Few-Unit-Cell MFI Zeolite Synthesized using a Simple Di-quaternary Ammonium Structure-Directing Agent

Article abstract of DOI:10.1002/anie.202104574

Synthesis of a pentasil-type zeolite with ultra-small few-unit-cell crystalline domains, which we call FDP (few-unit-cell crystalline domain pentasil), is reported. FDP is made using bis-1,5(tributyl ammonium) pentamethylene cations as structure directing agent (SDA). This di-quaternary ammonium SDA combines butyl ammonium, in place of the one commonly used for MFI synthesis, propyl ammonium, and a five-carbon nitrogen-connecting chain, in place of the six-carbon connecting chain SDAs that are known to fit well within the MFI pores. X-ray diffraction analysis and electron microscopy imaging of FDP indicate ca. 10 nm crystalline domains organized in hierarchical micro-/meso-porous aggregates exhibiting mesoscopic order with an aggregate particle size up to ca. 5 μm. Al and Sn can be incorporated into the FDP zeolite framework to produce active and selective methanol-to-hydrocarbon and glucose isomerization catalysts, respectively.

Full text of DOI:10.1002/anie.202104574

Angewandte
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Zeolites Very Important Paper
Few-Unit-Cell MFI Zeolite Synthesized using a Simple Di-quaternary
Ammonium Structure-Directing Agent
Peng Lu, Supriya Ghosh, Matheus Dorneles de Mello, Huda Sharbini Kamaluddin, Xinyu Li,
Gaurav Kumar, Xuekui Duan, Milinda Abeykoon, J. Anibal Boscoboinik, Liang Qi, Heng Dai,
Tianyi Luo, Shaeel Al-Thabaiti, Katabathini Narasimharao, Zaheer Khan, Jeffrey D. Rimer,
Alexis T. Bell, Paul Dauenhauer, K. Andre Mkhoyan, and Michael Tsapatsis*
Abstract: Synthesis of a pentasil-type zeolite with ultra-small
few-unit-cell crystalline domains, which we call FDP (few-unit-
cell crystalline domain pentasil), is reported. FDP is made
using bis-1,5(tributyl ammonium) pentamethylene cations as
structure directing agent (SDA). This di-quaternary ammoni-
um SDA combines butyl ammonium, in place of the one
commonly used for MFI synthesis, propyl ammonium, and
a five-carbon nitrogen-connecting chain, in place of the six-
carbon connecting chain SDAs that are known to fit well within
the MFI pores. X-ray diffraction analysis and electron
microscopy imaging of FDP indicate ca. 10 nm crystalline
domains organized in hierarchical micro-/meso-porous aggre-
gates exhibiting mesoscopic order with an aggregate particle
size up to ca. 5 mm. Al and Sn can be incorporated into the
FDP zeolite framework to produce active and selective
methanol-to-hydrocarbon and glucose isomerization catalysts,
respectively.
adsorption performance compared to conventional zeo-
[
5–10]
lites.
In this context, the quest for synthetic methods to
minimize the size of crystalline zeolitic domains while
accomplishing their arrangement to form hierarchical porous
[
11]
materials and thin film membranes persists. Of particular
importance is the synthesis of MFI with crystalline domains
on the order of one to few unit cells (ca. 10 nm or less) due to
[
5,12]
anticipated uses in catalysis, adsorption and membranes.
Moreover, since MFI in its all-silica (zeosil) form has been
studied extensively as a prototype for templated crystal
[
13–15]
growth,
the synthesis of MFI crystals as close as possible
to their nucleation stage is of fundamental significance. Ryoo
and co-workers, soon after their discovery of gemini-type
oligo-quaternary ammonium surfactants as organic structure-
directing agents (SDAs) leading to multilamellar 2-dimen-
[
3]
sional MFI, they reported the synthesis of mesoporous
materials with walls composed of few-unit-cell domains with
the zeolite beta (BEA) and MFI-like framework topolo-
[16,17]
Introduction
gies.
We have shown that simpler short chain mono- and
di-quaternary SDAs (i.e., without the dual porogenic ability
of tri- to penta-quaternary ammonium gemini-surfactant
SDAs with C18 alkyl chains) are also capable of directing
[1–4]
Zeolites composed of one- to few-unit-cell domains,
exhibit distinct, and for some uses superior, catalytic and
[*] Dr. P. Lu, Dr. T. Luo, Prof. M. Tsapatsis
Dr. J. A. Boscoboinik
Department of Chemical and Biomolecular Engineering &
Institute for NanoBioTechnology, Johns Hopkins University
Department of Materials Science and Chemical Engineering, State
University of New York at Stony Brook
3400 N. Charles Street, Baltimore, MD 21218 (USA)
100 Nicolls Rd, Stony Brook, NY 11794 (USA)
E-mail: tsapatsis@jhu.edu
Dr. L. Qi, Prof. A. T. Bell
S. Ghosh, X. Li, G. Kumar, X. Duan, Prof. P. Dauenhauer,
Prof. K. A. Mkhoyan
Chemical Sciences Division, Lawrence Berkeley National Laboratory
Berkeley, CA 94720 (USA)
Department of Chemical Engineering and Materials Science
University of Minnesota
and
Department of Chemical and Biomolecular Engineering
University of California, Berkeley, CA 94720 (USA)
421 Washington Avenue SE, Minneapolis, MN 55455 (USA)
Dr. M. Dorneles de Mello, Dr. J. A. Boscoboinik
Catalysis Center for Energy Innovation, University of Delaware
Newark, DE 19716 (USA)
H. Dai, Prof. J. D. Rimer
Department of Chemical and Biomolecular Engineering
University of Houston, Houston, TX 77204 (USA)
and
Prof. M. Tsapatsis
Applied Physics Laboratory, Johns Hopkins University
Center for Functional Nanomaterials
Brookhaven National Laboratory, Upton, NY 11973 (USA)
11100 Johns Hopkins Road, Laurel, MD 20723 (USA)
Dr. H. S. Kamaluddin, Prof. S. Al-Thabaiti, Prof. K. Narasimharao,
Prof. Z. Khan
Department of Chemistry, Faculty of Science
King Abdulaziz University, Jeddah 21589 (Saudi Arabia)
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.202104574.
