Syntheses of Exceptionally Stable Aluminum(III) Metal–Organic Frameworks: How to Grow High-Quality, Large, Single Crystals

Article abstract of DOI:10.1002/chem.201703682

The difficulty of obtaining large single crystals of aluminum carboxylate metal–organic frameworks (MOFs) for structure determinations has limited the development of these water and thermally stable MOFs. Herein, how large single crystals of known MIL-53(Al) and the first two tetrahedral ligand-based, visible-light-absorbing 3D Al-MOFs, [Al₃(OH)₃(HTCS)₂] (AlTCS-1) and [Al₅O₂(OH)₃(TCS)₂(H₂O)₂] (AlTCS-2; TCS=tetrakis(4-oxycarbonylphenyl)silane), are obtained in the presence of hydrofluoric or formic acid for conventional single-crystal diffraction measurements is presented. The technique of obtaining those single crystals has potential to be a general method for obtaining large and good-quality single crystals of Al-MOFs. AlTCS-1 and -2 are stable over a wide pH range (1–11), and AlTCS-1 is even stable in aqua regia solution for at least 24 h. The BET specific surface areas of AlTCS-1 and -2 are 11 and 1506 m² g^?1, respectively. AlTCS-2 takes up 51 cm³ (STP) g^?1 CO₂ and 15 cm³ (STP) g^?1 CH₄ at 298 K and 1 bar, which is relatively high among MOF materials. AlTCS-1 takes up 30 cm³ g^?1 CO₂ and 4.2 cm³ g^?1 CH₄ at 298 K and 1 bar. The rapid and stable photocurrent responses of AlTCS-1 and -2 under UV and visible-light illumination are observed. Moreover, AlTCS-1 photocatalyzes the water-splitting reaction under visible light with an average hydrogen evolution efficiency of 50 μmol g^?1 h^?1 for the first 10 h in a mixture of water and triethanolamine.

