Library Creation of Ultrasmall Multi-metallic Nanoparticles Confined in Mesoporous MFI Zeolites

Article abstract of DOI:10.1002/anie.202103007

The development of materials integrated with ultrasmall multi-metal nanoparticles (UMMNs) and mesoporous zeolite is a considerable challenge in chemistry and materials science. We designed a trifunctional surfactant, in which the pyridyl benzimidazole in the hydrophobic tail generates the mesopores through π–π stacking; the diquaternary ammonium in the hydrophilic headgroup direct the formation of MFI zeolite sheets and the nitrogen atoms in the heterocyclic rings coordinate with various metal ions to form UMMNs confined in the zeolite matrix after calcination and reduction. A library of 56 UMMNs confined within both micropores and mesopores of MFI zeolites (MMZs) with 4 mono-, 14 bi- and 38 tri-metallic nanoparticles (sizes of 1.3–4.7 nm) of combinations of Rh, Pd, Pt, Au, Fe, Co, Ni, Cu and Zn were made. An improved catalytic performance was exhibited in the sequence of Rh-MMZ

Full text of DOI:10.1002/anie.202103007

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International Edition: doi.org/10.1002/anie.202103007
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Zeolites
Hot Paper
Library Creation of Ultrasmall Multi-metallic Nanoparticles Confined
in Mesoporous MFI Zeolites
Xiaoli Jia+, Jingang Jiang+, Shihui Zou+, Lu Han, Haiyin Zhu, Qing Zhang, Yue Ma, Peng Luo,
Peng Wu, Alvaro Mayoral,* Xinbao Han,* Jun Cheng,* and Shunai Che*
Abstract: The development of materials integrated with ultra-
small multi-metal nanoparticles (UMMNs) and mesoporous
zeolite is a considerable challenge in chemistry and materials
science. We designed a trifunctional surfactant, in which the
pyridyl benzimidazole in the hydrophobic tail generates the
mesopores through p–p stacking; the diquaternary ammonium
in the hydrophilic headgroup direct the formation of MFI
zeolite sheets and the nitrogen atoms in the heterocyclic rings
coordinate with various metal ions to form UMMNs confined
in the zeolite matrix after calcination and reduction. A library
of 56 UMMNs confined within both micropores and meso-
pores of MFI zeolites (MMZs) with 4 mono-, 14 bi- and 38 tri-
metallic nanoparticles (sizes of 1.3–4.7 nm) of combinations of
Rh, Pd, Pt, Au, Fe, Co, Ni, Cu and Zn were made. An
improved catalytic performance was exhibited in the sequence
of Rh-MMZ < Rh/Pt-MMZ < Rh/Pt/Ni-MMZ for the mild
oxidation of methane to methanol or liquid acid.
loadable metals in mesoporous zeolites restrict their wide-
spread applications.[34–37]
Long-chain alkyl-multiple quaternary ammonium mole-
cules are well known as bifunctional templates of mesoporous
zeolites because of their head groups and hydrophobic tails
that can simultaneously direct the formation of MFI zeolite
frameworks and mesoscale micellar structures, respective-
ly.[27–29] It has been found that crystallographically ordered
mesoporous MFI zeolite can be formed by introducing
aromatic groups into the hydrophobic tail of a bifunctional
template owing to their p–p interactions that stabilizing the
mesoscale micellar structure and the geometric matching
between the configuration of the self-assembled aromatic tails
and the zeolitic framework.[30–33]
Here, in order to fabricate ultrasmall multi-metallic
nanoparticles (UMMNs) confined within mesoporous MFI
zeolites (MMZs), we designed a tri-functional template by
introducing a pyridyl benzimidazole group, with both self-
assembly and coordination ability, into the tail of a surfactant
with a diquaternary ammonium head group to finally form
C5H4-C7H4N2-C10H20-N+(CH3)2-C6H12-N+(CH3)2-C6H13-
(2BrÀ) (denoted as CPBI), see Figure 1 and Figure S1). The
synthesis procedure was divided into three steps.