ꢀ
2021 The Authors. Angewandte Chemie International Edition
Dr. M. Abeykoon
National Synchrotron Light Source II
Brookhaven National Laboratory, Upton, NY 11973 (USA)
published by Wiley-VCH GmbH. This is an open access article under
the terms of the Creative Commons Attribution Non-Commercial
NoDerivs License, which permits use and distribution in any
medium, provided the original work is properly cited, the use is non-
commercial and no modifications or adaptations are made.
&
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the growth of single- to few-unit-cell thick nanosheets by
[4,11]
hindering growth along the b-axis of MFI.
However, the
use of such simple SDAs to reduce crystalline domains down
to few unit cells in directions other than the MFI b-axis has
not yet been achieved. Here, we demonstrate that few-unit-
cell MFI, with a highly broadened XRD pattern, can be
synthesized using a relatively simple di-quaternary ammoni-
um (bis-1,5(tributyl ammonium) pentamethylene) cation
(
called here tri-Bu-dC5) as an SDA. All-silica, aluminosili-
cate, and stannosilicate MFI synthesis is reported along with
sorption and catalytic properties.
Synthesis of MFI and MEL with different crystal habit,
stacking fault sequence and presence of rotational inter-
Scheme 1. Hypothesized opposing trends of tri-Bu-dC5 for minimizing
[
18–20]
growths has been studied extensively.
We have demon-
growth along all directions to generate ultra-small crystallites. Black,
green and red colors denote propyl, five methylene chain, and butyl
groups, respectively.
strated that at early stages of crystal growth (i.e., before
crystal facets develop) bis-1,5(tripropyl ammonium) pentam-
ethylene cations (called here tri-Pr-dC5) hinder all growth
rates compared to those observed using tetrapropyl ammo-
nium (TPA), the typical SDA for MFI synthesis. Moreover,
we have shown that at early stages of growth, tri-Pr-dC5
favors growth along the b-axis compared to the other
crystallographic directions of MFI, while stacking faults and
rotational intergrowths attributable to the presence of MEL
confirmed our anticipation that the frustrated tri-Bu-dC5
SDAwill not be a very effective SDA for MFI or MEL. Below,
it is shown that it is possible to grow highly crystalline few-
unit-cell pentasil zeolite, which we call FDP (few-unit-cell
crystalline domain pentasil zeolite).
[11,19]
are not observed.
This finding combined with the well-
established trends in MFI synthesis using its most common
SDA, TPA cations, which favor growth along the c- and a- Results and Discussion
axes, lead us to hypothesize that at early stages of crystal
growth (i.e., before well-developed crystal facets emerge) the
pentamethylene moiety is responsible for reversing the crystal
shape of MFI from thin to long platelets along its b-axis. The
hypothesis that the pentamethylene moiety is responsible for
favoring growth along the b-axis, is further corroborated by
the finding that MFI growth using bis-1,6(tripropyl ammoni-
um) hexamethylene cations (tri-Pr-dC6) retains the b-axis as
a slower growing direction. We have also demonstrated that
when using tetrabutyl ammonium (TBA) or phosphonium
Characterization of the tri-Bu-dC5 SDA and its synthesis
procedure are provided in the Supporting Information. The
SDAwas used in hydroxide form (tri-Bu-dC5(OH) ) obtained
2
by anion exchange of its bromide form (tri-Bu-dC5(Br) ). The
2
synthesis parameters along with crystal size and composition
of the FDP zeolites synthesized at 1208C are summarized in
Table 1. We note here that conventional MFI was obtained at
the higher synthesis temperature of 1508C (Figure S2). The
SDA exhibits structure-directing role towards MFI and was
found to be preserved intact in the as-made product (Fig-
ure S3).
(
TBP) SDAs, growth along the b-axis is hindered while MEL
presence and rotational intergrowths are enhanced leading to
single-unit-cell thick intergrown MFI nanosheets, a material
The wide angle XRD pattern of the calcined Si-FDP (1)
zeolite (see Table 1 for sample denotation) shows two
[
4]
we call SPP (self-pillared pentasil). Scheme 1 illustrates
these hypothesized opposing
trends coded on bis-1,5(tributyl
ammonium) pentamethylene cat-
ions (tri-Bu-dC5). Specifically, the
favoring and hindering of (i)
growth along the b-axis, (ii) MEL
stacking faults, and (iii) rotational
intergrowths by different parts of
the molecule.
