Ultrasonic synthesis of a 3D Ni(II) Metal-organic framework at ambient temperature and pressure: New precursor for synthesis of nickel(II) oxide nano-particles

Article abstract of DOI:10.1016/j.ica.2012.02.017

Nano-particles of a Ni(II) metal-organic framework (MOF) with cubic building blocks and 1D open channels, i.e. {[Na₁₆(Ni ₈L₁₂)(H₂O)₂₀(H₃O) ₄](CH₃CN)(H₂O)_18.5} _∞ (1) (H₃L = 4,5-imidazoledicarboxylic acid) were synthesized by using ultrasonic method and characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), IR spectroscopy and elemental analysis. The effect of concentration of starting reagents on size and morphology of nano-structured compound 1 has also been investigated. Calcination of the bulk powder and nano-sized compound 1 at 700 °C under air atmosphere yields NiO nano-particles. Results show that the size and morphology of the NiO nano-particles are dependent upon the particles size of compound 1.

Full text of DOI:10.1016/j.ica.2012.02.017

Inorganica Chimica Acta 387 (2012) 327–331
Contents lists available at SciVerse ScienceDirect
Inorganica Chimica Acta
journal homepage: www.elsevier.com/locate/ica
Ultrasonic synthesis of a 3D Ni(II) Metal–organic framework at ambient
temperature and pressure: New precursor for synthesis of nickel(II) oxide
nano-particles
⇑
Arineh Tahmasian, Ali Morsali
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University, P.O. Box 14115-4838, Tehran, Islamic Republic of Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Nano-particles of a Ni(II) metal–organic framework (MOF) with cubic building blocks and 1D open chan-
Received 25 November 2011
Received in revised form 4 February 2012
Accepted 10 February 2012
Available online 24 February 2012
8 2 3 4 3 2 1 3
nels, i.e. {[Na16(Ni L12)(H O)20(H O) ](CH CN)(H O)18.5} (1) (H L = 4,5-imidazoledicarboxylic acid) were
synthesized by using ultrasonic method and characterized by scanning electron microscopy (SEM), X-ray
powder diffraction (XRD), IR spectroscopy and elemental analysis. The effect of concentration of starting
reagents on size and morphology of nano-structured compound 1 has also been investigated. Calcination
of the bulk powder and nano-sized compound 1 at 700 °C under air atmosphere yields NiO nano-parti-
cles. Results show that the size and morphology of the NiO nano-particles are dependent upon the par-
ticles size of compound 1.
Keywords:
Metal–organic framework
NiO
Ó 2012 Elsevier B.V. All rights reserved.
Nano-particles
4
,5-Imidazoledicarboxylic acid
1
. Introduction
organic framework (MOF) with ligand H
3 8
L, i.e. {[Na16(Ni L12)-
(
H
2
O)20(H O) ](CH CN)(H (1) (H L = 4,5-imidazoledicarb-
3
4
3
2
O)18.5
}
1
3
Metal–organic frameworks (MOFs) are a relatively new class of
oxylic acid) [14], were synthesized under ultrasonic irradiation
and the effect of concentration of initial reagents on size and mor-
phology of nano-structured compound 1 has been investigated.
Nano-structured nickel(II) oxide is a p-type semiconductor with
a stable, wide band gap (3.6–4.0 eV) [15]. Important applications of
nano-sized NiO include preparation of cathode materials for alka-
line batteries [16], electrochemical capacitors [17], smart windows
[18], active layers for gas sensors [19], and catalytic systems [20].
Different methods have been developed to synthesize of NiO nano-
crystals, such as thermal decomposition [21], sputtering [22], elec-
trodeposition [23], AAM template synthesis [24], and sol–gel
techniques [25]. Also, the solid-state decomposition method has
already been reported which involves thermal decomposition of
MOFs in dry condition under air atmosphere [26]. In this paper
nickel(II) oxide nano-particles were obtained by direct thermal
decomposition of compound 1 at 700 °C. The preparation of metal
oxide nanostructures through thermal decomposition of com-
plexes opens a new view for chemists since there are many advan-
tages in it such as: control of process conditions, particle size,
particle crystal structure, and purity.
hybrid nano-porous materials which have attracted considerable
attention in recent years. This is due to the variety of characteris-
tics they have which includes, large surface areas, low densities,
regular pore sizes, and tunable structure properties that make
them promising candidates in several applications. The applica-
tions consist of gas storage, heterogeneous catalysis, selective
guest adsorption, and sensor technology [1–4]. Compared with
well-known nano-porous materials such as carbons and inorganic
zeolites, these porous MOFs composed of metal ions or metal clus-
ters as nodes and organic ligands as linkers, have the advantage of
tailoring physical and chemical characteristics during their synthe-
sis. Usually, these porous materials are synthesized by slow diffu-
sion techniques, hydrothermal, and solvothermal synthesis
methods [5–7]. In these techniques generally long reaction time,
high reaction temperatures and pressures are required.
In the past two decades, sonochemical methods have been
widely used in the syntheses of MOFs [8–10] and organic materials
11]. Sonochemistry is the research area in which molecules under-
go a reaction due to the application of powerful ultrasound radia-
tion (20 kHz–10 MHz) [12]. Compared with traditional techniques,
sonochemical method is more efficient and easily controlled and
this has been widely used to fabricate nano-sized structures of a
variety of compounds [13]. In the present work, a nickel(II) metal–
[
2
. Experimental
2.1. Materials and physical techniques
⇑
Corresponding author. Tel.: +98 21 82884416; fax: +98 21 8009730.
E-mail address: morsali_a@modares.ac.ir (A. Morsali).
All reagents for the synthesis and analysis were commercially
available from Merck company and used as received. Doubly-
0
020-1693/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2012.02.017

