Rational encapsulation of atomically precise nanoclusters into metal-organic frameworks by electrostatic attraction for CO2 conversion

Article abstract of DOI:10.1039/c8ta04667k

Controlled encapsulation of atomically precise nanoclusters (APNCs) into metal-organic frameworks (MOFs) has been an efficient way to create new types of multifunctional crystalline porous materials. Such hybrids (APNCs@MOFs) provide ideal candidates for studying inherent structure-catalysis relationships owing to the well-defined compositions of both components. Moreover, modeling of APNCs@MOFs with precise structures would be more reliable. Herein, we have established an "Electrostatic Attraction Strategy" to synthesize APNCs@MOF catalysts and studied their performance as catalysts for the conversion of CO₂. The synthetic strategy presented here has been proved to be general, as evidenced by the syntheses of various APNCs@MOF catalysts including all the combinations of [Au₁₂Ag₃₂(SR)₃₀]^4-, [Ag₄₄(SR)₃₀]^4-, and [Ag₁₂Cu₂₈(SR)₃₀]^4- nanoclusters with ZIF-8, ZIF-67, and MHCF frameworks. In particular, the as-obtained Au₁₂Ag₃₂(SR)₃₀@ZIF-8 composite shows excellent performance in capturing CO₂ and converting phenylacetylene into phenylpropiolate under mild conditions (50 °C and ambient CO₂ pressure) with a TON as high as 18164, far exceeding those of most known catalysts. What's more, the catalyst is very stable and reused 5 times without loss of catalytic activity. We anticipate that this general synthetic approach may open up a new frontier in the development of promising APNCs@MOF catalysts, which can be applied in a broad range of heterogeneous catalyses in the future.

Full text of DOI:10.1039/c8ta04667k

View Article Online
View Journal
Journal of
Materials Chemistry A
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: L. sun, Y. Yun, H.
Sheng, Y. Du, Y. Ding, P. Wu, P. li and M. Zhu, J. Mater. Chem. A, 2018, DOI: 10.1039/C8TA04667K.
This is an Accepted Manuscript, which has been through the
Volume
4 Number 1 7 January 2016 Pages 1–330
Royal Society of Chemistry peer review process and has been
accepted for publication.
Journal of
Materials Chemistry A
Accepted Manuscripts are published online shortly after
Materials for energy and sustainability
www.rsc.org/MaterialsA
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. We will replace this Accepted Manuscript with the edited
and formatted Advance Article as soon as it is available.
You can find more information about Accepted Manuscripts in the
author guidelines.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the ethical guidelines, outlined
in our author and reviewer resource centre, still apply. In no
event shall the Royal Society of Chemistry be held responsible
for any errors or omissions in this Accepted Manuscript or any
consequences arising from the use of any information it contains.
ISSN 2050-7488
PAPER
Kun Chang, Zhaorong Chang et al.
Bubble-template-assisted synthesis of hollow fullerene-like
MoS2 nanocages as a lithium ion battery anode material
rsc.li/materials-a

Please do not adjust margins
Page 1 of 7
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C8TA04667K
Journal Name
COMMUNICATION
Rational Encapsulation of Atomically Precise Nanoclusters into
Metal-Organic Frameworks by Electrostatic Attraction for CO2
Conversion
Received 00th January 20xx,
Accepted 00th January 20xx
Lili Sun,† Yapei Yun,† Hongting Sheng,* Yuanxin Du, Yimin Ding, Pei Wu, Peng Li, Manzhou Zhu*
DOI: 10.1039/x0xx00000x
www.rsc.org/
Controlled encapsulation of atomically precise nanoclusters permanent porosity of MOF, combining with functional guest
(APNCs) into metal organic frameworks (MOFs) has been an species and MOF yields a synergistic effect for boosting
efficient way to create new types of multifunctional crystalline catalytic performance and/or expanding the range of
porous materials. Such hybrids (APNCs@MOFs) provide ideal reactions.3 Herewith, extensive efforts have been made to
candidates for studying of inherent structure-catalysis fabricate composites of MNPs@MOFs (MNPs: metal
relationships owing to their well-defined compositions of both nanoparticles), which exhibited excellent catalytic activities
components. Moreover, modeling on APNCs@MOFs with precise owing to the confinement effect preventing MNPs from
structures would be more reliable. Herein, we have established an growing during the catalysis.11-15 However, the clarification of
“Electrostatic Attraction Strategy” to synthesize APNCs@MOFs detailed mechanism over these MNPs@MOFs composites is
catalysts and studied their performance as catalysts for the seriously hampered by the unclear structure of MNPs.11-13