Table 1: Summary of synthesis parameters and compositions of calcined FDP zeolites obtained at
1
208C.
Material
Sol composition
Crystallite size
[nm]
Si/Al or
Si/Sn
t [days]
Rotation
or not
[
a]
[b]
H O/SiO
SDA/SiO2
2
2
Si-FDP (1)
Si-FDP (2)
Si-FDP (3)
Si-FDP (4)
Si-FDP (5)
Al-FDP (1)
Al-FDP (2)
Al-FDP (3)
Al-FDP (4)
Al-FDP (5)
Sn-FDP
38
38
13
13
8
8
8
8
8
0.15
0.25
0.15
0.25
0.15
0.15
0.15
0.15
0.15
0.15
0.15
6.0
5.3
7.3
5.2
4.0
6.6
7.5
7.1
7.7
7.6
8.0
–
–
–
–
7
9
3
7
3
3
3
3
3
5
7
yes
yes
yes
yes
yes
yes
yes
yes
yes
yes
no
We decided to test the hypoth-
esis that these opposing trends will
create frustration in the SDA char-
acteristics hindering crystal growth
in all directions and limiting the
resulting crystal size to few-unit-
cells. An earlier attempt to the
crystallization of MFI using this
SDA was inconclusive as it did not
–
157 (100)
172 (200)
260 (300)
42 (50)
49 (50)
105 (100)
8
8
[a] Calculated by Scherrer equation. [b] Obtained by ICP analysis; the numbers in parentheses indicate
[
21]
yield crystalline material,
but
the molar ratio in the synthesis sol.
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Figure 1. Characterization of Si-FDP (1). a) XRD patterns of (from top to bottom) calcined Si-FDP (1) zeolite, pure silica SPP zeolite synthesized
[22]
29
using TBPOH and simulated MFI from the International Zeolite Association. b) Solid-state Si NMR spectra of Si-FDP (1). c) Ar adsorption/
desorption isotherms of Si-FDP (1) and Si-SPP zeolites. d),e) Low and high magnification SEM images of the calcined Si-FDP (1) zeolite. f and
g) Medium magnification TEM images of calcined Si-FDP (1). h) Higher magnification image showing nanoparticle clusters. i) Wiener-filtered
HRTEM of individual MFI-nanoparticle oriented along the b-direction. Inset FFT is consistent with typical MFI spot pattern along b-axis. Scale
À1
bars: d) 2 mm; e) 200 nm; f) 200 nm; g) 20 nm; h) 20 nm, i) 5 nm, (i, inset FFT) 1 nm
.
resolved Bragg reflection peaks at d = 1.09 and 0.38 nm,
consistent with the MFI framework type, though broadened
outcome of interrupted crystal growth and/or aggregation of
few-unit-cell crystalline domains rather than templating by
the SDA. To our knowledge, this is the first time that
a mesostructured array of MFI nanocrystals is created using
a simple SDA. Pair distribution function (PDF) analysis was
performed to further assess the local structure of the FDP
zeolites. The results demonstrated consistency of Si-FDP with
the MFI structure, exhibiting similarity with the PDF of Si-
SPP while deviating from defect-free F-MFI (MFI zeolite
synthesized in fluoride medium) (Figure S4). The presence of
(
Figure 1a, black trace). The XRD patterns of pure-silica SPP
zeolite and simulated MFI framework are provided for
comparison (Figure 1, blue and cyan traces). Low angle
XRD (Figure 1a, inset) of the calcined pure silica FDP zeolite
showed a broad diffraction peak at around 1.38 2q, which
could be ascribed to a prevalent regular distance between
crystalline domains creating a short-range mesoscopic order-
ing. We notice that this mesoscopic order is created in the
absence of gemini surfactant SDAs, which are known to
À1
the characteristic absorbance band at 550 cm in FTIR
spectra (Figure S5) further confirmed that Si-FDP is consis-
[17,23,24]
template ordered mesoporosity,
Most likely, it is the
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À1
tent with the MFI topology. Also, the band at 950 cm , an
[
25]
indicator of structural defects in zeolitic materials,
observed in FDP zeolite and absent in F-MFI.
was
2
9
Three Si species were detected by solid-state Si magic
angle spinning (MAS) NMR for the pure silica FDP zeolite
(
Figure 1b). As expected, silanol groups were detected, as
2
3
indicated by the resonance signal of Q and Q species, which
in total comprise 26.9% of the Si species, a larger fraction
than that of the single unit cell thick Si-SPP zeolite (ca. 23%)
[
26]
reported previously. These silanol groups can be mostly
attributed to the surface termination of the small crystalline
domains in the FDP zeolites. Ar adsorption and desorption
isotherms are shown in Figure 1c, where the sorption data of
the pure silica SPP zeolite is also provided for comparison
(
the textural properties are summarized in Table S1). The
isotherms show that Si-FDP zeolite, possesses both micro-
and mesoporosity. The pore size distribution drawn up to
1
0 nm indicates micropores centered at 0.525 nm and meso-
pores with a broad distribution from 2–7 nm (Figure S6a),
which are comparable to that of SPP zeolite. The pore size
distribution of SPP and FDP zeolites are very similar in the
microporous region, but the latter exhibit larger mesopore
[26]
volumes (Figure S6b).
