Cellulose stabilized Fe3O4 and carboxylate-imidazole and Co-based MOF growth as an exceptional catalyst for the Knoevenagel reaction

Article abstract of DOI:10.1002/aoc.5516

In this study, Fe₃O₄ nanoparticles were functionalized with cellulose, and then hybridized with cobalt (II)-based metal-organic framework (Co-MOF) containing carboxylate and imidazole functionalities. FTIR, XRD, FE-SEM, TEM, BET, EDX

Full text of DOI:10.1002/aoc.5516

Received: 2 November 2019
DOI: 10.1002/aoc.5516
Revised: 3 January 2020
Accepted: 5 January 2020
F U L L P A P E R
Cellulose stabilized Fe O and carboxylate-imidazole and
3
4
Co-based MOF growth as an exceptional catalyst for the
Knoevenagel reaction
Elham Zare | Zahra Rafiee
Department of Chemistry, Yasouj
In this study, Fe O nanoparticles were functionalized with cellulose, and then
3 4
University, Yasouj, 75918-74831, Iran
hybridized with cobalt (II)-based metal-organic framework (Co-MOF) con-
taining carboxylate and imidazole functionalities. FTIR, XRD, FE-SEM, TEM,
BET, EDX, VSM and STA analyses were used to characterize the synthesized
samples. The resultant Fe O /cellulose/Co-MOF nanocomposite was applied
Correspondence
Zahra Rafiee, Department of Chemistry,
Yasouj University, Yasouj, 75918-74831,
Iran.
3
4
Email: z.rafiee@yu.ac.ir;
zahrarafiee2004@yahoo.com
efficiently as a powerful and economic heterogeneous catalyst in the condensa-
tion of a variety of different aromatic aldehydes with malononitrile under sol-
vent-free conditions at room temperature for 10 min and offered the
corresponding coupling products in high yields. The catalyst could be straight-
forwardly separated by a magnet from the reaction mixture and reused without
a noteworthy drop in catalytic activity at least five times. The use of Fe O /cel-
Funding information
Yasouj University, Grant/Award Number:
Gryu-89131307
3
4
lulose/Co-MOF catalyst outcomes under mild reaction conditions in very short
reaction time, outstanding catalytic activity, high recyclability and an easy
work-up process for Knoevenagel condensation.
K E Y W O R D S
3 4
cellulose, Fe O nanoparticles, Knoevenagel reaction, metal–organic framework, nanocomposite
[
15]
1
| INTRODUCTION
nanoparticles.
So far, diverse materials such as
[
16]
[17]
silanes,
activated carbon
have been efficiently utilized to modify Fe O
and biocompatible poly-
[
18]
Metal oxides nanostructures are especially of interest
mers
3
4
[
1–8]
because of their fascinating and unique properties.
Among these metal oxides, the magnetic iron oxide
Fe O ) nanoparticles are of huge attention, owing to
nanoparticles. Among these modifiers, cellulose as a bio-
polymer has attracted substantial attention owing to its
biodegradability, biocompatibility, and outstanding ther-
mal properties. Therefore, cellulose can be utilized as an
effective coating material for Fe O nanoparticles to yield
(
3
4
their low cost, easy preparation, and high magnetic per-
meability and various applications in diverse fields such
as catalysis, adsorption, and optoelectronics.
theless, the application of these nanoparticles is limited
by their instability in alkaline and acidic media and easy
aggregation, due to high surface free energy, specific sur-
3
4
[9–13]
Never-
environmentally friendly, biocompatible, and exciting
biopolymer-based nanocomposites.
[
19–21]
Metal–organic frameworks (MOFs) are as an attrac-
tive class of porous crystalline materials that have
attracted substantial attention owing to their unique and
valuable properties, such as extraordinary surface area,
outstanding porosity, order crystalline structures, adjust-
[14]
face area, and easy oxidation.
To overcome these
drawbacks, a variety of modification approaches were
attempted via adding various materials during or after
the construction process to enhance the stability, disper-
[
22–24]
able surface features, and tunable pore sizes.
