A [4+2] Condensation Strategy to Imine-Linked Single-Crystalline Zeolite-Like Zinc Phosphate Frameworks

Article abstract of DOI:10.1002/chem.201800149

Double-4-ring zinc phosphate (D4R), [Zn(dipp)(4-Py-CHO)]₄ (2) (dipp=diiminopyridine), bearing four formyl groups, has been utilized as a building block (SBU) for the synthesis of a new class of imine-linked [4+2] COF-like polycrystalline zinc p

Full text of DOI:10.1002/chem.201800149

DOI: 10.1002/chem.201800149
Full Paper
&
Metal–Organic Frameworks
A [4+2] Condensation Strategy to Imine-Linked Single-Crystalline
Zeolite-Like Zinc Phosphate Frameworks
Ritambhara Jangir+, Alok Ch. Kalita+, Dhananjayan Kaleeswaran+, Sandeep K. Gupta, and
Ramaswamy Murugavel*[a]
Dedicated to Professor Vadapalli Chandrasekhar on the occasion of his 60th birthday
Abstract: Double-4-ring zinc phosphate (D4R), [Zn(dipp)(4-
Py-CHO)]4 (2) (dipp=diiminopyridine), bearing four formyl
groups, has been utilized as a building block (SBU) for the
synthesis of a new class of imine-linked [4+2] COF-like poly-
crystalline zinc phosphate frameworks. Reactions of 2 with a
series of linear aromatic diamines results in the formation of
polycrystalline frameworks [Zn4(dipp)4(L)2]n (3–6) (L=L1 to
L4, diimines formed by condensation of 4-pyridine carboxal-
dehyde with diamines). Employing an alternative synthetic
strategy, through a diffusion-controlled slow reaction of 2
with the pre-synthesized 4,4‘-bispyridyl bisimine (L3),
[Zn4(dipp)4(L3)2]n (5’) has been obtained as single crystals.
Complex 5’ is a 3D-framework, exhibiting a rare eightfold in-
terpenetrated diamondoid network. The long spacer length
(19.6 ꢀ) results in extensive entanglement in 5’. Powder dif-
fraction data suggest that these compounds are isoreticular
3D-frameworks. To study the effect of the relative position of
pyridyl donors with respect to the central benzidine moiety,
3,3‘-bispyridyl bisimine (L5) was investigated as the spacer. A
slow reaction of 1b with L5 leads to the isolation of a 2D-
boxed-sheet coordination polymer [Zn4(dipp)4(L5)2]n (7). Se-
lective formation of 3D-framework 5’ from L3 and the 2D-
framework 7 from L5 is due to the angles created by the co-
ordination of para- and meta-pyridyl nitrogen centers at the
zinc centers of the D4R cubane. Compound 5’ has been uti-
lized as a catalyst for Knoevenagel condensation.
final periodic nets.[5] These multifunctional materials are of
great interest for promising applications in catalysis,[6] gas stor-
age,[7] gas separation,[8] chemosensing,[9] optoelectronics,[10]
and energy storage.[11]
Introduction
The process of assembling astutely designed well-defined sec-
ondary building units (SBUs) into predetermined ordered net-
works has been a promising methodology employed in
modern scientific literature for constructing newer porous
functional crystalline solids.[1,2] Two classes of porous solids
that have been under particular attention during the last two
decades are metal–organic frameworks (MOFs) and covalent
organic frameworks (COFs). The first family of materials, MOFs,
contain a network of polyatomic inorganic metal-containing
cluster SBUs that are connected by organic polytopic linkers.[3]
Similarly, the utility of the topological design principle in the
synthesis of porous organic frameworks connected through
covalent bonds (COFs) has gained importance in the last two
decades.[4] The sites for forming new linkages (bonds) between
the monomers would determine the connection patterns and
direct the geometry, topology, and the dimensionality of the
Phosphate-based porous crystalline solids have been actively
investigated ever since the first isolation of aluminophosphates
(AlPOs) by Flanigen and co-workers in 1981.[12] These porous
metallophosphate materials, displaying variable dimensionali-
ties and structures, have proven to be unexcelled for a long
time due to their applications in catalysis and other areas.[13–15]
Starting from a dibasic phosphoric acid monoester (instead of
the H3PO4) and a divalent main group or transition-metal ion
(instead of trivalent aluminum), our research group has exten-
sively investigated the synthesis of a variety of organic soluble
metal phosphate clusters[16] and their applications in MOF
chemistry,[16a–c] catalysis,[16g] molecular recognition,[16g,n] and mo-
lecular magnetism.[16o–p]
The fact that four zinc centers occupying the alternate cor-
ners of the cubane in 1 are highly Lewis acidic has led to the
successful joining of these cubanes by structurally diverse sub-
stituted pyridines[16a–c] or ditopic spacer ligands, such as 4,4’-bi-
pyridine (Scheme 1).[16k] An alternative strategy to build porous
solids starting from D4R zinc phosphate cubanes would be by
diligently combining the principles of both MOF and COF
chemistries. Such an approach to extended framework struc-
tures would make use of metal–organic SBUs decorated with
well-exposed reactive organic functionalities (such as a ÀCHO
[a] Dr. R. Jangir,+ Dr. A. Ch. Kalita,+ Dr. D. Kaleeswaran,+ Dr. S. K. Gupta,
Prof. R. Murugavel
Department of Chemistry
Institution Institute of Technology Bombay, Powai
Mumbai-400076 (India)
E-mail: rmv@chem.iitb.ac.in
[+] These authors contributed equally to this work.
Supporting information and the ORCID number(s) for the author(s) of this
article can be found under https://doi.org/10.1002/chem.201800149.
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Scheme 1. Hierarchical assembly of phosphate frameworks.
group) that are amenable for condensation reactions with ap-
propriate linear bifunctional organic molecules (e.g., p-phenyl-
enediamine), yielding COF-like MOFs.[17,18] The details of suc-
cessful applications of this strategy to prepare a new genera-
tion of framework solids are described in this contribution.
Results and Discussion
Synthesis strategy
The parent D4R cubane [Zn(dipp)(CH3OH)]4 (1a) (dipp=diimi-
nopyridine),[16a] synthesized in quantitative yields from the re-
action of Zn(OAc)2·2H2O with dippH2 in methanol, is readily
converted into
a
DMSO-decorated cubane cluster,
[Zn(dipp)(DMSO)]4 (1b), by the addition of a few drops of
DMSO to 1a (Scheme 1). The DMSO–cubane 1b is a versatile
starting material in terms of its solubility as well as reactivity
(1a is poorly soluble in most of the organic solvents) for fur-
ther derivatization reactions.[16] We have recently shown that
formyl pyridines can be used to substitute DMSO in 1b to
yield the corresponding tetraformyl-cubanes [Zn4(dipp)4(n-Py-
CHO)4] (n=2 or 4), in which the peripheral formyl groups have
been stabilized as hemiacetals if methanol is employed as the
solvent.[16s]
Scheme 2. a) Earlier reported and b) a new inorganic phosphate based
Particularly interesting among these products is
[Zn4(dipp)4(4-Py-CHO)4] (2), obtained by addition of 4-pyridine
carboxaldehyde to 1b in acetonitrile.[16s] Similar to molecules
that bear four functional groups pointing away from the four
vertices of the tetrahedron that have been used in the prepa-
ration of covalent organic polymers, frameworks, capsules, etc.
