Encapsulation of Silver Nanoparticles in an Amine-Functionalized Porphyrin Metal–Organic Framework and Its Use as a Heterogeneous Catalyst for CO2 Fixation under Atmospheric Pressure

Article abstract of DOI:10.1002/asia.201800815

A new porphyrin-based compound, [Zn₃(C₄₀H₂₄N₈)(C₂₀H₈N₂O₄)₂(DEF)₂](DEF)₃ (1; DEF=N,N-diethylformamide), has been synthesized by employi

Full text of DOI:10.1002/asia.201800815

CHEMISTRY
AN ASIAN JOURNAL
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Accepted Article
Title: Encapsulation of Ag-nanoparticle in an Amine-Functionalized
Porphyrin MOF and its Use as a Heterogeneous Catalyst for CO2
Fixation under Atmospheric Pressure
Authors: Srinivasan Natarajan, Gargi Dutta, Ajay Kumar Jana, M.
Eswaramoorthy, and Deeraj Kumar Singh
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Encapsulation of Ag-nanoparticle in an Amine-Functionalized
Porphyrin MOF and its Use as a Heterogeneous Catalyst for CO2
Fixation under Atmospheric Pressure
Gargi Dutta,[a] Ajay Kumar Jana,[a] Dheeraj Kumar Singh,[b] M. Eswaramoorthy,[b] Srinivasan
Natarajan*[a]
Abstract:
A
new
porphyrin
based
compound,
methodologies to reduce overall greenhouse emission. CO2 is
an attractive C1 building block for organic synthesis.[9] However,
carbon dioxide is a symmetrical linear molecule and difficult to
activate and involve in bond formation.[10] There has been
intense research activities during the last decade towards
fixation of CO2:carboxylation of organometallic reagents,[11]
epoxides,[12] carboxylative cyclization of propargylic amines and
alcohols[13] etc. Of these, the direct C-H carboxylation of terminal
alkynes employing CO2 as the carbon source is important as the
alkynyl carboxylic acid and its derivatives have important
industrial applications.[14] The carboxylation reactions, in general,
were carried out under homogeneous catalytic conditions. This
would prevent the recovery of the catalyst. In our efforts towards
fixation of CO2 into useful products we have recently employed a
MOF compound synthesized from tetra-(4-pyridyl)porphyrin
(H2TPyP) and 4,4′-Oxybis(benzoic acid) (H2OBA), which
catalyzes and converts CO2 into cyclic carbonates.[15] In
continuation of the theme, we have now attempted CO2 fixation
employing a Ag-nanoparticle loaded porphyrin based MOF,
[Zn3(C40H24N8)(C20H8N2O4)2(DEF)2](DEF)3 , 1. It may be noted
that the reports of metal loaded MOF materials for catalytic
conversion of CO2 are not many.[16] The porphyrin support
[Zn3(C40H24N8)(C20H8N2O4)2(DEF)2](DEF)3, 1 was prepared by
solvothermal method employing Zn(NO3)2.6H2O, tetra-(4-
[Zn3(C40H24N8)(C20H8N2O4)2(DEF)2](DEF)3 (1) has been synthesized
employing 5,10,15,20-tetrakis(4-pyridyl)porphyrin (H2TPyP), 1,2-
diamino-3,6-bis(4-carboxyphenyl)benzene and Zn2+ salt at 100ºC
under solvothermal condition. The structure, determined by single
crystal X-ray diffraction studies, is three dimensional with three-fold
interpenetration. The usefulness of free –NH2 groups in the ligand
was exploited for anchoring Ag-nanoparticles via a simple solution-
based route. The Ag-loaded sample, Ag@1, was characterized by
PXRD, EDS, HRTEM, SEM, XPS and ICP-MS analysis which clearly
indicate Ag-nanoparticles with size of 3.83 nm were uniformly
distributed within the MOF. The Ag@1 sample was evaluated for
possible catalytic activity for the carboxylation of terminal alkyne
employing CO2 under atmospheric pressure, which gave excellent
results. The Ag@1 catalyst was found to be robust, active and
recyclable. The present studies suggest that the porphyrin MOFs not
only exhibit interesting structures but also show good heterogeneous
catalytic activity towards fixation of CO2.