conversion of CO2. The synthetic strategy presented here has been APNCs with precise structures enable understanding the
proved to general, evidenced by the syntheses of various relationship between the structure and properties at atomic
APNCs@MOFs catalysts including all the combinations of level. Rational encapsulation of APNCs into MOFs is an
[Au12Ag32(SR)30]4-, [Ag44(SR)30]4-, [Ag12Cu28(SR)30]4- nanoclusters efficient way to create a promising multifunctional porous
with ZIF-8, ZIF-67, MHCF frameworks. Specifically, the as-obtained material with well-defined structures of both components. The
Au12Ag32(SR)30@ZIF-8 composite shows excellent performance in above idea was also explicitly put forward in the outlook of a
capturing
CO2
and
converting
phenylacetylene
into latest review on MOFs.1
phenylpropiolate under mild conditions (50oC and ambient CO2 Previously our group has reported the preparation of
pressure) with a TON as high as 18164, far exceeding those of monodisperse Au NCs supported on MOFs by an in-situ
most known catalysts. What’s more, the catalyst is very stable and chemical reduction method, including the Au11(PPh3)8Cl2@ZIF-
reused for 5 times without loss of catalytic activity. We anticipate 8 and Au13Ag12(PPh3)10Cl8@MIL-101 composites.16 However,
that this general synthetic approach may open up a new frontier the in-situ chemical reduction method for APNCs@MOFs
in the development of promising APNCs@MOFs catalysts, which composites has two shortcomings. First, it is difficult to
can be applied in a broad range of heterogeneous catalysis in the encapsulate all APNCs in the framework of the MOF by in-situ
future.
reduction so far. There are always some APNCs deposited on
the outer surface of MOF. When the composites were washed
by methylene chloride, some APNCs were detached from the
surface of MOFs, which resulted in poor recycling ability of the
composites during the catalytic process. Second, the method is
poorly controllable. This makes it difficult for designing and
regulating the structure of APNCs, which is bad for adjusting
APNC structure in elucidating structure-activity relationship.
Introduction
Recently metal–organic frameworks (MOFs) have attracted
extensive interest and stand out in a variety of applications,
especially in catalysis, because of their tailorability and
diversity.1-5 However, the categories of active sites in MOFs are
mainly restricted to the acid (or base) sites of unsaturated
metal nodes and organic linkers.3,6-10 Employing the
Therefore, there is
a critical need for well-designed
APNCs@MOFs nanomaterials and facile synthetic methods for
such materials.
Rosi et al. published a cation exchange method, which can
Department of Chemistry and Center for Atomic Engineering of Advanced
Materials, Anhui University, Hefei, Anhui 230601, China. *E-mail:
sht_anda@126.com; zmz@ahu.edu.cn
† L. Sun and Y. Yun contributed equally.
Electronic Supplementary Information (ESI) available.
successfully encapsulated
Au133(SR)52 into the MOF-102/106 crystal. However, the cation
exchange method requires H2O2 oxidant to pretreat Au
a pre-synthesized nanocluster
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 2 of 7
COMMUNICATION
nanoclusters in order to promote cation exchange-driven
Journal Name
The as-obtained Au12Ag32(SR)30@ZIF-8 composite was
View Article Online
diffusion.17 Recently, another new "coordination-assisted self- characterized by XPS, UV-vis, FT-IR and DXORDI: 1a0.n10a3ly9s/Ces8T(AF0ig46.617)K.
assembly” method has been established to synthesize First, we employed XPS analysis to confirm the existence of
Au25(SG)18@ZIF-8 (SGH = glutathione), which is like the “bottle- [Au12Ag32(SR)30]4- and ZIF-8 in the Au12Ag32(SR)30@ZIF-8
around-ship” technique of the Zn2+ ions coordination with the composite. The XPS result confirmed the existence of Au, Ag,
carboxyl group in the GS-ligand of Au25 NCs, lead to ZIF-8 Zn and S in the composite (Fig. 1A). The UV-vis spectra of fresh
growing surround the pre-synthesized Au25(SG)18 cores18. [Au12Ag32(SR)30]4- nanoclusters and the supernatant of
Whereas, the majority of well-defined APNCs are oil-soluble [Au12Ag32(SR)30]4- + Zn2+ + 2-MeIM were also measured (Fig.
nanoclusters with various thiol ligands. To sum up, there is a 1B). The purified [Au12Ag32(SR)30]4- nanoclusters showed two
urgent need to develop an simple and effective strategy for prominent peaks at 390 and 490 nm. The optical spectra were
rational encapsulation of such thiol-protected APNCs into similar before and after mixing Au12Ag32(SR)30 with Zn2+, and
4-
MOFs as highlighted contributions.
