Metal–Organic Frameworks with Organogold(III) Complexes for Photocatalytic Amine Oxidation with Enhanced Efficiency and Selectivity

Article abstract of DOI:10.1002/chem.201803161

Luminescent organogold(III) complex Au^III with highly emissive triplet excited state was encapsulated in two metal–organic frameworks (MOFs) with different pore sizes and structures (MOF1 and ZJU-28). Compared with the Au^III complex in solution, the resultant composites Au^III@MOF1 and Au^III@ZJU-28 exhibit enhanced emission intensity, lifetime, and quantum yield. Under irradiation, Au^III@MOFs are efficient, selective, and recyclable catalysts for light-induced aerobic C?N bond formation. When used as a heterogeneous catalyst for oxidizing secondary amines to the corresponding imines, Au^III@ZJU-28 achieved high TONs of 876–1548, which are about 2.8–3.5 times higher than that of the homogenous Au^III complex. In addition, different selectivities in oxidizing mixed substrates is realized by means of different host MOFs, and thus encapsulating the Au^III complex in an appropriate MOF allowed the desired product to be obtained. Inherent shortcomings of homogeneous catalysts in cyclic use are also overcome by using composite catalysts, and high conversion of the Au^III@ZJU-28 catalyst was still observed after ten cycles.

Full text of DOI:10.1002/chem.201803161

A Journal of
Accepted Article
Title: Metal-Organic Frameworks with Organogold(III) Complexes for
Photocatalytic Amine Oxidation with Enhanced Efficiency and
Selectivity
Authors: Qing Han, Yue-Lin Wang, Min Sun, Chun-Yi Sun, Shan-Shan
Zhu, Xin-Long Wang, and Zhong-Min Su
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To be cited as: Chem. Eur. J. 10.1002/chem.201803161
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Metal-Organic Frameworks with Organogold(III) Complexes for
Photocatalytic Amine Oxidation with Enhanced Efficiency and
Selectivity
Qing Han,[a] Yue-Lin Wang,[a] Min Sun,[a] Chun-Yi Sun,*[a] Shan-Shan Zhu,[c] Xin-Long Wang*[a] and
Zhong-Min Su[ab]
Abstract: Luminescent organogold(III) complex (AuIII) with highly
emissive triplet excited states is encapsulated into two metal-organic
frameworks with different porous size and structure, named MOF1
and ZJU-28. Contrast to AuIII complex in solution, the resultant
composites, AuIII@MOF1 and AuIII@ZJU-28, exhibit enhanced
emission intensity, lifetime and quantum yield. Under irradiation,
AuIII@MOFs are efficient, selective, and recyclable catalysts for light-
induced aerobic C-N bond formation. When using AuIII@ZJU-28 as
heterogeneous catalysts for oxidizing secondary amines to
corresponding imines, high TONs of 876 - 1548 is achieved which is
around 2.8 - 3.5 folds higher than that of homogenous AuIII complex.
In addition, different selectivity to oxidize mixture substrates is
realized based on different host MOFs which demonstrate that
encapsulating active AuIII complex into an appropriate MOF could
obtain the needed product. Inherent shortage of homogeneous
catalyst in cyclic issue is also overcome by using composite
catalysts and a high conversion of AuIII@ZJU-28 catalyst is still
observed after ten cycles.
activity in the hydrosilylation of ketones and alkenes.[3] Jiang et
al. reported PCN-777 (Zr6O4(OH)10(H2O)6(TATB)2) and Pt/PCN-
777 composite which showed high activity and selectivity in
hydrogen production and benzylamine oxidation.[4] The catalytic
activity of MOF materials can not only be generated from
skeletons but also arise from by guest species.[5] Pore size of
MOF materials varied from a few angstroms to several
nanometers, making them ideal for incorporating species
ranging from small gas molecules[6] to large inorganic[7] and
organic species.[8] Encapsulation of guest catalytic species into
the pores of MOFs provides an attractive avenue to realize MOF
functionalization. The defined pore conditions in MOFs provide a
unique platform to confine and stabilize guest species. What’s
more, the impossible size selective catalysis in homogeneous
catalyst can be expected after it was encapsulated into MOFs.
