Three novel metal-organic frameworks based on flexible porphyrin tetracarboxylic acids as highly effective catalysts

Article abstract of DOI:10.1016/j.jssc.2016.02.038

Targeted synthesis of metalloporphyrinic frameworks (MPFs) with Cu(II) (1), Ni(II) (2, 3) 5, 10, 15, 20-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (Cu(TCMOPP) and Ni(TCMOPP)) as building blocks afforded three new extended coordination polymers inter

Full text of DOI:10.1016/j.jssc.2016.02.038

Author’s Accepted Manuscript
Three novel metal-organic frameworks based on
flexible porphyrin tetracarboxylic acids as highly
effective catalysts
Zengqi Zhang, Xiaoqin Su, Fan Yu, Jun Li
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http://dx.doi.org/10.1016/j.jssc.2016.02.038
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DOI:
Reference:
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Journal of Solid State Chemistry
Received date: 14 December 2015
Revised date: 22 February 2016
Accepted date: 24 February 2016
Cite this article as: Zengqi Zhang, Xiaoqin Su, Fan Yu and Jun Li, Three novel
metal-organic frameworks based on flexible porphyrin tetracarboxylic acids a
highly
effective
catalysts, Journal of Solid State Chemistry
http://dx.doi.org/10.1016/j.jssc.2016.02.038
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Three novel metal-organic frameworks based on flexible porphyrin
tetracarboxylic acids as highly effective catalysts
Zengqi Zhanga,1 , Xiaoqin Sub,1, Fan Yua, Jun Lia,*
aKey Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of
Education, College of Chemistry & Materials Science, Northwest University, Xi’an, Shaanxi
710069, PR China.
bSchool of Materials and Chemical Engineering, Xi'an Technological University, Xi'an, Shaanxi,
710021, PR China.
Abstract
Targeted synthesis of metalloporphyrinic frameworks (MPFs) with Cu(II) (1), Ni(II) (2, 3) 5,
10, 15, 20-tetrakis[4-(carboxymethyleneoxy)phenyl]porphyrin (Cu(TCMOPP) and Ni(TCMOPP))
as building blocks afforded three new extended coordination polymers inter-linked by Zn(II) (1)
and K(I) (2, 3). 1 shows 2D frameworks while 2, 3 are 3D frameworks. The open channel are 7-17
Å wide and accessible to other guest/solvent molecules. Besides, the thermogravimetric analyses
(TGA) indicate that the framework structures of the three compounds are stable until 300 °C. In
addition, the catalytic activities of 1-3 to the alkylbenzenes oxidation are examined, and the results
indicate that
1
exhibit high catalytic activity to oxidation of ethylbenzene and
1,2,3,4-tetrahydronaphthalene with conversion of 64.1% and 80.3% respectively.
Keywords:Porphyrin; Cu(II) porphyrin; Ni(II) porphyrin; Crystal Structure; Catalytic
oxidation.
1.
Introduction
During the past decades, extensive research attention has been attracted to metal organic
frameworks (MOFs) materials for its highly efficient gas storage and catalysis [1-11]. Besides the
traditional solvothermal method to construct MOF, novel new synthetic methods, such as
surfactant-thermal method, have been developed [12-19]. Among the MOFs, metalloporphyrinic
frameworks (MPFs) has been intensively studied, mainly due to their fascinating framework
topologies and potentially interesting physical and chemical properties in applications, such as
1
These authors contributed equally to this work.
1