(Scheme 2a),[6b,7c,11a,19–21] cluster 2 can also be viewed as a zinc
tetrahedron bearing four formyl groups (Scheme 2b). Due to
this disposition, 2 can be conveniently employed as a building
block for the preparation of zinc phosphate frameworks by re-
acting it with a diamine, similar to the synthetic strategy that
is prevalent in COF chemistry.
building blocks for 4-connected COFs.
lated yields of the frameworks were found to be 70% or more.
As shown in Scheme 3, this reaction essentially leads to a D4R
cluster containing 3D COF surfaces that are additionally loaded
with a large amount of Schiff base (imine). IR spectral studies
provide strong evidence for the newly formed imine linkages
(ÀC=NÀ) between the cubane and the amines (Table 1). Al-
though a tetra-aldehyde and a diamine were used as starting
materials, the products did not exhibit any bands due to either
ÀCHO (n=1712 cmÀ1)[16s] or ÀNH2 (nꢀ3379 cmÀ1) groups, sug-
gesting complete conversion of the starting materials into
framework materials. The newly formed ÀN=CHÀ linkages are
responsible for the absorption at nꢀ1620 cmÀ1 (Figure 1). The
PÀO vibrations appear at n=1181, 1175, 1176, and 1177 cmÀ1
(Table 1) as strong bands for compounds 3–6, respectively.[17]
The MÀOÀP asymmetric stretching vibration appears at
nꢀ1020 cmÀ1 and the symmetric stretching vibrations at n
ꢀ920 cmÀ1 (Figure 1)
Frameworks 3–6
Condensation of [Zn4(dipp)4(4-Py-CHO)4] (2) with aromatic dia-
mines of different end-to-end length in a 1:2 molar ratio in
methanol at 608C yields MOF-like COFs [Zn4(dipp)4(L1)2]n (3),
[Zn4(dipp)4(L2)2]n (4), [Zn4(dipp)4(L3)2]n (5), and [Zn4(dipp)4(L4)2]n
(6) as a microcrystalline solid in each case (Scheme 3). The iso-
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Scheme 3. A combined MOF–COF approach to zinc phosphate frameworks 3–6.
Table 1. Spectral characterization data of compounds 3–7.
IR (n˜, [cmÀ1])
Solid-state NMR d [ppm]
13C
UV/Vis
lmax
n˜(CH=N)
n˜(P=O)
n˜(M-O-P)
31P
(N=CH)
[nm]
3
4
5
5’
6
7
1620
1618
1619
1619
1620
1623
1181
1175
1176
1174
1177
1173
1018
1019
1019
1019
1018
1021
157.48
159.19
160.02
160.00
159.04
159.18
À3.85
À3.97
À3.62
À3.95
À3.89
À3.86
402
400
401
401
405
380
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Figure 1. IR-spectra of compounds 3–7 (4000–450 cmÀ1 in KBr).
Further evidence for the presence of framework imine link-
ages comes from the CP-MAS 13C NMR spectra of the solid
samples of 3–6 (Figure 2a and Figures S6–S8, Supporting Infor-
mation). The resonance at dꢀ160 ppm for all the four frame-
works corresponds to the carbon atom of ÀC=NÀ linkages in
the frameworks. The resonances appearing in the range of d=
120–150 ppm are assignable to various carbon atoms of the ar-
omatic rings in these framework solids. The upfield resonances
(d=22–27 ppm) correspond to the methine and methyl
carbon atoms of the isopropyl groups of the dipp phosphate
and any alkyl substituents on the aryl rings of the linkers L3
and L4. The presence of a single resonance in the CP-MAS
31P NMR spectra of 3–6 at around dꢀ4 ppm reveals the struc-
tural integrity of the cubane core in the final framework (Fig-
ure 2b, Figures S9–S13, Supporting Information, and Table 1).
The relative stoichiometry of the constituents of the framework
Figure 2. a) CP-MAS 13C (125 MHz) and b) 31P NMR (202 MHz) spectra of com-
pound 3.
1
is established by solution H NMR spectroscopy through disso-
lution of 3–6 in [D6]DMSO,[22,16k] to produce the parent cubane
[Zn(dipp)(DMSO)]4 (1) and the respective Schiff-base linkers in
solution. The spectra obtained further confirm the presence of
ÀN=CHÀ linkages in 3–6 (Figures S14–S19, Supporting Infor-
mation).
PXRD studies carried out to probe the crystallinity of these
materials revealed the highly crystalline nature of the as-syn-
thesized compounds 3–6 (Figure 3). The presence of a very
similar diffraction pattern for all the four compounds further
indicates that all compounds adopt a similar framework topol-
ogy and are possibly isoreticular. The morphology of these
crystalline materials have been probed by SEM to glean further
insights into the crystallinity of these materials. The SEM
images shown in Figure 4 reveal the formation of larger aggre-
gates that are made up of several microcrystals. Barring 4, the
as-synthesized frameworks exhibit a ‘flower-like“ aggregation.
Further inspection of the magnified images reveal that the ag-
gregation in framework 3 is similar to that of an artichoke bud
(Figure 4a), whilst frameworks 5 and 6 display a broccoli-floret-
type of aggregation of bundled microcrystals (Figure 4b and
c). Surprisingly, compound 4 forms an aggregate of stacked
plates resembling the morphology of layered solids (Fig-
ure S20, Supporting Information).
Figure 3. PXRD pattern of compounds 3–6.
Synthetic route for single-crystalline frameworks
The combined PXRD and SEM studies of crystalline 3–6 (vide
supra) indicated the possibility of growing large enough crys-
tals that could be suitable for single-crystal X-ray diffraction in-
vestigations. However, owing to their insolubility, recrystalliza-
tion of these compounds to obtain larger crystals was ruled
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Scheme 4. Synthesis of 5’ and 7.
Figure 4. FEG–SEM images of a) 3, b) 5, and c) 6.
out. Hence we adopted a slightly different but efficient meth-
odology to obtain single crystals.
