Hydrated and dehydrated Ca-coordination polymers based on benzene-dicarboxylates: Mechanochemical synthesis, structure refinement, and spectroscopic characterization

Article abstract of DOI:10.1039/c7ce01906h

A series of Ca-based coordination polymers were prepared mechanochemically by milling Ca(OH)₂ with phthalic acid (H₂oBDC), isophthalic acid (H₂mBDC), and terephthalic acid (H₂pBDC). The hydrated compounds [Ca(oB

Full text of DOI:10.1039/c7ce01906h

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HIGHLIGHT
Tiddo J. Mooibroek, Antonio Frontera et al.
Towards design strategies for anion–π interactions in crystal engineering
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Hydrated and Dehydrated Ca-Coordination Polymers based on
Benzene-Dicarboxylates: Mechanochemical Synthesis, Structures
Refinement, and Spectroscopic Characterization.
1
, 2, 3
* 1
2
2
Abdal-Azim Al-Terkawi
, Gudrun Scholz , Carsten Prinz , Annett Zimathies , Franziska
*
2
* 1
Emmerling , Erhard Kemnitz
1
Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D – 12489
Berlin, Germany.
2
Federal Institute for Materials Research and Testing (BAM), Richard-Willstaetter- Str. 11, D –
1
2489 Berlin, Germany.
3
School of Analytical Sciences Adlershof (SALSA), Humboldt-Universität zu Berlin, Unter den
Linden 6, D – 10099 Berlin, Germany.
Corresponding authors:
*
PD Dr. G. Scholz, email: gudrun.scholz@rz.hu-berlin.de
*
Dr. F. Emmerling, email: franziska.emmerling@bam.de
*
Prof. Dr. E. Kemnitz, email: erhard.kemnitz@chemie.hu-berlin.de
1

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Abstract
A series of Ca-based coordination polymers were prepared mechanochemically by milling
Ca(OH) with phthalic acid (H oBDC), isophthalic acid (H mBDC), and terephthalic acid
2
2
2
(H pBDC). The hydrated compounds [Ca(oBDC)(H O)] (1), [Ca(mBDC)(H O) ] (2), and
2 2 2 3.4
[
Ca(oBDC)(H O) ] (3) were prepared for the first time via mechanochemical routes. The refined
2
3
structures were validated by extended X-ray absorption data. The new dehydrated compound
Ca(oBDC)] (1-H O), obtained after the thermal post-treatment of 1 in a reversible phase
[
2
transition process, was determined ab initio based on the powder X-ray diffraction (PXRD) data.
The materials were thoroughly characterized using elemental analysis, thermal analysis, and
spectroscopic methods: magic-angle spinning NMR and attenuated total reflection-infrared.
The specific surface areas and the sorption properties of the hydrated and dehydrated samples
were determined by the isotherms of gas sorption and dynamic vapor sorption measurements.
Introduction
Driven by the growing concern with respect to environmental issues, mechanochemistry has
lately been established as alternative synthesis method for producing various materials that
1
–3
range from small molecules to supramolecular polymers. Mechanochemical reactions can be
performed under solvent-free conditions, however small amounts of solvents can be added to
the powder mixture for ligand/liquid-assisted grinding (LAG) to accelerate the
mechanochemical reactions, enhance the mobility of the reactants, and subsequently to
4
improve the crystallinity of the resulting products. A certain crystallinity of the resulting
polycrystalline powders is essential for solving crystal structures ab initio from powder X-ray
diffraction (PXRD) data. The possibility of monitoring mechanochemical reactions in situ is an
interesting approach for investigating milling processes and obtaining reliable data for
5
,6
mechanistic studies.
Metal-organic coordination polymers (CPs) gained increasing interest in the recent decades for
7
,8
their wide applications in luminescence, semiconductors, storage, and biology. These
materials offer interesting architectures and topologies with the ability of post-synthetic
9
,10
modifications for altering physicochemical properties of the resulting CPs.
Typically,
2

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1
1,12
transition metals are used as nodes between the organic linkers,
alkaline earth (AE) ions as coordination centers.
less attention is paid to
AE metals have relatively large radii and high affinities for oxygen donors which make them
1
3
promising candidates for constructing CPs based on multifunctional carboxylate systems.
Coordination between metals and carboxylate ligands leads to the formation of one, two, or
three-dimensional compounds with the possibility of having an extensive connection driven by
1
4
noncovalent interactions, such as hydrogen bonds and π-π aromatic stacking.
1
5
Ca-based metal-organic complexes are found in nature. Moreover, calcium is an essential
element in biological systems. It plays a vital role in processes such as the activation of
enzymes, complexation with nucleic acids, nerve impulse transmission, muscle contraction, and
carbohydrate metabolism. Based on that and due to its non-toxicity and the relatively light
weight, calcium is a promising element for synthesizing CPs with the possibility of
1
4,16–18
implementations in biological and gas storage applications.
The abundant and
2
+
2+
2+
biocompatibility of AE ions (Mg , Ca , and Sr ) make them promising for constructing
1
6,19
economical and non-toxic CPs with interesting properties in gas sorption and separation,
1
8,20
21,22
photochromic,
as well as photoluminescence-sensing.
Based on our extensive search in literature and using the Cambridge Structural Database (CSD),
we found different Ca-CPs based on the ortho-, meta-, and para-isomers of benzene-
23
dicarboxylates. For instance, Ca-phthalate monohydrate was reported by Gupta et al.
1
6–18
(
Refcode: CAPHTH), Schuckmann et al. (CAPHTH01), and Zhang et al. (CAPHTH02).
