Crystal Growth & Design
Article
(
99.8%), hydrogen peroxide (30%), nonane (99%), p-cresol (99%),
maintained at 77 K after degassing at 150 °C for 12 h. Total specific
surface areas were calculated by the BET method. X-ray photo-
electron spectra (XPS) were obtained using a Kratos Axis Ultra X-ray
Photoelectron spectrometer with monochromatic Al Kα (1486.6 eV)
radiation at 150 W (15 kV, 10 mA). The binding energies were
calibrated by the C 1 s peak of adventitious carbon at 284.8 eV as a
reference. Ammonia-temperature programmed desorption (NH3-
TPD) data were collected using Belcat (Microtrac MRB) combined
with Belmass (Microtrac MRB). The samples were pretreated with Ar
o-cresol (99%), benzoic acid (99.5%), benzyl alcohol (99.8%), and
acetonitrile (99.8%) were purchased from Sigma-Aldrich without
further purification. AR grade methanol, ethanol, and 2-propanol were
purchased from Merck.
Synthetic Method. Modulating the HKUST-1 with Aluminium
Nitrate. HKUST-1 was synthesized by the solvothermal process,
34
which is similar to previous work with some modifications. About
.252 g of (1.2 mmol) H BTC was dissolved in 8 mL of a 1:1 mixture
0
3
of DMF and ethanol (solution A). In addition, 0.435 g of Cu (NO ) ·
3
for 30 min at 150 °C and then absorbed anhydrous NH at 100 °C for
3
2
3
H O (1.8 mmol) and 0, 0.12 and 0.24 mmol of Al (NO ) ·9H O
30 min. After being flushed with Ar for 60 min in order to remove
2
3
3
2
were dissolved in 4 mL of water (solution B). Then, solution A was
added dropwise into solution B in 5 min, and the as-obtained mixtures
were stirred for 15 min before transferring into Teflon-lined stainless-
steel autoclaves. After the hydrothermal reaction at 100 °C for 90
min, the autoclaves were cooled down at room temperature. The as-
prepared blue crystals were washed with methanol 6 times. Ultrasonic
was utilized for 2 h during each washing procedure. Finally, the
supernatant became clear, and the blue products were dried in a
vacuum oven at 60 °C for 8 h.
physisorbed NH , saturated samples were heated at 5 °C/min from
3
100 to 500 °C.
Catalytic Test. The catalyst performance of HKUST-1 on the
oxidation of toluene was studied in acetonitrile solution. In a typical
reaction, toluene (1.32 g), 30% hydrogen peroxide (3.18 g), and 13.5
mL of acetonitrile together with 60 mg of catalyst were placed in a
three-necked flask equipped with a thermometer and an S-shaped
condenser tube. The reaction mixture was purged with nitrogen and
heated at 60 °C for 4 h. The products were analyzed using GCMS-
6890 N (Agilent) equipped with an HP-5MS column (30 m × 250
μm × 0.25 μm).
Modulating HKUST-1 with CTAB. To compare the organic additive
effect on the formation of MOF, CTAB was used as a modulator to
19
change the morphology of HKUST-1 according to the literature.
CTAB (0, 0.364, and 1.82 g) was dissolved in 50 mL of the 1:1(v/v)
RESULTS AND DISCUSSION
■
mixture of deionized water and ethanol to get solution A. H BTC (2.1
3
Controlled Synthesis of HKUST-1 with Al3+ as the
Inorganic Modulator. The inorganic modulation strategy is
illustrated in Figure 1a using HKUST-1 as a representative.
The copper precursors and BTC ligands were mixed for the
nucleation of heterogeneous octahedral particles. After crystal
growth, uniform octahedral HKUST-1 (named as HKUST-1-
g, 0.01 mol) was dissolved in triethylamine (10 mL, 30 wt % in water)
to get solution B. Then, 6 mL of 0.1 M Cu (NO ) and 4 mL of
3
2
solution B were added into solution A successively under vigorous
stirring for 5 min. The resulting blue powder was isolated by
centrifugation, washed with ethanol 6 times, and dried in a vacuum
oven at 60 °C for 8 h.
Modulating MOF-14 with Aluminium Nitrate. The synthesis
3+
O) is obtained in the absence of Al because ν (111) is much
35,36
procedure of MOF-14 was slightly modified from the literature.