Low and high magnification SEM images (Figure 1, d and
e) show large spherical particles comprised of smaller
filamentous particles (ca. 200 nm), which are further com-
prised of much smaller crystallites (Figure 1, f and g). The
HRTEM image is consistent with the particles comprised of
nanocrystalline domains that are not crystallographically
aligned (Figure 1h). An individual MFI nanoparticle with
a size of ca. 5 nm oriented along its b-axis is shown in
Figure 1i. Synthesis with higher SDA content (Si-FDP (2)
Figure 2. Low magnification (a) and high resolution (b) TEM images
of Si-FDP (5) zeolite synthesized under low water content. Scale bar in
À1
(
a) is 100 nm, and in (b) is 10 nm, (b, inset FFT) 2 nm . c) Water
vapor adsorption at 258C for pure silica zeolites: Si-SPP (black
square), Si-FDP (1) (red circle), Si-FDP (2) (blue triangle), conven-
tional Si-MFI (pink inverted triangle), and F-MFI (green diamond).
with SDA/SiO = 0.25) also yields porous aggregates com-
2
prised of similarly sized nano-crystallites (see Figures S7 and
S8). The mean sizes of the crystalline domains calculated from
XRD peak broadening (Table 1) are in good agreement with
the anticipated values from inspecting the HRTEM images.
Similar XRD broadening has been reported by Ryoo
ratio are similar to its high H O/SiO counterpart. Si-FDP
zeolite is stable at 5508C, while it gradually loses crystallinity
at higher temperatures (Figure S10).
2
2
Water vapor adsorption isotherms on Si-FDP zeolites are
shown in Figure 2c. Si-SPP, conventional Si-MFI and F-MFI
are provided for comparison. Water sorption on Si-SPP and
Si-FDP zeolites can be attributed to the presence of silanol
groups on the external surfaces and the presence of meso-
pores between the crystalline domains. In contrast, as
anticipated, much lower water adsorption is observed on
commercial Si-MFI and even lower on F-MFI in the entire
pressure range.
[
3,17]
et al.,
when they synthesized hexagonally ordered meso-
porous molecular sieves with MFI-like microporous walls and
disordered MFI-like nanolayers interconnected in a disor-
dered manner. A distinguishing characteristic of the current
approach is that a simpler SDA is used and the ordered
mesostructure is not templated by a long tail of the SDA.
When the H O/SiO ratio was decreased from 38 to 13 and
2
2
below, crystalline FDP zeolites could be obtained faster
Table 1). The wide angle XRD patterns of the calcined Si-
(
To introduce sites for catalytic reactions, Al was incorpo-
rated into the FDP zeolite framework, as corroborated by the
FDP zeolites synthesized under low H O/SiO2 ratio are
2
2
7
similar to those of high H O/SiO ratio (Figure S9, a and b).
solid-state Al magic angle spinning (MAS) NMR (Fig-
ure S11a) and well dispersed as shown by the EDX mapping
(Figure S12). For Al-FDP (2) with lower Al content, a small
fraction of extra-framework Al was detected (ca. 1.7% by
peak area integration). Higher Al-containing FDP zeolites
(Al-FDP (4) and Al-FDP (5)) show increased amounts of
extra-framework Al, 18.4% and 12.1%, respectively (Fig-
2
2
The aggregate particle size decreased with decreased water
content, and its morphology changed from spheres of
diameter ca. 3–5 mm (Figure 1d and Figures S7a and S8a) to
filamentous aggregates of size ca.100–200 nm (Figure 2 and
Figure S9). Unlike SPP zeolite particles that consist of
orthogonally intergrown 2D nanosheets with single-unit-cell
thickness, the FDP zeolite particles obtained at low water
content display no orthogonal intergrowths. Ar adsorption
and desorption isotherms and pore size distribution analysis
2
9
ure S11a). Solid-state Si magic angle spinning (MAS) NMR
spectra (Figure S11b) for the Al-FDP zeolites show that the
2
3
percentages of Q and Q species for Al-FDP (2), Al-FDP (4)
and Al-FDP (5) (21.1%, 24.4% and 20.6%, respectively) are
(
Figure S6) of Si-FDP (3) synthesized using a low H O/SiO2
2
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reduced compared to those present in Si-FDP (1) (26.9%). To
determine the above cited percentages, the deconvolution of
the spectra was performed assuming that framework Al is
Sn-FDP zeolite than that of Si-FDP. The domain size of Sn-
FDP zeolite calculated using the Scherrer equation is larger
than those of the Si-FDP zeolites (Table 1). TEM images
(Figure S13, b and d) show that Sn-FDP particles are
composed of globular crystallites of few-unit-cell domains.
Additional experiments with spatially resolved energy dis-
persive X-ray (EDX) analysis in scanning transmission
electron microscopy (STEM) showed that Sn is presented
and uniformly distributed in the Sn-FDP particles (Figure S17
and Figure 3a). High angle annular dark field (HAADF)
STEM was used to examine the Sn distribution at higher
resolution, confirming that Sn was incorporated in the
framework and distributed evenly (Figure 3b) as no contrast
attributable to Sn clusters can be observed except in very few
images. The Si/Sn ratio in the product (105) is close to that of
the starting synthesis sol (100) (Table 1).