These
sibility, biodegradability, and biocompatibility of Fe O4
exciting properties of MOFs have led to their applications
3
Appl Organometal Chem. 2020;e5516.
wileyonlinelibrary.com/journal/aoc
© 2020 John Wiley & Sons, Ltd.
1 of 10
https://doi.org/10.1002/aoc.5516

2
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ZARE AND RAFIEE
in various fields including gas storage, separation, ion
exchange, chemical sensors, supercapacitors, medicinal
benzenedicarboxylic acid (1,4-BDC, terephthalic acid),
imidazole (IM), N,N-dimethylformamide (DMF), ethanol,
benzaldehyde, malononitrile, 4-nitrobenzaldehyde, 4-
[25–31]
and catalysis.
Nevertheless, the application of these
materials has been restricted because of their chemical
instability to aqueous and organic media, and strongly
acidic or alkaline environment and difficult recovery.
chlorobenzaldehyde,
2-chlorobenzaldehyde,
4-
methoxybenzaldehyde, 4-methylbenzaldehyde, 2-hydrox-
ybenzaldehyde were purchased from Merck Company
(Darmstadt, Germany) and used without further purifica-
tion. Cellulose (Cellulose powder, Cotton linters), fibers,
(medium) was supplied by Sigma Company (Milwaukee,
WI, USA).
[
32]
Recently, MOF-based composites have been fabricated
through hybridizing MOFs with other materials, such as
[
33]
[34,35]
[36]
metal nanoparticles,
and COFs,
polymers,
other MOFs
[37]
which display new properties that are supe-
rior to those of the individual components by the combi-
nation of features of two ingredients. The composites
containing magnetic metal oxides and MOFs displayed
magnetic characteristics and large specific surface area,
making them excellent candidates for the catalysts of
2.2 | Apparatus
FT-IR spectra were recorded with a Jasco-680 spectrome-
−
1
ter (Tokyo, Japan) in the range of 4000–400 cm . FT-IR
spectra of all compounds were collected by making their
pellets in KBr as a medium. The X-ray diffraction pat-
terns of the prepared materials were recorded in the
reflection mode using a Bruker, D8 Advance diffractome-
ter. The ultrasonic bath (Tecno-GAZ SPA Ultrasonic sys-
tem, Italy) was used at a frequency of 60 Hz and power of
130 W. The surface morphology of samples was studied
by scanning electron microscopy (SEM; EM10C-ZEISS,
80 KV, Zeiss Co., Germany) and transmission electron
microscopy (TEM, EM10C-ZEISS, Zeiss Co., Germany).
Nitrogen adsorption/desorption isotherm was measured
by Brunauer–Emmett–Teller analysis (Belsorp Mini II,
Japan).
[38]
organic reactions.
Knoevenagel reaction is accomplished via the con-
densation of the carbonyl compounds and activated
methylene linkages catalyzed by weak bases and acids to
[39–43]
form unsaturated compounds.
This condensation
reaction has led to the production of significant organic
intermediates that are adjustable to different synthetic
transformations and biologically significant compounds
[44]
[45]
[46]
such as heterocycles,
carbohydrates
and drugs.
Various catalysts including Lewis acids, zeolites, and dif-
ferent amines have been utilized to catalyze the
[47–49]
Knoevenagel reaction.
Recently, the various solid-
supported heterogeneous catalysts have been applied to
[
50]
Knoevenagel reaction including Hf (IV) MOF,
metal-
[
51]
coordinated, resorcin[4]arene-based molecular trimer,
2.3 | Preparation of Fe O nanoparticles
3
4
[52]
[53]
GO-supported PdNi nanoparticles,
amino-functionalized Zn/Cd-MOFs,
metal–organic macrocycle and framework,
Zn-based MOF,
[54]
Cu (II)-based
The Fe O4 nanoparticles were synthesized by the
3
coprecipitation method
[
55]
[58]
covalent
and Core-Shell MOF/
as follows: FeCl .6H O
3 2
[56]
organic frameworks (COFs)
(0.81 g) and FeCl .4H O (0.3 g) were dissolved in distilled
2
2
[57]
COF.