catalysis[20-24], optics [25,26], electrics[27], gas storage and separation[28-30]. To build new
MPFs with diverse structures, the choice of the peripheral substituents of porphyrins is extremely
important.
In
the
selection
of
porphyrins
scaffolds,
the
square-planar
tetradentatetetra(3-/4-carboxyphenyl)porphyrin (TpCPP/TmCPP) derivatives are widely employed
due to their capacity to interconnect into open quadrangular supramolecular networks[31-36].
Besides, to explore more adjustable MPFs materials, in 2010 Israel Goldberg et al. introduced the
flexible porphyrin tetraacids (TCMOPP, tetrakis[4-(carboxymethyleneoxy)phenyl]-porphyrin) as
building blocks to construct MPFs for the first time[37]. In spite of the disposition of the
carboxylic acid sites in TCMOPP is more versatile than that of TCPP, only two coordination
polymers (1D and 2D) has been observed so far.
Herein, we report three new open network coordination polymers involving Cu(TCMOPP)
and Ni(TCMOPP) building blocks inter-linked by external zinc and potassium metal ions (Figure
1). The MPFs referred to in this work include 3D supramolecular networks of Cu(TCMOPP)
intercoordinated by Zn(II) ion (1:{Zn[Cu(TCMOPP)]}·2HN(CH3)2), and 3D networks of
Ni(TCMOPP)
intercoordinated
by
K(I)
ion
(2:{K2[Ni(TCMOPP)]·DMF}and
3:{K2[Ni(TCMOPP)]2 (DMF)2}·DMF·H2O). Here we focus on not only their structural features
but also their catalytic oxidation activities. The results indicate that 1 exhibit high catalytic activity
to oxidation of ethylbenzene and 1,2,3,4-tetrahydronaphthalene with conversion of 64.1% and
80.3% respectively.
Figure 1
2. Experimental
2.1 Materials and methods
All reagents were purchased from Beijing Chemical Reagents Company. They were used
without further purification except pyrrole and DMF, which were distilled before use. All
chromatographic separations were carried out on silica gel (100–120 mesh).
Elemental analyses (C, H and N) were performed by Vario EL-III CHNOS instrument.
UV-vis spectra were measured on a Shimadzu UV 1800 UV-vis-NIR spectrophotometer. FT-IR
spectra were recorded on a BEQUZNDX-550 spectrometer on samples embedded in KBr pellets.
2

Mass spectrometry (MS) analysis were carried out on a matrix assisted laser desorption/ionization
time of flight mass spectrometer (MALDI-TOF MS, Krato Analytical Company of Shimadzu
Biotech, Manchester, Britain). The powder X-ray diffraction (PXRD) patterns were recorded on a
Bruker D8 diffractometer using graphite monochromatic copper radiation (Cu Kα) at 40 kV, 30
mA over the 2θ range from 5 to 30°. Thermal gravimetric analysis (TGA) were performed on a
Perkin-Elmer TGA-7 instrument in flowing N2 with a heating rate of 10 °C/min from 30 to
900 °C.
2.2 Synthesis
2.2.1. Synthesis of Cu(TCMOPP) and Ni(TCMOPP).
Scheme 1Synthesis of Cu(TCMOPP) and Ni(TCMOPP).
The synthetic routes to the porphyrins Cu(TCMOPP) and Ni(TCMOPP) are shown in
Scheme 1. 5, 10, 15, 20-tetrakis[4-(carboethoxymethyleneoxy)phenyl] porphyrin (H2(TEMOPP))
was synthesized by a reported method [37]. Firstly, metalloporphyrins Cu(TEMOPP) and
Ni(TEMOPP) were prepared by reaction of their corresponding H2(TEMOPP) (0.1 mmol) with
0.6 mmol M(OAc)2 (M=Cu, Ni). Then the crude products were purified by chromatography on a
silica-gel column with CH2Cl2 as eluant. The desired Cu(TEMOPP) and Ni(TEMOPP) were
obtained. Then, metalloporphyrins Cu(TCMOPP) and Ni(TCMOPP) were afforded by alkaline
hydrolysis as the method reported in the literature [38].
Cu(TCMOPP): Yield: 86%. Mp:>250°C. Anal.Calcd (found) for C52H36CuN4O12 (Mol.Wt:
971.16), %: C 64.36 (64.23), H 3.80 (3.73), N 5.73 (5.76). MS:m/z 1010.12 ( [M+K]+) amu.
UV-vis (CH2Cl2) λmax/nm: 416 (Soret band), 542 (Q-band). FT-IR (KBr): v, cm-1, 3427, 2922,
1724, 1602, 1498, 1433, 1337, 1291, 1214, 1070, 997, 802, 721.
Ni(TCMOPP): Yield: 90%. Mp: >250 °C. Anal.Calcd (found) for C52H36NiN4O12 (Mol.Wt:
3