Introduction
The use of metal nanoparticles to catalyse organic
reactions has attracted considerable attention over the years.[1]
The possible agglomeration of metal nanoparticles during the
catalytic reactions was avoided by employing suitable substrates
such as inorganic oxides, organic polymers etc.[2] The last few
years witnessed the use of metal nanoparticles anchored in
metal-organic framework (MOF) compounds to improve catalytic
and related properties, which appears to be superior to the
individual (unsupported) nanomaterials.[3] The metal loaded
(generally based on noble metals), MOF based heterogeneous
catalytic systems appear to exhibit advantages over traditional
catalysts; (a) shorter duration and (b) good recyclability. Many
metal@MOF systems have been explored and found to exhibit
good catalytic behavior towards olefin hydrogenation,[4] aerobic
oxidation of alcohol,[5] C-C coupling [6] etc. Among these, the Ag-
loaded MOFs have been known to exhibit good catalytic
activity.[7]
pyridyl)porphyrin
(H2TPyP)
and
1,2-diamino-3,6-bis(4-
carboxyphenyl)benzene as a linker. The free amine groups,
present in the linker, are attractive for anchoring Ag-
nanoparticles. The metal loaded MOF material (Ag@1) was
employed for the carboxylation of terminal alkyne employing
gaseous CO2 under 1 atm pressure. In this manuscript synthesis,
structure and heterogeneous catalytic activity of this compound
is presented.
Results and Discussion
Structure of [Zn3(C40H24N8)(C20H8N2O4)2(DEF)2](DEF)3 (1)
Compound 1 crystallizes in triclinic P-1 space group. The
asymmetric unit of 1 contains 58 non-hydrogen atoms (Figure
S1 in the Supporting Information) that includes two
crystallographically distinct Zn2+ ions: Zn(1) occupies a special
position (1a) with a site multiplicity of 0.50 and bonded with four
pyrrole nitrogen atoms [N(1), N(2), N(1)(#1) and N(2)(#2)] and
two oxygen atoms [O(1) and O(1)(#1)] from two DEF molecules
CO2 is an important greenhouse gas and there have been
considerable attempts to convert it into useful products.[8] It is
important to develop viable CO2 capture and sequestration
and has octahedral coordination whereas Zn(2) has
a
tetrahedral geometry formed by two oxygen atoms [O(2) and
O(5)] from the acid linker and two nitrogen atoms [N(3) and N(4)]
from the H2TpyP ligand. The Zn-N bond distances are in the
range of 2.044(3)-2.049(3) Å [average 2.045Å] and the Zn-O
bond distances are in the range of 1.931(2)-2.422 Å [average
2.178Å] (Table S1 in the Supporting Information). Zn(1)
occupies the plane of the porphyrin ring and Zn(2) links the
porphyrin units through the pyridyl nitrogens forming a one
dimensional unit (Figure 1a). The 1D chains are connected by
[a]
[b]
Dr. G. Dutta, A. K. Jana, Prof. S. Natarajan
Framework Solids Laboratory, Solid State and Structural Chemistry
Unit, Indian Institute of Science, Bangalore-560012, India
E-mail: snatarajan@iisc.ac.in
Dr. Dheeraj Kumar Singh, Prof. M. Eswaramoorthy
Chemistry and Physics of Materials Unit, Jawaharlal Nehru Centre
for Advanced Scientific Research, Bangalore -560064, India.
Supporting information for this article is given via a link at the end of
the document.
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10.1002/asia.201800815
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2D layer; (c) The connectivity between the 2D layers through another
carboxylate forming the 3D structure; (d) The topological view of the 3-fold
interpenetrated structure.
(a)
the dicarboxylate linker forming a 2D layer (Figure 1b). The 2D
layers are further crosslinked by another dicarboxylate linker
forming the 3D structure (Figure 1c). It may be noted that the
amine groups present in the carboxylate linker is free. The 3D
structure would have resulted in large cavities, which were
avoided by interpenetration of identical units. The structure,
infact, has a 3-fold interpenetrated porous framework (Figure 1d).
Inspite of the interpenetration a solvent accessible void of
2042Å3 per unit cell is available in this structure, which is
approximately 59.5% of the unit cell volume.