In the present work, Fe O /cellulose/Co-MOF was
water (25 ml) with stirring at room temperature. Then,
ammonia solution (25%, 1.5 ml) was added dropwise into
the reaction mixture with stirring at 80 C under a nitro-
3
4
ꢀ
hydrothermally prepared and utilized as an efficient and
cost-effective heterogeneous catalyst for the Knoevenagel
reaction under solvent-free conditions. The synergistic
ꢀ
gen atmosphere and stirred at 80 C for 1 hr. The resul-
tant precipitate was collected by an external magnet and
thoroughly washed with deionized water and dried at
effects of Fe O4 and Co-MOF based on 1,4-benzene
3
ꢀ
dicarboxylate and imidazole are expected to enhance cat-
alytic performance.
70 C under vacuum.
2
.4 | Preparation of Fe O /cellulose
3 4
nanocomposite
2
2
| EXPERIMENTAL
.1 | Materials
Fe O nanoparticles (0.15 g) were dispersed in 30 mL of
3
4
an aqueous solution containing NaOH (7 wt.%) and urea
ꢀ
(
12 wt.%) and cooled to −12 C for 1 hr. Then, cellulose
The reagents and chemicals including iron (II) chloride
tetrahydrate (FeCl .4H O), iron (III) chloride hexahy-
(0.1 g) was added into the reaction mixture with stirring
for 15 min. After freezing for 1 hr, the cellulose was dis-
solved fully. Then, deionized water was added into the
mixture and the Fe O /cellulose nanocomposite was pro-
2
2
drate (FeCl .6H O), ammonium hydroxide (NH OH,
3
2
4
2
5%), sodium hydroxide (NaOH), urea (CO (NH ) ),
2 2
3 4
cobalt (II) nitrate hexahydrate (Co (NO ) .6H O), 1,4-
duced. The resultant nanocomposite was collected by an
3
2
2

CELLULOSE STABILIZED FE3O4 AND CARBOXYLATE-IMIDAZOLE AND CO-BASED MOF
3 of 10
external magnet and washed with deionized water and
dried at 70 C under vacuum.
stirred under solvent-free conditions at room tempera-
ture. Thin-layer chromatography (TLC) was utilized to
monitor the progress of the reaction. After completion of
the reaction, warm ethanol (10 ml) was added to the
reaction mixture, Fe O /cellulose/Co-MOF was separated
ꢀ
2
.5 | Synthesis of Fe O /cellulose/Co-
3 4
MOF
3
4
using a magnet and washed with ethanol. The solvent
was evaporated and the solid was recrystallized from eth-
anol to produce the pure product. Then, the recovered
catalyst was reused in five runs under similar conditions
as the first run to exhibit the recyclability and stability of
the prepared catalyst.
Fe O /cellulose (0.2 g) was dispersed in DMF (60 mL)
3
4
and sonicated for 20 min to dissolve completely. Conse-
quently, a mixture of Co (NO ) .6H O (0.87 g, 3 mmol),
3
2
2
1
,4-BDC (0.49 g, 3 mmol) and IM (2 mmol, 0.136 g) was
added into the mixture and sonicated for 15 min to dis-
solve reagents. The vessel was sealed and stirred at
ꢀ
1
20 C for 48 hr, then cooled back down to room temper-
ature. The dark brown precipitate was collected using an
external magnet, washed with ethanol and dried at 70 C
under vacuum.