966.16), %: C 64.56 (64.55), H 3.80 (3.75), N 5.76 (5.79). MS:m/z 965.15 [M-H]- amu. UV–Vis
(CH2Cl2) λmax/nm: 419 (Soret band), 531 (Q-band). FT-IR (KBr): v, cm-1, 3427, 3032, 2922, 2854,
1726, 1633, 1604, 1502, 1433, 1352, 1286, 1213, 1174, 1074, 1002, 796, 713.
2.2.2. Synthesis of {Zn[Cu(TCMOPP)]}·2HN(CH3)2 (1).
A mixture of Cu(TCMOPP) (0.025 mmol) and Zn(CH3COO)2·2H2O (0.05 mmol ) was stirred
in DMF (12 mL), and then sealed in a 25 mL teflon-lined stainless reactor. The solution was
heated at 150 °C for 72 h, followed by slow-cooling to room temperature for 24 h. Purple
block-shaped crystals suitable for X-ray crystal analyses were isolated in 45% yield. Anal.Calcd
for C56H48CuN6O12Zn: C, 59.74; H, 4.30; N, 7.46%. Found: C, 59.82; H, 4.25; N, 7.48%. IR
spectrum (KBr, v/cm-1): 3427, 2925, 1608, 1502, 1409, 1386, 1344, 1286, 1222, 1176, 1107, 1068,
999, 883, 802, 719.
2.2.3. Synthesis of {K2[Ni(TCMOPP)]·DMF} (2) and {K2[Ni(TCMOPP)]2 (DMF)2}·DMF·H2O (3).
Ni(TCMOPP) (0.016 mmol) was dissolved in 4 mL DMF. And then two drops of aqueous
solution of KOH (2 mol/L) was added, and expect to get 3D metalloporphyrinic frameworks since
the potassium ions exhibited higher affinity for coordinating to the carboxylate porphyrin
functions [39]. The solution was slow evaporation at 35 °C for 7 days to give X-Ray quality
purple rod-like crystals of 2 in 80% yield. The solution with crystals 2 was continue evaporation at
35 °C for 5 days, 72% crystal 2 convert to purple block-shaped crystals suitable for X-ray crystal
analyses of 3. Anal.Calcd for C55H41K2N5NiO13 (2): C, 58.82; H, 4.68; N, 6.62%. Found: C, 59.15;
H, 3.70; N, 6.27%. IR spectrum (KBr, v/cm-1): 3431, 2925, 1664, 1604, 1504, 1467, 1434, 1409,
1384, 1353, 1294, 1228, 1176, 1109, 1072, 999, 879, 850, 800, 713. Anal.Calcd for
C113H93K2N11Ni2O28 (3): C, 60.36; H, 4.17; N, 6.85%. Found: C, 60.41; H, 4.08; N, 6.86%. IR
spectrum (KBr, v/cm-1): 3433, 2923, 1662, 1606, 1504, 1434, 1409, 1384, 1352, 1288, 1224, 1176,
1110, 1066, 1001, 881, 852, 800, 713.
2.3. Crystallographic data collection and refinement
The crystallographic data of 1, 2 and 3 were collected on a Bruker SMART CCD
diffractometer with graphite monochromated Mo Kα radiation (λ = 0.71073 Å). Absorption
corrections were performed by using SADABS program [40]. The structures were solved by direct
method and refined by full-matrix least-squares techniques using the program SHELXL-97[41,
42]. Anisotropic thermal parameters were assigned to all non-hydrogen atoms. Hydrogen atoms
4

were placed in geometrically calculated positions. The crystal parameters of compounds 1-3 are
given in Table 1. Selected bonds distances and angles are listed in Table S1. CCDC 1025961,
1025962 and 1025960 contain the supplementary crystallographic data for compounds 1-3.
Table 1The crystal parameters of compounds 1-3
Compounds
Empirical formula
M (g·mol-1)
θ range (°)
1
2
3
C56H46CuN6O12Zn C55H41K2N5NiO13 C113H93K2N11Ni2O28
1125.91
1116.84
2.02–25.00
Triclinic
P-1
2248.60
1.27–25.05
Triclinic
1.72–25.00
Triclinic
P-1
Crystal system
Space group
T (K)
P-1
296(2)
296(2)
296(2)
a (Å)
11.4697(8)
16.1662(11)
17.1103(13)
70.7630(10)
80.3490(10)
74.6200(10)
2877.0(4)
2
8.4470(14)
11.1251(19)
17.581(3)
77.882(3)
88.741(3)
79.060(3)
1585.7(5)
1
12.6368(13)
14.4827(15)
18.082(2)
83.373(2)
69.732(2)
85.888(2)
3081.8(6)
1
b (Å)
c (Å)
α (°)
β (°)
γ (°)
V (Å3)
Z
Calculated density (g·cm-3)
F (0 0 0)
1.300
1.170
1.212
1162
576
1166
μ (mm-1)
0.850
0.495
0.445
Reflections collected/unique
R (int)
14588/10095
0.0335
7887/5482
0.0557
15202/10714
0.0208
Date/parameters
R1 (wR2) [I >2sigma(I)]
R1 (wR2) (All data)
Goodness-of-fit on F2
10095/692
0.0776 (0.2350)
0.1154 (0.2801)
1.035
5482/371
0.1070 (0.2939)
0.1981 (0.3681)
1.061
10714/737
0.0649 (0.2161)
0.0789 (0.2320)
1.069
Largest diff. peak and hole (eÅ-3) 1.306 and -0.551
1.409 and -0.496 1.207 and -0.440
5

