline with nucleophiles under light.
I
However, the separated redox peaks also suggested that these Cu
instrument by using
a carbon paste working electrode.
III
and Ru ions were not interacted directly. It seems that CR–
Thermogravimetric analyses (TGA) were carried out at a ramp
BPY2 adsorbed the N-phenyl-tetrahydroisoquinoline in its pores
o
rate of 5 C/min in nitrogen flow with a SDTQ600 instrument.
and was a true reference to investigate the synergistic action
Electron paramagnanetic resonance (EPR) spectra were recorded
on a EMX-10/12 spectrometer. Scanning electron microscopy
II
between Cu –O–W(Ru) bimetal of CR–BPY1.
The catalytic activities of CR–BPY2 in the C–C coupling
reactions were examined under the same conditions using
nitromethane and N-phenyl-tetrahydroisoquinoline as the
reactants. About 1 mol% loading amount of the catalyst gave rise
to a 46% conversion, which was superior to the case when copper
(SEM) images were taken with a NOVA NanoSEM 450
microscope. All confocal laser scanning microscopy (CLSM)
micrographs were collected by Olympus Fluoview FV1000.
Products were purified by flash column chromatography on 200–
3
00 mesh silica gel SiO2.
Synthesis of CR–BPY1
K [SiW O Ru(H O)]·10H O were prepared according to the
(
II) salts and the K [SiW O Ru(H O)] were employed as
5 11 39 2
catalysts, indicating the significance of the two constitute parts
for CR–BPY2 as a photocatalyst. However, the catalytic
activities of CR–BPY2 were significantly weaker than that of
CR–BPY1 (Fig. 3b). It should be concluded that the directly
33
8
9
9
5
0
5
5
11 39
2
2
literature methods and characterized by IR spectrum and UV-Vis
spectrum, respectively. A mixture of K O)]⋅
0H O (70.0 mg, 0.02 mmol), 4,4′-bipyridine (19.3 mg, 0.12
5
[SiW11O39Ru(H
2
II
bridging of the copper and ruthenium by Cu –O–W(Ru) provided
1
2
a promising way to achieve the synergistic catalysis between
photocatalyst and metal catalyst, and the high reaction efficiency
in the reactions was dominated by the spacious environment of
the channels, like those of CR–BPY1.
mmol) and Cu(NO ) ·3H O (30.4 mg, 0.12 mmol) in mixed water
3
2
2
(5.0 mL) and acetonitrile (3.0 mL) was stirred and its pH value
–1
was adjusted to 4.4 with 1 mol·L HAc. The resulting suspension
was sealed in a 25 mL Teflon-lined reactor and kept at 120 °C for
three days. After cooling the autoclave to room temperature,
brownish black prismatic single crystals were separated, washed
with water and air-dried. (Yield: ca. 52% based on
Conclusions
In a summary, we reported the new example of copper MOFs
containing the ruthenium substituted polyoxometalate with the
aim of merging the synergistic Cu-catalysis/Ru-photocatalysis in
a single MOF. CR–BPY1 exhibited perpendicularly inter-
penetrated structure and the catalytic sites positioned in the robust
pores of MOFs. Luminescence titration and IR spectra of the
MOF-based material revealed the adsorbance and activation of N-
phenyl-tetrahydroisoquinoline and acetophenone, by the
ruthenium center and copper ions, respectively. The direct
K
5
[SiW11
O
39Ru(H
2
O)]·10H
K: C 12.32, H 1.55, N 2.87, Cu 4.84, W
1.92, Ru 2.61; Found: C 12.48, H 1.57, N 2.83, Cu 4.91, W
2
O). EA and ICP calcd (%) for
4
4
5
5
0
5
0
5
C
40
H
60
N
8
O
54SiW11RuCu
3
5
5
–
1
2.32, Ru 2.51. IR (KBr pellet; cm ): 3395 (br, s), 1865 (w),
1
00 1608 (s), 1413 (m), 1219 (w), 1068 (w), 1008 (w), 957 (m), 913
s), 881 (m), 788 (s).
(
Synthesis of CR–BPY2
5
–
The CR–BPY2 was synthesized by a diffusion method in a test
tube. A mixture of acetonitrile and water (1:1, 10.0 mL) was
2
connection of copper(II) ions to [SiW11O40Ru(H O)] not only
provided the possibility of the dual catalysts to individually
activate the substrates, but also enforced the proximity between
the intermediates, avoiding the unwanted side reactions or reverse
reactions. CR–BPY1 exhibited high activity for the photo-
catalytic oxidative coupling C–C bond formation with excellent
size-selectivity, suggesting the catalytic reactions occurred in the
channels of the MOF, not on the external surface.
1
05 gently
layered
on
O)]·10H
Cu(NO ) ·3H O (9.1 mg, 0.04 mmol) in water (5 mL). A solution
the
top
of
a
solution
of
K
5
[SiW11
O39Ru(H
2
2
O (70.0 mg, 0.02 mmol) and
3
2
2
of 4,4′-bipyridine (12.5 mg, 0.08 mmol) in acetonitrile (5 mL)
was added carefully as the third layer. Brownish black block
10 single crystals were separated after four weeks, washed with
acetonitrile and water, and dried in air. (Yield: ca. 59% based on
1
5 2 2
K [SiW11O39Ru(H O)]·10H O). EA and ICP calcd (%) for
Experimental section
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 5

Chemical Science
Page 6 of 9
C
40
H
58
N
8
O
52SiW11RuCu
2
K: C 12.63, H 1.54, N 2.95, Cu 3.31, W
Research Team in University (IRT1213).