3 | RESULTS AND DISCUSSION
3.1 | Synthesis of Fe O /cellulose/co-
ꢀ
3
4
MOF
2.6 | General procedure for the
Knoevenagel condensation using Fe O /
cellulose/Co-MOF as a catalyst
The synthesis route of Fe O /cellulose/Co-MOF
nanocomposite is displayed in Figure 1. First, Fe O /cel-
3 4
3
4
3 4
lulose was fabricated through chemical modification of
Fe O nanoparticles with cellulose in the presence of
urea/NaOH. Pre-treating Fe O4 nanoparticles with
3
A mixture of various aldehydes (1 mmol), malononitrile
1.5 mmol) and Fe O /cellulose/Co-MOF (15 mg) was
3
4
(
3
4
3 4
FIGURE 1 Preparation of Fe O /
cellulose/Co-MOF nanocomposite

4
of 10
ZARE AND RAFIEE
cellulose was increased their compatibility toward Co-
MOF and facilitated the growth of Co-MOF around
Fe O nanoparticles. Second, Fe O /cellulose was treated
crystal absorption peak of cellulose, C-O-C pyranoid ring
skeletal vibration and, the β-glycosidic units, respectively.
The peak appeared at 548 cm− in the spectrum of
Fe O /cellulose/Co-MOF nanocomposite is attributed to
1
3
4
3 4
with Co (NO ) .6H O (as an inorganic constituent), 1,4-
3
2
2
3 4
BDC and IM (as organic linkers) and DMF (as a solvent)
Fe-O stretching vibration and the absorption peaks
observed at 1588 and 1380 cm correspond to the asym-
ꢀ
−1
via heating to 120 C for 48 hr to form Fe O /cellulose/
3
4
Co-MOF nanocomposite. IM acts as a Lewis basic site
and coordination regulator, and improve the catalytic
performance of the fabricated nanocomposite. It is found
that the combination of 1,4-BDC with IM generates a M-
carboxylate coordination framework in which IM is coor-
dinated as a neutral ligand.
metric and symmetric stretching of the O=C-O bonded
to Co.
Figure 3 represents the XRD patterns of Fe O (a),
3
4
Fe O /cellulose (b) and Fe O /cellulose/Co-MOF (c). It
3
4
3 4
can be concluded by the XRD pattern of the Fe O /cellu-
3
4
lose nanocomposite that it is almost similar in the crystal
structure of Fe O nanoparticles after their congregation
3
4
on the cellulose surface. The XRD pattern of Fe O /cellu-
3
4
3
.2 | Characterization of the prepared
lose exhibits seven diffraction peaks at 2θ = 22.70, 30.5,
35.24, 43.20, 53.59, 57.13 and 62.76 , ascribing to the crys-
ꢀ
compounds
tal plane diffraction peaks of the (113), (220), (311), (400),
(422), (511) and (440) of Fe O nanoparticles. The XRD
Figure 2 displays the FT-IR spectra of Fe O , Fe O /cellu-
3
4
3
4
3 4
lose and Fe O /cellulose/Co-MOF. In the FT-IR spectrum
pattern of Fe O /cellulose/Co-MOF displays that visible
3 4
3
4
−
1
ꢀ
of Fe O , the broad absorption band at 3465 cm corre-
diffraction peaks at about 2θ = 8.95 and 15.88 are
assigned to the characteristic diffraction peaks of Co-
MOF.
3
4
sponds to O-H stretching vibration in adsorbed H O mol-
2
ecules in Fe O nanoparticles and the peak observed at
3
4
5
82 cm− is attributed to Fe-O stretching vibration. In the
1
Figure 4 displays the FE-SEM images of Fe O /cellu-
3
4
FT-IR spectrum of Fe O /cellulose, the two absorption
lose (a and b) and Fe O /cellulose/Co-MOF (c and d). As
3 4
shown in the FE-SEM images of the Fe O /cellulose, the
3 4
3
4
−
1
peaks observed at 3552 and 3418 cm are related to the
stretching vibrations of the O-H in cellulose, which
became weaker and broader, implies the strong bonding
morphology of this material is spherical with uniform
shapes and the average size of about 45 nm, while, the
Fe O /cellulose/Co-MOF consists of cellulose fibers that
between Fe O4 nanoparticles and cellulose molecules.