Ca-isophthalates were reported by Dale et al. (EMIDEJ) and Yu et al. EMIDEJ01).
terephthalate trihydrate was reported by Matsuzaki et al. (CATPAL), Groeneman et al.
Hydrated
2
7,28
Ca-
2
6,29–31
(CATPAL01), Dale et al. (CATPAL02), and Zhang et al. (CATPAL03).
All these
compounds were prepared via autoclave, hydro-, or solvothermal treatments. The latter
compound was also successfully prepared in our research group via a mechanochemical
3
2
synthesis route. A dehydrated Ca-terephthalate (Refcode: DIQGUH) was obtained after a
thermal post-treatment of the hydrated Ca-terephthalate in a reversible phase transition
3
2,33
process.
Previously, we reported on Ca-CPs based on coordination with
3
4,35
tetrafluoroterephthalate and tetrafluoroisophthalate.
Herein, we systematically study the
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mechanochemical synthesis, ab initio structures determination, Rietveld refinement, and the
physiochemical properties of series of Ca-CPs based on the nonfluorinated isomers of benzene-
dicarboxylates in their solid-state.
Methods
Materials
Commercially accessible Ca(OH) (Aldrich, chemical purity 96%) was used as an inorganic
2
precursor. Phthalic acid (H oBDC, Aldrich, chemical purity 99.5%) isophthalic acid (H mBDC,
2
2
Aldrich, chemical purity 99%), and terephthalic acid (H pBDC, Aldrich, chemical purity 98%)
2
were used as organic linkers. All chemicals were used without further purification.
Planetary Mill
All mechanochemical reactions were performed in a commercial planetary mill “Pulverisette 7
premium line” (Fritsch, Germany) under access of air. Each silicon nitride grinding bowl
(volume: 45 ml) was filled with 1 g of a powder mixture and assembled with five silicon nitride
balls (12 mm in diameter, 2.8 g each). A ball to powder mass ratio of 14 was ensured. All
samples were milled with a rotational speed of 600 rpm. For the short milling (1h), reactions
were not interrupted. In case of the milling run over 4 hours, the reactions were interrupted for
3
0 min every 60 min to cool down the equipment. The temperature was not controlled during
the milling. The milling direction was reversed in every cycle.
Synthesis
All hydrated compounds were synthesized by milling the calcium hydroxide source Ca(OH)2
with the respective organic precursor (phthalic acid H oBDC, isophthalic acid H mBDC, or
2
2
terephthalic acid H pBDC) with an applied molar ratio = 1:1. 130 µl H O was added to the
2
2
powder mixture. A typical time for milling was 1 h. The dehydrated compounds were obtained
after thermal post-treatments of the hydrated samples.
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Powder X-ray diffraction
Powder X-ray diffractograms were recorded with a XRD-3003-TT diffractometer (Seiffert & Co.,
Freiberg, Germany) with Cu-K radiation (λ = 1.542 Å; step scan: 0.05°, step time: 5 s).
α
3
6
Reflections were compared with diffractograms of the JCPDS-PDF database. The powder X-ray
diffraction (PXRD) measurements for structure solution were performed with a D8 Discover
diffractometer (Bruker AXS, Karlsruhe, Germany) operated in transmission geometry with Cu-
Kα1 radiation (λ = 1.54056 Å, step scan: 0.009°, step time: 5 s), equipped with a Lynxeye
detector. Samples were prepared in glass capillaries (diameter 0.5 mm) and were measured in a
2
θ range of 5° - 65°.
The Crystal structure of the dehydrated compound (1-H O) was determined ab initio starting
2
from the PXRD data. The PXRD pattern was indexed for the first 20 lines with the program
3
7,38
DICVOL implemented in the DASH software package and with TOPAS.
The adequacy of the
unit cell and the space group assignment was validated by the profile refinements of whole
3
9,40
patterns without structural parameters using the LeBail method.
Structure was solved using
3
7
DASH software and based on the simulated annealing (SA) routine. The best structural models
were refined along with the experimental PXRD data by the Rietveld method using the
fundamental parameter approach as reflection profiles (emission profiles with axial instrument
3
8
contributions and crystallite microstructure effects). Standard restraints were applied to bond
lengths and bond angles. Hydrogen atoms were located geometrically. The cell parameters and
refinement factors are given in Table 1. Wherein, R and R values refer to the Rietveld criteria
p
wp
4
1
of fit for profile and weighted profile defined by Langford and Louër.
Elemental Analysis
A EURO EA equipment (HEKAtech GmbH) was used for carbon and hydrogen content
determinations.
Thermal analysis
Thermogravimetry (TG) and differential thermal analysis (DTA) measurements were performed
simultaneously on a thermobalance TAG 24 (SETARAM, Caluire, France). For this purpose, the
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samples (initial mass ≈ 12 mg) were filled into 100 µl corundum-crucibles with corundum cover
and heated under a flow of argon and synthetic air at a rate of 10 K/min up to 600-1000 ˚C. For
simultaneous analysis of evolved gasses, a mass spectrometer (Balzers Quad-star 421) was
coupled by a heated (180 ˚C) quartz glass capillary (measurements were performed in MID
(multiple ion detection) mode.
Magic Angle Spinning NMR
1
1
13
H and H-> C CP MAS NMR spectra were recorded on a Bruker AVANCE 400 spectrometer
(
Larmor frequencies: ν = 400.1 MHz, ν =100.6 MHz) using both a 2.5 mm and a 4-mm
1H
13C
1
double-bearing magic angle spinning (MAS) probe (Bruker Biospin). H MAS studies were made
with a π/2 pulse length of 3.6 ꢀs and a recycle delay of 5 s. Values of the isotropic chemical
1
13
1
shifts of H and C are given with respect to TMS. A contact time of 10 ms was used for the H-
1
3
>
C CP MAS NMR experiments.