(b)
Optical Studies
The UV-Vis absorption spectra and photoluminescence studies
at room temperature were carried out on the powdered sample
of the porphyrin H2TPyP and 1 [Figure S3 in Supporting
Information]. The studies indicate typical features of the
porphyrin ligand exhibiting sharp Soret and Q bands arising from
the π- π* transitions. The as-synthesized compound 1 also
exhibits intense Soret band at 412 nm [a1u→eg (allowed)] and a
number of Q-bands [a2u→eg (forbidden)] in the range 450-600
nm. A red shift of the absorption bands observed in 1 with
respect to the ligand H2TPyP along with the reduction in the
number of Q-bands can be attributed to the successful insertion
of the Zn2+ ion within the porphyrin core.
The photoluminescence spectrum for compound 1 was also
investigated employing a excitation wavelength of 412 nm
(Figure S3(b) in Supporting Information). The observed broad
emission bands in the range 533-663 nm could be due to the
intraligand transitions from porphyrin ligand (H2TPyP). An
emission band observed around ~533 nm may correspond to eg
→ a1u transition. The emission bands
(c)
observed at 630 nm and 663 nm could
be attributed to eg → a2u transition.
IR Studies
IR spectra of 1,2-diamino-3,6-bis(4-
carboxyphenyl)benzene and 1 were
recorded at room temperature and
exhibited characteristic bands (Figure
S4, Table S2). Band centered around
3388, 3396 cm-1 respectively for ligand
and 1 in the IR spectra corresponds to
(d)
the –N-H stretch of the free amine
group. The bands at 2998 and 2977 cm-1 respectively for ligand
and compound 1 can be assigned to the aromatic C-H stretch.
Presence of sharp bands ~ 1684, 1668 cm-1 was attributed to
free and metal coordinated –COO group in ligand and
compound 1 respectively.
Thermogravimetric Studies
The TGA study of 1 (Figure S5(a) in Supporting information)
indicates a continuous two step weight loss of 32.7% in the
temperature range 30-215°C; which could be attributed to the
loss of 5DEF molecules (calcd 31.9%). A flat region in the
temperature range 215-350°C suggests that the framework may
Figure 1. (a) Zn-porphyrinic units connected by ZnO2N2 tetrahedra forming the
1D chains; (b) The 1D chains are connected by the dicarboxylate forming the
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be stable upto 350°C. A continuous weight loss beyond 350°C
suggests collapse of the framework. The final calcined product
was found to be ZnO by PXRD studies (JCPDS: 36-1451; Figure
S5(b) in Supporting information). To examine the framework
stability during solvent removal, the as-synthesized compound 1
was kept in a vacuum oven at 200°C for 1 day. The evacuated
and heated sample exhibits the same PXRD pattern as that of
the as-synthesized sample, which indicates that the framework
is retained (Figure S5(c) in supporting information). A TGA
analysis of the evacuated and heated sample exhibits a small
initial weight loss, possibly due to the surface adsorbed water
molecules. The vacuum treated sample appears to be stable
upto a temperature of 335°C after which it exhibits a sharp
weight loss of 67%, suggesting the collapse of the framework.
The calcined sample again was found to be ZnO by PXRD. The
vacuum treated sample was soaked in DEF, which readily
readsorbs the DEF molecules. The resolvated sample was again
analyzed by TGA, which exhibited comparable weight loss
behavior as that of the as-synthesized compound (Figure S5 (a)
in Supporting Information).
It may be noted that only 1.47% of silver nanoparticles could be
[18]
loaded on a porphyrin MOF reported by us
with no –NH2
group under the same condition (Table S3 in Supporting
Information).
Adsorption of CO2
The presence of free –NH2 groups in the structure prompted us
to investigate the possible CO2 adsorption in sample. Prior to the
adsorption measurement the as-synthesized 1 was kept in
MeOH for 5 days at room temperature for solvent exchange, by
refreshing the solvent every day.
