F. Nouri et al. / Molecular Catalysis 443 (2017) 286–293
287
Table 1
sis was carried out using a PHILIPS X-ray diffractometer system
(PW1800-Model). The CHN analysis was performed by a 2400 series
II elemental analyzer. An XR3E2, 8025-BesTec-Model twin anode X-
ray source system was used for X-ray photoelectron spectroscopy.
The nitrogen sorption curves was recorded by [5.0.0.3] Belsorp, BEL
Japan, INC. system for determination of specific surface area of the
nanostructures.
The results of the nitrogen adsorbtion-desorbtion experiments using BET and BJH
methods.
Experiment
IRMOF-3
IRMOF-3-BI-Pd
BET Surface area (m2 g−1
)
1263
1.29
0.69
594
2.60
0.43
Average Pore diameter (nm)
BJH pore volume (cm3 g−1
)
2.2. Preparation of the catalyst
ity to recognize optionally small to large molecules on the basis
of the structure [11]. Thus, they are applying in reversible gas
storage, sensing, biomedical imaging, drug delivery and catalysis
modification and immobilization of functional sites (coordinately
eties have been anchored onto different MOFs [14]. Among the
different MOFs, IRMOF-3 is a famous MOF having a cubic frame-
work which assembled from Zn(NO3)2 and 2-aminoterphtalic acid
[15]. Therefore, there are free amine functional groups which are
not joined to tetragonal ZnO4 as nodes, and provide a route to post-
synthetic modification of IRMOF-3 with various organometallic
lacetonate magnesium (II) complex onto IRMOF-3 and applied
it as a heterogeneous catalyst [16]. Also, Xin and his coworkers
anchored Au+3/Au0 species [17]. IRMOF-3 has also been modified
with pyridine-2-carbaldehyde by Koner and gave a porous sup-
port with bidentate Schiff base moiety which anchored PdCl2 and
indicates good catalytic activity in Suzuki cross-coupling reaction
[18]. Wang et al. have reported the modification of IRMOF-3 with a
copper-iminopyridine complex as well [19]. Additionally, IRMOF-
3 has been modified with some ligands such as chloroacetic acid,
glyoxylic acid, diethylmalonate and methyl vinyl ketone and it has
been used to coordinate Eu3+ and Nd3+ cations [20].
Therefore, as is observed, various functional groups and
organometallic moieties have been anchored onto IRMOF-3, but
to the extent of our knowledge, there is no report dealing with
modification of MOFs with a palladacycle. Hence, in continua-
tion of our interest in preparing heterogeneous catalysts [21], we
are intending to apply IRMOF-3 as host matrices to support the
iminopalladacycle with the hope to lead to the stability and high
efficiency of palladcycle catalyst for catalyzing the C C coupling
reaction even for the less reactive aryl chlorides. As a result, for the
first time, we report the preparation of a new and stable IRMOF-3
supported iminopalladacycle catalyst through post-synthetic mod-
ification strategy and present its excellent catalytic efficiency in
Suzuki-Miyaura reaction.
2.2.1. Preparation of IRMOF-3 (1), [Zn4O(ATA)3] (ATA = 2-amino
terephthalate).
IRMOF-3 was prepared according to the method previously
reported in the literature with a slight alteration [22]. Thus, 0.75 g
2-aminoterphtalic acid Eq. (1) and 3.00 g Zn(NO3)2·4H2O Eq. (3)
were dissolved in 50 mL DMF in a sealed reaction bottle. Then it
was heated at 110 ◦C in an oil bath. After 18 h, the amber brown
fine cubic crystals of IRMOF-3 were produced and stick on the wall
of dish. The hot mother liquor was decanted and the resulting solid
was washed with DMF several times and finally with chloroform.
The dried solid was dispersed in fresh chloroform every 12 h for
tree times. Then it was dried at 100 ◦C under vacuum conditions
and elemental analysis was applied on the solid; found: C 35.3%,
H 1.8%, N 5.21%; calculated for Zn4O(ATA)3: C 35.36%, H 1.85%, N
5.17%.
2.2.2. Preparation of IRMOF-3-BI (2), [Zn4O(ATA)2.67(BITA)0.33
(BITA = 2-benzyl-imine terephthalate)
]
In a round bottom flask, 0.318 g benzaldehyde was dissolved
in 20 mL acetonitrile. Then, 0.640 g IRMOF-3 was added to it. The
resulting mixture was stirred for one day at room temperature. The
crème-coloured product was centrifuged and washed with ethanol
several times and dried under vacuum condition. Then, elemen-
tal analysis was applied on the solid; found: C 37.39%, H 1.89%,
N 5.1%; calculated for Zn4O(ATA)2.67(BITA)0.33 (according to 11%
functionalized NH2 group): C 37.43%, H 1.93%, N 4.98%.
2.2.3. Preparation of IRMOF-3-BI-Pd (3),
[Zn4O(ATA)3−x(BITA-Pd-OAc)x]
0.130 g of the prepared IRMOF-3-BI was poured in a round
bottom flask containing 15 mL dichloromethane and then 0.010 g
Pd(OAc)2 was added to it. The resulting mixture was stirred at
room temperature for 18 h. Then, the final solid was centrifuged
and thoroughly washed with chloroform and dichloromethane sev-
eral times and allowed to dry under vacuum condition. According
to the inductively coupled plasma atomic emission spectroscopy
(ICP), the amount of Pd incorporated in the catalyst was 3.48%wt
which indicated 91% complexion. Then, elemental analysis was
applied on the solid; found: C 36.4%, H 1.9%, N 4.55%; calculated for
Zn4O(ATA)2.67(BITA)0.03 (BITA-Pd-OAc)0.30 (according to 11% func-
tionalized NH2 group and 91% incorporated palladium): C 36.26%,
H 1.95%, N 4.61%.
2. Experimental
All chemical materials were purchased from Sigma-Aldrich,
Fulka and Merck companies. A Thermo Scientific Nicolet 380 FT-IR
spectrometer was applied for ATR-FTIR spectrometry. The Suzuki
products in Table 3 were identified by 1H and 13C NMR spec-
troscopy using a Bruker Avance spectrometer at 300 and 75 MHz,
respectively and the spectra were provided with electronic sup-
plementary information (ESI). The metal content was determined
through inductively coupled plasma technique by the Varian Vista-
MPX system. TGA curve was recorded by the NETZSCH STA 409
PC system under nitrogen atmosphere. A scanning electron micro-
scope (Vega TESCAN model) equipped with energy dispersive X-ray
was applied for energy dispersive X-ray analysis and determination
of the structural morphology of IRMOF-3. X-ray diffraction analy-
2.3. General procedure for Suzuki–Miyaura coupling reaction of
aryl halides with olefins
In a 25 mL round bottom flask containing 1 mmol aryl halide,
1.1 mmol boronic acid derivatives, 1 mmol K2CO3 and 0.002 g
(6.5 × 10−2 mol%) catalyst (3), 3 mL H2O/EtOH mixture in 1:1 ratio
was added as solvent. Then the mixture was stirred at room temper-
ature for 20–60 min. The reaction was monitored by TLC (thin layer
chromatography). After completion of the reaction, the residue was
filtrated and organic phase extracted with dichloromethane. Then,
solvent was removed under vacuum conditions. Finally, the Suzuki
product was recrystallized by EtOH and water (92–98% in yield).