3
28
A. Tahmasian, A. Morsali / Inorganica Chimica Acta 387 (2012) 327–331
Scheme 1. Materials produced and synthetic methods.
Fig. 1. IR spectra of (a) nano-particles of compound 1 produced by sonochemical method in concentration of initial reagents [Ni2+] = 0.025 M, [HL ] = 0.0375 M and (b) bulk
2ꢁ
powder of compound 1.
distilled water was used to prepare aqueous solutions. Ultrasonic
generators were carried out on SONICA-2200 EP, input:
0–60 Hz/305 W. Melting points were measured on an Electrother-
mal 9100 apparatus. Microanalyses were carried out using a
Heraeus CHN-O-Rapid analyzer. IR spectra were recorded on a
SHIMADZU-IR460 spectrometer in a KBr matrix. The simulated
XRD powder pattern based on single crystal data were prepared
using MERCURY software [27]. X-ray powder diffraction (XRD) mea-
surements were performed using a Philips X’pert diffractometer
was dissolved in 10 ml sub-stoichiometric NaOH aqueous solution
then solution of 1 mmol (291 mg) Ni(NO O in 10 ml acetoni-
trile was added to the mixture and was refluxed for 2 h. The ob-
tained green precipitates were filtered off, washed with water
and then dried at room temperature. (57.4% yield), m.p. > 300 °C
a
)
3 2
ꢀ6H
2
5
26 4 2
(Anal. Calc. for C15.50H N6.25Na Ni O22.625: C, 21.35; H, 2.98; N,
ꢁ1
10.04. Found: C, 21.47; H, 2.78; N, 9.74%). IR (cm ) selected bands:
3344(vs), 1750(m), 1555(vs), 1469(vs), 1389(m), 1249(s), 1102(m),
792(m) and 656(m).
with monochromated Co k
were characterized by a scanning electron microscope (SEM)
Philips XL 30 and S-4160) with gold coating.
a radiation (k = 1.78897 Å). The samples
2.3. Synthesis of {[Na16(Ni8L12)(H O) (H O) ](CH CN)(H O)
nano-particles by using ultrasonic method
2
20
3
4
3
2
18.5 1
(1)
}
(
2
.2. Synthesis of {[Na16(Ni
8
L
12)(H
2
O)20(H
3
O)
4
](CH
3
CN)(H
2
O)18.5
}
1
(1)
To prepare nano-scale compound 1, 20 ml of a 0.0375 M solu-
tion of 4,5-imidazoledicarboxylic acid in a sub-stoichiometric
NaOH solution was placed in a high-density ultrasonic probe, oper-
ating at 50 Hz with a maximum power output of 305 W and 20 ml
The compound 1 was prepared according to reported method
14]. 1.5 mmol (234 mg) 4,5-imidazoledicarboxylic acid (H L)
[
3