Transition metal complexes with high-energy and highly
emissive triplet excited states have been well documented to
make enormous impact on the development of material science
and photochemistry.[9] Especially, the photocatalytic properties
of heavy-metal materials have been extensively explored.
Among them, gold(III) complexes with long-lived excited states,
up to several hundreds of microseconds, have exhibited
photocatalytic capability in various reaction for example C/C,
C/N and C/O bond formation.[5] However, the photocatalytic
application is largely restricted by the poor stability of gold(III)
complexes as well as recycling for long-term use.
Introduction
Metal–organic frameworks (MOFs) constructed from metal ions
and organic linkers via covalent bonds have emerged as a class
of highly promising porous materials with appealing applications
in
gas
storage/separation,
heterogeneous
catalysis,
Encapsulation of functional guest species into the pores of
MOFs by cation exchange approach has been a facile and
biomedicines, sensing, and proton/electrical conductivity.[1]
Taking advantage of tremendous choices of traditional inorganic
and organic materials with active catalytic sites, catalytic
properties of MOF materials can be engineered.[2] For example,
Lin and co-worker introduced mono(phosphine)−M (M−PR3; M =
Rh and Ir) complexes into triarylphosphine-based MOF through
postsynthetic metalation and the resultant material exhibited
convenient
post-synthetic
method
to
realize
MOF
functionalization. Via this approach metal catalysts and
luminescent metal ions/complexes have been successfully
incorporated into the pore of MOFs.[5, 10] In 2015, Che’s group
described the photocatalytic activity of luminescent gold(III)
complexes@MOF composites, but the selectivity of them didn’t
obtain enough attention.[5] In this regard, we are attracted to
employ the cation exchange method to synthesize luminescent
gold(III) complexes@MOF composited materials and investigate
their emission properties so as to develop the selective
heterogeneous photocatalysis applications. Thus, in this work,
one gold(III) complex with C^N^C ligand[11] was employed as
photocatalytic guest species being incorporated into two MOFs
with different porous structures. The resultant AuIII@MOF
composites displayed phosphorescent emission between 400
nm and 750 nm with lifetimes around 4 μs in the presence of air
at room temperature. Comparing with gold(III) complex in
solution, emission intensity, lifetime and quantum yield of
AuIII@MOFs were enhanced obviously and exhibited host
[a]
Q. Han, Y.-L. Wang, M. Sun, Dr. C.-Y. Sun, Prof. X.-L. Wang, Prof.
Z.-M. Su
National & Local United Engineering Laboratory for Power Batteries,
Key Laboratory of Polyoxometalate Science of Ministry of Education
Department of Chemistry, Northeast Normal University
Changchun, Jilin, 130024 (P.R. China)
[b]
[c]
Prof. Z.-M. Su
School of Chemistry and Environmental Engineering，Changchun
University of Science and Technology
S.-S. Zhu
School of Physical Education, Northeast Normal University
E-mail: suncy009@nenu.edu.cn; wangxl824@nenu.edu.cn
Supporting information for this article is given via a link at the end of
the document.
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depend behaviours. Furthermore, AuIII@MOFs are efficient,
selective, and recyclable catalysts for light-induced aerobic
amine oxidation.
incorporated into the corresponding framework materials by
immersing MOFs in acetonitrile solutions, which contains the
CF3SO3- salt of the AuIII. After 1 day, the light yellow solids were
obtained (Figure S1).[5] Contents of AuIII in AuIII@MOFs are
determined by inductively coupled plasma (ICP) spectroscopy.
There are indications that AuIII may reside in the channels/cages
of the corresponding framework materials according to the
following points: (i) the window sizes of MOF1 and ZJU-28 larger
than the size of the complex AuIII (6.1 × 11.1 × 12.1 Å3), to have
the possibility to incorporate AuIII into the pore of MOFs; (ii)
photographs of the corresponding materials irradiated by 365
nm UV light revealed the distinctive green emission of
AuIII@MOF1, congruent with AuIII and different from MOF1
(Figure S2); (iii) the scanning electron microscopy (SEM, Figure
S3) and electron dispersive X-ray spectroscopy (EDX, Figure
S4) studies for cross section of AuIII@MOF1 crystal revealed
that AuIII was random location at the section, and F element was
no detected in AuIII@MOF1 by EDX, to further confirm that AuIII
incorporated into the MOF hosts.