Introduction
Ultrasmall multi-metallic nanoparticles (UMMNs) con-
fined in zeolites are of great importance in catalysis due to the
integration of nanometallic properties, remarkably different
from their respective bulk counterparts and monocompo-
nents,[1–5] that display unique and excellent catalytic perfor-
mance within the zeolites.[6–9] Although several examples have
succeeded,[10–21] either the sole presence of micropores which
cause mass transfer limitations[22–33] or the few types of
(i) The MMZs were synthesized by self-assembly of the
C
PBI and the aluminosilicate source under basic hydrothermal
conditions. The strong p–p interactions between the pyridyl
benzimidazole groups of CPBI blocked the zeolite growth
along b direction to form lamellar mesopores. Meanwhile, one
[*] Dr. X. Jia,[+] Dr. X. Han, Prof. S. Che
Normal University
School of Chemistry and Chemical Engineering, State Key Laboratory
of Metal Matrix Composites, Shanghai Key Laboratory for Molecular
Engineering of Chiral Drugs, Shanghai Jiao Tong University
800 Dongchuan Road, Shanghai, 200240 (P. R. China)
E-mail: xinbao_han@163.com
3663 North Zhongshan Road, Shanghai, 200062 (P. R. China)
Dr. S. Zou[+]
Key Lab of Applied Chemistry of Zhejiang Province, Department of
Chemistry, Zhejiang University
38 Zheda Road, Hangzhou, 310036 (P. R. China)
chesa@sjtu.edu.cn
Homepage: http://che.sjtu.edu.cn
Dr. A. Mayoral
Instituto de Nanociencia Materiales de Aragon (INMA-CSIC),
University of Zaragoza
12, Calle de Pedro Cerbuna, 50009 Zaragoza (Spain)
Prof. L. Han, Prof. S. Che
Department School of Chemical Science and Engineering, Tongji
University
Prof. J. Cheng
1239 Siping Road, Shanghai, 200092 (P. R. China)
College of Chemistry and Chemical Engineering, Xiamen University
Xiamen, 361005 (P. R. China)
H. Zhu, Dr. Q. Zhang, Dr. A. Mayoral
Center for High-Resolution Electron Microscopy (ChꢀEM), School of
Physical Science and Technology, ShanghaiTech University
393 Middle Huaxia Road, Pudong, Shanghai, 201210 (P. R. China)
E-mail: amayoral@shanghaitech.edu.cn
Dr. J. Jiang,[+] Y. Ma, P. Luo, Prof. P. Wu
Shanghai Key Laboratory of Green Chemical Science and Chemical
Process, School of Chemistry and Molecular Engineering, East China
E-mail: chengjun@xmu.edu.cn
[+] These authors contributed equally to this work.
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202103007.
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Figure 1. Synthetic routes for the UMMNs confined in MMZ. a) Tri-functional template CPBI directing for MMZs: a1) a possible arrangement of
pyridyl benzimidazole groups in CPBI with p–p interactions directing for mesopores with both lamellar and intergrown structures, and diquaternary
ammoniums located in the straight channels to direct the MFI zeolite sheets; a2) the arrangement of pyridyl benzimidazole groups along the a-c
plane orientation matching MFI frameworks with both lamellar structure and intergrown structures. b) Formation of coordination bonding
between the metal and pyridyl benzimidazole groups: b1) a possible arrangement of pyridyl benzimidazole groups with both p–p interactions and
coordination bonding; b2) structural model of optimized metal-CPBI quadridentate; b3) the arrangement of pyridyl benzimidazole groups along the
a-c plane. c) Formation of UMMNs confined in MMZ: after calcination and subsequent reduction, UMMNs would be confined in micropores of
the MFI framework by collapsing single-crystalline lamellar structure (red line), and confined in the mesopores maintained due to 908 rotational
intergrowth.
of the quaternary ammonium groups of the template would
be located in the straight channel of the MFI framework
directing the formation of the microporous framework (Fig-
ure 1a1-2). The configuration of CPBI, optimized by Materials
(ii) Then, the metal ions would be introduced into the
layers of the as-made MMZs to coordinate with the pyridyl
benzimidazole groups (Figure 1b1). Figure 1b2 shows the
schematic representation of the quadridentate, in which two
À
Studio, shows that a single C C bond connects the planes of
CPBI molecules coordinate with one metal ion to form a strong
pyridyl and benzimidazole groups of CPBI (Figure S1a). Fig-
ure 1a shows one possible arrangement of CPBI in the
mesoporous layer by assigning one molecule in one channel.