The sequence of addition of the three components (DMSO
cubane 1b, 4-Py-CHO, and diamine) has been significantly al-
tered by choosing 2,2’,6,6’-tetraisopropylbenzidine as the
amine source. Thus, in the first step of the synthesis, 2,2’,6,6’-
tetraisopropylbenzidine was combined with 4-Py-CHO to pro-
duce the linear linker L3 which could be isolated in an analyti-
cally pure form and fully characterized (see below). This pre-
formed L3 was then allowed to diffuse into a dilute solution of
1b in a kinetically controlled crystallization reaction to yield
single crystals of [Zn4(dipp)4(L3)2]n, designated as 5’ hereafter
(Scheme 4). To introduce diversity in the topology of the
framework structure, the synthesis was repeated with 3-Py-
CHO in place of 4-Py-CHO, via the isolation of a new linker L5,
to produce single crystals of a new framework [Zn4(dipp)4(L5)2]n
(7).
Figure 5. CP-MAS 13C NMR spectra of compounds 5 and 5’ (a, b) and
31P NMR spectra of compounds 5’ and 7.
The single crystals of 5’ and 7 were subjected to extensive
analytical and spectroscopic measurements. These studies
reveal that single-crystalline 5’ is essentially the same material
as polycrystalline 5. For example, the IR spectrum (Figure 1),
solid-state 13C NMR spectrum (Figure 5), and solid-state
31P NMR spectrum (Figure S11, Supporting Information) of 5’
are essentially super-imposable on the corresponding spec-
trum of the polycrystalline 5. More significantly, the PXRD pat-
terns of 5 and 5’ are not only essentially the same but also
their patterns are identical to the simulated PXRD pattern of 5’
from single crystal data (Figure 6 and see below). The fact that
5 and 5’ show a similar PXRD pattern (Figure 3) and that the
Figure 6. PXRD pattern of compounds 5, 5’Exp and 5’calcd.
PXRD profiles of 3, 4, and 6 are the same as that of 5
(Figure 3), clearly proves that the COFs 3–6 are isoreticular, as
has been previously observed in the case of a few 2D COFs.[23]
Single-crystal X-ray diffraction studies
Crystals of 5’ were grown by layering 1b in methanol over a
dichloromethane solution of L3. Compound 5’ crystallizes in
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the monoclinic P21/c space group. A perspective view of the
repeating unit in 5’ is shown in Figure 7a. Single-crystal X-ray
This leads to the growth of a robust 2D sheet-like structure
featuring channels (Figure 8b, d, f, and h), in which the aver-
age intercubane distance has been found to be 20.893 ꢀ.
Topological analysis of the 2D framework 7 revealed that it is a
4c-uninodal layer structure (Figure 9b) that can be represented
by the point symbol {33.82.9}.[25]
¯
analysis of 7 reveals that it crystallizes in the triclinic P1 space
group. A perspective view of the repeating unit shown in Fig-
The major differences between the framework structures of
5’ and 7 essentially arise from the relative disposition of the
spacer ligands L3 or L5 with respect to the central Zn4 cubane
as well the position of the pyridinic nitrogen on the terminal
rings. For example, the larger distances observed between the
distal part of the spacer ligands in 5’ (N1ÀN3: 30.32; N4ÀN6:
30.44; N3ÀN6: 44.03, and N1ÀN4 44.16 ꢀ; Figure 7a), com-
bined with the fact that the pyridinic nitrogen atom is at the
para-position of the terminal rings, leads to the formation of a
diamondoid structure through the formation of a hexagonal
rings that exist in a chair conformation (Figure 8c and e). On
the other hand, the nonequal distances observed between the
distal part of the spacer ligands in 7 (very short N1ÀN8: 14.61
and N5ÀN4: 14.73 ꢀ and very long N4ÀN8: 41.26 and N5ÀN1:
41.36 ꢀ; Figure 7b), in addition to the presence of the pyridinic
nitrogen atom at the meta-position of the terminal rings, re-
sults in the formation of an unusual boxed-sheet structure
(Figure 8h), which is made up of laterally fused tetragonal
rings (Figure 8d). Thus the isolation of 5’ and 7 demonstrate
the ability to fine-tune the final framework structure just by
changing the position of pyridinic nitrogen atom on the
spacer, which in turn determines the connectivity pattern.
Figure 7. a) Repeating unit in 5’. b) Repeating unit in 7. Hydrogen atoms are
omitted for clarity.
Thermogravimetric analysis and hydrolytic stability
ure 7b. The asymmetric unit of 5’ contains a tetranuclear zinc
phosphate that resembles the D4R SBU of zeolites and two L3
ligands, [Zn4(dipp)4(L3)2]. Since L3 behaves like a ditopic bridg-
ing ligand, only two units of L3 are found per asymmetric part
of the unit cell that contains four zinc ions. Thus each
cubane[24] is surrounded by four L3 ligands that are shared by
four more zinc cubanes in the vicinity of the central cubane
(Figure 7a). Thus the D4R zinc phosphate cages in 5’ act as a
tetrahedral 4-connected nodes that are linked to one another
by L3, which has an end-to-end distance of 19.577 ꢀ. This re-
sults in the growth of a robust 3D diamondoid framework fea-
turing channels running along the c crystallographic axis (Fig-
ure 8a, c, e, and g), in which the average intercubane distance
has been found to be 23.699 ꢀ. Although the bulky isopropyl
substituents in L3 are expected to circumvent the formation of
interpenetrated networks, the relatively longer spacer length
overrides the bulkiness offered by the isopropyl groups, result-
ing in interpenetration of the frameworks.
Thermogravimetric analysis (TGA) for the frameworks 3–7 was
carried out in the temperature range of 30–11008C under a
continuous flow of nitrogen gas at the heating rate of
108CminÀ1 (Figure S24, Supporting Information). The TGA
curves reveal that the frameworks are stable up to ꢀ3008C. A
minor weight loss sets in after 3008C during which the organic
part/aryl moieties are eliminated to yield [ZnO3P(OH)]. Subse-
quent loss of water from [ZnO3P(OH)] at around 5008C yields
Zn2P2O7, which remains stable in the temperature range of
525–9508C. Further heating leads to the loss of P2O5 from all
the samples to yield ZnO as the final ceramic residue at tem-
peratures beyond 10008C. To evaluate the hydrolytic stability
of these framework materials, 5’ has been immersed in water
for 24 h at room temperature and the filtered sample exam-
ined by PXRD measurements. There has been no change in
the observed PXRD pattern between the as-synthesized and
water-treated samples (Figure S24, Supporting Information).
This confirms that the isopropyl group substituted lipophilic li-
gands (both spacer and the phosphate) do not permit any
water coordination at the metal or any possible ligand hydroly-
sis.
Topological analysis of the framework structure in 5’ re-
vealed that it has a rare eightfold interpenetrated diamondoid
network with 4c-uninodal structure with point symbol {33.123}
(Figure 9a).[25] The central Zn4 cubane in 7 is connected to four
L5 ditopic spacers, in a fashion very similar to the connectivity
observed for 5’ (Figure 7). The D4R zinc phosphate cages in 7
act as a tetrahedral 4-connected nodes that are linked to one
another by L5, which has an end-to-end distance of 18.457 ꢀ.