Results and Discussion
Syntheses and structures of MOFs
Two MOF materials, MOF1 and ZJU-28, were chosen in this
work to investigate the effect of MOF material porous structure
on the photochemical properties of complex AuIII (Figure 1a).
MOF1 was synthesized with CdCl2 and H6TATPT ligand under
solvothermal condition as described in the literature.[10a] MOF1
has a three-dimensional mesoporous anionic structure with two
types of nanocages (Figure 1b), truncated tetrahedral cage
(window size: 5.5 × 5.5 Å2) and truncated octahedral cage
(window size: 15.5 × 15.5 Å2).[10a] The truncated octahedron was
surrounded by four truncated tetrahedrons. Through sharing the
truncated tetrahedrons a 3D non-interpenetrated network is
formed. The pore structure can be considered as three crossing
1D channels (window size 15.5 × 15.5 Å2).[10a] The nano-scale
cages were occupied by disordered solvent molecules and
[Me2NH2]+ cations (the [Me2NH2]+ cations came from
decarbonylation of DMF).[10a, 12]
Figure 2. Emission spectra of AuIII@MOFs in N2 (black) and air atmosphere
(color) upon excitation at λ = 340 nm at room temperature. (a) AuIII@MOF1;
(b) AuIII@ZJU-28.
Table 1. Emission data of the AuIII complexes and AuIII@MOFs.
Compound
AuIII solid[e]
Conditions
τ0(μs)[a]
Φem(%)[b]
kr(103s-
)
knr(105s-
1 [d]
1
[c]
)
Air
Air
0.20
0.32
AuIII
(DMF
0.06
1.88
31.23
solution)[e]
Figure 1. (a) Complex AuIII used in this work；(b) Crystal structure of MOF1,
viewed along the c axis; (c) Crystal structure of ZJU-28, viewed along the c
axis.
N2
Air
N2
Air
N2
0.59
4.0
6.4
3.8
5.3
0.09
4.0
6.2
2.0
2.8
1.53
10.00
9.69
5.26
5.28
16.93
2.40
1.47
2.58
1.83
AuIII@MOF1
AuIII@ZJU-28
ZJU-28 was synthesized with InCl3 and H3BTB ligand under
solvothermal condition according to the literature.[10c] ZJU-28 has
two types of 1D channels along c–axis (Figure 1c) including
planar triangular channel (window size: 9.5 × 9.5 Å2) and
tetrahedral channel (window size: 9.8 × 14.7 Å2).[10c, 13] Every
tetrahedral channel is surrounded by two tetrahedral channels
and two triangular channels through sharing the edge and vertex.
The solvent molecules and cationic Me2NH2+ molecules reside in
channels and void spaces, and the effective free volume of
ZJU-28 is 64.7% of the total volume.[13]
[a] Emission lifetime. [b] Emission quantum yield. [c] Radiative decay rate
constant estimated by kr Φ/τ. [d] Non-radiative decay rate constant
estimated by knr = (1 - Φ)/τ. [e] Reprinted with permission from ref. 5. Copyright
2015 Royal Society of Chemistry.
=
The UV-vis diffuse reflectance spectra (Figure S5) of AuIII at
room temperature display two broad absorption band between
200-500 nm including an intense absorption band peaking at
250 nm and a moderately intense vibronic-structured band
Syntheses and characterization of AuIII@MOF composites
AuIII@MOFs including AuIII@MOF1 and AuIII@ZJU-28 were
synthesized via ion-exchange method. The AuIII complex was
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peaking at 385 nm.[14] AuIII@MOF1 has a broad absorption band
peaking at 289 nm and a shoulder peaking at 411 nm, the
shoulder peak is corresponding to the absorption band of AuIII.