2-MeIM,
demonstrating
that
the
[Au12Ag32(SR)30]4-
Electrostatic self-assembly is a well-established strategy to nanoclusters remains unchanged during the self-assembly
create well-mixed nanocomposites.19-21 It is the principle of process (Fig. 1B). To further confirm that [Au12Ag32(SR)30]4-
using oppositely charged species to attract each other. Based remains the structural integrity after attachment to MOFs, we
on this strategy, we envision that it would be crucial that treated the Au12Ag32(SR)30@ZIF-8 composite with an acetic
introducing oil-soluble anionic APNCs for subsequent MOFs acid solution (pH = 4) to dissolve the ZIF-8 and extract the
growth under mild conditions by electrostatic attraction confined [Au12Ag32(SR)30]4- nanoclusters. No spectral change
between anionic APNCs and cationic metal ions of MOFs. In was observed for the [Au12Ag32(SR)30]4- nanoclusters (Fig. 1B),
the current work, this strategy is demonstrated to be very hence, [Au12Ag32(SR)30]4- remains unchanged throughout the
successful, in which anionic [Au12Ag32(SR)30]4- nanoclusters22 uptake/release process. Subsequently, we used FT-IR
are encapsulated with good dispersity and fully confined inside spectroscopy to further verify the formation of
ZIF-8,23 ZIF-6724 and MHCF,25 respectively. More importantly, Au12Ag32(SR)30@ZIF-8 composite. From Fig. 1D, one can see
the method is also valid for various anionic nanoclusters such clearly that most peaks of the Au12Ag32(SR)30@ZIF-8, including
as [Ag44(SR)30]4- and [Ag12Cu28(SR)30]4-.22,26 Meanwhile, the as- those at 2928 cm-1, 1589 cm-1, 1176 cm-1, 756 cm-1 and 689
prepared Au12Ag32(SR)30@ZIF-8 composite displays excellent cm-1, were from ZIF-8. Other peaks (at 1496 cm-1 and 771cm-1)
catalytic performance in CO2 conversion under mild were benzene skeleton vibrational peaks and the adjacent di-
conditions.
substituted characteristic peaks, which were assigned to the
protecting ligand SPhF2 of [Au12Ag32(SR)30]4- nanoclusters (Fig.
1C). Finally, the Au12Ag32(SR)30@ZIF-8 nanocomposite was
characterized by XRD (Fig. 1D). All the diffraction peaks of the
Au12Ag32(SR)30@ZIF-8 nanocomposite perfectly overlapped
with those of the ZIF-8, indicating that ZIF-8 retained its
crystalline phase structure after in situ growth with the APNCs
encapsulated. On a note, the diffractions associated with Au
and Ag were not observed due the ultrasmall size of
[Au12Ag32(SR)30]4- (i.e. significantly weakened diffraction).
Summarizing the data obtained from FT-IR, UV-vis, XPS and
XRD analyses, we can conclude that the Au12Ag32(SR)30@ZIF-8
composite consists of intact [Au12Ag32(SR)30]4- nanoclusters and
ZIF-8. The Brunauer-Emmett-Teller (BET) surface area of
Au12Ag32(SR)30@ZIF-8 are determined to be 1528.7 m2/g. For
further confirming the position of the [Au12Ag32(SR)30]4-
nanoclusters, we analyzed the N2 absorption–desorption
isothermal and pore size distributions of Au12Ag32(SR)30@ZIF-8
with comparation with ZIF-8 (Fig. S1). Although the surface
area of Au12Ag32(SR)30@ZIF-8 composites decreased slightly in
comparison with that of pure ZIF-8 (1643.0 m2/g),23
Au12Ag32(SR)30@ZIF-8 and ZIF-8 have the similar isothermal
features and pore diameter. In this condition, [Au12Ag32(SR)30]4-
nanoclusters are inserted as multi-functional scaffolds rather
than embedded into the pores of ZIF-8. The results are similar
to those reported in the literature.18
Results and Discussion
The systematic approach to fabricating APNCs@MOFs is
shown in Scheme 1. Taking Au12Ag32(SR)30@ZIF-8 as an
example, the complete fabrication includes two self-assembly
processes: First, [Au12Ag32(SR)30]4- nanoclusters with negative
charges were prepared, followed by mixing with Zn2+ ions in
methanol. The [Au12Ag32(SR)30]4- nanoclusters quickly
assembled with positively charged Zn2+ by electrostatic
attraction. Subsequently, the solution of ZIF-8 precursors of 2-
Methylimidazole (2-MeIM) in methanol was slowed poured
into the above solution and mixed together. Finally, the
Au12Ag32(SR)30@ZIF-8 composite was obtained at room
temperature without stirring for 24 h. To the best of our
knowledge, this is the first report on the rational encapsulation
of oil-soluble APNCs into MOFs by the “bottle-around-ship”
method.