Along the b direction (Figure 1a2), all the pyridyl benzimida-
zole groups possess a favourable T-shaped (Figure S1) con-
figuration with well-defined networks along the a-c plane,
which generate the strong p-p stacking with the adjacent ones
(marked by black dotted lines, Figure 1a2). Along the c
direction (Figure S2), the planes of both pyridyl and benzi-
midazole groups are at an angle of 658 with respect to the a-c
plane. Under this conformation the distance between the
plane centers of pyridyl and benzimidazole groups is ꢀ 3.6 ꢀ,
which is accordance with the optimal and theoretical p-p
stacking distance (3.0–3.8 ꢀ)[38] (Figure S2). Based on this
geometrical matching (see Figure S2 for more detailed
description), the single crystalline lamellar zeolite could be
consequently formed; however, it would collapse with
calcination.[30,33] On the other hand, the mesopores formed
by epitaxial and 908 rotational intergrowth, a common
phenomenon in MFI zeolite, would be maintained even after
calcination.[22,39,40] The large interaction area between the
pyridyl benzimidazole groups would decrease the molecular
distance (green frame in Figure 1a1 and a2) matching with the
MFI framework intergrowths (see Figure S3 for more de-
chelate. The formation of the strong chelates would change
the configuration of CPBI because the angle between the
pyridyl and benzimidazole group changed from 508 to 58
(Figure S5). The unsaturated metal ions, with multi-coordi-
nation tendency, would be saturated by the coordination with
water molecules.
(iii) In the last step, the UMMNs confined in the MMZs
would be obtained by calcination that removes the organic
components and subsequent reduction (Figure 1c). Thus,
some of the UMMNs would be confined within the MFI
frameworks due to the collapse of the single crystalline
lamellar structure (marked by a red line in Figure 1c1 and c2);
while others would be confined in the mesopores generated
due to the epitaxial and 908 rotational intergrowth which was
maintained during the calcination process.[30–32] The stable
metal-organic complex described in the step (ii) could
effectively prevent the aggregation of metal species into
larger nanoparticles during the calcination procedure, which
make the formation of abundant types of UMMNs confined
in MMZs possible. Here, mono-, bi- and tri-metal nano-
particles were synthesized from the transition to the noble
metal region of the periodic table.
tailed description). Under these circumstances, the perpen- Results and Discussion
dicular crystal plates with a boundary relationship would
share a common c axis, in which the (100) faces are overgrown
Rhodium containing MFI was chosen as representative
over the (010) faces (Figure a1 and Figure S4).
material for demonstrating the process shown in Figure 1.
Figure 2 shows the structural characterizations of as-made
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Figure 2. Structural characterization of CPBI-MMZ-as, Rh/CPBI-MMZ-as and Rh-MMZ. a) Powder XRD patterns. b1, b2) N2 adsorption/desorption
isotherms and corresponding pore size distributions. c) SEM image of CPBI-MMZ-as, revealing a house-of-cards-like morphology. d) Low- (d1) and
high- magnification TEM images of CPBI-MMZ-as taken along the [001] (d2) and [010] (d3) axis. e) Low- (e1) and high-magnification Cs-corrected
STEM images of Rh/CPBI-MMZ-as taken along the [001] (e2) axis, and EDX mapping (e3) Annular dark field (ADF) image of the area subjected to
chemical analysis. f) Low- (f1) and high-magnification Cs-corrected STEM images of Rh-MMZ taken along the [001] (f2) axis, and EDX mapping (f3)
ADF image showing the Rh species concentrated on nanoparticles.
MMZs (CPBI-MMZ-as), Rh coordinated MMZs (Rh/CPBI
MMZ-as) and MMZ with confined ultrasmall Rh nano-
particles (Rh-MMZ) obtained by calcination and reduction.