AuIII@ZJU-28 has two broad absorption bands peaking at 250
nm and 385 nm, was similar to AuIII.
gave imine product with TONs of 453 while AuIII@MOF1 and
AuIII@ZJU-28 exhibited TONs of 75 and 1548 respectively; (ii)
the photo-reaction activity of free AuIII showed a dramatically
decrease after 1 h and almost no product was observed after 5h,
whereas AuIII@ZJU-28 exhibited high reactivity over 10 hours’
catalysis (Figure 3b); (iii) the AuIII@MOFs catalyst could be
reused by washing with acetonitrile several times and after ten
cycles, the conversion using AuIII@ZJU-28 as catalyst
maintained 43% (Figure 3c); (iv) control experiments using bare
The emission spectra (Table 1, Figure 2 and Figure S6) of
AuIII@MOFs solid were measured with the excitation of 340 nm
at room temperature under air and nitrogen atmosphere. Under
N2 condition, AuIII@MOF1 exhibit structured emission between
400-750 nm peaking at 450 nm, 478 nm and 511 nm (Figure 2a). MOFs as catalyst exhibited few product (Figure 3b); (v) As
The first emission band belongs to MOF1 and the left peaks are
the characteristic emission peaks of AuIII (Figure S6a and b). In
this condition, the lifetime of AuIII@MOF1 at 478 nm is 6.4 μs
which is around 10 folds higher than AuIII in degassed solution
(0.59 μs), and the quantum yield is 6.2% which is ~69 folds
higher than that of AuIII complex solution (0.09%). Under air
condition, all the above peaks are maintained but with 68%
decrease in the intensity. The lifetime of AuIII@MOF1 at 478 nm
is 4.0 μs which is 20 times longer than that of AuIII in the solid
state (0.20 μs) and around 10 folds higher than AuIII solution in
air condition. The quantum yield in air condition is 4.0% which is
~66 fold higher than that of AuIII complex solution (0.06%). For
AuIII@ZJU-28, in nitrogen atmosphere, the emission spectra of it
displayed emission band peaking at 450 nm, 478 nm and 511
nm (Figure 2b). The first emission band is ascribed to ZJU-28
and other peaks are owing to the characteristic emission peaks
of AuIII (Figure S6a and c). The lifetime of AuIII@ZJU-28 at 478
nm is 5.3 μs with the quantum yield of 2.8%. Under aerobic
condition, all the above peaks are retained but with 78%
reduction in the intensity, the lifetime of AuIII@ZJU-28 at 478 nm
is 3.8 μs with the quantum yield of 2.0% (Table 1). Compared
with AuIII in DMF solution, the emission lifetimes of AuIII@MOF1
and AuIII@ZJU-28 are longer and the non-radiative decay rate
constants (knr) of them are smaller (Table 1). This might result
from restrictions of molecular motion by MOF framework. What’s
more, with steady state, oxygen concentration in the inner pores
of AuIII@MOFs is probably lower than the oxygen dissolved in
the solvent and in the atmosphere.[15] This may reduce oxygen
quenching effect of AuIII@MOFs emission under aerobic
conditions. If the matrix and the surrounding environment are in
equilibrium, the activity of oxygen in the matrix would be equal to
in the external environment.[5] When using oxygen as an oxidant
in photocatalytic reactions (see the section below on the photo-
catalytic properties of the AuIII@MOF composites), a large-scale
transport of oxygen would go through the matrix and the above-
mentioned equilibrium may reach.
affirmed by the ICP measurements, the content of gold in
AuIII@MOFs after reaction was nearly the same as before
reaction (see Table S1); (vi) As revealed by PXRD data (see
Figure S7), both AuIII@MOF1 and AuIII@ZJU-28 are stable after
the photocatalytic reactions. These results above reveal that the
photo-catalytic activity of AuIII@MOF1 and AuIII@ZJU-28 is
significant different which may root in the difference in host MOF
structures. For oxidative reaction of N-isopropylbenzylamine,
around 1443 TONs was achieved by AuIII@ZJU-28 within 10
hours’ irradiation (Figure 4). In general, this catalytic reactivity is
comparable to the reactivity of used N-(tert-butyl)benzylamine as
substrate.