Full text of DOI:10.1002/chem.201703682

A Journal of
Accepted Article
Title: Syntheses of Exceptionally Stable Al(III) Metal-Organic
Frameworks: How to Grow High Quality Large Single Crystals?
Authors: Ya-Qian Lan, Yuanyuan Guo, Jun Zhang, Longzhang Dong,
Yan Xu, Wei Han, Min Fang, Hong-Ke Liu, and Yong Wu
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To be cited as: Chem. Eur. J. 10.1002/chem.201703682
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Syntheses of Exceptionally Stable Al(III) Metal-Organic
Frameworks: How to Grow High Quality Large Single Crystals?
Yuanyuan Guo,†[a] Jun Zhang,†[b] Long-Zhang Dong, Yan Xu, Wei Han, Min Fang,*
[a]
[c]
[a]
[a][d]
Hong-Ke
Liu,[a][d] Yong Wu* , Ya-Qian Lan*[a]
[a]
Abstract: The difficulty of obtaining large single crystals of aluminum carboxylate MOFs (Al-MOFs) for structure determinations has limited
the development of these water and thermally stable MOFs. In this work, how large single crystals of the known MIL-53(Al) and the first two
3 3 2 5 2 3 2 2 2
tetrahedral ligand based, visible light absorbing 3D Al-MOFs, [Al (OH) (HTCS) ] (AlTCS-1) and [Al O (OH) (TCS) (H O) ] (AlTCS-2) (TCS =
tetrakis(4-oxycarbonylphenyl) silane) are obtained in the presence of hydrofluoric or formic acid for conventional single-crystal diffraction
measurements is presented, demonstrating a general method of obtaining large and good quality single crystals of Al-MOFs. AlTCS-1 and -2
can be stable in a wide pH range (1-11), and AlTCS-1 can even be stable in aqua regia solution for at least 24 h. The BET specific surface
2
-1
3
3
area of AlTCS-1 and -2 are 11 and 1506 m g ，respectively. AlTCS-2 uptakes 51 cm (STP)/g CO
2
and 15 cm (STP)/g CH
4
at 298
at 298 K and 1 bar.
The rapid and stable photocurrent responses of AlTCS-1 and -2 under UV and visible light illuminations are observed. Moreover, AlTCS-1
3
-1
3
-1
2 4
K and 1 bar, which is relatively high among MOF materials. AlTCS-1 uptakes 30 cm g CO and 4.2 cm g CH
-
1
-1
photocatalyzes the water-splitting reaction under visible light with an average hydrogen evolution efficiency of 50 mol·g ·h for the first 10 h
in a mixed solvent of water and triethanolamine.
Introduction
to obtain single crystals of Al-MOFs for common XRD structure
determination. In addition, no tetrahedral shape carboxylic acid
ligand has been applied in the syntheses of Al-MOFs.
Visible light is the major component (43%) of the inexhaustible
and clean solar energy. Metal-organic frameworks (MOFs) can
be synthesized as visible light photocatalysts due to their
designability.[1] However, relatively low water and thermal
stabilities of most MOFs could be the key limitations for their
practical applications.[2] Al-MOFs show exceptionally water and
thermal stability. They are relatively light due to the low atomic
number of Al. Although not many of Al-MOFs are reported, they
have become of interest for industrial uses.[3] To the best of our
knowledge, only two MOFs have been promoted to the level of
commercial applications. A dense zinc glutarate[4] is currently
used as an epoxide-polymerization catalyst, while the
microporous aluminum fumarate A520 is employed as a sorbent
to store and deliver natural gas for automotive applications.[3, 5]
Up to now, the total number of structures of Al-MOFs is only 42
Loiseau et al. first applied HF aqueous solution to synthesize
single crystals of an Al-MOF (MIL-96) in 2006.[ They also
6]
utilized tetraethylortho silicate (Si(OC
2
H
5
)
4
, TEOS) and trimethyl
1,3,5-benzenetricarboxylate (C (CO
6
H
3
2
CH ), an ester ligand
3 3
)
instead of the acid ligand to facilitate the formation of Al-MOFs.
Since then, no single crystals of Al-MOFs were reported by
adding HF acid. The method of adding HF aqueous solution to
growth large crystals has been applied in related fields. For
example, large single crystals of AlPO
was synthesised by adding HF aqueous solution. Guo et al.
4
-34, a molecular sieve,
[7]
reported that the irregular particles of UiO-66,
a Zr(IV)
carboxylate MOF changed into regular shaped particles and the
sizes increased from 0.2-0.5 to 5-10 m through adding HF
acid.[ Simple organic acids were also applied in synthesizing
MOF single crystals, especially in the syntheses of Zr-MOFs.[9]
Despite of all the above progresses, obtaining large single
crystals of an Al-MOF is still a difficult task.
8]
(
Table S1 and Table S2 in Supporting Information (SI)), among
which only 16 structures are based on single crystal XRD
diffraction analyses (Table S2). Due to the small sizes, 9 of the
1
6
single crystal XRD diffractions were performed using
In this paper, single crystals of the known MIL-53(Al)
(previously obtained as powders), and two novel Al-MOF
synchrotron radiations, which are not readily accessible to
researchers. Therefore, it is necessary to find a general method
crystals,
Al (OH)
Al
3
(OH)
3
(HTCS)
2
(
AlTCS-1
)
and
[
5
O
2
3
(TCS)
2
(H O)
2
2
]
(
AlTCS-2), big enough for
conventional single-crystal diffraction measurements are
obtained by adding HF aqueous solution or formic acid,
demonstrating a general method for obtaining high quality
large single crystals of Al-MOFs. The syntheses,
structures, chemical and thermal stabilities, gas
adsorptions, photocatalytic water splitting, photoelectric
properties of AlTCS-1 and -2 are reported. Although
[
a]
YuanyuanGuo, Longzhang Dong, Dr. Wei Han, Prof. Min Fang, Prof.
Ya-Qian Lan, Prof. Hong-Ke Liu, Dr. Yong Wu
Department of Chemistry
Nanjing Normal University, Nanjing 210023, China
Email:fangmin@njnu.edu.cn, wuyong@njnu.edu.cn,
yqlan@njnu.edu.cn
[b]
[c]
[d]
[†]
Dr. Jun Zhang
Anhui Key Laboratory of Advanced Building Materials
Anhui Jianzhu University, Hefei, Anhui 230022, China.
Prof. Yan Xu
State Key Laboratory of Materials-Oriented Chemical Engineering
Nanjing Tech University, Nanjing 210009, China
Prof. Min Fang, Prof. Hong-Ke Liu
State Key Laboratory of Coordination Chemistry
Nanjing University, Nanjing 210093, China
These authors contribute equally to this paper.
Supporting information for this article is given via a link at the end of
the document.CCDC 1523998 (AlTCS-1),1523999 (MIL-53(Al single
crystal), and 1551336 (AlTCS-2).
4
H TCS ligand absorbs only UV light, AlTCS-1 and -2
absorbs visible light, and AlTCS-1 absorbs more visible
light than AlTCS-2. Their band gaps, and CB- and VB-edge
positions were determined using UV-Vis reflectance
spectra and an electrochemical method. AlTCS-1
photocatalyzes the water splitting with a hydrogen evolution
-1 -1
efficiency of 50
mol·g ·h for the first 10 h in a mixed
solvent of water and triethanolamine (4:1 volume ratio).
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Results and Discussion
Table 1. The effect of the amounts of reactants on the syntheses of AlTCS-1
using the 9 experiments designed using the L (3 ) orthogonal array.
9
4
[a]
Syntheses of the large single crystals of MIL-53(Al) and
No.