3
3 4
The absorption peaks at 1449, 1163, 1116, 1034 and
Co-MOF particles with an average size of about 40 nm
are dispersed on the surface of cellulose. The TEM analy-
sis of Fe O /cellulose/Co-MOF shows the presence of Co-
15 cm− implied the CH symmetric scissoring in the
1
6
2
pyranoid ring, C-O asymmetric bridge stretching, the
3
4
MOF on the cellulose surface (Figure 4 e and f).
The TGA/DTG analysis of Fe O /cellulose/Co-MOF
3
4
is presented in Figure 5. As the results exhibited, initial
ꢀ
TGA weight loss between 100 and 170 C belongs to the
removal of solvent and moisture from the framework.
With the increasing temperature, it was stable up to
ꢀ
3
50 C, with rapid weightlessness, which pointed out the
FIGURE 2 FT-IR spectra of Fe
Fe /cellulose/Co-MOF (c)
3
O
4
(a), Fe
3
O
4
/cellulose (b) and
FIGURE 3 XRD patterns of Fe
Fe /cellulose/Co-MOF (c)
3 4 3 4
O (a), Fe O /cellulose (b) and
3
O
4
3 4
O

CELLULOSE STABILIZED FE3O4 AND CARBOXYLATE-IMIDAZOLE AND CO-BASED MOF
5 of 10
3 4 3 4 3 4
FIGURE 4 FE-SEM images of Fe O /cellulose (a and b) and Fe O /cellulose/Co-MOF (c and d), TEM images of Fe O /cellulose/Co-
MOF (e and f)

6
of 10
ZARE AND RAFIEE
FIGURE 5 STA
thermogram of Fe
Co-MOF
3 4
O /cellulose/
loss of organic matter was belong to leaving the final
ꢀ
CoO. The final weightlessness occurred at 450 C signify-
ing that the MOF structure began to collapse and decom-
pose completely into oxides of Fe.
The magnetic properties of the materials were
investigated by VSM. Magnetization curves of Fe O4
3
(
(
a), Fe O /cellulose (b) and Fe O /cellulose/Co-MOF
3 4 3 4
c) are revealed in Figure 6. The magnetization curves
exhibit a magnetic hysteresis loop. The saturation mag-
netization values were determined as 79.0, 48.0 and
2
1.5 emu/g for Fe O (a), Fe O /cellulose (b) and
3 4 3 4
Fe O /cellulose/Co-MOF (c), respectively. Compared to
3 4 3 4
FIGURE 6 VSM analysis of Fe O (a), Fe O /cellulose (b) and
3
4
the as-synthesized Fe O and Fe O /cellulose, the satu-
3 4
Fe O /cellulose/Co-MOF (c)
3
4
3 4
ration magnetization of Fe O /cellulose/Co-MOF is
3
4
reduced, but it still perseveres at a high level. Also the
magnetic isolating of Fe O /cellulose/Co-MOF
3.3 | Catalytic activity test
3
4
nanocomposite is tested by setting a magnet near the
glass bottle of the nanocomposite.
In addition, the EDX analysis of the prepared catalyst
confirms the existence of Co in the modified framework.
It displays the presence of carbon, nitrogen, oxygen, Fe,
and Co (Figure 7).
The catalytic application of Fe O /cellulose/Co-MOF is
3 4
examined in the Knoevenagel reaction under diverse con-
ditions (Table 1). For the optimization of the reaction
conditions, the reaction between malononitrile with
benzaldehyde in the presence of Fe O /cellulose/Co-
3
4
MOF as a catalyst is designated as a model reaction. The
reaction progress is monitored by TLC. The model reac-
tion is performed at 5, 10, 15 and 20 mg of Fe O /cellu-
The porosity of Fe O /cellulose/Co-MOF is investi-
3
4
gated by measuring nitrogen adsorption–desorption iso-
3
4
therms at 77 K. Fe O /cellulose/Co-MOF exhibits typical
lose/Co-MOF loading. With increasing catalyst loading
from 5 to 15 mg, the yield is enhanced and the best result
in an appropriate time is obtained using 15 mg of catalyst
(Table 1, entry 4). By increasing the catalyst loading to
20 mg no change in the yield of the product is observed
(Table 1, entry 5). The effect of different solvents such as
H O, EtOH, CH Cl and CH CN and solvent-free condi-
3
4
type IV isotherms with a hysteresis loop, designating its
mesoporous feature. According to this analysis, the area
of the surface, the total volume of the cavities and the
2
3
mean diameter of the cavities were 98 m /g, 0.1309 cm /g
and 5.0875 nm, respectively. Furthermore, Fe O /cellu-
3
4
lose/Co-MOF has a wide pore-size distribution from 1 to
0 nm, signifying the coexistence of structural pores in
addition to interparticle pores.