The crystallization kinetics of FDP zeolites were inves-
tigated by monitoring the products collected at different
crystallization times. Figure 4 shows the low and high
magnification TEM images of as-made Si-FDP zeolites and
the corresponding XRD patterns and crystallization curves
are shown in Figure S18. No solid product could be collected
up to 12 h heating, but small particles of ca. 15 nm were
observed by TEM images (Figure 4a). HRTEM and corre-
sponding FFT confirm that the particles are MFI-type
(Figure 4, b and inset). No particles could be observed for
the sol collected at 6 h. The powder collected at 18 h exhibits
typical XRD pattern of FDP zeolite and high relative
crystallinity of 90%, despite the very low relative yield of
3.3% (Figure S18, a and b). TEM imaging of the powder
collected at 18 h shows polycrystalline particles with average
size of ca. 42 nm (Figure 4, c and d). Prolonged heating to 24 h
and above did not result in substantial changes of the
crystallinity, but the yield gradually increased (Figure S18,
a and b). Moreover, the particle size increased to ca. 69 nm,
112 nm and 180 nm for 24 h, 30 h and 48 h crystallization,
respectively (Figure 4, e to j; Figure S19). Si-FDP without
EtOH, Al-FDP and Sn-FDP show different nucleation and
growth behaviors. The induction
only present as Si(OSi) (OAl) species (i.e., neglects AlO-
3
[27,28]
SiOH-containing species).
The resonance at ca.
À107 ppm was assigned to Si(OSi) OAl while the others were
3
assigned to Si(OSi) (OH) (ca. À91 ppm), Si(OSi) (OH) (ca.
2
2
3
À102 ppm), and Si(OSi) (ca. À112 ppm and À115 ppm). It
4
was previously reported that Al incorporation can lead to
a decrease of the structural defects in zeolites synthesized in
[29]
hydroxide medium. The XRD patterns (Figure S11c) show
better resolved shoulder peaks for the aluminosilicate FDP
zeolites and the corresponding crystalline domain sizes
calculated by the Scherrer equation are generally larger than
those of the Si-FDP zeolites (Table 1). The Al incorporation
did not change the morphology of the FDP zeolites, as shown
by TEM images (Figure S13, a and c). Argon adsorption and
desorption isotherms and pore size distribution analysis
(
Figure S6) of the Al-FDP zeolite presented higher mesopore
volume than that of the Si-FDP zeolite. IR spectrum (Fig-
ure S14) of H-form Al-FDP (4) using pyridine as a probe
À1
shows absorption bands at 1455 cm that can be ascribed to
À1
Lewis acid sites from extra-framework Al, and at 1545 cm
that can be assigned to Brønsted acid sites (BAS). Brønsted
acidic properties of Al-FDP zeolites were characterized using
in situ titrations with pyridine and 2,6-di-tertbutylpyridine
(
DTBP) during ethanol dehydration (see Supporting Infor-
mation for details) and the results are shown in Table 2.
Higher initial rate of diethyl ether (DEE) formation was
observed on the higher Al containing FDP (Al-FDP (4)),
which showed comparable turnover frequency (TOF) com-
pared to its lower Al containing counterpart (Al-FDP (3)).
The external BAS fraction reached as high as 73.2% for Al-
[26]
FDP (4), which is much higher than that for Al-SPP (51%).
Sn was also incorporated into the FDP framework as
1
19
supported by the UV/Vis spectrum (Figure S15a), Sn MAS
NMR spectra (Figure S15b) and TEM imaging. The XRD
patterns (Figure S16) show better resolved shoulder peaks of
time (the period when no solid
could be collected) was ca. 6 h, 6 h
and 48 h for Si-FDP without
EtOH, Al-FDP and Sn-FDP, re-
spectively. EtOH and related alco-
hols could slow down crystalliza-
tion as reported in a previous
work. For Si-FDP, 24 h heating
rendered almost fully crystalline
products (Figure S18, a to d), while
it took longer for Al-FDP and Sn-
FDP, (Figure S18, e to h).
Table 2: Catalytic characterization results of Al-FDP zeolites in ethanol dehydration.
Material Initial rate of
DEE formation
TOF of
DEE formation
[molmolH
Total BAS count
[mmolg ]
Fraction
of exter-
nal
À1 [c]
À1
À1 [a]
+
Py
À1 À1 [b]
[mmolg min
]
h ]
[
d]
sites [%]
Al-FDP
3)
Al-FDP
4)
1.23
1.93
1.7Æ0.1
1.1Æ0.1
44
41Æ6
73Æ3
[
30]
(
101
(
[
a] Reaction conditions: T=144Æ18C, p
=5.2 torr, WHSV in the range 1.1–3.9 g EtOH/g cat./h,
EtOH
diluent flow rate 60 sccm. Only DEE was produced under the investigated conditions and no other
products were detected. [b] TOF was calculated from the slope of the trace obtained while plotting mass-
Methanol-to-hydrocarbon
À1 À1
normalized rates [mmolg
h
] under pyridine (EtOH:pyridine ca. 503) as a function of the cumulative
(MTH) reactions were performed
over the Al-FDP (5) zeolite and
comparisons were made with SPP
and commercial MFI (C-MFI) zeo-
lites. Three different temperatures
were tested, and it was found that
there was a temperature threshold
À1
uptake of pyridine [mmolg ] and errors represent standard errors in slope estimation. [c] Total BAS
counts were calculated from the cumulative pyridine uptakes for complete rate quenching assuming
a stoichiometry of 1:1. [d] Fraction of external sites was calculated using DTBP titration (EtOH:DTBP
ꢀ
808) using two methods, namely (i) fext =1À (rate after DTBP saturation/rate prior to DTBP
introduction), and (ii) f =cumulative uptake of DTBP/ cumulative uptake of pyridine, and the errors
ext
represent 95% confidence interval on the values obtained from the two methods for a single
experimental run.