Absorption spectra
The absorption spectra of compounds 3–7 were recorded in
the solid-state. The LMCT transitions (380–400 nm) occur from
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Figure 8. Left): Linking of D4R cages by a ditopic ligand with an angle of 1568 to form a diamondoid basic unit. Right): Linking of D4R cages by a ditopic
ligand with an angle of 1208 to form a 2D sheet via a clip-like basic unit.
the filled 3p orbitals of the ligands (HOMO) to the empty 4s or-
bital (LUMO) located at Zn2+ along with the ligand based p–p*
transitions, which occur at ꢀ250 nm in these compounds
(Figure 10).
2D-framework compound 7 (9 m2 gÀ1). Further, the surface area
has also been calculated using the Dubinin–Radushkevich (DR)
method micropore analysis and the values are presented in
Table 2.
In general, observation of a smaller surface area for all the
compounds than the expected larger values can be attributed
to partial contraction of the pores and/or pore breakdown at
liquid nitrogen temperature, as has been observed by Thalla-
paly and co-workers.[18] The nitrogen richness of the zinc
frameworks has been utilized to evaluate the CO2 uptake ca-
pacities. The CO2 uptake capacities were calculated to be
2.22 wt% for 3, 3.55 wt% for 4, 2.16 wt% for 5, 4.24 wt% for
5’, 3.24 wt% for 6 and 1.93 wt% for 7 at 273 K and 1 bar. The
room temperature CO2 uptake was ranging between 0.67–
2.0 wt% for all the compounds (Figure S25, Supporting Infor-
mation). The CO2 adsorption–desorption isotherms are com-
pletely reversible. This reversibility implies interaction between
CO2 and the frameworks is weak. The isosteric heat of adsorp-
tion was calculated using the Clausius–Claypran equation and
the values lie in the range of 27.7–43.1 kJmolÀ1 (Figure S26,
Supporting Information). These values are lower and compara-
Gas sorption studies
The permanent porosity of the zinc organophosphates 3–7 has
been investigated by measuring N2 adsorption isotherms at
77 K after degassing the activated samples at room tempera-
ture for 6–8 h. (Figure 11). The summary of the gas uptake ca-
pacities for all compounds along with the surface area (BET
and Langmuir) are listed in Table 2. The measured BET surface
area for the compounds containing isopropyl-substituted
spacers, that is, frameworks 5, 5’, and 6 were found to be mini-
mal (14, 21, and 28 m2 gÀ1), both on the account of the bulky
substitutions that reduce the pore volume as well as multiply
interpenetrated structures (Figure 9a). On the other hand, the
compounds with unsubstituted spacers show comparatively
larger surface areas (e.g. 124 m2 gÀ1 for 3 and 115 m2 gÀ1 for 4),
for which the reduction of surface area is primarily due to in-
terpenetration. The lowest surface area was observed for the
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Table 2. N2 adsorption (77 K and 1 bar) and CO2 adsorption data for 3–7
at 273 and 298 K and 1.0 bar.
Compd. SABET
[m2 gÀ1
SALang SADR
CO2 uptake CO2 uptake Qst
273 K [wt%] 298 K [wt%] [kJmolÀ1
]
]
[m2 gÀ1
]
[m2 gÀ1
]
3
4
5
5’
6
7
124
487
348
40
86
76
238
219
24
31
55
2.22
3.55
2.16
4.24
3.24
1.93
1.15
2.00
1.07
2.25
1.68
0.67
32.8
27.7
29.4
43.1
32.4
39.4
115
14
21
28
9
19
12
ble to those reported for amine-modified MCM-41 and zeo-
lites.[26]
Catalytic studies
The fact that the new framework structures contain a large
number of Schiff-base (ÀC=NÀ) linkages and that most of
them have accessible voids to act as reaction vessels, has
made them suitable frameworks to act as catalysts for Knoeve-
nagel condensation. Knoevenagel condensation is an impor-
tant base-catalyzed CÀC bond forming reaction in the classical
organic synthesis, especially for the synthesis of coumarin de-
rivatives.[27] Few of the base-functionalized MOFs, zeolites, and
imine-liked COFs have been utilized in Knoevenagel reactions
but the substrate scope has been found to be limited owing
to the size selectivity of the cavities in many of these reported
systems.[19a,28] As a representative example, the catalytic activity
of the framework 5’ has been investigated as the catalyst. The
catalysis was initially performed at RT for using p-nitrobenzal-
dehyde (1 mmol) and malononitrile (1 mmol) as the reactants
and 0.2 mol% of 5’ in benzene (2 mL). Complete conversion of
the reactants took place after 48 h, with an isolated yield of
90% of the expected product. Subsequently, the reaction tem-
perature was increased to 608C to accelerate the reaction,
which has led to the completion of the reaction within 20 h.
The reactivity and time of completion has been found to be
dependent on the para-substituent on the aldehydes. When a
cyano group was present as the para-substituent, the reaction
was found to be complete within 12 h, the completion of the
reaction was prolonged to 48 h in case of benzaldehyde
(Table 3). Further, to extend the substrate scope, the reaction
was performed with terephthaldehyde to give the double con-
densation product within 12 h in 73% yield (Table 2).
Figure 9. a) An unusual eightfold interpenetrated diamondoid network in 5;
b) 4c-uninodal layer structure of 7.
Figure 10. Solid-state absorption spectra of 3–7 in absorbance mode.
Conclusion
The utility of a D4R Zn4P4O12 SBU in assembling novel frame-
work structures has been showcased through careful design,
synthesis, and structural characterization of an unprecedented
class of isoreticular MOF–COF hybrid systems. The synthetic
methodology used here is two-pronged in the sense that it
not only offers a new means for connecting the zeolitic SBUs
through the well-known organic amine–aldehyde condensa-
tion reaction, but also provides ample scope for controlling
Figure 11. Nitrogen sorption isotherms of compounds 3–7 at 77 K and 1 bar.
&
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ries and are reported uncorrected. IR spectra were obtained on a
Perkin–Elmer Spectrum One FTIR spectrometer as KBr diluted discs.
Microanalyses were performed on a Thermo Finnigan (FLASH EA
1112) microanalyzer. Solution NMR spectra were recorded on either
a Bruker 400 or 500 MHz NMR spectrometer. 13C CP-MAS NMR
measurements were carried out on a Bruker Avance 500 MHz spec-
trometer at 300 K and the samples were packed in a 4.0 mm zircon
rotor. The ESI-MS studies were carried out on a Bruker MaXis
impact mass spectrometer. Thermogravimetric analyses were car-
ried out on a Perkin–Elmer Pyris Diamond thermal analysis system
Table 3. Knoevenagel condensation reaction catalyzed by 5’.[a]
Entry
R
Product
t
Isolated
yield [%]
[h]
under a stream of nitrogen gas at a heating rate of 108CminÀ1
.