The
morphology
and
composition
of
the
Au12Ag32(SR)30@ZIF-8 nanocomposite were characterized by
scanning electron microscopy (SEM), transmission electron
microscopy (TEM), high angle annular dark field-scanning
Scheme 1. Schematic illustration showing the rational encapsulation of APNCs@MOFs
by Electrostatic Attraction.
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 3 of 7
Journal of Materials Chemistry A
Journal Name
COMMUNICATION
transmission electron microscope (HAADF-STEM), and energy
dispersive X-ray spectroscopy (EDX). The SEM image shows
that the Au12Ag32(SR)30@ZIF-8 composite is of uniform rhombic
dodecahedral shape (Fig. S2). HAADF-STEM and TEM images
further confirmed that the uniform [Au12Ag32(SR)30]4-
nanoclusters are fully encapsulated in the ZIF-8 matrix with
View Article Online
DOI: 10.1039/C8TA04667K
good dispersity
(Fig. 2A and 2B). Unencapsulated
[Au12Ag32(SR)30]4- nanoclusters were not observed, indicating
excellent encapsulation of nanoclusters. Energy-dispersive X-
ray (EDX) spectroscopy element mapping was explored to
further investigate the distribution of [Au12Ag32(SR)30]4-
nanoclusters. The elemental maps of Zn, N, Ag, Au and S of
Au12Ag32(SR)30@ZIF-8 are shown in Fig. 3, along with the STEM
image and EDX spectrum. From the element mapping, it could
be clearly seen that [Au12Ag32(SR)30]4- nanoclusters are
uniformly dispersed in the ZIF-8 matrix. Therefore, the strategy
of introducing anionic [Au12Ag32(SR)30]4- for subsequent ZIF-8
growth is demonstrated to be very successful based on
electrostatic attraction.
Fig. 2. (A) HAADF-STEM image of the Au12Ag32(SR)30@ZIF-8 composite; (B)TEM images
of the Au12Ag32(SR)30@ZIF-8 composite; (C) the Au24Ag46(SR)32@ZIF-8 composite; (D) the
Ag44(SR)30@ZIF-8 composite; (E) the Ag12Cu28(SR)30@ZIF-8 composite.
Fig. 1. The characteristic of Au12Ag32(SR)30@ZIF-8. (A) XPS pattern of the
Au12Ag32(SR)30@ZIF-8 composite; (B) UV-vis spectra of [Au12Ag32(SR)30]4-, the
supernatant after impregnation over Zn2++2-MeIM, and the solution after
digesting the Au12Ag32(SR)30@ZIF-8 composite; (C) FT-IR spectra of
[Au12Ag32(SR)30]4-, ZIF-8 and Au12Ag32(SR)30@ZIF-8; (D) XRD patterns of ZIF-8 and
Au12Ag32(SR)30@ZIF-8.
To confirm the effectiveness and importance of
electrostatic attraction between [Au12Ag32(SR)30]4- and Zn2+ of
ZIF-8, we performed a control experiment using the cationic
[Au24Ag46(SR)32]2+ nanoclusters27 instead of the anionic
[Au12Ag32(SR)30]4- nanocluster, which [Au24Ag46(SR)32]2+
nanoclusters was structurally characterized by UV-vis
spectrum (Fig. S3). In the obtained product, only a few
[Au24Ag46(SR)32]2+ nanoclusters per MOF crystal were observed
to be adsorbed on the outer surfaces of the crystals, while the
majority of cationic nanoclusters remained free (Fig. 2C). This
control experiment implies that the charge interaction
between the APNCs and Zn2+ plays a critical role.
Fig. 3. STEM images and EDX spectrum of the Au12Ag32(SR)30@ZIF-8
composite. (A) STEM images of the Au12Ag32(SR)30@ZIF-8 composite; (B-F)
Elemental maps of Au12Ag32(SR)30@ZIF-8 composite Zn (B), N (C), Ag (D), Au
(E), S (F); (G) EDX spectrum of the Au12Ag32(SR)30@ZIF-8 composite.