Ag@1 Characterizations
It has been known that the free amine group of the ligand could
(a)
(b)
be employed for anchoring metal nanoparticles[17]
;
and it
Figure 2: (a) Figure shows the Ag-loaded MOF compound (Ag@1); (b)
HRTEM image of a Ag nanoparticle in Ag@1. The interplanar spacing of
0.226 nm corresponds to the (111) plane of Ag0
occurred to us that we could use the amine groups for the
encapsulation of Ag nanoparticle. Thus, the Ag@1 material was
synthesized employing AgNO3 as the precursor and NaBH4 as
the reducing agent. The PXRD pattern of the silver loaded
compound 1 (Ag@1) indicates that the framework remains intact
after Ag nanoparticle loading (Figure S2 in Supporting
Information). The characteristic peak of Ag(111) (2θ~38) and
Ag(200) (2θ~45) confirms successful deposition of Ag-
nanoparticle. The Ag@1 compound was characterized by EDS,
TEM, IR and ICPMS analysis. TEM study of the Ag-loaded
compound indicates that the particles are evenly distributed with
particle sizes in the range of 3.83 ± 0.05 nm (Figure S6(a) in
supporting information). The presence of silver nanoparticles
was confirmed from the energy-dispersive X-ray spectrum (EDS)
(Figure S6(b) in supporting information) and high resolution
transmission electron microscopy (HRTEM) (Figure2b). The
observed atomic lattice fringes with spacing of 0.236 nm
corresponds to the (111) plane of Ag (Figure 2b). The oxidation
state of the Ag nanoparticle was determined employing X-ray
photo electron spectroscopy (XPS) (Figure S7 in supporting
information). From the XPS analysis, the Ag core level binding
energies for Ag 3d5/2 and Ag 3d3/2 were found to be 368.08eV
and 373.66eV, respectively, which are generally observed for
silver in the native state [Ag(0)].[16] Inductively coupled plasma
(ICP) analysis indicated that the amount of Ag loaded in Ag@1
was 7.85% (Table S3 in Supporting Information). The IR spectral
studies of Ag loaded compound (Ag@1) indicated a shift of
45cm-1 compared to the as-synthesized 1 in the –N-H stretching
region (3351 cm-1) (Figure S4(c) in Supporting Information). It is
likely that the shift in the N-H stretching frequency is due to the
electrostatic interactions between the NH2 group and the silver
nanoparticle. Similar observations have been made before. [17b] It
is likely that the higher loading of Ag nanoparticles is due to the
presence of a number of available amino groups from the ligand.
The resulting methanol exchanged sample was heated at 100ºC
for 12 hrs under vacuum to get the activated 1. The CO2
adsorption was carried out at 298K and 195K and upto a relative
pressure P/P0= 1 (Figure 3). The maximum CO2 uptake capacity
at 298K and 195K was found to be 13.55 and 51.10 cm3g-1
respectively(Figure 3), which compares well with the reported
porphyrin based MOF.[19] The Ag@1 was examined under
identical condition which showed an uptake of 5.309 cm3g-
1(298K) and 37.9 cm3g-1(195K) of CO2 (Figure 3).
(a)
(b)
Figure 3: CO2 adsorption isotherm (a) at 298K; (b) 195K
Ag(0)@1
Cs2CO3 (1.2 mmol)
nBuI(1.2 mmol)
60C/DMF/6 hr
O
CO
R
+
R
H
2
1 mmol
R
(balloon)
O
nBu
Cs CO
+
R
H
2
3
[Ag]
CO2Bu
CsHCO3
nBuI
R
Ag
R
CO2Ag
CO2
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heterogeneous catalyst for the chemical fixation of CO2,
especially, towards the activation of terminal alkyne. For this
reaction we employed milder reaction conditions compared to
the known ones.
In a typical reaction terminal alkyne (1 mmol), Cs2CO3 (1.2
mmol), Ag@1 (5 mol %), nBuI (1.2 mmol) and 4 ml DMF were
introduced in a Schlenk flask. The reactants in the Schlenk flask
were put through a freeze-pump-thaw sequence to remove all
the dissolved gases. The resulting reaction mixture was heated
under CO2 atmosphere (99.99% balloon) at 60ºC for 6h. The
reaction mixture was cooled to room temperature and the
catalyst was recovered by filtration followed by extraction of the
products employing n-hexane. The hexane from the extracted
Scheme1. Carboxylation of terminal alkynes with CO2
Catalytic Studies
Silver nanoparticles immobilized on MOFs such as MIL-101 has
been shown to effectively catalyze the carboxylation of terminal
alkyne to the corresponding carboxylic acid.[16]
Table 1: Carboxylation of terminal alkyne using Ag@1
Entry Catalyst
Product
Yield
R
H
O
O
1
Ag@1
91%
Ph
H
Ph
nBu
O
2
3
Ag@1
Ag@1
87%
84%
Me
F
H
Me
F
O
nBu
O
H
O
nBu
nBu
O
4
5
Ag@1
Ag@1
83%
72%
MeO
H
MeO
Br
O
O
Br
Ph
Ph
H
O
nBu
6
7
No catalyst
1
-
No
product
H
O
14%
H
H
Ph
Ph
O
nBu
O
8
AgBF4
21%
Ph
O
nBu
solution was removed by evaporation and the crude product was
purified by column chromatography (silica gel, CHCl3/EtOAC) to
get the desired alkyl-2-alkylnoates.The yield of the products was
found to be good, in the range of 72-91% (Table1). The Ag@1
catalyst was examined for possible re-use in the same reaction
and we have observed that the catalyst remains active for
atleast three cycles (Figure 4).