Attenuated Total Reflection-Infrared Spectroscopy
Infrared spectra were measured using an Equinox 55 FT-IR spectrometer (Bruker, Ettlingen,
Germany). A CaF window was used. The Attenuated Total Reflection-Infrared (ATR-IR) spectra
2
−1
were recorded by averaging 100 scans at a 2 cm resolution.
Gas Sorption
Gas adsorption experiments were carried out on an ASAP 2010 and ASAP 2020 (Micromeritics,
Norcross, USA). Nitrogen was used as an adsorptive at a temperature of 77 Kelvin. Prior to the
measurements, samples were degassed at room temperature, 200 ˚C, 240 ˚C, 260 ˚C, 290 ˚C, or
3
90 for 24 h in vacuum. Specific surface areas were calculated by Brunauer-Emmett-Teller (BET)
4
2,43
44
method
with a molecular sectional area of 0.162 nm² according to ISO 9277 (2010).
Dynamic vapor sorption
The experiments of dynamic vapor sorption (DVS) were performed on the DVS-1 instrument
Surface Measurements Systems, London, UK). The DVS System is a gravimetric sorption
(
apparatus consists of a thermostated sample chamber for setting a constant temperature of
the sample and a flow controller for producing a controllably variable vapor pressure. The
adsorbed mass is determined by continuous weighing as a function of the relative pressure. The
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isotherms were measured over a range of 0 – 98% relative humidity (RH). For our experiments,
water and n-octane were used as adsorptive at a temperature of 25˚C.
X-ray Absorption Spectroscopy
The EXAFS (extended X-ray absorption fine structure) spectra were recorded for the Ca element
with absorption edges at 4.038 keV. Samples were measured at the B18 beamline (Diamond,
Oxford UK) in Rapid Access mode. The beam was monochromatized using a double-crystal
monochromator (DCM). The measurements were performed at the K edge for Ca at 4.038 keV.
The experiments were acquired in a quick-EXAFS mode in the range of 3.838-5.000 keV, and a
nominal step size of 0.3 eV was used. The Ca-samples were used as-synthesized, and the fine
powders were fixed between two strips.
The data treatments were carried out using the Demeter software package (Artemis & Athena).
4
5
These GUIs programs belong to the software package IFEFFIT (v. 1.2.11). For better
assignation of the coordination number and interatomic distances, EXAFS simulations of the
determined crystal structures were carried out in FEFF and compared with the measured
4
6
spectra.
Scanning Electron Microscopy
The SEM (scanning electron microscopy) imaging of the powder samples was performed on a
Zeiss Gemini Supra-40 instrument operated with an acceleration voltage of 10 kV at a working
distance of 8.5 mm.
Results and Discussion
[
Ca(oBDC)(H O)]
2
The hydrated Ca-phthalate [Ca(oBDC)(H O)] (1) was synthesized by milling phthalic acid
2
(
H oBDC) with Ca(OH) and 130 µL H O (Figure 1). The milling time was varied between 30 min,
2 2 2
1
h, and 4 h leading to the formation of the same compound 1 (see Figure 1b). In the absence of
water, compound 1 was formed after milling the powder mixture for 4 h. The structure of
compound 1 obtained after milling is similar to the reported crystal structures by Gupta et al.,
2
5,26
Schuckmann et al., and Zhang et al.
These compounds were synthesized via hydro- or
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solvothermal treatments. The measured PXRD pattern of compound 1 and the simulated PXRD
data from the previously known crystal structures are compared in Figure S1.
The structure of 1 was successfully refined via Rietveld method (Figure 2a). [Ca(oBDC)(H O)] (1)
2
crystallizes in the monoclinic space group P2 /c. The asymmetric unit consists of one calcium
1
2
-
II
ion, one oBDC , and one water molecule. The Ca ion is seven-fold coordinated (Figure 3a)
comprising six carboxylate oxygen atoms (O1, O1’, O2, O2’, O3, O4) from four organic anions
(Figure 5b) and one terminal water molecule (O1w). The water molecule is linked via hydrogen
bonds to the carboxylate oxygen atoms O1 and O2 (Figure 3d). The average bond length for Ca–
O(carboxyl) and Ca–O(aqua) are 2.4065 Å and 2.381 Å, respectively. Each CaO polyhedron
7
shares two edges (O1, O2) with the neighboring CaO polyhedrons (Figure 5b) to form infinite
7
chains along the crystallographic b-axis (Figure 3d). The intermetallic distance within the 1D
chains is 3.898(3) Å for each CaO -(O1, O2)-CaO unit. The 1D polymeric chains are bridged via
7
7
2
-
oBDC (O3, O4) along the crystallographic c-axis. Layers of the polymeric chains form the final
structure of 1 (Figure 3e). The distance between the bridged chains is 4.895(2) Å for each CaO7-
(
O3, O4)−CaO unit. The interlayer Ca···Ca distance amounts to 11.221(2) Å.