We found that the electrostatic attraction strategy could
be extended to other anionic APNCs. For example,
Ag44(SR)30@ZIF-8 and Ag12Cu28(SR)30@ZIF-8 were successfully
prepared using the same strategy (Fig. 2D and 2E, Fig. S2, Fig
S4). At the same time, the synthetic strategy presented here
has also been proven to be effective with other MOF
materials, such as ZIF-67 and MNHF. The corresponding hybrid
materials
Ag12Cu28(SR)30@ZIF-67,
Au12Ag32(SR)30@ZIF-67,
Ag44(SR)30@ZIF-67,
and
Au12Ag32(SR)30@MHCF
Ag12Cu28(SR)30@MHCF were all successfully achieved and
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 4 of 7
COMMUNICATION
Journal Name
structurally characterized by the FT-IR, UV-vis, XRD, SEM and the inductively coupled plasma (ICP) analysisV.iewOAurrticleinOintliinael
DOI: 10.1039/C8TA04667K
TEM analyses, respectively (Fig. S5-S11). The synthesis method studies focused on examining the catalytic performances for
in this report truly achieved intact APNCs are well dispersed generation of 3-phenylpropiolic acid at various conditions,
and fully encapsulated within the corresponding MOF crystallite including different bases, solvents and catalysts. As expected,
based on these analysis results.
up to 100% yield was obtained by using Au12Ag32(SR)30@ZIF-8
It is well known that utilizing renewable resources is an for the carboxylation reaction under mild conditions (0.24
o
effective
way
to
solve
the equiv. Cs2CO3 or K2CO3, 1 atm CO2, 60 mg catalyst and 50 C in
increasingly serious environmental problems. Carbon dioxide DMSO) (Table 1, entries 3 and 4). The TON (moles of product
(CO2) is the easiest resource to obtain, which has advantages per mole of nanocluster) reaches up to 18164 for
of being non-toxic, renewable, and inexpensive. However, few Au12Ag32(SR)30@ZIF-8, which is far exceeding those of previous
commercial run utilize CO2 as a renewable feedstock because heterogeneous catalytic systems such as Ag@MIL-101 (36),15
CO2 is a thermodynamically stable and unreactive molecule. It Ag@P-NHC (327),28 Ag@Shiff-SiO2 (705)29 and Pd0.2Cu0.8/MIL-
is noteworthy that MOFs with Lewis acid centers as the active 101 (691)30 under similar catalytic reaction conditions (Table
sites were exploited for the chemical fixation CO2 in previous S1). Among various solvents, DMSO is found to be most
research.14 In addition, Ag NPs@MOF composites were effective in our system because DMSO is not only a good
reported as highly effective catalysts for conversion of CO2 to solvent for Cs2CO3 or K2CO3 but also a good solvent for CO2,31
carbonyl compounds such as phenylpropiolic and carbonate which is consistent with the results of a previous report.30, 32 It
ester.14,15 Here, the accessibility of Au12Ag32(SR)30@ZIF-8 is also noteworthy that our catalytic system only used a slight
composite, which combines the catalytic properties of amount of base (0.24 equiv), while an excess of base (> 1.2
Au12Ag32(SR)30 nanoclusters and the CO2 fixation capability of equiv) was necessary in the reported systems.14,15,28-30 Thus,
the ZIF-8 support, is first examined in the carboxylation of our system has practical advantages over other approaches
phenylacetylene as a model system (Table 1). The loading of with bases in excess.
[Au12Ag32(SR)30]4- in the composite is 0.94 wt% determined by
Table 1. Synthesis of phenylpropiolic acid from CO2 and phenylacetylene with catalysts.[a]
Entry
Cat
ZIF-8
Solvent
DMSO
DMSO
Base
K2CO3
K2CO3
K2CO3
Yield(%)[b] TON[c]
1
2
3
4
5
6
7
8
51.8
50.7
100
100
25.8
12.7
12.4
8.9
9420
9223
18164
18164
4693
2310
2256
1619
Au12Ag32(SR)30/CNTs
Au12Ag32(SR)30@ZIF-8 DMSO
Au12Ag32(SR)30@ZIF-8 DMSO Cs2CO3
Au12Ag32(SR)30@ZIF-8 DMSO Na2CO3
Au12Ag32(SR)30@ZIF-8
Au12Ag32(SR)30@ZIF-8
DMF
ToL
K2CO3
K2CO3
K2CO3
Au12Ag32(SR)30@ZIF-8 CH3CN
[a] Reaction conditions: phenylacetylene (1.0 mmol), 60 mg catalyst (0.94 wt. % loading of [Au12Ag32(SR)30]4-, 5.50 × 10-5 mol ), base (0.24 mmol), CO2 (1.0 atm), 50
solvent (1 mL), 24 h. [b] Yield of isolated product. [c] TON (moles of product) (moles of nanoclusters in the catalyst)
℃,
=
/