CCDC
1025961
1025962
1025960
2
2
(R1 = Σ(|Fo|–|Fc|)/Σ|Fo|；wR2 = [Σw(Fo – Fc2)2/Σw(Fo ) 2]1/2
2.4. Catalytic Oxidation of Alkylbenzene
A mixture of alkylbenzene (0.4 mmol), tert-butylhydroperoxide (TBHP, 1.6 mmol), catalyst
(0.02 mmol) and acetonitrile (2.5 mL) was stirred at 80 °C for 20h. After the reaction, the identity
of the product was determined by using gas-chromatography (GC), compared with the authentic
samples analyzed under the same conditions. The yield of product was also obtained by GC
analysis with a flame-ionization detector (FID) using a capillary SE-54 column.
3. Results and discussion
3.1. The structure of {Zn[Cu(TCMOPP)]}·2HN(CH3)2 (1)
Figure 2.
The single crystal X-ray diffraction analysis reveals that compound 1 crystallizes in the
triclinic P-1 space group. As shown in Figure 2a, the Cu(II) ions inserted into the porphyrin core
with the coordination bonds of Cu-N (1.970 to 1.996 Å) to form a square geometry. The four
pyrrole rings being slightly twisted in an alternating manner either up or down with respect to the
mean plane of the saddled porphyrin macrocycle. The four pyrrole N atoms are displaced by
0.0752, -0.0936, 0.075 and -0.0747 Å from their mean N4 plane (which may represent the average
plane of the porphyrin core). The dihedral angles between adjacent pyrrole rings around the
macrocycle are 10.458, 15.579, 13.394 and 14.551 °, suggesting that the macrocycle mainly
adopts a saddle conformation. Each Zn(II) ion tetrahedron coordinates to four carboxylic groups
of four porphyrin ligands[Zn−O coordination bonds range from 1.944(5) to 1.989(5)Å]. Each
porphyrin ligand acts as a tetradentate ligand and connects four Zn(II) ions to propagate a
one-dimensional bi-chains (Figure 2c). And the bi-chains further links each other though Zn(II) to
form bilayer networks(Figure 2d). The lamellar 2D bilayered coordination polymersare packed by
hydrogen bond interactions (a, b of Figure S1) and C-H···π (c, d of Figure S1) between phenyl
and porphyrin macrocycle, and as a result 3D supramolecular framework is constructed.
6

