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Supporting material
A Facile Synthesis of UiO-66 Systems and their Hydrothermal Stability
Hirofumi Motegi, Kazuhisa Yano*, Norihiko Setoyama, Yoriko Matsuoka, Tetsushi
Ohmura, Arimitsu Usuki
1. Materials
2. Characterizations
3. Detailed synthesis and a large scale synthesis
4. SEM images of MOF particles
5. PXRD analysis of as-synthesized UiO-66 and MOF801 for hydrothermal tests.
6. Large-scale synthesis
7. Elemental analysis for MOF801 and UiO-66
8. Thermal Desorption-Gas Chromatograph/Mass Spectroscopy (TD-GC/MS) analysis
9. Pore activation by different solvent system for MOF801
1. Materials.
N,N-dimethylformamide (99.5%), acetone (99.0%), methanol (99.8%), formic acid
(98.0%), Zirconyl chloride octahydrate (99.0%), terephthalic acid (98.0%) and fumaric acid
(99.0%) were purchased from Wako pure chemical industries, ltd. All of the chemicals were
used without purification.
2. Characterizations
2.1. Powder X-ray diffraction (PXRD)
Each synthesized crystalline sample was measured by using Cu-Kα radiation
(Rigaku ULTIMA-IV, 40 kV, 40 mA).
2.2. Temperature-resolved PXRD
Each synthesized crystalline sample was measured by using Cu-Kα radiation
(Bruker AXS, D8 ADVANCE, 35 kV, 40 mA). Each sample was heated by 10 oC per minute
in order to reach the desired temperatures, which are 100 oC, 200 oC, 250 oC, 300 oC, 350
oC,
400 oC and 450 oC. When temperature was reached at each point, the temperature was
kept for 30 minutes prior to PXRD analysis.
2.3. Scanning electron microscopy
Scanning electron microscopy (SEM) images were recorded by using Hitachi
S-5500 microscope operated at an acceleration voltage of 1.0 kV. The crystalline samples
were coated with Pt or Os prior to the analysis.
2.4. Surface area analysis
Nitrogen adsorption and desorption isotherms were measured using a
Quantachrome autosorb MP-1.
2.5. Elemental Analysis
A bulk crystalline sample was analyzed with Perkin-Elmer PE2400 II for C, H and N
for as-synthesized UiO-66 and MOF801. In addition, the percentage of chloride anion for the
methanol exchanged UiO-66 was analyzed with Exeter Analytical CE-440 Elemental
Analyzer with ion chromatography.
2.6. Thermogravimetric(TG) analysis
Each crystalline sample was measured with a Rigaku thermoplus TG8210. About 3
to 10.0 mg sample was placed in a platinum sample pan. The TG profile of the sample was
obtained by heating from ambient temperature to 800 oC with heating rate 10 oC/min under
flow of air.
2.7. Hydrothermal stability
Hydrothermal stability tests were performed in a scintillation vial. About 150 mg of
crystalline solids were immersed in 10 mL of water and it was heated in an oven at 80 oC.
3. Detailed synthesis and a large scale synthesis
All of the reaction was performed in a round-bottom flask equipped with a reflux
condenser under nitrogen atmosphere. The system was heated with an aluminum block
reactor under a vigorous stirring condition. In our method, the nucleation starts within three
to five minutes after heating and the total reaction time is usually about two hours. The
filtration was performed while it was hot and washed with DMF followed by acetone.
3.1. Synthesis of UiO-66
ZrOCl2·8H2O (1.6 g, 5.0 mmol) and terephthalic acid (0.80 g, 4.8 mmol) were
dissolved in 30 mL of DMF at room temperature under stirring condition. Formic acid (15.0
mL, 397.5 mmol) was added and heated at 140 oC for 2 hours under vigorous stirring
condition. The white crystalline powder was filtered after cooling to room temperature and
washed with 20 mL of DMF once and 50 mL of acetone. Then, the collected solids were
dried under vacuum for overnight. (Yield: 1.61 g; containing possible lattice solvents and
unreacted ligands)
Figure S1. (i) PXRD patterns of UiO-66 (a) simulated and (b) as-synthesized, (ii) TG profile
of UiO-66 for as-synthesized and methanol-treated crystalline sample.