The alkynyl carboxylic acid and its derivatives have been known
as key synthons in many biologically active molecules:
spiroindoles (antimalarial behavior)[14c,20]; spirobenzofuranones
[14a]
(antifungal behavior)
;
coumarin and its derivatives
(cholesterol lowering activity)[14d]; to name a few. In many of
these compounds, propiolic acid derivatives are the main
component, which can be prepared through a number of
approaches: (i) oxidation of propargylic alcohol or aldehyde
derivatives [21]; and (ii) insertion of CO2 into the alkynyl species,
obtained by the deprotonation of alkynes employing alkali metal
hydride or organometallic reagents.[22] In addition, metal
catalyzed insertion of CO2 onto the alkynyl group has also been
established.[23] There is a need to look for newer catalysts that
can be employed for this organic transformation in
a
heterogeneous manner. Thus, we explored the Ag@1 as a
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Figure 5: Hot filtration experiment for carboxylation of terminal alkyne
Figure 4: Recyclability studies for carboxylation reaction of terminal alkynes
employing Ag@1
Conclusions
In summary, the synthesis, structure and catalytic studies of a
new three-fold interpenetrated 3D framework compound
[Zn3(C40H24N8)(C20H8N2O4)2(DEF)2](DEF)3, 1, employing H2TPyP,
1,2-diamino-3,6-bis(4-carboxyphenyl)benzene
Zn(NO3)2.6H2O under solvothermal conditions has been
accomplished. Ag nanoparticles
We have also examined the structural integrity of the catalyst by
PXRD (Figure S8 in Supporting Information) as well as SEM,
TEM and HRTEM studies (Figure S9 and S10 in Supporting
Information) to probe the framework structural damage as well
as changes in the morphology of Ag-nanopartcles. Our studies
did not reveal any major noticeable change in the framework
structure (PXRD) and also no agglomeration of Ag-nanoparticles
was noticed.
and
HO
O
O
O
O
O
We have also made studies employing samples with different
Ag-loadings (3% and 15%). The TEM image of 3% Ag-loaded
compound indicates that the Ag-nanoparticles have particle
sizes in the range 3.07±0.14. In addition, the Ag nanoparticles
are also evenly distributed across the compound. The higher
loading (15%), on the other hand, results in agglomeration of the
Ag-nanoparticles (Supporting Information Figure S11). We have
carried out the catalytic reaction with 3% Ag-loaded compound
under the same experimental conditions taking phenyl acetylene
as a substrate. We observed a conversion of 66% with 3% Ag-
loaded sample. This is lower than the conversion obtained with
the 7.85% Ag-loading. It is likely that the 7.85% Ag-loading could
be the optimal one.
NH2
NH2
N
N
NH2
NH2
KOH/THF/MeOH
Zn/AcOH
S
120C/12hr
H2O/90C/12h
O
O
O
O
HO
O
were deposited on the MOF employing simple solution route to
get Ag@1. The Ag@1
The present studies clearly suggest that the catalyst is reusable
as well as stable under the conditions of carboxylation studies. It
may be noted that the efficiency of Ag@1 was comparable with
other Ag-nanoparticle supported catalysts (Table S4 in
supporting information). We have also carried out hot filtration
experiment to confirm the heterogeneous nature of the reaction
(Figure 5). A reaction mixture of phenyl acetylene (1 mmol),
Cs2CO3 (1.2 mmol), Ag@1 (5 mol %), nBuI (1.2 mmol) and 4 ml
DMF was heated at 60ºC under CO2 atmosphere. After 1h
Ag@1 was taken out from the reaction mixture by centrifugation
and the reaction was allowed to continue at 60ºC. No further
increase of the yield of the product was observed during the
course of the reaction in the absence of Ag@1. In order to
confirm the encapsulated Ag-nanoparticles were responsible for
catalytic activity few controlled experiments were also carried
out. In the absence of any catalyst there was no conversion
(Table 1, entry 6). When 1 was used as the catalyst we obtained
a 14% conversion (Table 1, entry 7) and employing AgBF4 as a
catalyst a 21% conversion was obtained (Table 1, entry 8).