The molar ratio of
Al(NO ·9H O:
TCS: HF : H
Product (size in mm)
[
Al
3 3 2
(OH) (HTCS) ] (AlTCS-1)
)
3 3
2
H
4
2
O
In order to obtain single crystals of new Al(III) carboxylate
1
2
3
4
5
1 : 1 : 0 :2850
1 : 1: 1.1 :4270
1 : 1: 2.1 : 5700
2 : 1:0: 4270
Powder
MOFs, we first tried to obtain the single crystal of a known Al-
Small block crystals of AlTCS-1
Long needles (Figure S6(a))
Powder
.
MOF, MIL-53(Al). A common Al(NO
3
)
3
9H
2
O : H
2
BDC : H
2
O
molar ratio for the synthesis of MIL-53(Al) powder is 2.0 : 1 :
78.[6] By simply adding HF aqueous solution to the above
mixture (Table S7), the particles of MIL-53(Al) increases (Figure
1
2: 1 :1.1 : 5700
Large block crystals of AlTCS-1
(
0.17 x 0.040 x0.030) (Figure 1(d))
Large block crystals of AlTCS-1
0.20 x 0.040 x0.020)
6
2 :1 : 2.1: 2850
1
0
(a)-(b)), and eventually large block single crystals of 0.25 ×
.14 × 0.07 mm (Figure 1(c)) obtained using a HF: H TCS molar
(
4
7
8
3 : 1 : 0 : 5700
3 : 1 : 1.1: 2850
Powder
ratio of 4.4. The single-crystal structure was determined using
the common single-crystal XRD diffraction analysis and
Large block crystals of AlTCS-1
(0.10 x 0.050 x0.050) (Figure S5(c))
9
3 : 1 : 2.1: 4270
Needles + AlTCS-1 block crystals
consistent with that determined based on the PXRD data (Table
S3, Figure S3 and S4).[4] In 2015, Seoane et al. obtained MIL-
[a] The amount of H
4
TCS (40 mg, 0.078 mmol) was kept being constant
and the other synthetic procedures and conditions were as the same as
the typical synthesis of AlTCS-1
5
3(Al) single crystals of the size of 0.8 x 0.9 x 0.4 m,[10] which is
.
not big enough for the structure determination using a common
single-crystal XRD diffractometer.
in Table 1. Large block-shape single crystals of a new phase
were obtained in three experiments (No. 5, 6 and 8). One of the
crystal was structurally determined by the single-crystal X-Ray
3 3 2
diffraction analysis as [Al (OH) (HTCS) ] (denoted as AlTCS-1).
The above results demonstrate the efficiency of the orthogonal
experimental design method. Just by 9 experiments, pure and
large single crystals of AlTCS-1 were harvested and the crystal
structure was obtained using a common single-crystal XRD
diffractometer. This systematic analysis tool is widely used in
biochemistry and various fields of chemistry,[ however few
reports were published in the field of coordination networks. By
applying formic acid instead of HF aqueous solution, we also
successfully obtained large single crystals of AlTCS-1 using 10
12]
mg (0.020 mmol) H
ratio of Al3+ : H
TCS : HCOOH : H
Table S8, Figure S6 and S7).
4
TCS in each preparation (the overall molar
4
2
O = 3.9-6.5 : 1 : 680 : 17000)
(
Syntheses of the high quality large single crystals of
Al (OH) (TCS) (H O) ] (AlTCS-2)
AlTCS-1 has a low porosity 16.8% due to the pore filling
[
5
O
2
3
2
2
2
effect of the -COOH containing arm of each ligand. In the
following endeavors, we successfully obtained a novel Al-
carboxylate MOF based on the completely deprotonated TCS4-
Figure 1. Morphologies of large single crystals of MIL-53(Al) (c) and AlTCS-
5 2 3 2 2 2
ligand, [Al O (OH) (TCS) (H O) ], which is denoted as AlTCS-2.
1
(d). The SEM images of products prepared using the same procedure of the
Selected experiments and results are given in Table 2, the
corresponding PXRD results and pictures of the selected
crystals given in Figure 2 and Figure 3. In the beginning, we
obtained the powder phase of AlTCS-2 (No. 1 in Table 2). We
thought it was a potential target of a new Al-MOF since its PXRD
pattern has a peak at low 2 angle, 6.02° (No. 1 in Figure 2),
which is smaller than the first PXRD peak of AlTCS-1 (6.63°),
suggesting it might have bigger pores than those in AlTCS-1.
Subsequently, in a more concentrated solution and with a slower
heating and cooling rate of the oven, powders of higher
crystallinity (No. 2 in Figure 2) were obtained as indicated by the
intensity increase of the peak at 6.02° (from 1500 to 4500).
Based on No. 2, by increasing the acidity of the system, using a
more dilute reactant mixture and a faster cooling rate, rhombic
crystals were obtained (No. 5-6 in Table 2), however the
crystallinity is low (Figure 2). Raising the temperature from 120
to 130C, we obtained perfect looking, large rhombic crystals
synthesis of the MIL-53(Al) single crystal but using different HF : H
ratio (0.39 for (a), 2.3 for (b)) are also given for comparison.
4
TCS molar
To synthesize single crystals of a new Al(III)-MOF based on
4
the H
was applied.[11] The
experiments considering 4 influencing factors and three different
conditions for each factor. The factors we considered are the
4
TCS ligand, the L
9
(3 ) orthogonal array design approach
9
L 9 representative
(34) array gives
.
molar ratio of Al(NO
molar ratio of HF to H
.0 and 8.0 mL) and the fourth factor was kept as the same (e.g.
3
)
3
9H
2
O to H
4
TCS (1:1, 1:2 and 1:3), the
4
TCS (0, 1.1, 2.1), amounts of water (4.0,
6
reaction time). The expriments designed by this method are
given in Table 1. Other synthetic procedures are the same as
that of the synthesis of the MIL-53(Al) single crystal except that
the heating and cooling rates of the oven temperature were
slowed down and controlled. The experimental results are listed
(
0.15 x 0.10 x 0.030 mm, No. 8 in Figure 3). Its PXRD diffraction
intensity of the peak at 6.02° is high, but the peaks are broad,
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Table 2. Syntheses of single crystals of AlTCS-2.[a]
No.
The molar ratio of
Products (size in mm)
3
+
4 2
Al :H TCS:HCOOH:DMF:H
O[b]
1[d]
2[c]
3
4.0 (293 mg) :1.0 (10) : 680 (0.50) : 2660 (4.0) : 0
6.0(351) : 1.0(30) : 226 (0.5) : 443 (2) : 0
AlTCS-2, powder
AlTCS-2, powder
6.0 (234) : 1.0(20): 374 (0.55) : 670 (2): 0
5.8 (227): 1.0(20): 340(0.5): 670 (2): 0
Phase C, glassy particles
4
Phase C, rhombic crystals, (0.040x0.030x0.010) (Figure S8)
AlTCS-2, rhombic single crystals
5 [c]
6
6.0 (234): 1.0(20): 340 (0.5) : 670 (2) : 0
6.0 (117): 1.0(10): 680 (0.5): 1990 (3) : 0
AlTCS-2, rhombic single crystals (0.14 x0.10x0.040)
Phase D, glassy particles
7 [c]
8[e]
9
6.0 (117): 1.0(10): 1090 (0.8) : 1990 (3) : 0
5.8 (227) : 1.0(20): 340 (0.5) : 670(2) : 0
AlTCS-2, rhombic single crystals (0.15 x0.10x0.030)
AlTCS-2, block-like single crystals (0.20x0.10x0.030)
AlTCS-2, block-like single crystals (0.28 x0.12 x0.045)
AlTCS 2, block-like single crystals (0.20x0.10x0.020)
AlTCS-2, block-like single crystals (0.15 x0.08 x0.020)
AlTCS-2, block-like single crystals (0.20x0.10x0.020)
AlTCS-2, block-like single crystals (0.08 x0.030 x0.015)
5.8 (227) : 1.0(20) : 270 (0.4): 500 (1.5) :710 (0.5)
5.8 (227):1.0(20) : 270 (0.4) : 500 (1.5):710(0.5)
5.8(227) : 1.0(20): 310 (0.45) : 500 (1.5):710 (0.5)
5.8 (227) : 1.0(20) : 310 (0.45) : 500 (1.5):710(0.5)
5.8 (227) : 1.0(20): 270 (0.4) : 470 (1.4) :850 (0.6)
5.8 (227): 1.0(20) : 270 (0.4) : 470 (1.4):850 (0.6)
1
1
1
1
1
0[c]
1
2[d]
3
4[d]
[