7
[
Ca(oBDC)]
The thermoanalytical data of 1 indicate the formation of a dehydrated compound around 290
C which is stable up to 400 °C (Figure 8a). Upon this result, a thermal post-treatment was
°
performed for the hydrated compound 1 at 290 °C. The PXRD patterns of the resulting
dehydrated Ca-phthalate [Ca(oBDC)], named (1-H O), and the hydrated compound 1 are
2
compared in Figure 1. The results of the elemental analysis are given in Table S1. The crystal
structure of the new dehydrated compound (1-H O) was determined ab initio from the PXRD
2
data and subsequently refined via Rietveld method (Figure 2b). The new structure of (1-H O)
2
II
was solved in the monoclinic space group P2 /c. The asymmetric unit is composed of one Ca -
1
II
ion and one phthalate anion. Ca -ion is surrounded by eight carboxylate oxygen atoms (Figure
4
a) from six organic ligands (Figure 4b). The average Ca-O(carboxyl) distance is 2.446 Å, which is
slightly longer than the corresponding one in the hydrated compound 1. Each polyhedron
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shares edges with the neighboring polyhedrons to from 1D chains along the crystallographic b-
axis (Figure 4b). The intermetallic distance within a 1D polymeric chain is 3.561(5) Å for each
Ca-(O2,O3,O4)-Ca unit. The chains are alternately bridged via two carboxylate oxygen atoms
(Figure 4d). The distance is 3.633(5) for each Ca-(O1,O1’)-Ca unit. Layers of the 2D polymeric
chains form the final structure of (1-H O) (Figure 4e).
2
[
Ca(mBDC)(H O) ]
2
3.4
The hydrated Ca-isophthalate (2) was prepared by milling the organic precursor isophthalic acid
H mBDC) with Ca(OH) and a small amount of water for 1 h (Figure 5, blue PXRD pattern). In
(
2
2
the absence of water, a poor crystalline product was formed by milling of the powder mixture
for 4 h (Figure S2). The results of the elemental analysis are given in Table S1. The structure of
the compound 2 is similar to the two reported structures by Yu et al. and by Dale et al. and can
2
7,28
be identified, for simplicity, as [Ca(mBDC)(H O) ].
More precisely, a composition of
2
3.4
[
{Ca (mBDC) (H O) }·4H O] (2) can be assigned. Both reported structures were synthesized
2
.5
2.5
2
4.5
2
via hydrothermal treatments. The measured PXRD pattern of 2 and the calculated PXRD
patterns from the reported crystal structures are compared in Figure S3.
The structure of 2 was successfully refined (Figure 2c). Compound 2 crystallizes in the
2
+
monoclinic space group C2/c. The asymmetric unit of 2 contains three independent Ca
positions (Ca1 and Ca2 in general positions while Ca3 lies on a twofold axis). The water
molecules comprise four Ca-bound water molecules (O3, O4, O10, O14), a bridging water
molecule (O11), and four co-crystallized water molecules (O1w, O2w, O3w, and O4w). Ca1 has
a coordination number of eight comprising six carboxylate oxygen atoms, and two terminal
coordinating water molecules (Figure 6a). Like Ca1, Ca2 is eight-fold coordinated except for one
of the two coordinating water molecules that bridge Ca2 to the next metal center Ca3 (Figure
6
b). The third cation Ca3 is nine-fold coordinated with six carboxylate oxygen atoms, one
terminal water molecule, and two bridging water molecules in the coordination sphere (Figure
c). The carboxylate oxygen atoms and the water-oxygen atoms bridge the metal centers and
6
subsequently lead to the formation of 1D helical strands (Figure 6e-f). The Helices are
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connected via extensive hydrogen-bonding network (HBN) that originates between the metal-
coordinating water molecules, water molecules of crystallization, and carboxyl oxygen atoms
and form 3D arrays (Figure 6g-h). The Ca···Ca distances are 3.977(1) Å, 3.8747(2) Å, 3.6414(1)
for the units Ca1-(O1,O1’)-Ca1, Ca1-(O6,O7)-Ca2, and Ca2-(O8,O12,O11)-Ca3, respectively. The
angles around Ca ions vary from 48.2° to 170.4°. The Ca-O(carboxylate) bond lengths range
from 2.3626(1) – 2.6567(1) Å. The Ca-O(aqua) distances range between 2.3446(1) – 2.6373(1) Å.
[
Ca(pBDC)(H O) ]
2
3
3
2
The synthesis of the hydrated Ca-terephthalate (3) was described elsewhere. The resulting
compound is similar to the reported structures via solvothermal treatments by Matsuzaki et al.,
2
6,29–31
Groeneman et al., Dale et al., and Zhang et al.
The measured PXRD pattern of 3 is
compared to the simulated PXRD patterns from the reported crystal structures in Figure S4.
The crystal structure of compound 3 obtained by milling was successfully refined via Rietveld
method. The result of the refinement is shown in Figure 2d. [Ca(pBDC)(H O) ] crystallizes in the
2
3
2-
monoclinic space group P2 /c with an asymmetric unit consisting of one Ca atom, one pBDC
1
II
anion, and three water molecules. Ca -ion is surrounded by eight oxygen atoms (Figure 7a)
comprising four carboxylate oxygen atoms (O1, O1’, O2, O2’) from three organic anions, two
bridging water-oxygen atoms (O2w, O2w’), and two terminal water molecules (O1w, O3w)
(
Figure 7b). Each CaO polyhedron shares three edges (O1,O2,O2w) with each neighboring CaO
8
8
polyhedrons and extending the inorganic connections into 1D polymeric chains along the
crystallographic c-axis (Figure 7d). The Ca-(O1,O2,O2w)-Ca unit is 3.640(1) Å. The 1D chains are
linked to a 3D array by a hydrogen-bonding network including the non-coordinating carboxyl
groups (O3,O4) and the water molecules in addition to the aromatic π–π stacking (Figure 7e).