Powder X-ray diffraction was carried out on a Philips X’pert Pro
(PANalytical) diffractometer by using CuKa radiation (l=1.5419 ꢀ).
I
ÀH
48
20
12
36
63
90
72
68
The morphologies of all the samples were investigated using field-
emission gun-scanning electron microscopy (FEG-SEM) on a JEOL
model JSM-7600F field-emission gun-scanning electron micro-
scope, operating at an accelerating voltage of 0.1 to 30 kV. The
samples were prepared by drop-casting onto a carbon substrate
and sputtered with platinum prior to the imaging. Solid-state ab-
sorption spectral studies were performed on a Shimadzu MPC-
3100 UV/Vis spectrophotometer. Gas sorption and uptake measure-
ments were performed on a Quantachrome Autosorb-1C analyzer
by using UHP-grade gases. N2-sorption measurements were evalu-
ated at 77 K and 1 bar. CO2 adsorption measurements were per-
formed at 273 and 298 K, and 1 bar. Prior to gas adsorption meas-
urements, the samples were dried under air for 24 h and evacuated
at RT for 6–8 h under ultrahigh vacuum.
II
ÀNO2
ÀCN
ÀBr
III
IV
V[b]
ÀCHO
12
73
[a] Reaction conditions: catalyst 5’ (0.2 mol%), arylaldehyde (1 mmol), ma-
lanonitrile (1 mmol), benzene (2 mL), temperature (608C). [b] Catalyst 5’
(0.4 mol%), terephthaldehyde (1 mmol), malanonitrile (2 mmol).
Commercial grade solvents such as methanol, dimethoxyethane
(DME), THF, dichloromethane, and diethyl ether were purified by
employing conventional procedures[29] and chemicals such as
Zn(OAc)2·2H2O (S.d.Fine-Chem.), p-phenylenediamine (Merck), and
benzidine (Merck) were used as received. 2,6-Diisopropylphenyl di-
hydrogen phosphate,[30a] 2,2’,6,6’-tetraisopropylbenzidine,[30b] and
boronic acid[30c] were synthesized according to published proce-
dures.
the topology of the final framework through a proper choice
of formyl pyridines (e.g. meta vs. para). A further novelty of
this approach is the ability to assemble all these structures hi-
erarchically at ambient conditions without the use of any pres-
sure reactors or ovens. It has also been demonstrated that the
single crystals of representative examples can be grown
through slow diffusion of a preformed COF fragment to the
cluster solution and thereby establish the precise structure of
these isoreticular 3D COFs. This is in contrast to the inability to
grow single crystals of any organic COFs, the structures of
which are normally derived by a combined PXRD–ab initio cal-
culations approach. The synthetic methodology presented
here appears to be very general and it should be possible to
extend this approach not only to incorporate other metal ions
in COFs but also to modify the linker to incorporate additional
functionalities through which these systems can be rendered
electro-, photo-, and catalytically active. This would open up
new possibilities in areas such catalysis, gas adsorption/cap-
ture, and separation. We are currently investigating these pros-
pects.
Synthesis of B
Boronic acid (A) (16.8 g, 43.9 mmol), Na2CO3 (12.7 g, 120 mmol),
and [Pd(PPh3)4] (0.69 g, 0.60 mmol) were weighed into a Schlenk
flask and dried under vacuum. Degassed DME (220 mL), degassed
water (55 mL), and 1,4-dibromobenzene (4.72 g, 20.0 mmol) were
added to the flask which was then sealed and heated at 1008C for
48 h. The solution was cooled to room temperature to deposit a
yellow solid that was filtered off and washed with water and cold
hexane. The yellow product B was then dried under vacuum. Yield:
1
6.10 g (40%); m.p. >2508C; H NMR (CDCl3, 400 MHz): d=7.82 (d,
J=6.7 Hz, 4H, o-H), 7.61 (s, 1H), 7.25–7.51 (m, 12H ), 7.22 (s, 1H),
7.13 (d, J=6.1 Hz, 4H, o-H), 2.92 (septet, 4H, CH), 1.19 (d, J=
6.3 Hz, 12H, CH3), 0.99 ppm (d, J=6.3 Hz, 12H, CH3); elemental
analysis calcd (%) for C56H56N2: C 88.84, H 7.46, N 3.70; found: C
88.21, H 7.62, N 3.94; EI-MS: m/z (%): 757.56 [M+H]+, 678.42
[MÀPh]+, 602.38 [MÀ2Ph]+.
Synthesis of C
Experimental Section
Compound B (3. 78 g, 5.0 mmol) was dissolved in THF (100 mL)
and 2n HCl (50 mL) was added. After the solution was stirred at
608C for 12 h, water was removed by rotary evaporator. The white
solid obtained was thoroughly washed with diethyl ether and cold
THF to remove benzophenone and the dihydrochloride salt C was
dried under vacuum. Yield: 2.15 g (86%); m.p. 226–2288C; H NMR
(CDCl3, 400 MHz): d=7.69 (s, 4H), 7.40 (s, 4H), 3.26 (septet, J=
6.7 Hz, 4H, CH), 1.26 ppm (d, J=6.7 Hz, 24H, CH3); elemental analy-
Methods and materials
All the experimental manipulations were carried out in a well-venti-
lated fume hood. Since all the starting materials used and the
products obtained were found to be highly stable towards both
moisture and air, no specific precaution was taken to rigorously ex-
clude air. Melting points were measured in unsealed glass capilla-
1
Chem. Eur. J. 2018, 24, 1 – 14
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ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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sis calcd (%) for C30H42Cl2N2: C 71.84, H 8.44, N 5.59; found: C
(s), 1620 (vs.), 1467 (s), 1440 (s), 1426 (s), 1181 (vs.), 1018 (vs.), 918
(vs.), 771 cmÀ1 (vs.); CP-MAS 13C NMR (125.7 MHz, 295 K): d=
157.48, 150.82, 149, 40, 148.94, 143.09, 141.69, 134.91, 121.03,
120.27, 26.40, 24.25 ppm; 31P NMR (202 MHz, 295 K): d=
71.43, H 8.67, N 5.52; EI-MS: m/z (%): 429.30 [MÀHÀ2Cl]+.