a] PXRD patterns are given in Figure 2 and pictures of selected products are given in Figure 3; [b] Data in parentheses are the amount of Al(NO
3
)
3
aq.( 1.0 M,
O are 2.0
L)( except for No. 1 in which solid Al(NO .9H O was applied), H TCS (mg), HCOOH (mL), DMF (mL) and H O (mL). The total volume of DMF and H
)
3 3
2
4
2
2
mL except for No. 1 in which 4 ml of DMF was applied; the temperature of the oven was raised from room temperature to 120 °C with a 1.0 °C/min heating ramp,
kept at 120 °C for 3 d, and then cooled to 25 °C with a rate of 10.0 °C/h. [c] Same as [b] except that the cooling rate is 2.0 C/h to 25 C; [d] The autoclave was put
into an oven, and the temperature of the oven increased from 25 to 120 °C naturally, kept at 120 °C for 3 d and then cooled to room temperature naturally; [e]
Reaction temperature is 130 °C, heating ramp and cooling rate are the same as [b].
indicating that there exist disorders in the crystals causing the
broadening of the peaks. Only a few or no single crystal XRD
diffraction points were observed from all rhombic crystals
obtained in DMF. Increasing the acidity of the system and
cooling rate (10 °C/h) resulted in a dense phase (Phase C, No. 3
and 4). This phase can also be obtained as rhombic crystals (No.
4, Figure S8). Even higher acidity resulted in another dense
phase (Phase D, No. 7).
Figure 3. Pictures of the synthesized AlTCS-2 single crystals by the
experiments given in Table 2. The length of the minimum grade in the pictures
is 0.01 mm.
Figure 2. The PXRD patterns of AlTCS-2, phase C and Phase D produced
from experiments given in Table 2, compared with the simulated PXRD
patterns based on the cif file of AlTCS-2 using Mercury software.
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Figure 4. The structures of AlTCS-1 ((a)-(d)) and AlTCS-2 ((e)-(h)). The coordination environments ((a) and (e)), the Al3+ chains ((b) and (f)), the packings along
c axis ((c) and (g), and the topologies ((d) and (h)) are given.
To grow better quality crystals of AlTCS-2, we then changed
the polarity of the solvent by using mixed solvents of DMF and
H O. The total amount of the solvent was kept at 2.0 mL to
2
maintain the concentration. Block-like crystals were obtained in
this system (No. 9-14 in Table 2, Figure 2-3). Contrary to our
expectation, it was found that increasing the cooling rate would
increase the crystallinity of AlTCS-2 (No. 14 versus No. 13; No.
environments of the ligand and metal ions of AlTCS-1 are
shown in Figure 4(a). The carboxylate groups all act as
bidentate ligands, bridging two adjacent Al(III) ions. Six
coordinated Al3 ions (Al1 and Al2) are bridged by carboxylate
+
-
groups and OH groups to form zig-zag planar chains along c
axis as shown in Figure 4(b). 29 out of the total 42 Al-MOF
structures contain 1-D metal oxide chains (Table S1 and Table
S2). However, only MIL-96,[6] 467-MOF[15] contains zig-zag
chains as those in AlTCS-1. The chains are connected by
HTCS3- ligands forming a 3D framework, showing rhombic
channels of 6.4(4.7) x 9.1(7.4) Å[ along c axis (Figure 4(c) and
1
2 versus No. 11). The diffraction intensity of the peak at 6.02°
of the No. 14 product reaches 21000 and the peaks are very
sharp. Only with single crystals of this experiment, we obtained
good diffraction data with a qualified resolution and the single
crystal structure of AlTCS-2 was solved. Data obtained from
other block-like crystals all have poor resolutions (> 1.0). Tsao et
al. also found that high-quality MOFs can be synthesized as the
cooling rate increases.[13] In the synthesis of AlTCS-1, we also
found that faster cooling rate would increase its crystallinity
41]
4
Figure S10). The unprotonated arm of H TCS has filled the
pores of AlTCS-1, making it having a small porosity of 16.8%
(probing radius: 1.2 Å) and the solvent accessible volume/unit
cell: 995.2 Å3 as calculated by the PLATON program.
[16]
The
3
pore volume calculated based on the above data is 0.13 cm /g.
Based on the topology analysis using ToposPro program,[17] the
3D framework of AlTCS-1 can be simplified as a 3-nodal 6,6,6-c
(
Figure S17).
The position of the simulated PXRD pattern of AlTCS-2
3
2
7
3
4 2 2 4 2
based on the crystal structure is consistent with the observed
patterns; however the intensities were different (Figure 2). This
could be due to the crystal for the structure determination was
measured with solvents inside the pores, however the observed
PXRDs were obtained after the samples were dried 60-90 °C for
net (Si
2
4
(Al1)(Al2)
3
2
) with a point symbol of (3 4 5 6 )
2
(3 4 5 6 7 8)
4
4
(3 4 5 6 )
2
as shown in Figure 4(d). To the best of our
knowledge, this is a new topology.
Single-crystal X-ray diffraction analysis reveals that AlTCS-
2 ([Al
5
O
2
(OH)
3
(TCS)
2
(H
2
O)
2
]) is a 3D framework, crystallizes in
1 (Table S4). All carboxylate
1
2 h. The peak intensities of the PXRD pattern of a sample
the trigonal space group P3 2
1
which was soaked in water for three days (Figure 7(b)) are more
consistent with the simulated PXRD pattern based on the crystal
structure. Thus phenomena have been observed by us and
others.[14] Intensity differences between observed patterns are
probably due to the different orientation preferences of prepared
AlTCS-2 since we have prepared them in different shapes.
Some small additional peaks at the low angles are probably due
to small amounts of impurities.
groups act as bidentate ligands, bridging two adjacent Al(III) ions
as in AlTCS-1. Al3 ions (Al1, Al2 and Al3) are all six-coordinated
and bridged by carboxylate groups, O2- (O9), OH (O1H and O10)
+
-
2
and H O (O1w) groups (Figure 4(e)) to form spiral chains along
c axis as shown in Figure 4(f).To our knowledge, this spiral
shape aluminum oxide chain is a new type of substructural
buliding unit (SBU) for Al-MOFs. In contrast, the zig-zag
aluminum oxide chains in AlTCS-1 are planar. Each TCS4-
ligand connects with three Al3+ chains as shown in Figure S11,
Structures of AlTCS-1 and -2
forming a 3D framework, showing elliptical channels of 4.6(3.0) x
.4(7.7)Å[ (channels shown in a and b direction), 7.5(5.9) and
0.4(8.7) x 5.8(4.0) Å[41](channels shown in c direction) (Figure
(g) and Figure S10)). It has a large porosity of 57.4% (probing
41]
9
1
4
The minimum unsymmetrical units of AlTCS-1 and -2 are
given in Figure S9. Single-crystal X-ray diffraction analysis
reveals that AlTCS-1 has a 3D framework, crystallizes in the
monoclinic space group C2/c (Table S3). The coordination
radius: 1.2 Å), and the solvent accessible volume/unit cell is
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4
449 Å3 as calculated by the PLATON program.[16] The pore
3
volume calculated based on the above data is 0.70 cm /g.
Based on the topology analysis using ToposPro program,[17] the
3D framework of AlTCS-2 can be simplified as a 4-nodal
4
,5,6,8-c net (Si
2
4
(Al1)
2
3
(Al2)
2
(Al3)) with a point symbol of
4
7
12
5
4
5
2
3
3
2 1 2
(
3 4 5 6 )
2
(3 4 5 6 )
2
(3 4 5 6)
2
(3 4 5 6) as shown in Figure
4
(h). To the best of our knowledge, this is a new topology.
Adsorption properties of AlTCS-1 and -2
2
AlTCS-1 absorbed very limited N and H molecules at
2
7
7 K as shown in Figure S12, consistent with its small
2
-1
porosity. The Langmuir specific surface area is 12.1 m g
2
-1
(BET: 11 m g
）
based on nitrogen adsorption isotherm at
0
77 K. In the region of P/P > 0.70, the isotherm began to
increase sharply, indicating the presence of some textural
mesopores.[18] The H uptake is 29.4 ml g-1 (1.31 mmol g-1,
.26 wt%) under 1 bar and 77 K. The CO uptakes at 273
2
Figure 5. N
adsorption/desorption isotherms of AlTCS-2.
2 2 2 4
(77 K), H (77 K), CO (273 and 298 K) and CH (273 and 298 K)
0
2
-
1
and 298 K under 1 atm are 38 and 30 ml g (1.70 and 1.34
-
1
similar (Figure S14), consistent with the fact that they have
similar bonds in the frameworks. When the CuBTC MOF
mmol g ; 7.5 and 5.9 wt%), respectively; and increased to
-
1
1
12 and 97 ml/g (5.0 and 4.3 mmol g ; 22 and 19 wt%)
(BTC = 1,3,5-benzene tricarboxylate) was subjected in high
under 9 atm (Figure S12). The CH uptakes at 273 and 298
4
K under 1 atm are 6.1 and 4.2 ml g- (0.27 and 0.19 mmol g-
1
humidity environment, the most notable changes in its IR
spectra were the gradual appearance of bands at 1708 and
1;
0.44 and 0.30 wt%), respectively; and increased to 35
-
1
and 26 ml g-1 (1.56 and 1.16 mmol; 2.5 and 1.9 wt%) under
1243 cm , which were assigned to the corresponding to the
[
24]
C=O and C–O stretching bands of the COOH group.
9
atm. Thus, AlTCS-1 absorbs CO
suggesting it might be applied to remove CO
gas. The uptake amount of CO is high considering its low
We observed hystereses in
2
a lot more than CH
4
,
-
1
Based on this finding, the sharp peak at 3690 cm , the
strong peaks at 1704 and 1286 cm-1 in the IR spectrum of
AlTCS-1 were assigned to the free OH of COOH stretching,
the C=O (usually very strong) and C-O stretching modes of
COOH group, respectively, which are absent in the IR
spectrum of AlTCS-2, consistent with the fact that AlTCS-2
2
from natural
2
-
1 [19]
pore volume (0.13 ml g ).
those sorption experiments (Figure S12). MOFs having
pores of diameters less than 10 Å could result in hysteresis
phenomena due to their small pore nature as reported by
Kim et al. [20]
does not contain -COOH group. Since the IR intensity of
-