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for initiating the reaction for FDP zeolite. As shown in
Figure 5a, only dimethyl ether (DME) was produced at
508C for FDP zeolite, while SPP and C-MFI demonstrated
3
much higher activity to form hydrocarbons. When the
temperature increased to 4008C and then to 4508C, consid-
erable DME can still be detected in FDP zeolite, but it is
hardly detectable for SPP and C-MFI zeolites. Methanol
conversion increased along with the elevated temperature for
the three catalysts, but FDP showed slightly lower conversion
(95.7% at 4508C). A plausible reason for the existence of the
temperature threshold to initiate MTH reaction could be due
to the predominant BAS external acid fraction for FDP
zeolite (> 70%, see Table 2). Moreover, at external sites,
hydrocarbon pool species accumulation may be hindered
favoring the olefin-based cycle exhibiting higher ratio of
[32–35]
propylene to ethylene.
Indeed, FDP zeolite exhibited
higher P/E (propylene to ethylene) ratio than SPP and C-
MFI, e.g., 11.3 versus 4.7 and 5.6 at 4508C. However, we note
here that earlier studies demonstrated that different P/E
ratios can be obtained using SPP zeolites when assessed under
[32–35]
different reaction conditions, e.g., time-on-stream (TOS).
Therefore, proper attribution of the higher P/E ratio for FDP
requires further studies.
Isomerization of glucose (GLU) to fructose (FRU) over
the Sn-FDP zeolite was carried out as a probe reaction,
[
36]
following the procedures reported previously.
Sn-FDP
zeolite achieved a FRU yield of 60% at 96% GLU
conversion (Figure 5b, black solid square). This performance
is comparable to that of Sn-SPP zeolite (Figure 5b, gray solid
circle), where the high activity and selectivity was ascribed to
the synergistic effect of Brønsted and Lewis acid sites along
with the easy access to those active sites. Considering the
similar framework topology and morphology resemblance
between Sn-FDP and Sn-SPP zeolites, the proposed mecha-
nism for Sn-SPP should also be applicable here. For the
recyclability of the catalyst, we performed 3 consecutive
reaction-regeneration cycles (see details in Supporting In-
Figure 3. a) STEM-EDX elemental maps along with corresponding
HAADF-STEM image and b) HAADF-STEM image of another particle
showing uniform contrast from Sn-FDP with Si/Sn atomic ratio of 105.
Scale bars: a) 500 nm; and b) 10 nm. These experiments were per-
[
31]
formed on aberration-corrected FEI Titan G2 60–300 STEM.
Figure 4. Low and high magnification TEM images of as-made Si-FDP zeolites collected from different crystallization times: a, b) 12 h; c, d) 18 h;
e, f) 24 h; g, h) 30 h and i, j) 48 h. The synthesis sol composition is 1SiO :0.15 tri-Bu-dC5(OH) :13H O:4EtOH. Scale bars are: a) 100 nm;
2
2
2
À1
b) 5 nm, FFT 2 nm ; c, e, g, i,) 200 nm; d) 10 nm; f, h, j) 20 nm. Synthesis performed at 1208C with a rotating autoclave.
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Acknowledgements
The authors extend their appreciation to the Deputyship for
Research & Innovation, Ministry of Education in Saudi
Arabia for funding this research work through the project
number (721). Partial support for this work (certain catalysis
experiments and characterizations) was also provided by the
Catalysis Center for Energy Innovation, an Energy Frontier
Research Center funded by the U.S. Department of Energy,
Office of Science, Office of Basic Energy Sciences under
Award No. DE-SC0001004. Parts of this work were carried
out in the Characterization Facility, University of Minnesota,
which receives partial support from the NSF through the
MRSEC (Award Number DMR-2011401) and the NNCI
(Award Number ECCS-2025124) programs. S.G. and K.A.M.
were supported by the NSF through the University of
Minnesota MRSEC under award number DMR-2011401.
The authors are grateful for Dr. Renato N. Sampaio and Dr.
Javier Concepcion, Chemistry Division of Brookhaven Na-
tional Laboratory, for providing the experimental setup for
glucose isomerization catalysis experiments. J.D.R. acknowl-
edges support primarily from the U.S. Department of Energy,
Office of Science, Office of Basic Energy Sciences (Award
DE-SC0014468) and additional support from the Welch
Foundation (Award E-1794). A.T.B. and L.Q. acknowledge
support from the Office of Science, Office of Basic Energy
Sciences, of the U.S. Department of Energy under Contract
No. DE-AC02-05CH11231, L.Q. also acknowledges support
from the Dalian Institute of Chemical Physics, Chinese
Academy of Sciences, Peopleꢀs Republic of China.