Synthesis of D
1
À3.87 ppm; H NMR ([D6]DMSO, 500 MHz): d=8.91 (s, 1H, ÀN=CHÀ
3
3
To a suspension of C (2.5 g, 5.0 mmol) in diethyl ether (100 mL)
was added an aqueous KOH solution (1.0 N, 150 mL) and the mix-
ture was stirred for 3 h at room temperature. The mixture was
then extracted with ether. The ether extracts were collected and
the product was further extracted from the water phase with addi-
tional diethyl ether (100 mL). The combined organic phase was
dried with anhydrous MgSO4 and the solvent was removed on a
rotary evaporator to give D as a white crystalline solid, which was
), 7.78 (d, 2H, JHH =5.90 Hz, ortho(Py)-H), 7.49 (d, 2H, JHH =5.90 Hz,
3
meta(Py)-H), 7.07 (m, 3H, JHH =6.61 Hz, ArH), 6.65 (s, 2H, ArH), 3.76
(septet, 2H, JHH =6.10 Hz, iPrCH), 1.24 ppm (d, 12H, JHH =6.80 Hz,
iPrCH3).
3
3
Compound 4: Yield: 88%; M.p: >2758C; elemental analysis calcd
(%) for [C96H104N8O16P4Zn4]: C 57.33, H 5.21, N 5.57; found: C 55.00,
H 5.51, N 5.62; FTIR (KBr): n˜ =3430 (br), 2963 (vs.), 2926 (s), 2868
(s), 1618 (vs.), 1458 (s), 1440 (s), 1384 (s), 1175 (vs.), 1019 (vs.), 918
(vs.), 772 cmÀ1 (vs.); CP-MAS 13C NMR (125.7 MHz, 295 K): d=
159.19, 148, 40, 148.72, 145.18, 145.40, 141.11, 141.28, 123.08,
124.02, 117.09, 117.15, 26.29, 22.91 ppm; 31P NMR (202 MHz, 295 K):
1
found to be pure by its H NMR spectrum and hence was used for
the next reaction without any further purification. Yield: 1.92 g
(89%); m.p. 170–1728C; FTIR (as KBr disc): n˜ =3389, 3375 cmÀ1 (NÀ
H); 1H NMR (CDCl3, 400 MHz): d=7.60 (s, 4H), 7.32 (s, 4H), 3.81
(brs, 2H, NH), 2.99 ppm (septet, J=6.8 Hz, 4H, CH), 1.34 (d, J=
6.8 Hz, 24H, CH3); elemental analysis calcd (%) for C30H40N2: C
84.06, H 9.41, N 6.54; found: C 83.76, H 9.52, N 6.46; EI-MS: m/z
(%): 429.34 [M+H]+.
1
d=À3.97 ppm; H NMR ([D6]DMSO, 500 MHz): d=8.92 (s, 1H, ÀN=
3
CH), 8.47 (d, 2H, 3JHH =5.90 Hz, ortho(Py)-H), 7.92 (d, 2H, JHH
=
5.90 Hz, meta(Py)-H), 7.69 (d, 2H, 3JHH =5.90 Hz, ortho(Ar)-H), 6.91
3
3
(d, 2H, JHH =5.91 Hz, meta(Ar)-H), 7.05 (m, 3H, JHH =6.64 Hz, ArH),
3
3.75 (septet, 2H, 3JHH =6.09 Hz, iPrCH), 1.15 ppm (d, 12H, JHH
=
6.72 Hz, iPrCH3).
Synthesis of L3 and L5
Compound 5: Yield: 70%; M.p: >2758C; elemental analysis calcd
(%) for [C120H152N8O16P4Zn4]: C 61.39, H 6.53, N 4.77; found: C 60.80,
H 6.77, N 4.82; FTIR (KBr): n˜ =3444 (br), 2962 (vs.), 2934 (s), 2868
(vs.), 1619 (vs.), 1462 (s), 1439 (s), 1256 (s), 1176 (vs.), 1019 (vs.), 918
(vs.), 771 cmÀ1 (vs.); CP-MAS 13C NMR (125.7 MHz, 295 K): d=
160.02, 148.05, 148.20, 145.30, 140.26, 138.02, 137.25, 122.39,
123.15, 123.08, 27.38, 26.00, 23.10 ppm; 31P NMR (202 MHz, 295 K):
d=À3.62 ppm; 1H NMR ([D6]DMSO, 500 MHz): d=8.78 (d, 2H,
3JHH =5.67 Hz, ortho(Py)-H), 8.45 (s, 1H, ÀN=CHÀ), 7.93 (d, 2H,
2,2’,6,6’-Tetraisopropylbenzidine (1.0 g, 2.84 mmol) was dissolved in
CH3OH (50 mL). To this solution, 4-pyridine carboxaldehyde or 3-
pyridine carboxaldehyde (0.6 g, 5.60 mmol) was added with stirring
along with catalytic amounts of formic acid to accelerate the reac-
tion. The yellow solution was refluxed for 12 h. During the reflux, a
yellow precipitate was obtained. This precipitate was collected by
suction filtration and washed with hot CH3OH (3ꢂ20 mL) and dried
under vacuum. X-ray quality single crystals have been obtained
from a CH3OH/CH2Cl2 (3:1) solution on standing at room tempera-
ture.
3
3JHH =5.90 Hz, meta-H), 7.35 (s, 2H, ArH), 7.01 (m, 3H, JHH =6.64 Hz,
3
3
ArH), 3.68 (septet, 2H, JHH =6.08 Hz, iPrCH), 2.90 (septet, 2H, JHH
=
6.80 Hz, iPrCH), 1.20 (d, 12H, 3JHH =6.84 Hz, iPrCH3), 1.08 ppm (d,
12H, 3JHH =6.74 Hz, iPrCH3).
Compound L3: Yield: 1.5 g (79%); elemental analysis calcd (%) for
C36H42N4: C 81.47, H 7.98, N 10.56; found: C 81.05, H 8.02, N 10.10;
FTIR (KBr disc): n˜ =3419 (b), 2960 (s), 2927 (s), 2869 (s), 1637 (s),
1595 (s), 1440 (s), 1318 (s), 1177 (w), 870 (w), 826 (w), 698 cmÀ1 (w);
Compound 6: Yield: 75%; M.p: >2758C; elemental analysis calcd
(%) for [C132H160N8O16P4Zn4]: C 63.41, H 6.45, N 4.48; found: C 63.41,
H 6.84, N 3.70; FTIR (KBr, cmÀ1): n˜ =3442 (br), 2960 (vs.), 2934 (vs.),
2867 (vs.), 1620 (vs.), 1460 (s), 1441 (s), 1255 (s), 1177 (vs.), 1018
(vs.), 920 (vs.), 772 cmÀ1 (vs.); CP-MAS 13C NMR (125.7 MHz, 295 K):
d=159.04, 150.24, 149.90, 148.39, 145.37, 140.90, 137.70, 131.48,
123.07, 121.19, 27.24, 25.90, 22.16 ppm; 31P NMR (202 MHz, 295 K):
d=À3.89 ppm; 1H NMR ([D6]DMSO, 500 MHz): d=8.79 (d, 2H,
3JHH =5.67 Hz, ortho(Py)-H), 8.47 (s, 2H, ÀN=CHÀ), 7.88 (d, 2H,
3JHH =5.88 Hz, meta-H), 7.76 (s, 2H, ArH, 7.28 (s, 2H, ArH), 7.00 (m,
3
1H NMR (400 MHz, CDCl3): d=8.81 (d, 4H, J=5.8 Hz ArH), 8.25 (s,
3
2H, HÀC=N), 7.80 (d, 4H, J=3 Hz, ArH), 7.35 (s, 4H, ArH), 2.95 (m,
3
3J=8.89 Hz, 4H, iPrCH), 1.24 ppm (d, 24H, J=6.88 Hz, iPrCH3); ESI-
MS: m/z: 531.17 [M+1]+.