-
The powder X-ray diffraction (XRD) pattern corresponding
to the CPBI-MMZ-as shows that most of the sharp peaks are
associated with h0l reflections of the MFI framework,
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indicating a very good crystallinity along the a-c plane
The porous structure of Rh/CPBI-MMZ-as and Rh-MMZ,
(Figure 2a). The diffraction peaks observed in XRD patterns
of Rh/CPBI-MMZ-as and Rh-MMZ are also consistent with
the MFI framework with no reflections associated to any Rh
form.
as well as the ultrasmall Rh nanoparticles were characterized
by spherical aberration-corrected (Cs-corrected) scanning
transmission electron microscopy (STEM) using a dark field
detector, as it is sensitive to the atomic number of the
elements (Figure 2e and f). Figure 2e1 and f1 show the Cs-
corrected STEM images of Rh/CPBI-MMZ-as and Rh-MMZ.
It is evident that the intergrown MFI structure was main-
tained. The morphology and distribution of Rh species in Rh/
As shown in Figure 2b1, the N2 adsorption-desorption
isotherms of CPBI-MMZ-as exhibited low gas amount ad-
sorbed because the organic components blocked the pores.
The amount of gas adsorbed by Rh/CPBI-MMZ-as is higher
than CPBI-MMZ-as, as part of the template was removed by its
dissolution in water during the coordination process (Fig-
ure S6–7). On the other hand, Rh-MMZ exhibited a type-IV
isotherm with H4-type hysteresis loop. The uptake step below
P/P0 = 0.02 indicate the presence of micropores, similar to
conventional MFI zeolite. The capillary condensation and
hysteresis loop at relative medium pressures P/P0 = 0.4–0.6
suggest the existence of disordered mesopores. The pore size
distribution obtained from the desorption branch shows
a mesopore size of about 3.5 nm (Figure 2b2). The Bruna-
uer–Emmett–Teller (BET) surface area and the micropore
and mesopore volumes were summarized in Table S1. As
expected, CPBI-MMZ-as and Rh/CPBI-MMZ-as show a low
BET surface area and micropore volume, as the organic
compounds partially filled pores; while the BET surface area
and mesopore volume of Rh-MMZ were as high as 512 m2 gÀ1
and 0.33 cm3 gÀ1 respectively.
To visualize morphology of the zeolites crystallites,
scanning electron microscopy (SEM) observations were
performed (Figure 2c). The morphology of MMZ displayed
an extraordinary boundary structure based on the 908 rotation
of the adjacent faces, as it was proposed in the growing
mechanism, and a dominant standard house-of-cards-like
morphology, which remained unchanged after metal incor-
poration (see Rh-MMZ, Figure S8).
The meso- and microstructure of CPBI-MMZ-as charac-
terized by transmission electron microscopy (TEM) is pre-
sented in Figure 2d. The specimens were prepared by slicing
the sample which was previously embedded in epoxy resin.
The low magnification TEM image taken along [001]
direction (Figure 2d1), revealed the abundant intergrown
structure of CPBI-MMZ-as. The mesostructure was directly
observed in the high-resolution transmission electronic mi-
croscopy (HRTEM) images (Figure 2d2 and d3), where MFI
layers were organized along the b direction forming a super-
mesostructure with both, lamellar and epitaxial 908 rotational
intergrowth structures.[30–32]
C
PBI-MMZ-as and Rh-MMZ were characterized by energy-
dispersive X-ray (EDX) spectral mapping. To corroborate the
existence and location of the metals within the zeolitic
structures, we turned to Cs-corrected STEM coupled with
a high angle annular dark field detector (HAADF), as this is
the most accurate approach to characterize metal loaded
zeolites.[41]
The EDX mapping of Rh/CPBI-MMZ-as show the homo-
geneous distribution of the Rh signal, which indicates that
those regions are occupied by Rh atoms between the MFI
sheets (Figure 2e3) proving the existence of homogeneous
coordination bonds in the template layer. Some nanosized Rh
particles appeared in Figure 2e2 would be small Rh agglom-
erates probably formed during the drying process. Ultrasmall
Rh nanoparticles with an average size of 1.3 nm are clearly
identified as they appear brighter in comparison with the
zeolite framework. In Figure 2 f2, it can be observed, pointed
by arrows, how these nanoparticles are well-encapsulated
within both micropores (yellow arrow) and mesopore (white
arrow) of MMZ after calcination and reduction (Figure S11).