Figure 3. (a) Photo-catalytic oxidation of N-(tert-butyl)benzylamine to imine;
(b) Turn over number of the oxidation by AuІІІ, MOFs, and AuІІІ@MOFs; (c)
substrate conversion in recycling stability experiments using the AuІІІ@ZJU-28
catalyst.
Photocatalytic properties of AuIII@MOF composites
It is recently reported that the cyclometalated alkynylgold(III)
complexes can produce 1O2 upon light excitation which could
induce amine oxidation. Using the previous reaction as an
example, we studied the photo-catalytic activities of AuIII@MOF
composites in oxidizing secondary amines to imines.[16] The
photochemical reactions were carried out in acetonitrile. The
reaction mixture was implemented taking AuIII@MOFs as
photocatalysts under light irradiation (λ > 300 nm) with bubbling
of oxygen gas. As a control, homogeneous AuIII solution was
employed as catalyst.
Figure 4. (a) Photo-catalytic oxidation of N-isopropylbenzylamine to imine; (b)
Turn over number of the oxidation by AuІІІ, MOFs, and AuІІІ@MOFs; (c)
substrate conversion in recycling stability experiments using the AuІІІ@ZJU-28
catalyst.
Experimental results for the reaction with N-(tert-
butyl)benzylamine as substrate showed as following: (i) free AuIII
Selective oxidation of secondary amines to corresponding
imines is
a
significant area in organic synthesis.[17] The
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AuIII@MOFs as catalysts in the photocatalysis depicted above
show beneficial effects of encapsulating the AuIII complex into
the pores of the MOFs. Based on the mechanism suggested for
the AuIII system, AuIII used as the catalyst and O2 acted as the
oxidant along with the light irradiation.[16a] 1O2 sensitized from the
triplet state of AuIII is suggested to be a terminal oxidant in this
reaction. Therefore, a similar mechanism is suggested for the
AuIII@MOF system. The improvement of photocatalytic activity
upon the formation of AuIII@MOF might be attributed to the
enhanced stability and reduced non-radiative decay of the MOFs
results in triplet excited state.
From the porous structure of ZJU-28, we could find that, every
tetrahedral channel is surrounded by three planar triangular
channels. The window size of the two channel is larger than the
size of N-(tert-butyl)benzylamine and N-isopropylbenzylamine.
As for MOF1, the large truncated octahedral cage is encircled by
four small truncated tetrahedrons and the N-(tert- 5butyl)
benzylamine or N-isopropylbenzylamine can’t access the
truncated tetrahedral cages. Therefore, the oxidation reactivity of
MOF1 is largely restricted. The extended catalytic lifetime of
ZJU-28 might result from the enhanced stability of AuIII in the
pores of ZJU-28.
Figure 6. (a) Photo-catalytic oxidation of R-(+)-N-Benzyl-1-phenylethylamine;
(b) Turn over number of the oxidation by AuІІІ, MOFs, and AuІІІ@MOFs; (c)
substrate conversion in recycling stability experiments using the AuІІІ@ZJU-28
catalyst.
Table 2. Photo-catalytic oxidation of N,N-bis(4-methoxybenzyl)amine using
AuІІІ, AuІІІ@MOF1 and AuІІІ@ZJU-28 as catalysts. [a]
Similar photocatalytic reactivity among AuIII@MOFs and AuIII
solution emerged in oxidize dibenzylamine (Figure 5) which has
large size than N-(tert-butyl)benzylamine. Around 1122 TONs
was achieved by AuIII@ZJU-28 within 10 hours’ irradiation.
Catalyst
Time(h)
10
TON
261
43
Conversion (%)
Yield (%)
46.5
Comparing
with
the
oxidizing
reaction
of
N-(tert-
AuІІІ
48.7
30.5
89.0
butyl)benzylamine, this catalytic reactivity decrease around 27%.