Cu(NO ) ·3H O (67.6 mg) and different amounts of Al(NO ) ·
3+
slower than ν (100). When the Al is involved in the
3
2
2
3 3
solvothermal process, the growth rate along the {100} facet
of HKUST-1 is restrained (ν (111) ≈ ν (100)), leading to the
formation of tetrakaidecahedral HKUST-1 (HKUST-1-T).
9
H O (0 and 2 mg) were dissolved in a solvent mixture of ethanol (3
2
mL) and water (2 mL) in a glass vial. Subsequently, 3 mL of DMF
solution of 22.8 mg of H BTB and 6.2 mg of pyrazine were added into
3
3
+
the vial. The mixture was stirred for 30 min at room temperature and
then heated in stainless steel autoclaves at 65 °C for 24 h. After
washing with methanol 3 times, the products were dried at 60 °C for
With further increasing the Al , the growth rate along the
{100} facet was limited profoundly (ν (111) > > ν (100)).
Thereby, the cubic HKSUT-1 (HKUST-1-C) was obtained.
As shown in Figure 1b−d, by increasing the aluminium
nitrate amount, the shape of the resultant HKUST-1 changes
from octahedron (no aluminium nitrate) with eight exposed
8
h in a vacuum oven.
Modulating Cu-MOF-74 with Aluminium Nitrate. For Cu-MOF-
4, typically, a solid mixture of H dhtp (0.1486 g), Cu (NO ) ·3H O
7
(
2
3
2
2
0.3624 g), and Al (NO ) ·9H O (0 and 56.3 mg) was dissolved in a
3 3 2
3+
2+
{
111} facets to tetrakaidecahedron (Al /Cu = 1/15) with
mixture of DMF (14 mL) and 2-propanol (1 mL). The resulting
slurries were then transferred to stainless steel autoclaves. After being
heated at 85 °C for 18 h, brown crystals were collected and then
washed with methanol 3 times. The as-obtained crystals were dried
under vacuum at 60 °C for 8 h.
Time-dependent experiments were conducted under the same
synthesis condition of HKUST-1. After heating for a certain time, the
autoclave was cooled down with flowing water for 5 min, and then,
ultra-high-speed centrifuge was utilized to separate the crystal
products and solution. The supernatant was collected for the ICP
test. The solid products were washed with methanol 3 times and
collected by centrifugation.
3
+
both {111} facets and {100} facets and then to the cube (Al /
2
+
Cu = 2/15) with six fully exposed {100} facets. Figure 1e
shows the comparison of the XRD patterns of all HKUST-1
samples. The sharp and strong identical diffraction peaks of the
three morphologies of HKUST-1 are well-indexed compared
with the pattern of simulated HKUST-1, indicating the high
crystallinity of the produced HKUST-1. In addition, the
relative intensity of the (200) lattice to that of the (222) lattice
3+
increases significantly with the addition of Al , which indicates
3
+
the exposure of {100} facets with the addition of Al . Figure
S1 shows a localized scan of as-obtained HKUST-1. There is
no Al signal observed at 1.486 keV, indicating that no
aluminium was incorporated into the HKUST-1 crystals. ICP-
OES was also conducted to investigate the elemental
S1, only a trace amount of Al was residual in final products.
Consequently, high crystallinity and purity of HKUST-1
samples with different exposed facets were synthesized
Characterization. The X-ray diffraction (XRD) spectra were
recorded on a Bruker Advanced X-ray diffractometer (40 kV, 30 mA)
under Cu Kα radiation (λ = 0.15406 nm) with a scanning rate of 1
°/min. Scanning electron microscope images were obtained using a
JEOL JSM-7001F scanning electron microscope with X-ray energy-
dispersive analysis spectroscopy. Thermogravimetric (TGA) analysis
was conducted using a Perkin Elmer Instruments STA 6000 Thermo
Gravimetric Analyser with a heating rate of 5 °C from 30 to 800 °C
under N . The FTIR spectra were collected using the PerkinElmer
2
3+
successfully by simply varying the Al concentration under
controlled solvothermal duration.
STA 6000 equipment. ICP-OES analysis was carried out using a
Perkin Elmer Optima 8300 DV. Gas sorption isotherms were carried
out using a Micromeritics TriStar II 3020. Raman spectra were
recorded on a Renishaw Raman microscope and spectrometer (514
Thermal stability and BET surface area were investigated to
3
+
study the impact of Al on the HKUST-1. As shown in Figure
1f, the BET surface areas of the HKUST-1-O, HKUST-1-T,
nm laser and 1% output power). The N sorption measurement was
2
9
28
Cryst. Growth Des. 2021, 21, 926−934
Wang, Zhanke