The EDX mapping of Rh-MMZ shows that Rh species
concentrated on nanoparticles different from Rh/CPBI-MMZ-
as.
Figure 3 shows the Cs-corrected STEM analysis of Rh/Pt-
MMZ, Rh/Ni-MMZ and Rh/Pt/Ni-MMZ. As for the mono-
metallic case, the powder XRD patterns of these three
samples (Figure S12–14) exhibit the characteristic MFI re-
flections, with no diffraction peaks corresponding to any
metals, while the SEM images all show house-of-cards-like
morphology. As shown in the Cs-corrected STEM data
(Figure 3a1–c1 and a2–c2), the crystalline MFI framework is
well retained after the different metal incorporation which
resulted in the formation of nanoparticles with uniform size
and homogeneous distribution along the framework. The
average particle size obtained from the high-magnification
STEM images (Figure 3a2, b2, c2) was 1.5 nm, 1.7 nm and
2.5 nm for Rh/Pt-MMZ, Rh/Ni-MMZ and Rh/Pt/Ni-MMZ,
respectively. EDX mapping of UMMNs showed that bimet-
allic or trimetallic nanoparticles were obtained (see in
Figure 3a3, b3, c3). The correspondent EDX spectrum profiles
are shown in Figures S12–14, where the metal signals are
clearly evidenced. Furthermore, the EDX mapping and
profiles of Rh/Pt/Au-MMZ (Figure S15), Rh/Pd/Pt-MMZ
(Figure S16) and Pd/Pt/Fe-MMZ (Figure S17) were also
obtained corroborating that the nanoparticles presented the
expected composition. The amount of metal loading was
measured by inductively coupled plasma-atomic emission
spectrometry (ICP-AES), given in each Figure caption.
Furthermore, CO-DRIFTS measurements were employed
to characterize the structure and distribution of UMMNs
Solid 1H-13C cross polarization-magic angle spinning (CP-
MAS) NMR was carried out to verify that no degradation of
CPBI occurred during the high-temperature crystallization
(Figure S9). UV-visible spectroscopy was used to study the
stereoregularity of the surfactant molecules (Figure S10). The
two adsorption bands appearing at 245 nm and 296 nm (blue
curve) correspond to the template in dilute water and they are
ascribed to n–p* and p–p* interactions, respectively. For
MMZ-as (red), the red-shift of the band at 296 nm, which
appears at 316 nm corresponding to the p–p interactions,
indicates the arrangement of the pyridyl benzimidazole
blocking the zeolite growth along the b direction leading into
the formation of the mesopores.
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Figure 3. Characterization of Rh/Pt-MMZ (a), Rh/Ni-MMZ (b) and Rh/Pt/Ni-MMZ (c). Cs-corrected STEM HAADF images (a1–c1 and a2–c2) of Rh/
Pt- (a1,a2), Rh/Ni- (b1,b2) and Rh/Pt/Ni- MMZ (c1,c2) taken from [001], [001] and [010] direction, respectively. The images and the corresponding
EDX mapping images (a3–c3) showed that metal components are concentrated on the nanoparticles. The metal loading is Rh 0.56 wt% and Pt
0.25 wt% in Rh/Pt-MMZ, Rh 0.56 wt% and Ni 0.20 wt% in Rh/Ni-MMZ and Rh 0.24 wt%, Pt 0.20 wt% and Ni 0.08 wt% in Rh/Pt/Ni-MMZ,
respectively.
species (Figure S18). Two peaks at 2114 and 2047 cmÀ1 are
attributed to the CO molecules adsorbed on Rh or Rh/Ni
atoms and clusters, respectively. No obvious peaks appeared
in the range of 1840–1850 cmÀ1, indicating no large particles
were formed.