3.2. Synthesis of MOF801
ZrOCl2·8H2O (1.6 g, 5.0 mmol) and fumaric acid (0.60 g, 5.2 mmol) were dissolved
in 20 mL of DMF at room temperature under stirring condition. Formic acid (7.0 mL, 185.5
mmol) was added and heated at 140 oC for 2 hours under vigorous stirring condition. The
white crystalline powder was filtered after cooling to room temperature and washed with 20
mL of DMF once and 50 mL of acetone. Then, the collected solids were dried under vacuum
for overnight. (Yield: 1.46 g; containing possible lattice solvents and unreacted ligands)
3.2.1. Synthesis of MOF801 with defects; a possible inclusion of formate anion.
When we added 10 mL (265.0 mmol) of formic acid rather than 7.0 mL (185.5
mmol) for the reaction system, the PXRD pattern was slightly different than the reported
PXRD patterns and the synthetic condition we performed in 3.2 (Figure S2). We did not
investigate further synthetic conditions in terms of concentration of formic acid and DMF at
this time.
Figure S2. (i) PXRD patterns of MOF801 (a) simulated, (b) DMF:HCOOH=20:7 and (c)
DMF:HCOOH=20:10, (ii) TG profiles of MOF801 for as-synthesized and water-treated
crystalline sample.
As-synthesized UiO-66 particles were refluxed in MeOH for 6 hours, whereas
MOF-801 particles were refluxed in water for 2 hours. We evaluated our results of TG
profiles before and after the post-treatment in order to investigate residual solvents. It is
difficult to tell whether DMF molecules were fully exchanged with methanol for UiO-66
system (Figure S1 (ii)) and MOF801 (Figure S2 (ii)). Thus, we have performed TD-GC/MS to
inspect residual DMF or other possible unreacted starting molecules (Figure S15 and S16).
3.3 Temperature-resolved PXRD
Figure S3. Temperature-resolved Powder X-ray diffraction: PXRD patterns for UiO-66 (a)
as-synthesized and (b) methanol treated and for MOF801 (c) as-synthesized and (d) water
treated.
Temperature-resolved Powder X-ray diffraction (TR-PXRD) was used to confirm
the crystallinity and thermal stability of UiO-66 and MOF801 (Figure S3). In a case of
as-synthesized UiO-66, PXRD patterns were maintained up to 300 oC. Then, between 300
and 350 oC, the peak intensity was dramatically decreased and thus this is an indication of
structural decomposition. In a case of as-synthesized MOF801, PXRD patterns were
maintained up to 250 oC. Then, between 250 and 300
oC,
the peak intensity was
dramatically decreased and thus this is an indication of structural decomposition.
4. SEM images of MOF particles
Figure S4. SEM images of as-synthesized (a) UiO-66 and (b) MOF801, after hydrothermal
test for 14 days(c) UiO-66 and (d) MOF801.
Each crystalline particle was observed as relatively uniform-shape and size by this
synthetic method. In a case of MOF801, the particle size was about one third smaller than
that of UiO-66. These 100-300nm size particles of MOF801 were highly crystalline and
showed excellent hydrothermal stability as shown in Figure 4 and S4.
5. Large-scale synthesis
5.1. A 1.0L(100 gram)-scale synthesis of UiO-66
ZrOCl2·8H2O (85.0 g, 264mmol) and terephthalic acid (41.5 g, 250 mmol) were dissolved in
1.0 L of DMF at room temperature under stirring condition. Formic acid (0.50 L, 13.25 mol)
was added and heated at 150 oC for 4 hours under vigorous stirring condition. The white
crystalline powder was filtered while it was hot and washed with 100 mL of DMF once and
100 mL of acetone. Then, the collected solids were dried at 45 oC for overnight under air.
Figure S7. PXRD patterns of UiO-66-1.0L(100 gram)-scale synthesis.
Figure S8. A TG profile of UiO-66-1.0L(100 gram)-scale synthesis.
Figure S9. A SEM image of UiO-66-1.0L(100 gram)-scale synthesis.