The space-filling model of the channeled structure of 1 is shown in Figure 3a. The crystal
architecture is characterized by extended channels that propagate through the crystal parallel to the
a axis. These channels are approximate 13.191×7.402 Å size. And the voids are filled with a large
number of dimethylamine which are not coordinated to the polymeric lattice and can be readily
exchanged by other guest components. PLATON calculations indicate that 1 contains 18.6% void
space. When we treat Cu(TCMOPP)2- unit and Zn2+siteas a 4-connected node, respectively, the
framework of 1 can be simplified to a binodal (4, 4)-connected(43.63) (Figure 3b).
Figure 3.
3.2.
The
structure
of
{K2[Ni(TCMOPP)]DMF}
(2)
and
{K2[Ni(TCMOPP)]2(DMF)2}·DMF·H2O (3)
X-Ray quality purple isomorphous crystals of 2 and 3 were obtained respectively by slow
evaporation from DMF solvent in the presence of the strong KOH base in different evaporation
time, which both crystallize in the triclinic P-1 space group. The Ni(II) ions inserted into the
porphyrin core reveal high propensity for a square-planar coordination environment in 2 (Ni-N =
1.948(4) Å, 1.955(4)Å) (Figure 4a). The four pyrrole N atoms are displaced by ±0.0741 and
±0.0745 Å from their mean N4 plane. The dihedral angles between adjacent pyrrole rings around
the macrocycle are 16.608, 17.592, 15.063 and 16.959 °.
In the two structures, the porphyrin moieties are interconnected to each other through the
potassium ion auxiliaries. The coordination environment around the K(I) in crystals 2 can be
described as distorted pentagonal bipyramid coordination geometry (Figure 4b) with four
carboxylic/carboxylate oxygen atoms (K-O=2.766(5)–2.798(4)Å) from different [Ni(TCMOPP)]2-
units, two ether oxygen atoms also coordinated to the K+ (K-O = 2.906(4)Å, 3.096(4)Å), and the
oxygen atom of DMF occupies the last coordination site (K-O = 2.804(7)Å). The coordination
geometry of the two adjacent K(I) ions is shown in the Figure 4b.Two carboxylic groups at every
Ni(TCMOPP) site are deprotonated to balance the charge of the two potassium ions. Two
trans-related carboxylates bind simultaneously to two K(I) ions with two carboxylate O atoms of
each group. The two other carboxylic groups bond simultaneously to two K+ ions with a single
carboxylic O atom of each group. And all the ether oxygen atoms involved in coordination
7

(Figure 4a). Each of [Ni(TCMOPP)]2- unit associates directly with eight different K+ centers
results in the formation of a 2D network (Figure 4c), and the networks further though
coordination bond between to form a 3D porous framework (Figure 4d) with two kinds of 1D
channels (14.213×10.812 Å, 17.023×7.929 Å) along the a axis. In 2, only one kind of the voids is
found in the space-filling model. PLATON calculations indicate that 2 contains 15.4 % void space,
which is accessible to the guest molecules.
Figure 4.
In the crystals 3, the porphyrin core in 3 adopts a four-saddle conformation (Figure 5a), with the
four pyrrole rings being slightly twisted in an alternating manner either up or down with respect to
the mean plane of the saddled porphyrin macrocycle and the coordination bonds of Ni-N range
from 1.9296(17) to 1.9457(15)Å. The coordination environment around the K(I) can be described
as distorted quadruple prisms geometry (Figure 5b) with six carboxylic/carboxylate oxygen atoms
(K-O = 2.700(2)–2.9892(16) Å) from different [Ni(TCMOPP)]- units, wherein a ether oxygen
atom also coordinates to the K(I) (K-O = 3.1349(16)Å), and the oxygen atom in DMF molecule
occupy the last coordination site (K-O = 2.827(3)Å). Besides, every two adjacent K(I)ions
coordinated with eight carboxylic/carboxylate from different [Ni(TCMOPP)]－units. One of the
carboxylic acid groups at every Ni(TCMOPP)－site are deprotonated to balance the charge of the
potassium ion. Each [Ni(TCMOPP)]－ unit associates directly with six different K(I) centers
results in the formation of a1D chains structure(Figure 5c). The lamellar 2D networks are
formed by assembly of chains through bridged K(I) ion (Figure 5d). And the networks further
connects each other though K(I) ion to form a 3D porous framework with1D channels
(14.371×10.201 Å2) along the a axis (Figure 5e).
The space-filling model of the channeled structure is shown in Figure S2a (Supporting
Information). The voids are filled with some coordinated DMF molecules and a large number of
uncoordinated water molecules and DMF solvent molecules which can be readily exchanged by
other guest components. PLATON calculations indicate that 3 contains16.9% void space. Finally,
in topological analysis for 3, we treat porphyrin unit as a 4-connected linker and the coordination
network of the two adjacent K ions as a 8-connectednode,the framework of 3 can be simplified to
8