Coordination systems and EXAFS data
In their coordination to the Ca-atom, the three isomers of benzene-dicarboxylate exhibit
different coordination modes depending on the geometry of each ligand.
1
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2
-
II
In the hydrated compound 1, benzene-ortho-dicarboxylate (oBDC ) coordinates to four Ca -
ions via the two carboxylic groups (Figure 3c). One carboxyl group (O1, O2) chelates one Ca-
atom and bridges another two to form infinite chains of CaO polyhedrons. Each oxygen atom
7
in the other carboxyl group (O3, O4) acts as a monodentate and bridging the 1D chains into 2D
layers (Figure 3e). Notably, the two carboxyl groups are connected via one Ca-atom
2
-
(
O2−Ca−O3) with an angle of 79.832(3) Å. In the dehydrated compound (1-H O), oBDC
2
II
connects six Ca -ions via the two carboxylic groups (Figure 4c). Each of the four carboxylate
oxygen atoms acts as a bidentate ligand. The two carboxyl groups are bridged via one Ca-atom
(O2−Ca−O3) with an angle 76.832(3) Å. In the crystal structure of 2, benzene-meta-
2
-
II
II
dicarboxylate (mBDC ) coordinates to four Ca -ions. Each carboxylic group chelates one Ca -ion
2
-
and bridges another one (Figure 6d). In the structure of 3, para-isomer (pBDC ) coordinates to
II
four Ca -ions via one carboxylic group (O1,O2). The second carboxylic group (O3,O4) does not
2
-
participate in the coordination (Figure 7c). In contrast to 3, both carboxylate groups of pBDC in
the dehydrated compound (3-H O) equally participate in the coordination system. Each
2
carboxyl group is coordinated to three Ca-atoms (see Figure S13 for more details).
II
In their coordination to benzene-dicarboxylates, the Ca -ions are arranged in infinite polymeric
chains (structures of 1, 1-H O, 2, 3). These chains can be bridged via carboxylate oxygen atoms
2
to extend into 2D layers (structures of 1, 1-H O) or via intermolecular H-bonds to form 3D
2
supramolecular arrays (structures of 2 and 3). In general, the design of these structures and
coordination environments are strongly dependent on the geometries of the organic linkers.
The coordination number (CN) of the central Ca-atom is seven (in the crystal structure of 1),
eight (in the crystal structures of (1-H O), Ca1 and Ca2 in 2, and 3), and nine (Ca3 in 2). The two
2
3
4,47
CNs = 7 and 8 are well known, but CN = 9 is rarely described for Ca-coordination systems.
The average Ca-O bond length is 2.4 Å which is consistent with related Ca-compounds that are
2
3
deposited in the Cambridge Structural Database (CSD). Crystal data derived from the refined
structures of 1, 1-H O, 2, and 3 are given in Table 1. Selected bond lengths, distances, hydrogen
2
bonds, and angles derived from the crystal structure of 1, 1-H O, 2, and 3 are summarized in
2
Tables S2-S3. Crystal data derived from the refined structures and those derived from the
reported crystal structure are compared in Tables S4-S6.
1
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II
The local coordination environments around Ca -ions in the refined structures were
investigated by extended X-ray absorption spectroscopy (EXAFS) data. The fits of the
experimental data along with the simulated spectra are shown in Figure S5 indicating good
II
agreements between the first coordination spheres around the respective Ca -ion with those of
the determined structures. The Ca–O bond lengths, scattering paths, and fit parameters are
given in Table S7.
Thermal properties
The thermoanalytical curves depict the expected mass losses belonging to the loss of water
molecules in the hydrated compounds. For compound 1 (Figure 8a), the release of the
coordinating water molecule is complete at 290 ˚C with a total ∆m = -10.1% (calc. 10% for
1
H2O). The already water-free framework [Ca(oBDC)] is stable up to 430 ˚C and then begins to
decompose. The TG curve of compound 2 (Figure 8b) depicts consecutive mass losses with a
total ∆m = -23.5% which correspond to the liberation of the water molecules (calc. 23.1% for
3
.4H O). The release of the water molecules is complete at 457 ˚C. The decomposition of the
2
already water-free frameworks [Ca(mBDC)] continues with a massive mass loss of 15.8%
between 457 °C - 602 °C. In contrast to [Ca(oBDC)] (1-H O) which depicts long range of stability
2
(
290 – 430 °C), the water-free [Ca(mBDC)] (2-H O) does not show long stability and begins
2
immediately to decompose after the liberation of the coordinating and co-crystallizing water
molecules from the crystal structure. For compound 3, the release of the three coordinating
water molecules is completed up to 200 °C. The water-free [Ca(pBDC)] (3-H O) is stable up to
2
3
2
4
00 °C.
Thermal-post treatments were performed for the hydrated compounds 1, 2, and 3 based on the
results of the thermal analysis. A new crystalline compound [Ca(oBDC)] (1-H O) was formed
2
after thermal annealing of 1 at 290 °C (Figure 1c). The thermal post-treatment of compound 2
at 240 °C, 260 °C, and 360 °C formed poor crystalline products (Figure S6). The thermal
3
2
annealing of the mechanochemically synthesized compound 3 (Scholz et al.) resulted in the
formation of a dehydrated compound [Ca(pBDC)] which is identical to the reported crystal
3
3
structure by Mazaj et al.