Moreover, the reaction was conducted by using plain ZIF- illustrating the ability of ZIF-8 support to fix and activate CO2,
8 crystals and carbon nanotube-suppored [Au12Ag32(SR)30]4- we measured the CO2 adsorption-desorption isotherms and
(Au12Ag32(SR)30/CNTs) as catalysts for comparation under the FT-IR spectra. From Fig. S12, the absorptive capacity of CO2
above optimized conditions. Both showed lower catalytic reached 20.96 and 10.72 mg/g (at 273 K) for ZIF-8 and
activity under the same conditions, affording 51.8% and 50.7% Au12Ag32(SR)30@ZIF-8, respectively, ensuring the possibility for
yield of 3-phenylpropiolic acid, respectively (Table 1, entries 1 the subsequent CO2 transformation. The decrease in the
and 2). Based on the above results, the significantly enhanced amount of CO2 uptake by Au12Ag32(SR)30@ZIF-8 in comparison
catalytic activities of Au12Ag32(SR)30@ZIF-8 was endowed by with ZIF-8 is attributed to the encapsulation of the
the synergistic effect of [Au12Ag32(SR)30]4- and ZIF-8. For [Au12Ag32(SR)30]4- into the pores of ZIF-8. From Fig. S13, a
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
Page 5 of 7
Journal of Materials Chemistry A
Journal Name
COMMUNICATION
distinct absorption peak was observed at 1647 cm-1 in ZIF- higher yields than those with electron withdrawing groups
View Article Online
DOI: 10.1039/C8TA04667K
(Table 2, entries 1–4). When ethynylcyclopropane was used as
8+CO2 infrared spectrum, which should be assigned to the C=O
stretching vibration of a specie generated from Zn2+ and CO2 an alkyl acetylene substrate, the reaction also proceeded
result from the fact that the signal was absent in ZIF-8. So, it is smoothly and the yield of desired 3-cyclopropylpropiolic acid
evident that CO2 could be fixed and activated by ZIF-8 to form can reach 89.8% (Table 2, entry 5).
CO2-Zn(2-MeIM)n complexes. To further elucidate the effect of
In general, Au12Ag32(SR)30@ZIF-8 catalyzed carboxylation
encapsulated [Au12Ag32(SR)30]4- nanoclusters, we investigatied reactions of both aryl- and alkyl- terminal alkynes with CO2.
the FT-IR spectra of phenylacetylene + [Au12Ag32(SR)30]4-, Based on the above results and the literature reports,15,29,33 we
phenylacetylene and [Au12Ag32(SR)30]4-, respectively (Fig. S14). rationalized a possible mechanism for our catalytic system
For phenylacetylene + [Au12Ag32(SR)30]4-, phenylacetylene was
(
Scheme 2). First, [Au12Ag32(SR)30]4- nanocluster activates the
Au12Ag32(SR)30
joined into the [Au12Ag32(SR)30]4- nanoclusters (in DMSO terminal alkyne with base to form a Ph-C≡C
┅
solution) in the presence of K2CO3 under N2 atmosphere at 50 intermediate I; Meanwhile, CO2 is fixed and activated by ZIF-8
°C for 4h, which is similar to the reaction conditions in this to generate an intermediate CO2-Lewis acid complex II. The
work. In sharp contrast with phenylacetylene, on the surface activated CO2 would then be inserted into the nearby M–C
of deprotonation and coordination with the [Au12Ag32(SR)30]4- bond to generate the carboxylate III. Following the product
nanoclusters, the
3500 cm-1 broad band likely originated from H2O) and the C
C stretching downshifts from 2113 cm-1 to 2098 cm-1. It is [Au12Ag32(SR)30]4- nanocluster and ZIF-8 enormously enhanced
therefore that phenylacetylene and [Au12Ag32(SR)30]4- the catalytic activity of our hybrid system.
≡
C-H stretching (3293 cm-1) disappear (the formation, the intermediate I is regenerated by metathesis
with alkyne. The synergistic effect between the
≡
nanocluster coordinated to form a Ph-C≡C
┅Au12Ag32(SR)30
intermediate, leading to lowing the C C bonding order.
≡
Interestingly, the Au12Ag32(SR)30@ZIF-8 composite
maintains its high activity in the five consecutive catalytic runs
(
Fig. S15). The results clearly demonstrate that
Au12Ag32(SR)30@ZIF-8 composite shows robust stability and
recyclability as heterogeneous catalyst for the CO2
a
transformation to propiolic acids. The structure and
composition of recycled Au12Ag32(SR)30@ZIF-8 were almost the
same as those of the fresh catalyst, evidenced by the TEM
image, UV-Vis spectrum, FT-IR and XRD pattern (Fig. S16).