2
2
2
3
6
tions is also investigated and the results reveal that H O
2
and EtOH provide moderate yields (Table 1, entries 6 and

CELLULOSE STABILIZED FE3O4 AND CARBOXYLATE-IMIDAZOLE AND CO-BASED MOF
7 of 10
3 4
FIGURE 7 EDS spectrum of Fe O /
cellulose/Co-MOF
electron-donating and electron-withdrawing groups.
Based on the obtained results all substrates give the
corresponding products in relatively high yield in very
short reaction time as reveal in Table 2. The benzalde-
hyde derivatives containing electron-withdrawing groups
such as -NO2, and -Cl are transformed to the
corresponding products with a high yield (Table 2, entries
TABLE 1 Effect of catalyst loading and solvent in the
Knoevenagel condensation of malononitrile with benzaldehyde
2–4), whereas the benzaldehyde derivatives possessing
electron-donating moieties including -OCH , -CH , and -
3
3
Catalyst
Entry (mg)
Time
Solvent (min.)
Yield
(%)
OH provide the lower yields (Table 2, entries 5–7). This
result proves that the benzaldehyde derivatives having
electron-withdrawing groups are slightly reactive com-
pared to those with electron-donating moieties. Addition-
ally, the catalytic effect of Fe O and cellulose alone and
1
2
3
4
5
6
7
8
9
-
-
240
10
10
10
10
10
10
10
10
-
5
-
86
90
94
94
68
75
65
55
10
15
20
15
15
15
15
-
3
4
-
Fe O /cellulose was investigated on the model reaction.
3 4
It is observed that Fe O and cellulose alone could not
-
3 4
catalyze the reaction efficiently and the product is
obtained in low yields (44% and 32%) in long reaction
times (6 and 12 hr). It is also found that Fe O /cellulose
H
2
O
EtOH
3
4
CH
2
3
Cl
2
CH
CN
TABLE 2 The Knoevenagel condensation of several aromatic
Reaction conditions: benzaldehyde (1 mmol), malononitrile (1.5 mmol),
catalyst (15 mg), room temperature.
aldehydes with malononitrile in the presence of Fe
Co-MOF
3
O
4
/cellulose/
Entry
R
Time (min)
Yield (%)
7
). Based on the obtained results the yields in H O and
2
EtOH solvents are lower than solvent-free conditions. It
might be attributed to the solvation of the active func-
tional groups by these solvents and hydrogen-bonding
between active protonic sites of Fe O /cellulose/Co-MOF
and these solvents which declines the catalytic efficiency.
Hence, the use of 15 mg of the catalyst under the solvent-
free conditions at room temperature is designated as opti-
mum conditions. After the optimization of the condi-
tions, the generality and the scope of this system are
examined using several aromatic aldehydes bearing both
1
2
3
4
5
6
7
H
10
8
94
97
98
97
88
89
78
4-NO2
4-Cl
2-Cl
4-MeO
4-Me
2-OH
10
45
15
60
15
3
4
Reaction conditions: aldehyde (1 mmol), malononitrile (1.5 mmol), catalyst
(15 mg), room temperature.

8
of 10
ZARE AND RAFIEE
provides the product in 53% yield for 8 hr. The experi-
mental results show that Co-MOF is enhanced catalytic
performance of modified Fe O nanoparticles.
mixture after 5 min, and the resulting filtrate was further
stirred for 5 min. The conversion yield of the benzalde-
hyde remains unchanged for the filtrate even at extended
time, indicating that the catalytic process is heteroge-
neous and there is not any progress for the reaction in
the homogeneous phase.