Hence we believe that loaded Ag(0) nanoparticles embedded on
the MOF may be responsible for the observed heterogeneous
catalytic activity.
Scheme 2: Synthesis of 1,2-diamino-3,6-bis(4-carboxyphenyl)benzene
sample was examined as a heterogeneous catalyst towards
converting CO2 via a carboxylation reaction of terminal alkyne
through C-H bond activation under mild conditions (1 atm, 60ºC).
The studies indicate that Ag@1 exhibits good catalytic activity,
excellent stability as well as good recyclability for this reaction.
Our continuing investigations reveal that the porphyrin based
MOFs could be good heterogeneous catalysts for other
reactions as well, which are being pursued currently.
Experimental Section
Materials: The metal salts and other chemicals were procured
from commercial suppliers [SD fine (India), Alfa Aesar (USA),
Sigma Aldrich (USA), TCI (India) etc.] and used without further
purifications. The Solvents were purified by standard procedures
prior to use.
The ligand employed in the present synthesis was prepared
from dimethyl 4,4′-(benzothiadiazole-4,7-diyl)dibenzoate[24]. The
procedure is as follows:
Synthesis of 1,2-diamino-3,6-bis(4-methoxycarbonylphenyl)
benzene
4,4′-(benzothiadiazole-4,7-diyl)dibenzoate (1.00 gm, 2.5 mmol)
was dissolved in 200 ml of 1,4-dioxane/AcOH (1:1) mixture. Zn-
dust (2.60 gm, 40 mmol) was added to it slowly. The resulting
mixture was refluxed at 110°C for 12 hrs and filtered hot. The
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10.1002/asia.201800815
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resultant filtrate was concentrated on a rotary evaporator. The
obtained residue was washed with distilled water to get the pure
product. Yield: 0.677 gm, (72%).
(Figure S4 in Supporting Information). UV-Vis spectra (Perkin
Elmer, Lambda-35) and solid state photoluminescence (Perkin–
Elmer model-LS55 instrument) of the compound
1 were
Synthesis of 1,2-diamino-3,6-bis(4-carboxyphenyl)benzene
The synthesized 1,2-diamino-3,6-bis(4-methoxycarbonylphenyl)
benzene (0.500gm, 1.3 mmol) was dissolved in a mixture of
MeOH (10 ml), THF (10 ml) and water (5 ml). KOH (2.91gm, 52
mmol,) was added to the above solution and the mixture was
refluxed at 80°C for 12 h. The resulting mixture was cooled to
room temperature and conc. HCl was added slowly to obtain a
pH of 2. The resultant precipitate was filtered, washed with water
and dried under vacuum. Yield: 0.430 gm, (95%).
recorded at room temperature. (Figure S3 in supporting
Information). The PXRD patterns were recorded in the 2θ range
5-50°C (Philips X’pert) (CuKα radiation). The simulated PXRD
pattern from the single crystal structure was generated
employing Mercury software (1.4.1) (Figure S2 in supporting
information). Thermogravimetric analysis (TGA) (Metler-Toledo)
was carried out in N2 atmosphere (flow rate = 20 mL/min) in the
temperature range 30-1000°C (heating rate = 10°C/min) (Figure
S5 in Supporting Information). The transmission electron
microscopy (TEM), high-resolution TEM (HRTEM) images
(Figure2) and energy-dispersive X-ray spectroscopy (EDS) were
obtained employing a JEM 2100F, JEOL transmission electron
microscope with an accelerating voltage of 200 kV( Figure S6 in
supporting information).
Synthesis
of
[Zn3(C40H24N8)(C20H8N2O4)2(DEF)2](DEF)3(1)
Compound 1 was prepared by employing a solvothermal
method (Scheme 3). A mixture of H2TPyP (0.02 mmol, 0.012gm),
1,2-diamino-3,6-bis(4-carboxyphenyl)benzene
(0.04mmol,0.015gm) and Zn(NO3)2.6H2O (0.1 mmol, 0.029 gm)
was placed in a 7 mL Teflon lined stainless steel autoclave and
heated at 100°C for 3 days.This resulted in purple colored
crystals, which were filtered, washed with dry methanol and
vacuum dried at room temperature. Yield≈0.019 gm, 62% based
on H2TPyP. Elemental analysis calcd (%) C 68.57, H 5.21, N
12.95; found: C 68.51, H 5.19, N 12.97.