sym(COO ) is usually weaker than the IR intensity of
asym(COO ), the peaks at around 1610 and 1385 cm in the
The permanent porosity of AlTCS-2 has been confirmed
-
-1
by nitrogen and hydrogen sorption experiments at 77 K
uptakes is 385 cm3 (STP) g . The
-1
IR spectra of AlTCS-1 and -2 were assigned to the
(Figure 5). The N
2
-
-

asym(COO ) and sym(COO ) modes.
Brunauer−Emmett−Teller (BET) specific surface area is
2
-1
2
-1
1
506 m g
，the Langmuir surface area is 1642 m g ，and
Water and thermal stability of AlTCS-1 and -2
3
-1
the pore volume is 0.55 cm g . The type I adsorption curve
Thermogravimetric (TG) curves of AlTCS-1 and -2 are given
in Figure 6. The weight loss of 2.3% (AlTCS-1) and 2.4%
2
suggests the micropore nature of AlTCS-2. The H uptake
is 201 ml g-1 (1.79 wt%) under 1 bar and 77 K, which is
moderate among MOF materials. For example, ZIF-8 (BET:
(
AlTCS-2) before 200 °C are due to the adsorbed water
2
-1
2
-1
molecules. The second weight loss of 6.2% in the TG of AlTCS-
1 occurred in the range of 230 to 390 °C corresponds the
decomposition of the framework, consistent with the fact that it
completely lost crystallinity after being heated at 400 °C for 4 h
1
630 m g ) absorbs 1.27 wt%, MOF-5 (BET: 3362 m g )
[
21]
absorbs 1.32 wt% under 1 bar and 77 K.
2
The CO and
3
-1
CH
4
uptakes at 298 K and 1 bar are 51 cm (STP) g (2.3
-
1
3
-1
-1
mmol g , 10 wt%) and 15 cm (STP) g (0.67 mmol g , 1.1
wt%), respectively. The CO and CH uptakes increase to
(
Figure 7(a)). However, the PXRD (Figure 7(a)) and IR (Figure
2
4
3
-1
-1
3
S15) studies indicate that the framework kept intact even after
being heated at 350 °C for 4 h.
9
g
2 cm (STP) g (4.1 mmol g , 18 wt%) and 27 cm (STP)
-
1
-1
(1.2 mmol g , 2.0 wt%) at 273 K and 1 bar. To our
and CH adsorption capacities of
AlTCS-2 are relatively high among the reported values of
knowledge, the CO
2
4
[
19c,
the known MOFs measured under the same conditions.
2
2]
UiO(bpdc) (a Zr-MOF based on 2,2-bipyridine-5,50-
dicarboxylate (bpdc) ligand) was recently reported as a
material has high CO and CH and
uptakes.[23] The CO
CH uptakes of AlTCS-2 are higher than that of UiO(bpdc),
which has a much larger BET surface area (2646 m g )
and absorbs 8.0 wt% CO or 1.0 wt% CH at 1 bar and 293
K; and 13.0 wt% CO
at 1 bar and 273 K.[
2
4
2
4
2
-1
2
4
23]
2
IR and Raman Spectra of AlTCS-1 and -2
The IR and Raman spectra of AlTCS-1 and -2 are very
Figure 6. TG curves of AlTCS-1 and -2.
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Figure 7. Thermal and water stability of AlTCS-1 (a) and AlTCS-2 (b) checked by PXRD.
The second weight loss of 3.6% in TG of AlTCS-2 (Figure 6)
occurred in the range of 257-320 °C, which was assigned to the
loss of the coordinated water (theoretical amount: 2.8%). The
PXRD (Figure 7(b)) studies indicate that the framework kept
intact even after being heated at 350 °C for 4 h. The IR spectra
of the sample heated at 250-350 °C (Figure S15）indicate that
AlTCS-2 gradually decomposes at temperatures above 250 °C,
suggested by the increase of the peak intensities due to the
formation of –COOH group at 1707 (C=O stretching) and 1263
applying electron-rich metal nodes based on limited
[
1b]
experimental and theoretical results. A possible explanation
for the absorbance difference between AlTCS-1 and -2 is given
below.
A structural motif, namely donor-( bridge)-acceptor (Organic
-systems end-capped with an electron donor (D) and an
electron acceptor (A)) are widely applied in designing efficient
organic dyes applied in Dye Sensitized Solar Cell (DSSC).[
Due to the D–A interaction, or the so-called intramolecular
charge-transfer (ICT), a new low-energy molecular orbital (MO)
25]
cm-1
(C-O stretching) (Figure S15(i)). AlTCS-1 and -2 can be
stable in wide pH range (1-11) for at least 24 h (Figure 7), and
AlTCS-1 can even be stable in aqua regia solution for 24 h
without the loss of crystallinity as indicated by PXRD pattern
is being formed. Facile excitation of the electrons within the new
MO can be achieved using visible light.[
25c]
For example,
whereas aniline and nitrobenzene only absorbs in the UV region,
4-nitroaniline showed intense and bathochromically shifted long-
wavelength absorption maxima (CT-band), and absorbs in the
visible light region. On the contrary, 3-nitroaniline showed only a
(
Figure 7)) and IR and Raman spectra (Figure S14). In contrast,
aque regia destroys AlTCS-2. Thus, AlTCS-1 shows greater
chemical and thermal stability than AlTCS-2, which could be
due to its low porosity.
diminished CT-band as
arrangement of the amino donor and the nitro acceptor.
AlTCS-1 can be viewed as a D--A system due to its
unsymmetrical structure caused by its carboxyl groups. -SiR
3
a
result of
a
non-conjugating
[
25c]
UV-Vis diffuse reflectance spectra of AlTCS-1, AlTCS-2 and
the H
4
TCS ligand
can be seen as the electron donor; phenyl ring is the  bridge;
and the –COOH is the electron acceptor, thus it starts to absorb
visible light. In contrast, the symmetric structure of AlTCS-2
makes it not a D--A system. Consistently, it absorbs little
visible light.
The UV-Vis diffuse reflectance spectra of H
and AlTCS-2 in the form of absorption coefficient versus
wavelength are given in Figure 8 (The plot of R% versus
4
wavelength are given in Figure S16). The ligand H TCS
basically only absorbs UV light, while AlTCS-1 and -2 can
absorb visible light and the absorbance of AlTCS-1 is greater
than that of AlTCS-2. The above results demonstrate that Al ,
which is not an electron rich ion, could also decrease the band
gaps of MOFs to make them absorbing visible light. This
function of Al3+ has not been recognized. Lu et al. proposed that
the band gaps of semiconducting MOFs can be decreased by
4
TCS, AlTCS-1
The band gaps of materials can be calculated by the
following equation:[26]
3
+