Compound L5: Yield: 1.1 g (73%); elemental analysis calcd (%) for
C36H42N4: C 81.47, H 7.98, N 10.56; found: C 81.15, H 8.10, N 10.37;
FTIR (KBr disc): n˜ =3419 (b), 2961 (s), 2929 (s), 2871 (s), 1638 (s),
1597 (s), 1442 (s), 1320 (s), 1176 (s), 873 (w), 828 (w), 699 cmÀ1 (w);
1H NMR (400 MHz, CDCl3): d=9.08 (s, 2H, ArH), 8.80 (dd, 2H, ArH),
8.42 (dd, 2H, 3J=3 Hz, ArH), 8.35 (s, 2H, H-C=N), 7.53 (dd, 2H,
3
3
3H, JHH =6.80 Hz, ArH), 3.67 (septet, 2H, JHH =6.08 Hz, iPrCH), 2.90
(septet, 2H, 3JHH =6.80 Hz, iPrCH), 1.22 (d, 12H, 3JHH =6.9 Hz,
iPrCH3), 1.07 ppm (d, 12H, 3JHH =7.0 Hz, iPrCH3).
3
ArH), 7.40 (s, 4H, ArH) 3.01 (m, J=6.92 Hz, 4H, iPrCH), 1.29 ppm
3
(d, 24H, J=6.88 Hz, iPr-CH3); ESI-MS: m/z: 531.35 [M+1]+.
Synthesis of 5’ and 7
Synthesis of 3–6
The preformed Schiff-base ligand L3/L5 (0.1 mmol) was dissolved in
dichloromethane and [Zn(dipp)(DMSO)]4 (0.07 g (0.05 mmol) in
methanol was layered on top of the ligand solution and the solu-
tion was kept undisturbed for crystallization. Crystals of 5’ and 7
were obtained from this solution after one week.
To a solution of [Zn(dipp)(4-Py-CHO)]4 (2) (0.03 mmol) dissolved in
MeOH (25 mL), the corresponding diamine (0.06 mmol) dissolved
in MeOH (25 mL) was added. The resultant solution was heated at
608C for 1 h under stirring, during which time, the solution
became yellow. This solution was kept undisturbed for about 24 h,
which produced the corresponding framework as a yellow crystal-
line solid that was isolated by filtration and dried for further char-
acterization.
Compound 5’: M.p: >2758C; elemental analysis calcd (%) for
[C120H172N8O26P4Zn4]: C 57.01, H 6.86, N 4.43; found: C 56.55, H 5.95,
N 4.61; FTIR (KBr): n˜ =3440 (br), 2962 (vs.), 2929 (s), 2868 (s), 1619
(vs.), 1463 (s), 1439 (s), 1174 (vs.), 1019 (vs.), 919 (vs.), 771 cmÀ1
(vs.); CP-MAS 13C NMR (125.7 MHz, 295 K): d=160.00, 148.04,
148.20, 145.30, 140.25, 138.03, 137.25, 122.39, 123.14, 123.08,
27.38, 26.00, 23.09; 31P NMR (202 MHz, 295 K): d=À3.95 ppm;
Compound 3: Yield: 65%; M.p: >2758C; elemental analysis calcd
(%) for [C84H96N8O16P4Zn4]: C 54.27, H 5.20, N 6.03; found: C 54.87,
H 5.33, N 6.03; FTIR (KBr): n˜ =3429 (br), 2963 (vs.), 2928 (s), 2868
&
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3
1H NMR ([D6]DMSO, 400 MHz): d=8.78 (d, 2H, JHH =5.68 Hz, ortho-
could not be assigned to any meaningful molecule, squeeze has
been applied to obtain reasonable R values.
H), 8.45 (s, 1H, acetylene-H), 7.92 (d, 2H, 3JHH =5.92 Hz, meta-H),
3
7.35 (s, 2H, ArH), 7.02 (m, 3H, JHH =6.64 Hz, ArH), 3.67 (septet, 2H,
3JHH =6.09 Hz, iPrCH), 2.89 (septet, 2H, 3JHH =6.80 Hz, iPrCH), 1.19
(d, 12H, 3JHH =6.84 Hz, iPrCH3), 1.08 ppm (d, 12H, 3JHH =6.74 Hz,
iPrCH3).
Compound 7: M.p: >2758C; elemental analysis calcd (%) for
[C126H168Cl4N8O18P4S2Zn]: C 56.59; H 6.33, N 4.19; found: C 56.72, H
5.93, N 5.03; FTIR (KBr): n˜ =3444 (br), 2961 (vs.), 2868 (s), 1623 (vs.),
1439 (s), 1382 (s), 1320 (s), 1256 (s), 1173 (vs.), 1021 (vs.), 919 (vs.),
772 (vs.), 699 (s), 553 cmÀ1 (s); CP-MAS 13C NMR (125.7 MHz, 295 K):
d=159.18, 150.03, 148.07, 141.15, 140.96, 139.89, 139.19, 135.99,
130.85, 131.86, 121.77, 122.86, 123.55, 26.84, 25.53, 22.66 ppm;
31P NMR (202 MHz, 295 K): d=À3.86 ppm; 1H NMR ([D6]DMSO,
400 MHz): d=9.11 (s, 1H, ortho-N), 8.76 (m, 1H, 3JHH =4.80 Hz,
Catalytic studies
A solution of arylaldehyde (1 mmol) and malononitrile (1 mmol) in
benzene (2 mL) was heated to 608C with catalyst 5’ (0.2 mol%).
The yellow product obtained was recrystallized form ethanol.
1
Entry I (benzaldehyde): Yield: 63%; H NMR (CDCl3, 500 MHz): d=
7.91 (d, 2H, ArH), 7.78 (s, 1H, ÀCH=CÀ), 7.63 (t, 1H, ArH), 7.54 ppm
(t, 2H, ArH); 13C{H} NMR (CDCl3, 125 MHz): d=160.1, 134.8, 131.1,
130.9, 129.8, 113.8, 112.7, 83.1 ppm.