3
4
The synthesized catalyst in this study has both Lewis
2+
acidic sites (Co ) and basic sites (IM), hence it is an effi-
cient heterogeneous catalyst for the Knoevenagel reac-
tion. A mechanism for the Fe O /cellulose/Co-MOF-
3
4
catalyzed the Knoevenagel reaction of aldehyde and
malononitrile was proposed (Scheme 1). Initially, the
3.4 | Reusability of Fe O /cellulose/Co-
MOF
3
4
2+
aldehyde is activated by Co ion as a Lewis acid site
intermediate I). Uncoordinated IM adsorbed in Co-MOF
(
To examine the reusability of Fe O /cellulose/Co-MOF,
3 4
serves as a base to promote the deporotonation of the
methylene for the production of a carbanion intermediate
after the completion of the reaction, the catalyst is col-
lected, separated, and then reused under similar condi-
tions as the first run. This experiment is repeated five
times and it is found that Fe O /cellulose/Co-MOF is sta-
ble under the applied conditions and can be reused at
least five times without a considerable decreasing in its
catalytic activity (Figure 8).
(II). Next, the nucleophilic attack of the formed carban-
ion takes place on the activated carbonyl group. Lastly,
the addition intermediate (III) can be rapidly converted
to the benzylidenemalononitrile after protonation and
3
4
[59]
dehydration.
In order to prove the heterogeneity of the catalyst, the
filtration experiment of Fe O /cellulose/Co-MOF was
3
4
performed. The catalyst was separated from the reaction
3.5 | Comparison of the proposed
catalyst with the previously reported
catalysts for the Knoevenagel condensation
The comparison between the performance of the
Knoevenagel condensation based on the Fe O /cellulose/
3
4
Co-MOF catalyst and some previously reported catalysts
involving the Knoevenagel condensation is listed in
Table 3. It is found that Fe O /cellulose/Co-MOF exhibits
3
4
SCHEME 1 Proposed mechanism for the Knoevenagel
reaction catalyzed by Fe
3
O
4
/cellulose/Co-MOF
3 4
FIGURE 8 Reusability of Fe O /cellulose/Co-MOF
TABLE 3 Comparison of the proposed catalyst with reported catalysts for the Knoevenagel condensation of benzaldehyde and
malononitrile
ꢀ
Catalyst
Amount
19 mg
Time
7 hr
Solvent
Temp. ( C)
Conversion (%)
Ref.
[
[
[
[
[
[
60]
61]
62]
54]
54]
59]
Au@Cu (II)-MOF
Toluene/MeOH
Toluene
r.t.
r.t.
r.t.
60
99
Fe
3
O
4
@ZIF-8
4 mol%
20 mg
3 hr
94
ZIF-8
3 hr
Toluene
100
99.9
99.8
99
Amino-functionalized Zn-MOF
Amino-functionalized Cd-MOF
MOF-5
0.02 mmol
0.02 mmol
50 mg
6 hr
Solvent-free
Solvent-free
Solvent-free
Solvent-free
6 hr
60
48 hr
10 min
25
Fe
3
O
4
/cellulose/Co-MOF
15 mg
r.t.
94
Our work

CELLULOSE STABILIZED FE3O4 AND CARBOXYLATE-IMIDAZOLE AND CO-BASED MOF
9 of 10
advantages in terms of cost-effectiveness and simplicity,
low temperature and very short reaction time. Addition-
ally, it consumes very short reaction time and mild condi-
tions in the Knoevenagel condensation compared with
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How to cite this article: Zare E, Rafiee Z.
Cellulose stabilized Fe O and carboxylate-
3
4
imidazole and Co-based MOF growth as an
exceptional catalyst for the Knoevenagel reaction.
Appl Organometal Chem. 2020;e5516. https://doi.
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