Single-crystal structure determination:
A suitable single crystal of 1 was carefully selected and mounted
onto a thin fibre loop using paratone oil. Single crystal data was
collected at 110K on an Oxford Xcalibur (Mova) diffractometer
equipped with an EOS CCD detector. X-ray generator operated
at 0.8 mA and 50 kV (Mo Kα , λ = 0.71073 Å) during data
collection. Crysalis Red [25] was used for cell refinement and data
collection. The structure was solved by Direct Methods and
refined using WINGX suit of program (version 1.63.04a)[26]. The
hydrogen atoms of the ligands were located from the difference
fourier map and were fixed in geometrically idealized positions
and refined using a riding model. Hydrogen positions of the
disordered solvent molecules could not be located and the
solvent molecules were accounted using the SQUEEZE option
present in the WinGX PLATON program. The final refinements
included the atomic positions for all the atoms, anisotropic
thermal parameters for all the non-hydrogen atoms, and
isotropic thermal parameters for all the hydrogen atoms. The
details of the structure solution and final refinement parameters
are given in Table 2. CCDC 1842924 contains the
supplementary crystallographic data for this paper. This data
can be obtained free of charge from The Cambridge
Crystallographic Data Centre.
COOH
N
NH2
NH
N
N
Zn(NO3)2.6H2O
DEF/100oC/3days
N
N
1
+
HN
NH2
N
COOH
Scheme 3: Synthesis of 1 by solvothermal method
Synthesis of Ag@1
The as synthesized crystals of 1 (0.1 gm, 0.063 mmol) were
dispersed in 10 ml acetonitrile and transferred to a 25 ml RB
flask. AgNO3 (0.010 gm; 0.058 mmol) dissolved in 1 ml of
acetonitrile was added to it and the reactants were stirred for.
The RB flask was kept in ice bath and methanolic solution (1 ml)
of NaBH4 was slowly added. The resulting mixture was stirred
for another 4 hrs at room temperature. The product was
separated through centrifugation and washed with acetonitrile
(3x10 mL) to obtain the desired Ag@1.
Table 2: Crystal Data and Structure Refinement Parameters for
the prepared compound
1
Empirical Formula
FormulaWeight
Crystal System
Space Group
a(Å)
C80H40N16O10Zn3
1581.45
Initial Characterizations
The ligand 1,2-diamino-3,6-bis(4-carboxyphenyl)benzene, and
the products from the catalytic studies were characterized by
NMR spectroscopic studies (Figure S14-S19 in supporting
information) using a Bruker 400 MHz spectrometer. Chemical
shifts are reported in ppm employing tetramethylsilane as the
internal reference. The IR spectrum of the prepared compounds
was recorded as KBr pellets in the mid IR region (4000-400 cm-
1) using FTIR spectrometer (PerkinElmer, model no: L125000P)
Triclinic
P-1
14.2899(13)
16.1798(15)
16.5216(16)
69.713(4)
b(Å)
c(Å)
α (deg)
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10.1002/asia.201800815
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β (deg)
88.135(4)
73.712(4)
3430.3(6)
1
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SN is thankful to the Science and Engineering Research Board
(SERB), Government of India for the award of the J. C. Bose
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Keywords: Porphyrin
Carboxylation • Catalysis
•
MOF
•
Nanoparticle
•
CO2
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Synthesis and single crystal
Gargi Dutta,[a] Ajay Kumar Jana,[a]
Dheeraj Kumar Singh,[b] M.
Eswaramoorthy,[b] Srinivasan
Natarajan*[a]
structure of an amine-functionalized
three-fold interpenetrated 3D
porphyrin MOF is described. The
free amine groups present in the
MOF have been utilized for
Page No. – Page No.
Encapsulation of Ag-nanoparticle in
an Amine-Functionalized Porphyrin
MOF and its Use as a
Heterogeneous Catalyst for CO2
Fixation under Atmospheric
Pressure
encapsulating Ag nanoparticles.
The Ag@MOF exhibits
heterogeneous catalytic activity for
the conversion of terminal alkyne to
propiolic acid derivatives employing
CO2 under atmospheric pressure.
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