5
3.24, Ru 2.68; Found: C 12.88, H 1.69, N 2.89, Cu 3.39, W 53.41,
–1
View Article Online
DOI: 10.1039/C4SC02362E
Ru 2.58. IR (KBr pellet; cm ): 3404 (br, s), 1610 (s), 1415 (m),
220 (w), 1075 (w), 1005 (w), 955 (m), 911 (s), 872 (m), 784 (s).
Notes and references
a
1
State Key Laboratory of Fine Chemicals, Dalian University of
5
Table 3 Crystallographic data structure refinement for compounds CR–
BPY1 and CR–BPY2.
35 Technology, Dalian, 116024, P.R. China. E-mail: cyduan@dlut.edu.cn
b
College of Chemistry and Chemical Engineering, Henan University,
Kaifeng, 475004, P.R. China.
CR–BPY1
CR–BPY2
†
Electronic Supplementary Information (ESI) available: Crystal data in
C
40
H
60
N
8
O
54
40 58 8 52
C H N O
SiW11RuCu
CIF files, CCDC numbers 997028 for CR–BPY1 and 997029 for CR–
40 BPY2, experimental details and additional spectroscopic data, see
DOI: 10.1039/b000000x/
Empirical formula
SiW11RuCu
3898.19
3
K
2
K
–
1
M, g·mol
3800.63
Crystal system
Space group
a, Å
Tetragonal
Orthorhombic
Pccn
1
2
3
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P42 m
6
933.
24.415(3)
24.415(3)
15.337(4)
9142(3)
4
17.866(1)
22.192(2)
22.284(2)
8835.3(10)
4
4
5
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b, Å
c, Å
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V, Å
Z
50
–
3
Dcalcd, g·cm
2.777
2.857
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296(2)
296(2)
1
02–113.
6
R
1657 / 10865
int = 0.1270
42658 / 7765
Rint = 0.0688
Refl. collected / unique
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6
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0
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–
1
μ, mm
14.762
15.044
GOOF
0.972
1.022
a
6
7
R
1
(I > 2σ(I))
0.0509
0.0753
b
wR
a
2
(I > 2σ(I))
0.1256
0.1918
R
1
(all data)
0.1156
0.0971
b
wR
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(all data)
0.1708
0.2042
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35, 17105–17110.
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010, 110, 4606–4655; (b) L. Yang, S. Kinoshita, T. Yamada, S.
–
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Diff peak and hole, e·Å
2.937 / –1.494
5.265 / –4.627
65
8
9
2
a
b
2
2
2 2 1/2
R
/[σ (F
1
= ∑||F
o
| – |F
c
2
||/∑|F
o
|. wR | )/∑w(F
2
= [∑w(|F
o
2
| – |F
c
o
) ] ; w =
Kanda, H. Kitagawa, M. Tokunaga, T. Ishimoto, T. Ogura, R.
Nagumo, A. Miyamoto and M. Koyama, Angew. Chem. Int. Ed.,
2
2
2
1
o
) + (xP) + yP], P = (F + 2F )/3, where x = 0.1000, y = 0.0000
o c
for CR–BPY1; x = 0.0874, y = 678.0471 for CR–BPY2.
2
010, 49, 5348–5351.
7
7
8
8
9
0
5
0
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0
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D. D. Liang, K. Z. Shao, Y. H. Ren and Z. M. Su, J. Am. Chem. Soc.,
1
0
X-ray crystallography
Data of CR–BPY1 and CR–BPY2 were collected on a Bruker
Smart APEX CCD diffractometer with graphite-monochromated
Mo-Kα (λ = 0.71073 Ǻ) using the SMART and SAINT
2
009, 131, 1883–1888; (c) S. Hasegawa, S. Horike, R. Matsuda, S.
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atoms were found by direct methods using the SHELXTL-97
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926.
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1
2
2
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0
5
3
5
program package.
Crystallographic data for them are
2
summarized in Table 3. Except some partly occupied solvent
water molecules, the other non-hydrogen atoms were refined
anisotropically. Hydrogen atoms within the ligand backbones
were fixed geometrically at their positions and allowed to ride on
the parent atoms. In both of the two structures, the ruthenium
atoms were disordered in the equivalent positions of tungsten
atoms. For CR–BPY2, several bond distances constraints were
used to help the refinement on the BPY moiety, and thermal
parameters on adjacent oxygen atoms of the polyoxometalate
anion were restrained to be similar.
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We gratefully acknowledge financial support from the Natural
Science Foundation of China (21025102 and 21171029), the
Basic Research Program of China (Grant no. 2013CB733700)
and the Program for Changjiang Scholars and Innovative
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5
A new approach to merge Cu-catalysis/Ru-photocatalysis within one single MOF was achieved by incorporating of the photoredox
catalyst [SiW11O39Ru(H O)] into the pores of Cu–BPY MOFs. The hybrid catalysts prompted oxidative C–C bond formation from N-
2
5
–
phenyl-tetrahydroisoquinoline and acetophenones in high conversion and size-selectivity. The method takes advantage of visible light
photoredox catalysis to generate intermediate iminium ions under mild conditions and easily combination with Cu-catalyzed activation of
nucleophiles.
1
0
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