Under optimization of the reaction conditions, various alkyne
substrates were subjected to this carboxylation reaction (0.24
equiv K2CO3, 1 atm CO2, DMSO, 50oC). From Table 2, it is
obvious that Au12Ag32(SR)30@ZIF-8 catalyst was very effective
for terminal alkynes. These substrates are transferred to the
corresponding products in satisfactory yields. The substrates
with electron donating groups on aryl groups gave rise to
Scheme 2. Proposed reaction mechanism toward CO2 and phenylacetylene over
Au12Ag32(SR)30@ZIF-8.
Table 2. Synthesis of phenylpropiolic acid by Au12Ag32(SR)30@ZIF-8.[a]
Entry
Alkyne
Product
Yield(%)[b] TON[c]
1
2
97.4
99.6
92.2
79.0
89.8
17719
18119
16773
14371
16263
3
4
5
[a] Reaction conditions: various alkyne (1.0 mmol), 60 mg catalyst (0.94 wt % Au12Ag32(SR)304- loading, 5.50 × 10-5 mol), K2CO3 (0.24 mmol), CO2 (1.0 atm), 50
(1 mL), 24 h. [b] Yield of isolated product. [c] TON = (moles of product) / (moles of nanoclusters in the catalyst).
℃, DMSO
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
Journal of Materials Chemistry A
Page 6 of 7
COMMUNICATION
Journal Name
13. Z. Guo, C. Xiao, R. V. Maligal-Ganesh, L. Zhou, T. W. Goh, X.
View Article Online
Li, D. Tesfagaber, A. Thiel and W. Huang, ACS Catal., 2014, 4,
DOI: 10.1039/C8TA04667K
Conclusion
1340-1348.
14. N. N. Zhu, X. H. Liu, T. Li, J. G. Ma, P. Cheng and G. M. Yang,
Inorg. Chem., 2017, 56, 3414-3420.
In conclusion, we have established an “Electrostatic
Attraction Strategy” to create new types of APNCs@MOFs in a
controllable way, which provide ideal candidates for the study
of structure-activity relationship due to their well-defined
compositions and tunable structures of both components. The
method is applicable to synthesis of various APNCs@MOFs
catalysts including all the combinations of [Au12Ag32(SR)30]4-,
[Ag44(SR)30]4-, [Ag12Cu28(SR)30]4- nanoclusters with ZIF-8, ZIF-67,
15. X. H. Liu, J. G. Ma, Z. Niu, G. M. Yang and P. Cheng, Angew.
Chem. Int. Ed., 2015, 54, 988-991.
16. L. Liu, Y. Song, H. Chong, S. Yang, J. Xiang, S. Jin, X. Kang, J.
Zhang, H. Yu and M. Zhu, Nanoscale, 2016, 8, 1407-1412.
17. C. Liu, C. J. Zeng, T. Y. Luo, A. D. Merg, R. C. Jin and N. L. Rosi,
J. Am. Chem. Soc., 2016, 138, 12045–12048.
18. Y. Luo, S. Fan, W. Yu, Z. Wu, D. A. Cullen, C. Liang, J. Shi and
C. Su, Adv. Mater., 2017, 30, 1704576.
19. X. Zhou, Y. X. Yin, L. J. Wan and Y. G. Guo, Adv. Energy Mater.,
2012, 2, 1086-1090.
20. J. Yang, J. W. Kim and H. S. Shin, Adv. Mater., 2012, 24, 2299-
2303.
21. K. L. Niece, J. D. Hartgerink, J. J. J. M. Donners and S. I. Stupp,
J. Am. Chem. Soc., 2003, 125, 7146-7147.
22. H. Yang, Y. Wang, H. Huang, L. Gell, L. Lehtovaara, S. Malola,
H. Hakkinen and N. Zheng, Nature commun., 2013, 4, 2422.
23. G. Lu, S. Li, Z. Guo, O. K. Farha, B. G. Hauser, X. Qi, Y. Wang,
X. Wang, S. Han, X. Liu, J. S. DuChene, H. Zhang, Q. Zhang, X.
Chen, J. Ma, S. C. Loo, W. D. Wei, Y. Yang, J. T. Hupp and F.
Huo, Nature Chem., 2012, 4, 310-316.
MHCF
frameworks.
Moreover,
the
as-obtained
Au12Ag32(SR)30@ZIF-8 composite shows excellent performance
in capturing CO2 and converting phenylacetylene into
phenylpropiolate under mild conditions (50 oC and ambient
CO2 pressure), which encompass the benefits of porous and
molecular sieving behavior characterized by the MOF matrix
together with the functional behavior characteristic of APNCs.