Figure S10. N2 isotherm for the 1.0L(100 gram)-scale synthesis of UiO-66.
For the 100 gram scale synthesis of UiO-66, the quality of crystallinity was lower
than that of two-gram scale synthesis. In the SEM investigation, the bulk crystalline solids
were observed as a range of 500 nm size or smaller and we could not identify octahedral
crystalline solids in the same magnification as two-gram synthesis. Secondary particles
were constructed and N2 sorption resulted to show macroporous behavior.
5.2. A 1.0L(100 gram)-scale synthesis of MOF801
ZrOCl2·8H2O (80 g, 248mmol) and fumaric acid (30 g, 259 mmol) were dissolved in
1.0 L of DMF at room temperature under stirring condition. Formic acid (0.35 L, 9.275 mol)
was added and heated at 140 oC for 4 hours under vigorous stirring condition. The white
crystalline powder was filtered while it was hot and washed with 50 mL of DMF once and
100 mL of acetone. Then, the collected solids were dried at 45 oC for overnight under air.
Figure S11. PXRD patterns of 1.0L(100 gram)-scale synthesis of MOF801
PXRD patterns were recorded at each time interval during hydrothermal tests for a
bulk sample of 1.0L-scale synthesis of MOF801. The crystallinity of as-synthesized
1.0L-scale MOF801 was maintained after 14 days. Thus, the large scale synthesis of
MOF801 was successfully shown its hydrothermal stability. The intensity of PXRD was
slightly lower than that of the as-synthesized sample. This could be due to the insufficient
amount of sample for PXRD analysis.
Figure S12. TG profiles of MOF801-1.0L(100 gram)-scale synthesis
Figure S13. A SEM image of 1.0L(100 gram)-scale synthesis for MOF801.
The morphology of bulk material was revealed by SEM. The bulk material was
revealed to be particle aggregation with some degree of fine reflection and shapes of
octahedron. The morphology of 1.0L scale synthesis was different than the smaller scale
synthesis, especially the size of particle was about forty times larger than that of gram-scale
synthesis (Figure S3). This could be due to insufficient stirring during the synthesis. We may
need to perform mechanical stirring method for larger scale synthesis to maintain
homogeneous mixing and heat transfer in the reaction system
.
Figure S14. N2 isotherm for the 1.0L(100 gram)-scale synthesis of MOF801.
The BET surface areas were observed as 838 m2/g for 0h, 789 m2/g for 4 days and
784 m2/g for 14 days after hydrothermal test. This result of hydrothermal test was slightly
different than that of the smaller scale synthesis(Figure 4). We hypothesized that hot
filtration may have caused higher surface area to start for as-synthesized 1.0L-scale batch.
The unreacted ligand and solvent molecules could have removed by this filtration method.
Also, there is a hysteresis between 0.4-0.6 on P/P0 axis after hydrothermal tests. This could
be a potential cracks on bulk particles. The overall surface area after hydrothermal test
showed a similar trend as the small scale.
6. Elemental analysis for UiO-66 and MOF801
Table S2 a crystalline sample of UiO-66 after methanol treatment
C(%)
H(%)
N(%)
Cl(%)
Observed (before)
29.94
1.79
0.72
0.143
Observed (after)
27.99
1.72
0.39
0.166
Calculated*
29.78
1.74
0.73
0.138
Table S3 crystalline sample of MOF801 after water treatment
C(%)
H(%)
N(%)
Observed
17.05
1.47
-0.11
Calculated**
19.13
0.80
0.00
Each crystalline sample was thermally treated equipped with vacuum line at 150 oC
for 3 hours prior to the analysis. This treatment could remove lattice DMF, H 2O or methanol
molecules in order to get a precise CHN values. However, those activated UiO-66 and
MOF801 may contain residual solvent or unreacted reagent molecules because TG profiles
cannot tell if the crystalline sample can be fully activated by a simple thermal treatment
under vacuum. Thus, it is very difficult to determine molecular formula based on elemental
analysis. Thus, in section 8, we have analyzed TD-GC/MS for a better understanding of
chemical composition of each crystalline particle.