Based on the above general strategy, a library of 56
UMMNs confined MMZs, including mono-, bi- and tri-
metallic ultrasmall nanoparticles, were obtained and sum-
marized in Table 1. The average particle size was obtained
from the TEM data through the statistics of 500–1000
nanoparticles and the metal loading was measured by ICP-
AES (Figure S19–67). (i) For mono-UMMNs (green frame):
The top and bottom row represents mono-UMMNs (Fe, Co,
Ni, Cu, Zn, Rh, Pd, Pt, Au), which are widely used as
heterogeneous catalysts. Among the nine metals, four noble
UMMNs, Pd, Pt, Rh, and Au (green cells in the top row) were
successfully synthesized; while non-noble metals: Fe, Co, Ni,
Cu, Zn resulted in the formation of large and non-uniform
particles (Figure S68). The particle size of the four noble
metals was Rh < Pd = Pt < Au. (ii) For bi-UMMNs (steel blue
and coral cells): The cells intersected by top row@right
columns and bottom row@left column in the two diagonals
represent Rh- and Pd-based bi-UMMNs. Eight Rh- and six
Pd-based metals with average particle size in the range of 1.5–
3.2 nm and 3.0–4.1 nm were formed, respectively. (iii) For tri-
UMMNs (light blue and light pink cells): The cells intersected
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Table 1: The types and average size of synthesized 56 UMMNs confined
overall size still remains small (less than 5 nm) (Figure S70b).
MMZs. The light green, steel blue and coral, and light pink and light blue
cells are representative to ultrasmall mono-, bi-, and tri-metallic
nanoparticles, respectively. The grey cells are representative to samples
with large ununiform particle sizes.
Rh- and Rh/Ni-MMZ were ion exchanged with ammonium to
obtain acidic sites (Figure S71), in which no damage or
leaching of UMMNs were caused. The Si/Al ratio of MMZ
were tuned from pure silica to about 50, therefore, their
acidity can be controlled consequently. The acidity of Rh-
MMZ and Rh/Ni-MMZ were determined by IR spectra with
pyridine adsorption (Figure S72).
The library of MMZs confined UMMNs provides a prom-
ising platform to study and overcome catalytic limitations in
challenging chemical reactions. Herein, mild oxidation of
methane, a “holy grail” in chemistry,[42–44] was selected as
a probe reaction to evaluate the catalytic performance. Five
Rh-based MMZs of mono-, bi- and tri-metals confined
MMZs: Rh-, Pt-, Rh/Pt-, Rh/Ni- and Rh/Pt/Ni-MMZ were
chosen from the library. Rh, Ni and Pt elements have the
À
ability to catalyse methane transformation via C H activa-
by top row@right column and bottom row@left column in
upper right and left lower areas represent Rh- and Pd-based
tri-UMMNs. A more detailed description of this table is
provided in SI (Figure S69). Twenty-three Rh- and fifteen Pd-
based metals with average particle size in the range of 1.6–
3.9 nm and 3.0–4.4 nm were formed, respectively.
To successfully obtain UMMNs with tunable composition,
it was found to be imperative that the maximum number of
moles of the multi-metals should be constant. The content of
trifunctional surfactant and UMMNs were characterized by
thermogravimetric analysis (TG) (Figure S6,7) and ICP,
respectively. The results (Table S2) show that the molar ratio
of CPBI and metal is about 2:1, following the designed strategy.
All the characterization data of 56 UMMNs confined MMZs,
including XRD, SEM, TEM, ICP-AES, are shown in Sup-
porting Information (Figure S19–67).
To investigate the effect of coordination bonding stability,
between the organic surfactant and the metal ions, on the
formation of UMMNs, the binding energies of the metal-CPBI
complexes, were calculated by using density functional theory
(Table S3). The more negative the coordination bonding
energies, the more stable the metal-CPBI complexes are, and
the easier it is to prevent the aggregation of metal particles
leading to the formation of ultrasmall metallic nanoparticles.
The binding energies of noble metal–CPBI complexes (Rh–
tion, yet too strong or too weak adsorption energy of the
intermediate species is not conducive to the reaction.[43,45,46]
Importantly, the incorporation of different metals would
modulate the coordination environment and electronic struc-
ture to improve the intrinsic catalytic activity.[47,48] Therefore,
the combination of Rh, Ni and Pt may help tune or optimize
the adsorption energy. For comparison, the metal nano-
particles supported MMZs were synthesized by impregnation
(IMP) method.