h

= A(h
 - E
g
)n/2
Where
, , E , and A are absorption coefficient, light
g
frequency, band gap, and a constant, respectively. n is
determined by the optical transition type of the
semiconductor (i.e., n equals 1 for direct allowed transition
[
26a]
and 4 for indirect forbidden transition)
Because  is
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2
proportional to F(R) (F(R) equals (1−R) /(2R) where R isthe
pH = 5.01 H SO aqueous solution (Figure S2). That is, the
2
4
[
26c,
reflectance in the UV-Vis diffuse reflectance spectra.),
CB and VB potentials of AlTCS-1 and AlTCS-2 are -0.86
and 1.68 V; -0.76 and 1.78 versus the normal hydrogen
electrode (NHE), respectively and the band gaps of both
AlTCS-1 and -2 were found both to be 2.54 by the EC
method, which is very close to the values determined
based on UV-Vis reflectance spectra assuming they are
indirect bandgap semiconductors, indicating that both
AlTCS-1 and -2 are indirect band gap semiconductors.
2
6d]
2
the energy intercept of a plot of (F(R)h
) yields E for a direct allowed transition when the linear
region is extrapolated to zero coordinate, and the energy
versus energy (h) yields
for a indirect allowed transition. The bandgaps of
AlTCS-1 and -2 are determined as 2.59 and 2.72 eV,
respectively, assuming they are indirect bandgap
semiconductors or 3.10 or 3.59 eV, respectively, assuming
they are direct bandgap semiconductors (Figure S16(b)).
) versus energy
(h

g
1
/2
intercept of a plot of (F(R)h

)
E
g
Figure 8. Optical properties of AlTCS-1 and-2. (a) UV-Vis reflectance spectra
4
of H TCS, AlTCS-1 and -2 in the form of absorbance versus wavelength; (b)
1/2
The bandgaps of AlTCS-1 and -2 determined by the plotting of (F(R)h)
versus h.
Figure 9. Cathodic and anodic linear potential scans for determining the
positions of the conduction band (CB) and valence band (VB) edges of
AlTCS-1 using two different electrolytes. The red curves are the currents of
the electrolytes using the unmodified ITO electrodes ((a)-(b): the pH = 5.01
H SO aqueous solution, (c)-(d): a phosphate buffered saline (PBS, 0.1 M,
2 4
pH=7.4)).
Determination of band gaps and conduction and valence band
edges of AlTCS-1 and -2 by an electrochemical method
To figure out whether they are direct or indirect
bandgap semiconductors, the conduction-band (CB) edge
(LUMO) and valence-band (VB) edge (HOMO) positions of
materials were also determined by an electrochemical
method, i.g. the linear potential scan method which can be
viewed as partial cyclic voltammetry curves. This method is
well established in the literature.[27] The first oxidation
potential (Eox) and the first reduction potential (Ered) can be
observed by the separate cathodic and anodic scans,
respectively, and equals to the energy levels of the HOMO
Photoelectric properties of AlTCS-1 and -2
The photoelectrical properties of AlTCS-1 and -2 were
studied in
a
three-electrode set-up. Rapid and stable
photocurrent responses of AlTCS-1 and -2 under UV and visible
light illuminations are observed (Figure 10). The anodic
photocurrent response indicates the n-type semiconductor
characteristic of these two materials.[29] The current increases
upon irradiation at shorter wavelength, which is consistent with
the higher light absorbances of AlTCS-1 and -2 at shorter
wavelength compared to those at longer wavelength. Similar
phenomenon was also reported by Ardo et al.[30] The generated
photocurrent increases with increasing applied bias potential.
Such phenomena of other materials were also oberved by Liu
and Zhang et al.[ The photocurrent densitues of AlTCS-1 and
(the conduction band edge) and LUMO (the valence band
edge) of the material, respectively. The bandgap is the the
difference of Eox and Ered. However, sometimes not both
[
27c]
potentials were observed,
which is probably due to the
redox reactions of the electrolytes during the processes.
We therefore, different from the literatures, used two
different electrolytes (the phosphate buffered saline (PBS,
0.1 M, pH=7.4) solution and a H
2 4
SO aqueous solution (pH
31]
=
5.01)), so that we could observe both redox potentials
−
2
-
2 reaches 100 and 60 nAcm , respectivley at 0.6 V (vs.
[
28]
and crosscheck the results. When determining the band
edges, the current curves (in red) of the electrolytes
obtained using unmodified ITO electrodes under same
scan conditions were compared with the observed current
curves obtained using the modified ITO electrodes as
shown in Figure 9 (AlTCS-1) and Figure S2 (AlTCS-2) in
order to distinguish the redox positions of the materials
Ag/AgCl). A higher photocurrent density often means a higher
[
29b,
ability in separating the photogenerated electrons and holes.
3
2]
The above results suggest that faster recombinations of
photogenerated electrons and holes occur under lower potential
bias.[33] Under the same condition, the photocurrent intensity
increases in the order of AlTCS-2 < AlTCS-1, consistent with
the fact that AlTCS-1 absorbs more UV light and visible light
than AlTCS-2, which suggested that AlTCS-1 had a more
efficient separation for the photogenerated electron–hole
pairs.[32b]
from those of the electrolytes. As shown in Figure 9
， the
VB band edge of AlTCS-1 (1.48 V) was more obviously
observed in the anodic scan using the PBS (PBS, 0.1 M,
pH=7.4) solution, and the CB band edge of AlTCS-1 (-1.06
V) was more obviously observed in the cathodic scan using
2 4
the pH = 5.01 H SO aqueous solution. The VB band edge
of AlTCS-2 (1.58 V) was found in the anodic scan using the
PBS (0.1 M, pH=7.4) solution, and the CB band edge of
AlTCS-2 (-0.96 V) was found in the cathodic scan using the
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hydrogen under visible light. Bao et al. reported that
a
nanocrystalline CoO photocatalyst can carry out overall water
-
splitting with a hydrogen production efficiency of 71,429 mol·g
1
-1
·
h
without using sacrificial agent under the illuminaton of an
AM 1.5G solar simulator.[38] To our knowledge, one of the best
performance of non-MOF containing material is the Ni
CdSe/CdS core/shell QDs which ccould produce 153 mmol·g-
1·h-1 hydrogen under visible light;[38b, 39] and one of the best TiO
containing material is the carbon/TiO /CNTs composite which
h
-
Figure 10. AlTCS-1(a) and -2(b) illuminated with 385 and 430 nm light at 0.4
and 0.6 V.
2
2
-1
-1
could a hydrogen evolution efficiency of 37600 mol·g ·h
under the light of an AM 1.5G solar simulator.[
38b, 40]
Although
Photocatalytic water splitting using AlTCS-1
the photocatalytic water splitting property of AlTCS-1 is far
inferior to the above materials, it is the first report on the
photocatalytic water splitting property of crystals of an Al-MOF.
The CB and VB band-edge positions suggest that AlTCS-1
and -2 could have application as visible light photocatalysts for
[
34]
+
-
water splitting based on the known photocatalytic mechanism,
since the positions of redox potentials of neutral water is -0.41
2H + 2e →H
O + 4e + 4H → H O
2 2
2
+
E˚´= -0.65 V
E˚´= 0.58 V
(1)
(2)
-
0
+
0
and 0.82 V for E (H /H
2
) and E (O
2
/H
2
O), respectively. However
(E˚´ is the reduction potential in pH = 11.0 aqueous
solution)
TEOA + e → TEOA
no photocatalytic water splitting properties of AlTCS-1 and -2
were observed in neutral water under visible light, probably due
to the low visible light absorbance and poor photogenerated
charge (electrons and holes) separation efficiencies. When 10
mg AlTCS-1 (synthesized by the typical synthesis of AlTCS-1
which applied a rather slow cooling rate) was put into a mixed
solvent of water and triethanolamine (TEOA) (4:1 volume ratio,
pH = 11.0, 100 mL), the evolved hydrogen reaches the
maximum 500 mol/g after 10 h with an average rate of 50
+
0
E = 0.82
(3)
(
a)
-1
-1