1
2

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MAS NMR and ATR-IR Spectroscopies
1
In the H MAS NMR spectrum (Figure 9a), the presence of water molecules embedded within
the crystal structures of 1 and 2 is indicated by the contributions at chemical shifts at 4.8 ppm
(blue spectrum) and 4.5 ppm (magenta spectrum), respectively. The small contribution at δ =
6
.4 ppm in compound 1 (not visible in the shown spectrum), at δ = 6.9 ppm in the dehydrated
compound (1-H O), green spectrum, are mainly due to the C―H bond within the aromaꢀc
2
rings. The narrower line at δ = 8.9 ppm in compound 2 is assigned to stronger bridged protons.
1
13
The H→ C CP MAS NMR spectra (Figure 9b) depict different contributions and are assigned to
different types of carbon atoms in carboxylate groups at δ = 181 and 177 ppm for compound 1
(
blue spectrum), at δ = 182, 180, and 177 for compound (1-H O), green spectrum, and at δ =
2
1
76, 175, and 172 ppm for compound 2 (magenta spectrum). These contributions are
attributable for the different coordination modes of carboxylic groups in their coordinations
with Ca-atoms. The chemical shifts around δ = 142, 135, 130, 129, and 127 ppm in 1, at δ = 142,
1
37, 135, 130, 128, and 124 in (1-H O), and around δ = 135, 133, 132, 130, and 128 ppm in 2 are
2
assigned to non-equivalent crystallographic positions of carbon atoms in the aromatic ring.
In the ATR-IR spectra (Figure S7), the main vibrational bands assigned to carboxylate stretching
-1
-1
in compounds 1 are at 1544 cm for asymmetric stretching and at 1408 cm for symmetric
stretching (blue spectrum). In the dehydrated compound (1-H O), the main contributions
2
-1
correspond to asymmetric and symmetric stretching are assigned at 1528 and 1406 cm ,
respectively (red spectrum). In compounds 2, vibrational bands assigned to carboxylate
-
1
-1
stretching appear at 1528 cm for asymmetric stretching and 1392 cm for symmetric
stretching (black spectrum). The separations between the two vibrational modes (Δas-s = ν ―
as
-
1
ν ) in compounds 1, (1-H O), and 2 are 136 cm . The separations are attributable to the
s
2
4
8,49
multidentate coordination mode of carboxylate groups in compounds 1, (1-H O), and 2.
The
2
-1
broad contributions around 3400 cm in compounds 1 and 2 are mainly due to the crystal
water molecules and the formation of hydrogen-bonding networks along the crystal
2
8
structures. The absence of the latter vibrational bands in the red spectrum indicates that
compound (1-H O) is free of water.
2
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Gas sorption and dynamic vapor sorption
The BET surface areas were determined based on N adsorption isotherms. The hydrated
2
2
compound 1 depicts a small specific surface area (4.2 m /g) which increases in the dehydrated
2
compound (1-H O) to 14.3 m /g. The surface areas of compound 2 remain almost unchanged
2
even after thermal pretreatments at different temperatures. These results are summarized in
Table S1. The corresponding adsorption/desorption isotherm curves are shown in Figures S8-
S10.
For more investigations, the dynamic vapor sorption (DVS) of n-octane on samples of the
hydrated compound 1 and the dehydrated compound (1-H O) were performed. The adsorption
2
properties of the dehydrated sample are notably enhanced compared to the hydrated
compound 1 as shown in Figures S11a-b. The isotherm curves for the DVS of water on the
dehydrated compound (1-H O) depict that water is chemically adsorbed over the dehydrated
2
sample and indicate the formation of a new rehydrated compound (Figure 10a). The PXRD
pattern of the sample after controlled rehydration is identical to the PXRD pattern of the
sample as-synthesized and indicate that the phase transition is a reversible process (Figure
1
0b). SEM images for compounds 1, 1-H O, 2, and 3 are shown in Figure S12.
2
Structural trends in Ca-benzene-dicarboxylates and their fluorinated counterparts
In addition to the influence of geometries of benzene-dicarboxylate isomers on determining the
crystal structures of the Ca-based CPs, the crystal structures can also vary by using Sr-atoms as
alkaline earth metals or by the substitutions of hydrogen atoms in benzene rings by fluorine
atoms. For example, the two hydrated compounds of Ca-phthalate 1 and Sr-phthalate are
5
0
different from each other in their water contents and subsequently in their structures. Ca-
phthalate comprises one terminal Ca-bound water molecule with extended metal-polymeric
chains that are crosslinked by the organic linkers. The Sr-based CP crystallizes as a 2D-CP via
inorganic connectivity and comprises two half-bridging, one terminal, and one co-crystal water
2
+
molecules. In the crystal structure of 1, the Ca -ion has a CN of seven. In the crystal structures
1
4

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II
of the fluorine-free Sr-phthalate and the fluorinated Sr-tetrafluorophthalate, the CN of Sr ions
is nine comprising six carboxylate oxygen atoms, one terminal, and two half bridging water
5
0
molecules. In addition, Sr-phthalate exceeds its fluorinated counterpart by having one more
co-crystallized water molecule.
Ca- and Sr-isophthalates exhibit similar structural and thermal properties (the latter is not yet
reported) but they both differ from their fluorinated counterparts. Ca-CP based on isophthalic
acid crystallize as a 1D-CP that rise into 3D-supramolecular arrays via extensive hydrogen-
bonding networks (HBNs). Ca- and Sr-tetrafluoroisophthalates crystallize isomorphous as 3D-
3
5
fluorinated CP.