A. Tahmasian, A. Morsali / Inorganica Chimica Acta 387 (2012) 327–331
329
Fig. 3. SEM photograph and the corresponding particle size distribution histogram
of compound 1 nanoparticles prepared by ultrasonic generator 305 W in concen-
Fig. 2. XRD patterns; (a) simulated pattern based on single crystal data of
compound 1, (b) bulk powder of compound 1 and (c) nanoparticles of compound
tration of initial reagents [Ni2 ] = 0.025 M, [HL ] = 0.0375 M.
+
2ꢁ
1
[
prepared by sonochemical process in concentration of initial reagents
Ni2+] = 0.025 M, [HL ] = 0.0375 M.
2ꢁ
of a 0.025 M acetonitrile solution of Ni(NO
3
)
2
ꢀ6H
2
O was added
drop wisely to that solution during 1 h and at ambient tempera-
ture. Green precipitates obtained were collected by filtration,
washed with water and then dried in air. (53.9% yield),
ꢁ1
m.p. > 300 °C (Found: C, 21.22; H, 2.59; N, 10.27%). IR (cm ) se-
lected bands: 3340(vs) 663(m), 1745(m), 1501(vs), 1248(m),
1
124(m), 790(m) and 641(m).
For studying the effect of concentration of initial reagents on
size and morphology of nano-particles of compound 1, the above
processes were done under the following concentration condition
3ꢁ
2+
of initial reagents: [L ] = 0.075 M, [Ni ] = 0.05 M.
2.4. Preparation of NiO nano-particles
For preparation of NiO nano-particles and also to investigate the
size effect of compound 1 on the size and morphology of the NiO
nano-particles, calcination of bulk powder and nano-sized com-
pound 1 were done at 700 °C in static atmosphere of air for 4 h.
IR spectrum and powder XRD diffraction shows that calcination
was completed and the entire organic compound was decomposed.
3
. Results and discussion
The reaction of aqueous solution of 4,5-imidazoledicarboxylic
acid and NaOH with acetonitrile solution of Ni(NO
formation of 3D metal–organic framework {[Na16(Ni
O)20(H O) ](CH CN)(H (1). Nano-particles of com-
pound 1 were obtained under ultrasonic irradiation in a mixed
solution of H O/CH CN (1:1, v/v), at ambient temperature and
3
)
2
ꢀ6H
2
O led to
a
8
L12)-
Fig. 4. SEM photograph and the corresponding particle size distribution histogram
of compound 1 nanoparticles prepared by ultrasonic generator 305 W in concen-
(
H
2
3
4
3
2 1
O)18.5}
tration of initial reagents [Ni2 ] = 0.05 M, [HL ] = 0.075 M.
+
2ꢁ
2
3
atmospheric pressure while the bulk powder of compound 1 was
methods used for the synthesis of compound 1 using the two dif-
obtained using reflux method. Scheme 1 gives an overview of the
ferent routes.