mol·g ·h under visible light (420-800 nm). TEOA acts as a
sacrificial electron donor, and the reduction potential of
0
+
[35]
E (TEOA /TEOA) equals 0.82 (Eq. (3)).
TEOA molecules
donate electrons to the valence band to eliminate the holes
generated by visible light and thus increase the charge
separation efficiency (Figure 10b). The reduction potential of
(
b)
0
’
+
E (H /H
2
) at pH =11.0 is -0.65 V, thus the photogenerated
+
electrons in the conduction band of the AlTCS-1 can reduce H
into H
reaction, in which H
and itself is oxidized to O
2
O as shown in Figure 11(b). The kinetics of the half
O donates electrons to the conduction band
(Eq. (2)) is rather slow and was not
2
2
observed. The amount of evolved hydrogen decreases after 10
h, which is probably due to the gradual deterioration of AlTCS-1
as indicated by the decreased cystallinity of the recovered solid
shown by its PXRD pattern (Figure S17). Since every hour a
portion of gas in the reaction vessel would be extracted to be
analyzed, when the hydrogen production is too slow or stops,
the apparent hydrogen production would decrease. Under the
same reaction condition as that of AlTCS-1, AlTCS-2 did not
show photocatalytic water splitting property under visible light,
probably due to its very low visible light absorbance, and no
hydrogen observed also under UV light (300 W Xe lamp without
using filter).
2
Figure 11. (a) Photocatalytic H evolution amounts for AlTCS-1 (synthesized
by the typical synthesis of AlTCS-1) as a function of light irradiation time, (b)
Proposed mechanism of the photocatalytic water splitting process of AlTCS-1
in a 4:1 volume ratio mixed solvent (100 mL, pH =11.0) solution of H
TEOA.
2
O and
Conclusions
The hydrogen evolution efficiency of AlTCS-1 is better than
the efficiency of the rhodamine B/UiO-66(Zr) reported by Wang
and Yan et al.,[36] which reaches the maximum (170 mol/g, 34
We demonstrated how to grow high quality, large single
crystal aluminum carboxylate MOFs in three cases, resulting in
two novel Al-MOFs, AlTCS-1 and -2. Based on our experiences,
we proposed an efficient method of preparing large and good
quality single crystals of Al-MOFs. The method includes the
corporation of three techniques: 1) Adding a simple inorganic or
organic acid (e.g. HF or formic acid); 2) Applying an efficient
experimental method, i.g. the orthogonal array design approach;
-
1
-1

mol·g ·h ) after
5 h under similar reaction conditions.
However, it is less efficient than that of Al-PMOF[2]
-1
-1
[
Al
2
(OH)
2
(H
2
2
TCPP)] (200 mol·g ·h , H TCPP = meso-tetra(4-
[
37]
carboxyl-phenyl) porphyrin,) and that of MOF-253-Pt
(4680
-1
-1

mol·g ·h , MOF-253: Al(OH)(bpydc), bpydc = 2,2‘-bipyridine-
5,5‘-dicarboxylate) under visible light. To our knowledge, one of
3) Using PXRD to check the crystallinity and identity of the
2
the best performance of MOF related materials is the MoS /UiO-
product during the investigation process. Good quality open
framework Al-MOF single crystals should usually have a PXRD
-1
-1
6
6/CdS composite which could produce 32500 mol·g ·h
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5 2 3 2 2 2
Synthesis of [Al O (OH) (TCS) (H O)
] (AlTCS-2).
pattern which has a peak at a 2θ angle lower than 10, high
crystallinity and sharp peaks. In addition, we found changing
solvent polarity and faster cooling rate are favorable to
synthesize good quality large single crystals. This method is
possibly also useful to synthesize other MOF single crystals. In
addition, AlTCS-1 and -2 are the first examples of Al-MOFs
synthesized based on a tetrahedral shape ligand. AlTCS-2 is
also the first Al-MOF which contains a spiral chain SBU. AlTCS-
In an optimized preparation for the best quality single crystals of
AlTCS-2, H TCS (0.020 g, 0.039 mmol), Al(NO ·9H O (227μL,
.0 M Al(NO ·9H O aqueous solution, 0.227 mmol)), formic acid
(0.40 mL, 10.6 mmol), DMF (N,N-dimethylformamide, 1.4 mL, 18.2
mmol) and H O (0.6 mL, 33.3 mmol) were stirred for 10 min in a 14
mL glass vial. The overall molar ratio of Al(NO : H TCS :
HCOOH : DMF : H O = 6.0 : 1 : 270 : 470 : 850. The glass vial was
4
3
)
3
2
1
3
)
3
2
2
3
)
3
4
2
then sealed in an autoclave equipped with a Teflon liner (25 mL)
and put into an oven. The temperature of the oven was raised to
1
and -2 can be stable in wide pH range (1-11), and AlTCS-1
can even be stable in aqua regia solution. We also found that
1
20 °C naturally, kept at 120 °C for 3 d, and then cooled to 25 °C
naturally, resulting in colourless block-like crystals. The crystals
were collected by filtration, washed with DMF and then with H
and dried in a 90 °C oven for 12 h. The overall yield is 16.2 mg, 63
wt% based on H TCS. The PXRD was obtained and shown in
Figure 2 no 14. IR (KBr): = 3451 (w, br) ( (O-H) of absorbed
O), 1707 (w), 1620 (s) ( asym(COO )), 1595 (s), 1546(s), 1506 (s),
443 (s), 1390 (w) ( sym(COO )), 1315 (w), 1259 (w), 1191 (w),
105 (s), 1021 (m), 976 (w), 957 (w), 857 (s), 777 (s), 741 (s), 729
3
+
Al , not electron rich ions, could transform a UV light absorbing
ligand (i.g. H TCS) to absorb visible light, which has not been
4
2
O
recognized before.
4