Entry II (p-nitrobenzaldehyde): Yield: 90%; 1H NMR (CDCl3,
400 MHz): d=8.39 (d, 2H, ArH), 8.08 (d, 2H, ArH), 7.88 ppm (s, 1H,
ÀCH=CÀ); 13C{H} NMR (CDCl3, 100 MHz): d=157.0, 135.9, 131.5,
124.8, 112.8, 111.5, 87.4 ppm
3
ortho-N), 8.46 (s, 1H, acetylene-H), 8.41 (m, 1H, JHH =3.80 Hz, meta-
3
N), 7.62 (m, 1H, JHH =4.92 Hz, para-H), 7.33 (s, 2H, ArH), 7.00 (m,
3
3
3H, JHH =6.56 Hz, ArH), 3.67 (sept, 2H, JHH =6.84 Hz, iPrCH), 2.92
(septet, 2H, 3JHH =6.89 Hz, iPrCH), 1.19 (d, 12H, 3JHH =6.88 Hz,
iPrCH3), 1.08 ppm (d, 12H, 3JHH =6.88 Hz, iPrCH3).
Entry III (p-cyanobenzaldehyde): Yield: 72%; 1H NMR (CDCl3,
500 MHz): d=8.01 (d, 2H, ArH), 7.85 (s, 1H, ÀCH=CÀ), 7.83 ppm
(d, 2H, ArH); 13C{H} NMR (CDCl3, 125 MHz): d=157.4, 134.4, 133.3,
130.8, 117.5, 117.4, 113.0, 111.8, 87.1 ppm
X-ray crystallography
Entry IV (p-bromobenzaldehyde): Yield: 68%; 1H NMR (CDCl3,
500 MHz): d=7.78 (d, 2H, ArH), 7.71 (s, 1H, ÀCH=CÀ), 7.69 ppm (d,
2H, ArH); 13C{H} NMR (CDCl3, 125 MHz): d=158.6, 133.3, 132.0,
130.1, 129.8, 113.6, 112.5, 83.7 ppm
Entry V (terephthaldehyde): Yield: 73%; 1H NMR ([D6]DMSO,
400 MHz): d=8.6 (d, 2H, ArH), 8.09 ppm (d, 2H, ArH); 13C{H} NMR
(CDCl3, 100 MHz): d=159.8, 135.3, 130.9, 113.8, 112.8, 84.7 ppm
Suitable crystals of L3, L5, 5’, and 7 were mounted on a Rigaku
Saturn 724+ ccd diffractometer for unit-cell determination and 3D
intensity data collection. 800 frames in total were collected at low
temperature. Data integration and indexing using CrystalClear-SM
Expert followed by calculations were carried out by using the pro-
grams in WinGX module[31] and finally solved by direct methods
(SIR-92).[32] The final refinement of the structure was carried out
using full least-squares methods on F2 by using SHELXL-97[33] and
resulted in the structure determination for all the compounds (de-
tails in Table 4). Since there are large solvent-accessible voids in
the structure of 7, residual electron density present in the molecule
CCDC 1485857, 1485868, 1485869, and 1485878 contain the sup-
plementary crystallographic data for this paper. These data are pro-
vided free of charge by The Cambridge Crystallographic Data
Centre.
Table 4. Crystal data and structure refinements details for L3, L5, 5’, and 7.
L3
L5
5’
7
Identification code
Formula
Fw
RJ-4-Py-SB
C72H86N8O
1079.48
120(2)
RJ-3-Py-SB
C36H42N4
530.74
AK 462
AK611
C120H152N8O16P4Zn4
2347.86
C124H164N8O18P4S2Zn4
2504.10
93(2)
T [K]
150(2)
150(2)
Ccrystal system
Space group
a, [ꢀ]
b, [ꢀ]
c, [ꢀ]
monoclinic
C2/c
27.116(19)
12.233(7)
24.139(18)
90
123.4770(10)
90
6679(8)
4
triclinic
¯
P1
monoclinic
P21/n
24.323(1)
14.308(7)
43.13(2)
90
94.191(10)
90
14970(1)
4
triclinic
¯
P1
8.889(3)
17.953(6)
19.898(8)
86.94(1)
81.911(14)
79.764(11)
3092.5(19)
4
17.904(1)
19.050(1)
24.624(1)
111.818(8)
90.558(3)
111.143(9)
7171(8)
a, [8]
b, [8]
g, [8]
V, [ꢀ3]
Z
2
1 (calcd), [gcmÀ3
]
1.074
1.140
1.041
1.087
crystal size, [mm3]
q range, [8]
0.20ꢂ0.10ꢂ0.05
2.84 to 24.99
24218
5843
1.177
0.25ꢂ0.08ꢂ0.03
2.50 to 24.99
23392
10835
1.088
0.21ꢂ0.15ꢂ0.14
2.997 to 22.499
81826
19350
1.015
0.2ꢂ0.2ꢂ0.02
2.985 to 22.500
42987
18644
1.230
no. of rflns collected
independent reflns (I0 >2s(I0)
GOF
R1(I0 >2s(I0)
0.0966
0.0883
0.0994
0.1324
wR2 (all data)
largest hole and peak [eꢀÀ3
0.2878
À0.486, 0.522
0.2429
À0.481, 0.634
0.3113
À0.60, 0.96
0.3769
À1.234, 1.903
]
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Mater. 2016, 6, 1600110; e) D. Kaleeswaran, R. Antony, A. Sharma, A.
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This work was supported by SERB, New Delhi (SB/S1/IC-48/
2013) and IIT-Bombay Bridge Funding. R.M. thanks SERB, New
Delhi for J.C. Bose Fellowship (SB/S2/JCB-85/2014). R.J. thanks
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A.K. thanks IIT Bombay for research fellowships.
Conflict of interest
The authors declare no conflict of interest.
Keywords: covalent organic frameworks · linking · metal–
organic frameworks · Schiff bases · zinc
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Manuscript received: January 12, 2018
Version of record online: && &&, 0000
Chem. Eur. J. 2018, 24, 1 – 14
www.chemeurj.org
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ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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These are not the final page numbers! ÞÞ

Full Paper
FULL PAPER
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Metal–Organic Frameworks
R. Jangir, A. Ch. Kalita, D. Kaleeswaran,
S. K. Gupta, R. Murugavel*
&& – &&
A [4+2] Condensation Strategy to
Imine-Linked Single-Crystalline
Zeolite-Like Zinc Phosphate
Frameworks
Diamond in the rough! The utility of a
D4R Zn4P4O12 SBU in assembling novel
framework structures (see scheme) has
been showcased through careful
terization of an unprecedented class of
isoreticular metal–organic framework
(MOF)–covalent organic framework
(COF) hybrid systems.
design, synthesis, and structural charac-
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&
Chem. Eur. J. 2018, 24, 1 – 14
www.chemeurj.org
14
ꢁ 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
ÝÝ These are not the final page numbers!