a binodal (42, 8)-connected 3D (412.612.84)(46)2 net (Figure S2b, Supporting Information).
Figure 5.
3.3. Structural comparison between compounds 2 and 3.
In several respects, crystal structures of 2 and 3 reveal similar features to those observed in
the
structures
of
the
(Pd-TCPP)4-·4K+·6H2O·(CH3)2NCHO
and
(Pt-TCPP)4-·4K+·6H2O·C6H5Nreportedearlier [30]. To the best of our knowledge, this type of
connection in 2 and 3 had never been reported in those MPFs based on TCMOPP or M(TCMOPP).
Unexpectedly, when the crystalline samples of compound 2 were soaked in DMF, they can convert
to compound 3. Evidently, the configuration of porphyrin units and the coordination environment
of K(I) in 3 is different from that in 2. And the porphyrin core in 3 is slightly twisted to optimize
the coordinative bond. It leads to the efficient offset stacking of adjacent porphyrins along the
a-axis normal direction as shown in Figure 5e. Besides, the voids in 2 only contain some
coordinated DMF solvent molecules. While the voids in 3 are filled with not only some
coordinated DMF molecules but also a large number of uncoordinated water molecules and DMF
solvent molecules which can be readily exchanged by other guest components. It also indicates
that the voids in 3D networks of 2 and 3 are accessible to other guest/solvent molecules, which is
need for further research.
3.4. Powder X-ray diffraction, UV-vis spectra and thermogravimetric analyses
The phase purity for MPFs 1-3 is confirmed by powder X-ray diffraction (PXRD) analysis in
bulk amount (Figure S3, Supporting Information). The PXRD results show that all of the
measured peaks closely matched those in the simulated pattern generated from the single-crystal
XRD data, indicating that 1-3 keeps the crystalline nature and porous structure with the pore
comparable to those revealed in the single crystal. The UV-vis spectra show one Soret band and
one/two Q bands (Figure S4). Compared with metal-free porphyrin, the decreased number of Q
bands in 1-3 is due to the symmetry increase of porphyrin macrocycle when the metal ions
coordinate with the N atoms of porphyrin ring. The Soret band position of 1 is in 389 nm while
that of 2, 3 in 420, 419 nm. The blue shift of Soret band of 1 is due to arrangement pattern. The S,
9

Q bands of 2, 3 are in similar position.
To study the thermal stability of 1-3, thermogravimetric analysis (TGA, Figure S5 Supporting
Information) is carried out in the temperature range from 25 to 1000 °C under a flow of N2 with a
heating rate of 10 °C·min−1. The TG curve of 1 shows an initial weight loss of 8.51% at 60-150 °C,
corresponding to removal of two solvent molecules (cal. 8.02%). Significant weight loss upon
350°C is assigned to framework decomposing. Similarly, there is 7.24% weight loss for 2 at
50-180°C, corresponding to the loss of DMF molecule (cal. 6.54%), and the porphyrin framework
start to decompose at 292°C. For 3, 10.87% weight loss at 60-160°C is observed due to the loss of
H2O and DMF molecules, and the porphyrin framework start to decompose when the temperature
higher than 300°C.
3.5. Catalytic Activities of Compounds
We examined 1, 2 and 3 for its catalytic oxidation to alkylbenzene. The alkylbenzene
oxidation was performed in solvent of acetonitrile at 80 °C using tert-butylhydroperoxide (TBHP)
as the oxidant, with GC monitored throughout the reaction. The results (Table 2) show that 1 can
catalyze efficiently the conversion of ethylbenzene to the only product of acetophenone
quantitatively in 64.1% yield. After reaction finished, solid 1 was easily recovered by centrifuging
and filtration then subsequently used in successive runs with only slightly decreased product
yields. 2 and 3 displays the basic catalytic activity with only about 21%, 13%
acetophenoneproduced (Table 2). The significant difference between 1 and 2, 3in their catalytic
properties clearly indicates the crucial role of the metal ion in the center of porphyrin ring. In the
process of porphyrin catalyzing oxidation of ethylbenzene, according to reports [43, 44], the
central metal ion will lose electron to form high oxidation state ion. It is worth to note that
acetophenone is oxidized to only product acetophenone in the presence of 1-3 with the
selectivity >99%. The catalytic oxidations of 1 with differentsubstrateswere also tested. And the
results indicate that the 1-phenylpropane, 1,2,3,4-tetrahydronaphthalene and diphenyl methane can
also be catalytic oxidized with 1,but the conversions are decreased to 40.6, 80.3 and 37.5%
respectively.
10