-
H
1
1
2

Experimental Section
-

Synthesis of the MIL-53(Al) single crystal
(
s), 710 (m), 631(m), 610 (m), 556 (m), 507 (m), 460 (w); elemental
analysis calcd (%) for [Al (OH) (TCS) (H O) O) (Sample
].(H
was washed thoroughly with H O and dried over 120 °C for 12 h
before measurement.): C 48.77, H 3.73, N 0.0; found: C 48.56, H
.35, N, 0.00.
5
O
2
3
2
2
2
2
6
In
Al(NO
9
1
a
typical synthesis,
·9H O (1.56 g, 4.160 mmol)
.11 mmol, 40% aq.) and H O (6.0 mL, 330 mmol) were stirred for
0 min in a 14 ml glass vial (diameter: 2.0 cm, height: 5.6 cm).
: H BDC: HF: H O = 2.0: 1: 4.4 :
60. The glass vial was then sealed in an autoclave equipped with
H
2
BDC (0.3456 g, 2.080 mmol),
2
3
)
3
2
，
hydrofluoric acid (403 μL,
2
3
The overall molar ratio of Al(NO
1
)
3 3
2
2
X-ray crystallography
a Teflon liner (25 mL) and put into an oven. The oven was heated
up to 220 °C over 1 h, kept at this temperature for 3 d, and then
turned off. The autoclave was cooled down to room temperature
naturally in the oven, resulted in colourless block crystals (Figure
Suitable single crystals were selected for single crystal X-ray
diffraction. The data were collected at 296 (2) (AlTCS-1) and
2
91(2) K (MIL-53) and 150(2) K (AlTCS-2) on a Bruker Smart CCD
di ractometer with graphite-monochromatic radiation (λ
.71073 Å) from an enhanced optic X-ray tube. Raw data for the
ff
K
α
=
1
(c)) and white powders. The single-crystal X-ray diffraction
0
analysis was carried out on one of the block crystal, the simulated
PXRD spectrum of which is given in Figure S1(b). The product was
dried in an oven for 12 h at 70-90 °C, the PXRD pattern (25 °C) of
which is shown in Figure S3(g). In a separate preparation, the
crystals were separated from the white powders utilizing their
density difference, and dried in an oven at 70-90 °C for 12 h, the
PXRD pattern of which is shown in Figure S3(h).
structure were obtained using SAINT, and absorption correction
was applied using SADABS programs. The structures of AlTCS-1
and MIL-53 were solved by direct methods and refined by full
2
matrix least-squares on F , using the SHELXS-2014 and SHELXL-
2
014 programs. The structure of AlTCS-2 were solved by intrinsic
2
phasing method and refined by full matrix least-squares on F ,
using the SHELXT-2014 and SHELXL-2016 programs. A summary
of the crystallographic data, data collection, and refinement
parameters for complex is provided in Table S3 (ESI). Selected
bond distances and angles are given in Table S4 (ESI).
3 3 2
Synthesis of [Al (OH) (HTCS) ] (AlTCS-1)
In a typical synthesis using HF aqueous solution, H
.078 mmol),Al(NO ·9H O (468 μL,1.0 M Al(NO ·9H
solution, 0.468 mmol)), hydrofluoric acid (80μL,10% aqueous
solution, 4.1 mmol), and H O (8.0 mL, 444 mmol) were stirred for
0 min in a 14 ml glass vial. The overall molar ratio of Al(NO
TCS: HF: H O = 6.0 : 1 : 5.3 : 5700. The glass vial was then
4
TCS(0.040 g,
0
3
)
3
2
3
)
3
2
O aqueous
2
Acknowledgements
1
3 3
) :
H
4
2
We thank National Natural Science Foundation of China (NSFC)
sealed in an autoclave equipped with a Teflon liner (25 mL) and put
into an oven. The temperature of the oven was raised from room
temperature to 220°C with a 1.0 °C/min heating ramp, kept at
(
No. 21622104, 21371099, 21471080, 21071082 and
21671003), the Key International (Regional) Joint Research
Program of NSFC (No.21420102002), the Natural Science
Foundation of JiangsuProvince (BK20161553) ， the Natural
Science Foundation of Education Department of Jiangsu
Province (No. 16KJB150021), the Priority Academic Program
Development of Jiangsu Higher Education Institutions, and the
Foundation of Jiangsu Collaborative Innovation Center of
Biomedical Functional Materials for their funding support.
2
20°C for 3 d, and then cooled to 120 °C with a rate of 1.0 °C/h,
and to 25 °C with a rate of 10 °C/h. The resulted colourless block
crystals (when grounded to powder, showing light yellow colour)
were collected by filtration, and washed with DMF and then with
H
2
O and dried in a 90 °C oven for 12 h. The overall yield is 39 mg,
8 wt% based on H TCS. Its purity was checked by PXRD (Figure
). IR (KBr): = 3685 (w) ( (O-H) of COOH), 3425 (w), 3020 (w),
659 (w), 2536 (w), 1948 (w), 1704 (s) ( (C=O) of COOH), 1625(s)
asym(COO )), 1589 (s), 1540 (s), 1503 (s), 1439 (vs), 1385 (s)
7
7
2
4
̃


-
(
(


-
sym(COO )), 1135 (w),1318 (w), 1286 (m) ((C-O) of COOH),
Keywords: single crystal • Al(III) metal-organic framework •
water splitting • visible light• semiconductor
1
8
4
255 (w), 1192 (w), 1099 (s), 1022 (w), 995 (m), 971 (m), 904 (w),
56 (w), 781 (s), 733 (s), 709 (s), 633(m), 611 (m), 564 (w), 505 (s),
-
1
74 (w), 452 (w), 413 (w) cm ; elemental analysis calcd (%) for
(OH) (HTCS) O): C 57.41, H 3.46, N, 0.29; found:
].(DMF)0.25(H
[1]
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a) S. Wang, X. Wang, Small 2015, 11, 3097-3112; b) M. Usman, S.
Mendiratta, K.-L. Lu, Adv. Mater. 2016, 29, 1605071.
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HCOOH regent, the heating procedure is as that of the syntheses
A. Fateeva, P. A. Chater, C. P. Ireland, A. A. Tahir, Y. Z. Khimyak, P. V.
Wiper, J. R. Darwent, M. J. Rosseinsky, Angew.Chem. Int. Ed. 2012,
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Yuanyuan Guo, Jun Zhang, Long-Zhang
Dong, Qi Li, Tao Chen, Yan Xu, Wei
Han, Min Fang,* Hong-Ke Liu, Yong
Wu,* Ya-Qian Lan*
The first two tetrahedral ligand based,
visible light absorbing aluminum
carboxylate MOFs (AlTCS-1 and -2)
4
based on H TCS were synthesized and
Page No. – Page No.
fully characterized including their water
splitting photocatalytic properties; the
successful syntheses of large single
crystals of AlTCS-1 and -2 and MIL-
(
(Insert TOC Graphic here: max.
Syntheses of Exceptionally Stable
Al(III) Metal-Organic Frameworks:
How to Grow High Quality Large
Single Crystals?
width: 5.5 cm; max. height: 5.0 cm))
53(Al) demonstrate a general method of
obtaining single crystals of Al-MOFs
large enough for common structure
determinations.
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