However, for using AuIII@MOF1 as catalyst, the decrease in
reactivity reached 41%. As for homogeneous catalysis, around
322 TONs of dibenzylemine was obtained by AuIII. Compared to
N-(tert-butyl)benzylamine substrate, this reactivity is reduced
28% which is similar to that of AuIII@ZJU-28 system. The
reaction with R-(+)-N-Benzyl-1-phenylethylamine as substrate
showed that the TONs of the product catalyzed by free AuIII,
AuIII@MOF1 and AuIII@ZJU-28 were 310, 36 and 876,
respectively (Figure 6). When substrate was changed into N,N-
bis (4-methoxybenzyl)amine, only 224 TONs was achieved by
AuIII@ZJU-28 within 10 hours’ reaction and around 261 TONs
was obtained by AuIII (Table 2). It can be make a rough
conjecture that with the raise of substrate size, the reactivity of
heterogeneous catalyst becomes low, because of the larger size
of the substrate was more difficult to enter the channel. The
AuІІІ@MOF1
AuІІІ@ZJU-28
10
29.2
10
224
87.5
[a] Control experiment using MOF1 and ZJU-28 as catalysts resulted in < 10%
conversion (reaction time: 10 h).
substrates entered into channels difficultly, however, the bigger
size Au(III) complexes can encapsulated into the channels are
attributed to the followings: (i) AuIII occupied the channel made
substrates hard to enter the channel; (ii) When the anionic
MOFs were accommodating the guest species, besides the strict
size selectivity, they also exhibited remarkable selectivity of
charge characteristics. AuIII was easier to be incorporated into
MOFs via ion-exchange method.
Figure 5. (a) Photo-catalytic oxidation of dibenzylamine; (b) Turn over number
of the oxidation by AuІІІ, MOFs, and AuІІІ@MOFs; (c) substrate conversion in
recycling stability experiments using the AuІІІ@ZJU-28 catalyst.
Figure 7. (a) Photo-catalytic oxidation of 1,2,3,4-Tetrahydroisoquinoline; (b)
Turn over number and mole quantity of product within 10 hours’ reation; (c)
substrate conversion in recycling stability experiments using the AuІІІ@ZJU-28
and AuІІІ@MOF1 catalysts.
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AuIII@MOFs can also catalyze the photoinduced oxidation of
1,2,3,4-tetrahydroisoquinoline. Homogeneous catalysis gave two
kinds of products, isoquinoline and 3,4-dihydroisoquinoline with
TONs of 200 and 2090, respectively (Figure 7b). For
heterogeneous catalysis, AuIII@MOF1 and AuIII@ZJU-28 also
exhibited the two types of products. Around 40 TONs of
isoquinoline and 1059 TONs of 3,4-dihydroisoquinoline was
achieved by AuIII@MOF1. The total yield of AuIII@ZJU-28 is 1.2-
fold enhancement than AuIII@MOF1 and the mole ratio of
isoquinoline and 3,4-dihydroisoquinoline is 1:15. Recycle
experiment demonstrate the photoactivity of AuIII@MOF1 and
AuІІІ@ZJU-28 keeps with 80% and 92% of its original reactivity
(Figure 7c).
species AuIII in an appropriate pore of MOF could obtain the
needed product.
Scheme 2. Size selective photocatalysis of S2 and S3.
Conclusions
In conclusion, the luminescent AuIII was encapsulated into two
MOFs with different porous size and structure via cation
exchange. Comparing with AuIII in solution, the resultant
AuIII@MOFs composites, AuIII@MOF1 and AuIII@ZJU-28,
display enhanced emission lifetimes and quantum yield in both
aerobic and N2 conditions. In addition, AuIII@MOFs are efficient,
selective, and recyclable catalysts for light-induced aerobic
amine oxidation. AuIII@MOF1 provide an equivalent oxidizing
ability to homogeneous AuIII solution while AuIII@ZJU-28 present
high reactivity in oxidizing secondary amines to corresponding
imines with TONs of 876 - 1548 which is around 2.8 - 3.5 folds
higher than that of homogenous AuIII complex. Different
selectivity to oxidize mixture substrates is realized based on
different host MOFs. Around 97.4% selectivity of oxidizing
1,2,3,4-tetrahydroisoquinoline is achieved by AuІІІ@MOF1 with
the solution containing N-(tert-butyl)benzylamine simultaneously.
Very low selectivity is obtained by AuIII@ZJU-28 and AuIII
complex in solution under the same condition. For large sized
Scheme 1. Size selective photocatalysis of S1 and S2.