As shown in Table S4 and Figure S73, UMMNs confined
in MMZs (i) exhibit much higher catalytic activity than their
counterparts synthesized by IMP; and (ii) exhibit a clear
activity trend for the production of oxygenates, that is,
trimetallic > bimetallic > monometallic catalyst, regardless
of the similar particle size and overall mass loading. The
productivity of oxygenates over Rh/Ni-MMZ was five times
than that over Rh/Ni-MMZ-IMP. The superior catalytic
activity of UMMNs is likely due to the ultrasmall size of
nanoparticles and the mesoporous structure of zeolite sup-
ports, which increase the number and accessibility of active
sites. Considering that UMMNs feature a uniform elemental
distribution, the activity trend clearly reveals a synergistic
effect between different metal components.[49]
C
C
PBI: À121.86, Pd–CPBI: À178.21, Pt–CPBI: À187.49 and Au– Conclusion
PBI: À584.18 kJmolÀ1) are lower than that of non-noble
metals (Fe–CPBI: À2.09, Co–CPBI : 227.51, Ni–CPBI: 213.24,
Cu–CPBI: 200.36 and Zn–CPBI: 287.00 kJmolÀ1), indicating the
coordination bonding of noble metal-CPBI are more stable
than that of non-noble metals, which is consistent with the
experimental results. The different uniformity and size of the
noble metal nanoparticles formed during the calcination
process may be due to the different surface energies of metal
nanoparticles. The surface energies of multi-metals would be
between noble and non-noble metals, which led to the
formation of ultrasmall Rh- and Pd-based multi-metallic
nanoparticles rather than non-noble metals alone.
In summary, a common strategy based on the use of
a trifunctional surfactant has been successfully developed to
synthesize a library of 56 UMMNs confined MMZs. The
template that can both self-assemble to form a structural
matching between the mesostructure and the zeolite frame-
work, and coordinate with metal ions to form stable
coordinates that can effectively prevent metal aggregation
during the calcination process are the key factors in the
formation of MMZs confined with homogeneously mixed
UMMNs. Based on this directing concept, a huge number of
UMMNs could be easily confined in both micropores and
mesopores of various supports leading to widespread appli-
cations far beyond the mild oxidation of methane. The multi-
combination of low-cost metals would give unique properties
to those of high-cost noble metal catalysts.
Hydrothermal stability measurements were carried out by
steaming at 973 K for 6 h (Figure S70). The structure of
mesoporous MFI zeolite was well maintained (Figure S70a)
and the particle size of UMMNs was increased a bit, but the
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We thank Prof. Osamu Terasaki (ShanghaiTech University)
for HRTEM characterization of the materials and Mouhai
Shu for the synthesis of template. This work was supported by
the National Natural Science Foundation of China (Grant No.
21533002, 21931008, S.C.; 21873072, 21922304, L.H.;
21850410448, 21835002, A.M.). To the Centre for High-
resolution Electron Microscopy (CꢀhEM), supported by SPST
of ShanghaiTech University under contract No. EM02161943,
to the Spanish Ministry of Science (RYC2018-024561-I) and
to the regional government of Aragon (DGA E13_20R).
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The authors declare no conflict of interest.
Keywords: MFI zeolite · molecular sieves ·
multi-metallic nanoparticles · templating route · zeolites
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Version of record online: && &&
,
&&&&
&&&&
www.angewandte.org
ꢀ 2021 Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 9
These are not the final page numbers!

Angewandte
Research Articles
Chemie
Research Articles
Zeolites
X. Jia, J. Jiang, S. Zou, L. Han, H. Zhu,
Q. Zhang, Y. Ma, P. Luo, P. Wu,
A. Mayoral,* X. Han,* J. Cheng,*
S. Che*
&&&& — &&&&
Library Creation of Ultrasmall Multi-
metallic Nanoparticles Confined in
Mesoporous MFI Zeolites
A library of ultrasmall multi-metallic
nanoparticles confined in both micro-
and mesopores of molecular sieves was
created by the trifunctional templating
route.
Angew. Chem. Int. Ed. 2021, 60, 2 – 9
ꢀ 2021 Wiley-VCH GmbH
www.angewandte.org
&&&&
These are not the final page numbers!