Figure 5. Catalytic evaluation of the FDP zeolite catalysts. (a) MTH
reaction over Al-containing catalysts: Al-FDP (5), SPP (Si/Al: 36), and
C-MFI (Si/Al: 40) (commercial MFI, Zeolyst CBV8014). The TOS was
1
0 min and the conversion and selectivity were calculated on C%
molar basis. b and c) Glucose isomerization to fructose over Sn-
containing zeolites: b) glucose conversion versus fructose yield and
(
(
c) reaction time versus fructose yield. The numbers in parentheses in
b) denote the Si/Sn ratios. The gray data points in (b) and (c) were
[
36]
obtained from previous work.
Conflict of Interest
formation). The rate constant for different reaction cycles was
calculated assuming pseudo-first-order in glucose concentra-
tion (Figure S20). The data suggests that moderate deactiva-
tion occurs after each reaction cycle. However, the selectivity
to fructose remains the same (Table S2).
The authors declare no conflict of interest.
Keywords: adsorption · catalysis ·
di-quaternary structure directing agents · pentasil ·
ultrasmall crystalline domain
Conclusion
[
1] P.-S. Lee, X. Zhang, J. A. Stoeger, A. Malek, W. Fan, S. Kumar,
W. C. Yoo, S. Al Hashimi, R. L. Penn, A. Stein, M. Tsapatsis, J.
Am. Chem. Soc. 2011, 133, 493 – 502.
Using a simple SDA containing moieties with conflicting
effects on early crystal growth rates of MFI, we synthesized an
MFI zeolite consisting of few-unit-cell crystalline domains
[2] J. Pꢁrez-Ramꢂrez, C. H. Christensen, K. Egeblad, C. H. Chris-
tensen, J. C. Groen, Chem. Soc. Rev. 2008, 37, 2530 – 2542.
[
3] M. Choi, K. Na, J. Kim, Y. Sakamoto, O. Terasaki, R. Ryoo,
Nature 2009, 461, 246 – 249.
(
below ca. 10 nm) that are not crystallographically aligned. It
exhibits distinct adsorption and catalytic properties from
those of conventional MFI, while it shows similarities but also
differences in performance when compared to SPP, another
prototypical hierarchical zeolite with distinct structure. This
work contributes to the quest for single-unit-cell zeolites and
provides a first assessment of the adsorption and catalytic
properties of few-unit-cell MFI zeolites.
[
4] X. Zhang, D. Liu, D. Xu, S. Asahina, K. A. Cychosz, K. V.
Agrawal, Y. Al Wahedi, A. Bhan, S. Al Hashimi, O. Terasaki, M.
Thommes, M. Tsapatsis, Science 2012, 336, 1684 – 1687.
5] M. E. Davis, Nature 2002, 417, 813 – 821.
[
[6] A. Corma, Chem. Rev. 1995, 95, 559 – 614.
[7] N. Rangnekar, N. Mittal, B. Elyassi, J. Caro, M. Tsapatsis, Chem.
Soc. Rev. 2015, 44, 7128 – 7154.
[
8] M. A. Camblor, A. Corma, S. Valencia, Microporous Mesopo-
rous Mater. 1998, 25, 59 – 74.
[
9] L. Wei, K. Song, W. Wu, S. Holdren, G. Zhu, E. Shulman, W.
Shang, H. Chen, M. R. Zachariah, D. Liu, J. Am. Chem. Soc.
2019, 141, 8712 – 8716.
[
10] H. J. Cho, P. Dornath, W. Fan, ACS Catal. 2014, 4, 2029 – 2037.
&
&&&
www.angewandte.org
ꢀ 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 10
These are not the final page numbers!

Angewandte
Research Articles
Chemie
[
11] M. Y. Jeon, D. Kim, P. Kumar, P. S. Lee, N. Rangnekar, P. Bai, M.
[25] M. A. Camblor, A. Corma, A. Mifsud, J. Pꢁrez-Patriente, S.
Shete, B. Elyassi, H. S. Lee, K. Narasimharao, S. N. Basahel, S.
Al-Thabaiti, W. Xu, H. J. Cho, E. O. Fetisov, R. Thyagarajan,
R. F. DeJaco, W. Fan, K. A. Mkhoyan, J. I. Siepmann, M.
Tsapatsis, Nature 2017, 543, 690 – 694.
Valencia, Stud. Surf. Sci. Catal. 1997, 105, 341 – 348.
[26] Y. Guefrachi, G. Sharma, D. Xu, G. Kumar, K. P. Vinter, O. A.
Abdelrahman, X. Li, S. Alhassan, P. J. Dauenhauer, A. Navrot-
sky, W. Zhang, M. Tsapatsis, Angew. Chem. Int. Ed. 2020, 59,
9579 – 9585; Angew. Chem. 2020, 132, 9666 – 9672.
[27] X. Zhao, S. Zeng, X. Zhang, Q. Deng, X. Li, W. Yu, K. Zhu, S.