5
1
Ca- and Sr-terephthalates crystalize as 1D-CPs which rise into 3D-arrays via HBNs. In both
II
structures, the M O polyhedra comprise four carboxylate-oxygen atoms and three water
8
molecules. Differently, the two isomorphous structures of Ca- and Sr-tetrafluoroterephthalates
consist of 1D inorganic chains which are bridged via the organic linkers to form layers of 2D-
FCPs.
These structural differences between the nonfluorinated CPs and their fluorinated counterparts
are strongly influenced by the presence of fluorine atoms in the benzene ring. The electrostatic
repulsions between the highly electronegative fluorine atoms and the lone-pair electrons of
carboxylate oxygen atoms lead to the twisting of carboxylate groups out the planar plane of the
5
2
benzene ring. Such nonplanarity is mainly the reason for increasing the organic connectivity
within the fluorinated CPs and subsequently their high dimensionalities compared to their
nonfluorinated counterparts. Structural properties of Ca-CPs based on benzene-dicarboxylates
and their fluorinated counterparts are compared in Table 2. Crystal structures of the hydrated
and dehydrated Ca-benzene dicarboxylates are depicted in Figure S13.
Conclusions
In summary, Ca-coordination polymers based on benzene-di-carboxylates [Ca(BDC)(H O) ] were
2
n
synthesized by milling powders of Ca(OH) with phthalic acid (H oBDC), isophthalic acid
2
2
(
H mBDC), or terephthalic acid (H pBDC). Mechanochemical reactions were performed in a
2
2
1
5

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planetary mill. The stoichiometric ratio between the inorganic and organic reactants was 1:1.
The best results were obtained when a small amount of water (130 µl H O) was added to the
2
powder mixture. Like Ca-terephthalates, a dehydrated compound [Ca(oBDC)] (1-H O) was
2
obtained after the thermal post-treatment of the hydrated Ca-phthalate (1) in a reversible
phase transition process. The thermal annealing of [Ca(mBDC)(H O) ] (2) resulted in very poor
2
3.4
crystalline products. The dehydrated Ca-terephthalate is known from literature. The new crystal
structure of the dehydrated compound (1-H O) was solved ab initio based on the powder X-ray
2
diffraction data. The structures of compounds 1, 1-H O, 2, and 3 were refined by Rietveld
2
method. The structural topologies and coordination environments in the resulting Ca-based
coordination polymers are determined by the chemical nature and geometries of organic
linkers. In their coordination with Ca-atoms, both ortho- and meta-isomers bridge Ca atoms in
an exo-bidentate fashion to propagate the polymeric network in 2D or 1D-networks,
respectively. The para-systems acts as a unidentate to extend the polymeric chains in 1D
connections. The connections rise into a 3D network via hydrogen bonds. In addition to the
covalent Ca–O interaction, intensive networks of the non-covalent interactions stabilize the
II
hydrated crystal structures. We studied the coordination environments around Ca -ions and the
physical-chemical properties of the resulting compounds by MAS NMR, ATR-infrared, and
EXAFS spectroscopic methods. Further characterizations using thermal analysis, BET
measurements, dynamic vapor sorption, and SEM imaging were applied.
Acknowledgements
We are grateful for the funding received from the Excellence Initiative of the German Research
Foundation (DFG project: GSC 1013) and the Graduate School of Analytical Sciences Adlershof
(SALSA). We acknowledge Dr. Ana Guilherme Buzanich for EXAFS measurements, Dr. Stefan
Reinsch for DTA-TG measurements, Mrs. Sigrid Benemann for providing SEM images, and Mrs.
Anka Kohl for ATR-IR measurements. We thank Dr. Andrea Zehl and Mrs. Jenny Odoj for
elemental analysis. We also thank Dr. Giannantonio Cibin and his team in B18 Core XAS,
Diamond (Oxford, UK) for performing the EXAFS measurements.
1
6

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Notes and References
(1)
(2)
(3)
(4)
Friščić, T. New opportunities for materials synthesis using mechanochemistry. J. Mater.
Chem. 2010, 20 (36), 7599–7605.
Boldyreva, E. Mechanochemistry of inorganic and organic systems: what is similar, what
is different? Chem. Soc. Rev. 2013, 42 (18), 7719–7738.
Julien, P. A.; Mottillo, C.; Friščić, T. Metal–organic frameworks meet scalable and
sustainable synthesis. Green Chem. 2017, 19, 2729–2747.
Friščić, T.; Reid, D. G.; Halasz, I.; Stein, R. S.; Dinnebier, R. E.; Duer, M. J. Ion- and Liquid-
Assisted Grinding: Improved Mechanochemical Synthesis of Metal-Organic Frameworks
Reveals Salt Inclusion and Anion Templating. Angew. Chem. Int. Ed. 2010, 49 (4), 712–
7
15.
(
5)
6)
Friščić, T.; Halasz, I.; Beldon, P. J.; Belenguer, A. M.; Adams, F.; Kimber, S. a J.; Honkimäki,
V.; Dinnebier, R. E. Real-time and in situ monitoring of mechanochemical milling
reactions. Nat. Chem. 2013, 5 (1), 66–73.
Batzdorf, L.; Fischer, F.; Wilke, M.; Wenzel, K.-J.; Emmerling, F. Direct In Situ Investigation
of Milling Reactions Using Combined X-ray Diffraction and Raman Spectroscopy. Angew.
Chem. Int. Ed. 2015, 54 (6), 1799–1802.
(
(
7)
8)
Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The Chemistry and Applications
of Metal-Organic Frameworks. Science 2013, 341 (6149), 1230444–1230444.
Du, S.; Zhang, H. Metal-Organic Frameworks for Photonics Applications; Chen, B., Qian,
G., Eds.; Structure and Bonding; Springer Berlin Heidelberg: Berlin Heidelberg, 2014; Vol.