The presented different reactivity above inspires us to study the
selective photocatalysis of AuІІІ@MOF1 and AuIII@ZJU-28. The
research using AuІІІ@MOF1 or AuIII@ZJU-28 as catalyst
actualized by adding the same amount substrates of S1 (1,2,3,4-
tetrahydroisoquinoline) and S2 (a slightly larger size substrate,
N-(tert-butyl)benzylamine) in a reaction (Scheme 1).[1b, 1c] With
AuІІІ@MOF1 as photocatalyst, oxidative product of S1 (P1) was
detected after 1 hour’s irradiation while only tiny amounts of
product of S2 (P2) was detected, the P1/P2 yield ratio is around
38:1. These results illuminate that the selectivity towards the
oxidation of S1 is almost 97.4%. However, when employing
AuIII@ZJU-28 as catalyst, the yield ratio of P1/P2 is 1.9/1
(Scheme 1). Homogeneous AuIII solution exhibited non-selective,
with the yield ratio is around 1 : 1 (Scheme 1). When choose S2
(N-(tert-butyl)benzylamine) and large size S3 (bis(2-
naphthalenylmethyl)amine) as substrates (Scheme 2), P2 was
substrates,
N-(tert-butyl)benzylamine
and
bis(2-
naphthalenylmethyl)amine mixture, AuIII@ZJU-28 shows almost
100% selectivity of oxidizing N-(tert-butyl)benzylamine while
homogeneous reaction only exhibits 64.3% selectivity. What’s
more, the composite catalyst also present advantage in
recycling and a high conversion of AuIII@ZJU-28 catalyst is still
observed after ten cycles. In conclusion, the facile method of
incorporating the transition complexes with long-lived emissive
excited state into MOF materials provides a way to develop
novel category of useful heterogeneous photo-catalysts.
detected after
1
hour’s irradiation with AuIII@ZJU-28 as
photocatalyst while no product of S3 was detected. Therefore,
the selectivity of AuIII@ZJU-28 towards oxidation of S2 is almost
100%. Given the low reactivity of AuІІІ@MOF1 in oxidizing S2
and large substrates, the selective photocatalysis of
AuІІІ@MOF1 didn’t carry out. Contrast to the heterogeneous
catalyst, homogeneous AuІІІ solution could trigger the oxidation
reaction of both S2 and S3 and the yield ratio is around 1.8 : 1
(Scheme 2) corresponding to a 64.3% selectivity to S2 oxidation.
These results indicate that encapsulating active catalysis
Experimental Section
Synthesis of AuIII@MOFs composites.
MOF1 (10 mg) and ZJU-28 were immersed in 2 mL of
acetonitrile solutions containing 1 × 10–6 mol of AuIII complex,
respectively. After shaking for 1 day, the sample were taken out
of the solutions and washed with acetonitrile several times to
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remove residual AuIII complex on the surface. The
concentrations of AuIII complex in AuIII@MOF1 and AuIII@ZJU-
28 composites were confirmed by ICP spectroscopy and shown
in Table S1.
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This work was financially supported by the NSFC of China (No.
21601032, 21671034, and 21471027), Changbai Mountain
Scholars of Jilin Province, the China Postdoctoral Science
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Keywords: Metal–organic frameworks • Microporous materials •
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10.1002/chem.201803161
Chemistry - A European Journal
FULL PAPER
Entry for the Table of Contents
FULL PAPER
Luminescent AuIII complex with long-
lived emissive excited state was
Qing Han,[a] Yue-Lin Wang,[a] Min Sun,[a]
Chun-Yi Sun,*[a] Shan-Shan Zhu,[c] Xin-
Long Wang*[a] and Zhong-Min Su[ab]
encapsulated
into
MOFs
and
enhanced reactivity and selectivity
were achieved when employing
Page No. – Page No.
AuIII@MOFs
as
heterogeneous
Metal-Organic
Organogold(III)
Frameworks
Complexes
with
for
photocatalysts in amine oxidation
reaction.
Photocatalytic Amine Oxidation with
Enhanced Efficiency and Selectivity
This article is protected by copyright. All rights reserved.