Xu, J. Liu, L. Han, Angew. Chem. Int. Ed. 2021, 60, 13959 –
13968; Angew. Chem. 2021, 133, 14078 – 14087.
[28] J. K. Reddy, K. Motokura, T. Koyama, A. Miyaji, T. Baba, J.
Catal. 2012, 289, 53 – 61.
[29] H. Koller, R. F. Lobo, S. L. Burkett, M. E. Davis, J. Phys. Chem.
1995, 99, 12588 – 12596.
[
[
12] A. Corma, M. E. Davis, ChemPhysChem 2004, 5, 304 – 313.
13] S. Yang, A. Navrotsky, D. J. Wesolowski, J. A. Pople, Chem.
Mater. 2004, 16, 210 – 219.
[
14] T. M. Davis, T. O. Drews, H. Ramanan, C. He, J. Dong, H.
Schnablegger, M. A. Katsoulakis, E. Kokkoli, A. V. McCormick,
R. L. Penn, M. Tsapatsis, Nat. Mater. 2006, 5, 400 – 408.
15] A. I. Lupulescu, J. D. Rimer, Science 2014, 344, 729 – 732.
16] K. Na, C. Jo, J. Kim, K. Cho, J. Jung, Y. Seo, R. J. Messinger, B. F.
Chmelka, R. Ryoo, Science 2011, 333, 328 – 332.
[
[
[30] C.-H. Cheng, D. F. Shantz, J. Phys. Chem. B 2005, 109, 19116 –
19125.
ˇ
ˇ
[
[
[
[
[
17] C. Jo, R. Ryoo, N. Zilkovꢃ, D. Vitvarovꢃ, J. Cejka, Catal. Sci.
Technol. 2013, 3, 2119 – 2129.
18] L. W. Beck, M. E. Davis, Microporous Mesoporous Mater. 1998,
[31] J. S. Jeong, M. L. Odlyzko, P. Xu, B. Jalan, K. A. Mkhoyan, Phys.
Rev. B 2016, 93, 165140.
22, 107 – 114.
[32] R. Khare, D. Millar, A. Bhan, J. Catal. 2015, 321, 23 – 31.
[33] R. Khare, A. Bhan, J. Catal. 2015, 329, 218 – 228.
[34] S. Svelle, F. Joensen, J. Nerlov, U. Olsbye, K.-P. Lillerud, S.
Kolboe, M. Bjørgen, J. Am. Chem. Soc. 2006, 128, 14770 – 14771.
[35] L. Qi, Y. Wei, L. Xu, Z. Liu, ACS Catal. 2015, 5, 3973 – 3982.
[36] L. Ren, Q. Guo, P. Kumar, M. Orazov, D. Xu, S. M. Alhassan,
K. A. Mkhoyan, M. E. Davis, M. Tsapatsis, Angew. Chem. Int.
Ed. 2015, 54, 10848 – 10851; Angew. Chem. 2015, 127, 10998 –
11001.
19] G. Bonilla, I. Dꢂaz, M. Tsapatsis, H.-K. Jeong, Y. Lee, D. G.
Vlachos, Chem. Mater. 2004, 16, 5697 – 5705.
20] T. O. Drews, M. Tsapatsis, Curr. Opin. Colloid Interface Sci.
2005, 10, 233 – 238.
21] S. H. Keoh, W. Chaikittisilp, K. Muraoka, R. R. Mukti, A.
Shimojima, P. Kumar, M. Tsapatsis, T. Okubo, Chem. Mater.
2016, 28, 8997 – 9007.
[
22] C. Baerlocher, L. B. McCusker, Database of Zeolite Structures:
http://www.iza-structure.org/databases/. Accessed on March
th
2
9 , 2021.
[
23] C. E. A. Kirschhock, R. Ravishankar, L. V. Looveren, P. A.
Jacobs, J. A. Martens, J. Phys. Chem. B 1999, 103, 4972 – 4978.
24] D. D. Kragten, J. M. Fedeyko, K. R. Sawant, J. D. Rimer, D. G.
Vlachos, R. F. Lobo, M. Tsapatsis, J. Phys. Chem. B 2003, 107,
Manuscript received: April 2, 2021
Revised manuscript received: June 11, 2021
Accepted manuscript online: June 29, 2021
[
10006 – 10016.
Version of record online: && &&
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Research Articles
Zeolites
A simple di-quaternary ammonium cation
was used as structure-directing agent to
prepare few-unit-cell (ca. 10 nm) MFI
type zeolite catalysts and adsorbents with
a wide range of composition (pure silica,
aluminosilicate and stannosilicate). The
SDA design was selected based on simple
heuristic arguments regarding con-
tributions of its structural elements to
early crystal growth characteristics of
MFI.
P. Lu, S. Ghosh, M. Dorneles de Mello,
H. S. Kamaluddin, X. Li, G. Kumar,
X. Duan, M. Abeykoon, J. A. Boscoboinik,
L. Qi, H. Dai, T. Luo, S. Al-Thabaiti,
K. Narasimharao, Z. Khan, J. D. Rimer,
A. T. Bell, P. Dauenhauer, K. A. Mkhoyan,
M. Tsapatsis*
&&&& — &&&&
Few-Unit-Cell MFI Zeolite Synthesized
using a Simple Di-quaternary Ammonium
Structure-Directing Agent
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