Table 2. Selective oxidation of alkylbenzenes catalyzed by compounds 1-3
Entry Substrate Catalyst Product Conv.(%) Select.(%)
1
2
3
4
5
6
7
8
9
10
64.1
62.9
21
﹥99
﹥99
﹥99
﹥99
﹥99
﹥99
95
1
1c
2
13
3
40.6
37.5
80.3
6
1
1
1
Cu(CH3COO)2
Ni(CH3COO)2
no
68
5
71
trace
-
aConditions: Amixture of catalyst (0.02 mmol), alkylbenzene (0.4 mmol), and TBHP (1.6
b
c
mmol) in acetonitrile (2.5 mL) was stirred at 80 °C for 20 h. Based on GC analysis. After three
cycles.
4. Conclusions
Three novel MPFs (1-3) were synthesized by the coordination ofmetal ions with
tetracarboxylic
acid
metalloporphyrinsligands
Cu(TCMOPP)
and
Ni(TCMOPP).TheMPFsobtained in this workinclude 2D networks ofCu(TCMOPP)
intercoordinated by Zn(II) (1), and 3D networks of Ni(TCMOPP) intercoordinated by K(I) (2 and
3). Compound 1 revealsthe binodal (4, 4)-connected 2D network with 43.63 topological structure,
and compound 3 is the binodal (42,8)-connected 3D (412.612.84)(46)2 net offlu-type topology.
PLATON calculations indicate that compounds 1-3 contain 18.6%, 15.4% and 16.9% void space,
11

respectively. The open channel-type, 7-17Å wide, architecturesare accessible to other
guest/solvent molecules. Besides, thermogravimetric analysesindicate that the framework
structures of MPFs 1-3 are stable until 300 °C. In addition, 1 shows highly catalyticactivity to
oxidation reaction ofalkylbenzene.
Acknowledgement
The authors acknowledge the research grant provided by the National Nature Science
Foundation (21271148).
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Figure Captions
Figure 1 The chemical structure of the flexible metalloporphyrins tetra-acid as building blocks.
Figure 2. Crystal structure of 1 (a) Coordination environments of Cu(II) and Zn(II) ions; (b) The
distorted tetrahedral coordination geometry of Zn(II); (c) The 1D Zn-bridged bi-chain porphyrin
assemblies; (d) The 2D bilayer constructed from 1D bi-chain. (The dimethylamine trapped in the
interporphyrin voids and hydrogen atoms are omitted for clarity).
Figure 3 (a) The space-filling model of thechanneled structure viewed down the a axis. It shows
the hollow architecture, with channel voids accessible to other components that propagate parallel
to this axis. (b)The simplified network structure of 1. The Cu(TCMOPP)2- units and the peripheral
Zn2+ sitesare indicated by pinkand blue, respectively.
Figure 4.Crystal structure of 2(a) Coordination environments of Ni(II) and K(I) ions. Note that
each porphyrin unitis in direct coordination contact through its carboxylic/carboxylate groups with
eight K(I)ions, two at every carboxylic/carboxylate end; (b) The distorted pentagonal bipyramid
coordination geometry of K(I) and the coordination geometry of the two adjacentK ions; (c) The
K-bridged 2Dmetalloporphyrinic layer (K(I) linkersare seven-coordinate).(d) The 3Dporous
metalloporphyrinic frameworks constructed from layers. (The hydrogen atoms are omitted
forclarity).
Figure 5. Crystal structure of 3(a) Coordination environment of Ni(II) and K(I) ions; (b) The
13

distorted quadruple prisms coordination geometry of K(I); (c) The1D porphyrin chain bridged by
K(I); (d) The2D network formed by porphyrin chain;(e) The 3D porous framework constructed by
porphyrin network. (The water molecules and DMFsolvent molecules trapped in theinterporphyrin
voids and hydrogen atoms are omitted forclarity).
14

Figure 1
HO
O
O
OH
N
N
N
N
O
O
M
O
O
HO
O
O
OH
M = Cu(Ⅱ) and Ni (Ⅱ)
15

Figure 2.
16

Figure 3.
17

Figure 4.
18

Figure 5.
19

*Graphical Abstract Legend (TOC Figure)
Three novel metal-organic frameworks based on flexible porphyrin
tetracarboxylic acids as highly effective catalysts
Zengqi Zhanga,1, Xiaoqin Sub,1, Fan Yua, Jun Lia,*
Three novel metalloporphyrinic frameworks (1, 2, 3) were synthesized based on tetracarboxylic
Cu(II) (1), Ni(II) (2, 3) metalloporphyrin inter-linked by Zn(II) (1) , K(I) (2, 3), and 1 shows high
catalytic activity to oxidation reaction of alkylbenzenes with conversion 80.3%.