3
30
A. Tahmasian, A. Morsali / Inorganica Chimica Acta 387 (2012) 327–331
Fig. 5. XRD pattern of NiO nanoparticles prepared by calcination of bulk powder of
compound 1 at 700 °C.
Fig. 7. SEM image of NiO nanoparticles prepared by calcination of compound 1
nanoparticles prepared by sonochemical process in concentration of initial reagents
2+
2ꢁ
[
Ni ] = 0.025 M, [HL ] = 0.0375 M, at 700 °C.
L ligands, producing the slightly distorted octahedral coordination
geometry [14].
The reaction between of 4,5-imidazoledicarboxylic acid (H
and Ni(NO O provided a crystalline material of the general
ꢀ6H
formula {[Na16(Ni 12)(H O)20(H O) ](CH CN)(H (1). To
3
L)
3
)
2
2
8
L
2
3
4
3
2 1
O)18.5}
investigate the role of the concentration of initial reagents on the
nature of products, reactions were performed with two different
concentrations of initial reagents under ultrasonic irradiation.
The morphology and size of obtained samples were characterized
by scanning electron microscopy (SEM). Fig. 3 shows the SEM
images and the corresponding particle size distribution histogram
2
ꢁ
of the compound 1 obtained under 0.0375 M concentration of HL
2
+
and 0.025 M concentration of Ni
completed on different concentration of acetonitrile solution of
Ni(NO O and aqueous solution of ligand H idc and NaOH.
ꢀ6H
. Also further tests were
3
)
2
2
3
The resultant SEM images and the particle size distribution histo-
gram are illustrated in Fig. 4. Appropriate nano-sized particles of
compound 1 were obtained under both concentrations of initial re-
agents (Figs. 3 and 4). Comparison of IR spectra and XRD patterns
show that the reaction at both concentrations of initial reagents
produces the same product. However the results indicate that the
resultant nano-particles size is dependent on the concentration of
initial reagents as with increasing of the concentration of initial
reagents the size of the nanoparticles also increase.
Fig. 6. SEM image and the corresponding particle size distribution histogram of NiO
nanoparticles prepared by calcination of bulk powder of compound 1 at 700 °C.
The elemental analysis and IR spectra of the nano-structured
compound 1 produced by the sonochemical method and of the
bulk material produced by reflux method are indistinguishable
The TG curve of 1 indicates the release of guest molecules up to
100 °C to give its desolvated form. At 265 °C, the ligand molecules
start to be released and the decomposition process of the frame-
work is completed at 700 °C [14].
(Fig. 1).
Fig. 2 shows the comparison of XRD patterns, one simulated
from single crystal X-ray data (Fig. 2a) against the bulk powder
of compound 1 (Fig. 2b) and that of a typical sample of compound
prepared by the sonochemical process, respectively (Fig. 2c). The
Fig. 5 provides the XRD pattern of the residue obtained from
calcination of compound 1. The obtained pattern matches with
the standard pattern of cubic NiO with the lattice parameters
a = 4.1771(8) Å, S.G. = Fm3m(225) and Z = 4 which is the same as
the reported values (JCPDS card number 47-1049). No characteris-
tic peaks of impurities are detected in the XRD pattern.
Fig. 6 shows the SEM image and the corresponding particle size
distribution histogram of NiO nanoparticles obtained from calcina-
tion of bulk compound 1 at 700 °C. As the calcination process was
successful for the preparation of NiO nano-particles, the nano-
sized compound 1 prepared by the sonochemical process was also
calcinated at 700 °C. The XRD pattern of the residue shows that the
resulting residue was again NiO with the same lattice parameters
which are mentioned above. Fig. 7 shows the SEM image of result-
ing NiO nano-particles.
1
comparison between these XRD patterns indicates acceptable
matches with slight differences in 2h. This finding proves the for-
mation of compound 1 under reflux and sonochemical processes.
The significant broadening of the peaks in the pattern of nanopar-
ticles compound 1 (Fig. 2c) indicates that the particles are of nano-
meter dimensions. Compound 1 is a 3D metal–organic framework
crystallized in the orthorhombic space group Pnnm and consists of
2
0ꢁ
20ꢁ
12
[
M
8
L
12
]
cubes bridged by sodium ions. Each [M
8
L
]
unit
II
consists of eight Ni ions occupying the vertices of the cube, and
are linked in a bi-chelating fashion by 12 L ligands. Each Ni ion
II
is coordinated to three N and three O atoms from three separate

A. Tahmasian, A. Morsali / Inorganica Chimica Acta 387 (2012) 327–331
331
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. Conclusions
3
A nano-sized 3D metal–organic framework (MOF) based on
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(H
3
8
L12)(H
O)20(H O)
2 3 4
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CN)(H O)18.5
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[
[
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[
[
(
(
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[
7
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