The promising APNCs@MOFs materials are also expected to
find wide applications in the synthesis of fine chemicals.
24. X. Ge, Z. Li and L. Yin, Nano Energy, 2017, 32, 117-124.
25. H. Pang, Y. Zhang, T. Cheng, W. Y. Lai and W. Huang,
Nanoscale, 2015, 7, 16012-16019.
26. J. Yan, H. Su, H. Yang, C. Hu, S. Malola, S. Lin, B. K. Teo, H.
Hakkinen and N. Zheng, J. Am. Chem. Soc., 2016, 138, 12751-
12754.
Conflicts of interest
There are no conflicts to declare.
27. S. Wang, S. Jin, S. Yang, S. Chen, Y. Song, J. Zhang and M.
Zhu, Sci. Adv., 2015, 1, e1500441.
Acknowledgements
The work is supported by National Natural Science Foundation 28. D. Yu, M. X. Tan and Y. Zhang, Adv. Synth. Catal., 2012, 354,
969-974.
of China (21372006, U1532141, 21631001, 61601001), Natural
Science Foundation of Education Department of Anhui
Province (KJ2014A013, KJ2017A009, KJ2016A017), and 211
Project of Anhui University.
29. Z. Wu, L. Sun, Q. Liu, X. Yang, X. Ye, Y. Hu and Y. Huang,
Green Chem., 2017, 19, 2080-2085.
30. M. Trivedi, Bhaskaran, A. Kumar, G. Singh, A. Kumar and N. P.
Rath, New J. Chem., 2016, 40, 3109-3118.
31. A. Gennaro, A. A. Isse and E. Vianello, J. Electroanal, J.
Electroanai. Chem., 1990, 289, 203-215.
32. Z. Wu, Q. Liu, X. Yang, X. Ye, H. Duan, J. Zhang, B. Zhao and Y.
Huang, ACS Sustainable Chem. Eng., 2017, 5, 9634-9639.
33. R. A. Molla, K. Ghosh, B. Banerjee, M. A. Iqubal, S. K. Kundu,
Notes and references
1. Q. Yang, Q. Xu and H. L. Jiang, Chem. Soc. Rev., 2017, 46,
4774-4808.
2. Y. Zhang, J. Guo, L. Shi, Y. Zhu, K. Hou, Y. Zheng and Z.Tang,
Sci. Adv., 2017, 3, e1701162.
S. M. Islam, A. Bhaumik, J. Colloid Interf. Sci., 2016, 477
220–229.
,
3. R. Ghorbani-Vaghei, D. Azarifar, S. Daliran and A. R. Oveisi,
RSC Adv., 2016, 6, 29182-29189.
4. J. Yang, F. Zhang, H. Lu, X. Hong, H. Jiang, Y. Wu and Y. Li,
Angew. Chem. Int. Ed., 2015, 54, 10889-10893.
5. H. K. Lee, C. S. L. Koh, Y. H. Lee, C. Liu, I. Y. Phang, X. Han, C-
K. Tsung and X. Y. Ling, Sci. Adv., 2018, 4, eaar3208.
6. L. Tao, C.Y. Lin, S. Dou, S. Feng, D. Chen, D. Liu, J. Huo, Z. Xia
and S. Wang, Nano Energy, 2017, 41, 417-425.
7. J. Liang, R. P. Chen, X. Y. Wang, T. T. Liu, X. S. Wang, Y. B.
Huang and R. Cao, Chem. Sci., 2017, 8, 1570-1575.
8. J. Xu, R. Sinelnikov and Y. Huang, Langmuir, 2016, 32, 5468-
5479.
9. D. Wang, R. Huang, W. Liu, D. Sun and Z. Li, ACS Catal., 2014,
4, 4254-4260.
10. F. Vermoortele, R. Ameloot, A. Vimont, C. Serre and D. De
Vos, Chem. Commun., 2011, 47, 1521-1523.
11. A. Dhakshinamoorthy, A. M. Asiri and H. Garcia, ACS Catal.,
2017, 7, 2896-2919.
12. B. An, J. Zhang, K. Cheng, P. Ji, C. Wang and W. Lin, J. Am.
Chem. Soc., 2017, 139, 3834-3840.
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 7
Journal of Materials Chemistry A
View Article Online
DOI: 10.1039/C8TA04667K
Table of contents
The composites APNCs@MOFs have been successfully synthesized by electrostatic attraction strategy, which served as
excellent catalysts for converting CO2.