(
1
57.
(9)
Moulton, B.; Zaworotko, M. J. From Molecules to Crystal Engineeringꢁ: Supramolecular
Isomerism and Polymorphism in Network Solids B . Crystal Engineering vs Crystal
Structure. Chem. Rev. 2001, 101, 1629–1658.
(
10) Cook, T. R.; Zheng, Y. R.; Stang, P. J. Metal-organic frameworks and self-assembled
supramolecular coordination complexes: Comparing and contrasting the design,
synthesis, and functionality of metal-organic materials. Chem. Rev. 2013, 113 (1), 734–
7
77.
(
(
(
(
(
(
11) Rao, C. N. R.; Natarajan, S.; Vaidhyanathan, R. Metal carboxylates with open
architectures. Angew. Chem. Int. Ed. 2004, 43 (12), 1466–1496.
12) Kitagawa, S.; Kitaura, R.; Noro, S. Functional porous coordination polymers. Angew.
Chem. Int. Ed. 2004, 43, 2334–2375.
13) McGuire, C. V.; Forgan, R. S. The surface chemistry of metal–organic frameworks, 2nd
ed.; Kaskel, S., Ed.; WILEY-VCH: Weinheim, 2015; Vol. 51.
14) Banerjee, D.; Parise, J. B. Recent advances in s-block metal carboxylate networks. Cryst.
Growth Des. 2011, 11 (10), 4704–4720.
15) Fromm, K. M. Coordination polymer networks with s-block metal ions. Coord. Chem. Rev.
2
008, 252 (8–9), 856–885.
16) Noro, S. I.; Mizutani, J.; Hijikata, Y.; Matsuda, R.; Sato, H.; Kitagawa, S.; Sugimoto, K.;
Inubushi, Y.; Kubo, K.; Nakamura, T. Porous coordination polymers with ubiquitous and
biocompatible metals and a neutral bridging ligand. Nat. Commun. 2015, 6, 1–9.
1
7

CrystEngComm
Page 18 of 50
View Article Online
DOI: 10.1039/C7CE01906H
(
(
(
17) Banerjee, D.; Zhang, Z.; Plonka, A. M.; Li, J.; Parise, J. B. A calcium coordination
framework having permanent porosity and high CO 2/N 2 selectivity. Cryst. Growth Des.
2
012, 12 (5), 2162–2165.
18) Han, L.; Qin, L.; Xu, L.; Zhou, Y.; Sun, J.; Zou, X. A novel photochromic calcium-based
metal–organic framework derived from a naphthalene diimide chromophore. Chem.
Commun. 2013, 49 (4), 406–408.
19) Caskey, S. R.; Wong-Foy, A. G.; Matzger, A. J. Dramatic tuning of carbon dioxide uptake
via metal substitution in a coordination polymer with cylindrical pores. J. Am. Chem. Soc.
2
008, 130 (33), 10870–10871.
(
20) He, Y.; Li, B.; O’Keeffe, M.; Chen, B. Multifunctional metal-organic frameworks
constructed from meta-benzenedicarboxylate units. Chem. Soc. Rev. 2014, 43 (16), 5618.
21) Douvali, A.; Papaefstathiou, G. S.; Gullo, M. P.; Barbieri, A.; Tsipis, C.; Malliakas, C. D.;
Kanatzidis, M. G.; Papadas, I.; Gerasimos, S.; Tsipis, A. C.; et al. Alkaline Earth Metal
Ion/Dihydroxy–Terephthalate MOFs: Structural Diversity and Unusual Luminescent
Properties. Inorg. Chem. 2015, 150603100102005.
(
(
22) Shustova, N. B.; Cozzolino, A. F.; Reineke, S.; Baldo, M.; Dinc??, M. Selective turn-on
ammonia sensing enabled by high-temperature fluorescence in metal-organic
frameworks with open metal sites. J. Am. Chem. Soc. 2013, 135 (36), 13326–13329.
23) Groom, C. R.; Bruno, I. J.; Lightfoot, M. P.; Ward, S. C. The Cambridge Structural Database
(
(
(
(CSD). Acta Cryst. 2016, B72, 171–179.
24) Gupta, M. P.; Sinha, R. P. Ca Phthalate monohydrate (Ref. was entered manually/pdf is
not avaliable). Cryst. Struct. Commun. 1975, 4, 207–210.
25) Schuckmann, W.; Fuess, H.; Bats, J. W. Refinement of the structure of calcium phthalate
monohydrate. Acta Crystallogr. Sect. B Struct. Crystallogr. Cryst. Chem. 1978, 34 (12),
3
754–3756.
(
26) Zhang, X.; Huang, Y.-G.; Zhang, M.-J.; Zhang, J.; Yao, Y. A Series of Ca(II) or Ba(II)
Inorganic−Organic Hybrid Frameworks Based on Aromaꢀc Polycarboxylate Ligands with
the Inorganic M− O−M (M = Ca, Ba) Connecꢀvity from 1D to 3D. Cryst. Growth Des. 2012,
1
2 (6), 3231–3238.
(
27) Dale, S. H.; Elsegood, M. R. J. {[Ca5(C8H4O4)5(H2O)9].8H2O}n: The first
crystallographically characterized non-transition metal salt of isophthalic acid. Acta
Crystallogr. C 2003, 59, 540–542.
(28) Yu, L. C.; Chen, Z. F.; Liang, H.; Zhou, C. S.; Li, Y. A triple helical calcium-based
coordination polymer with strong blue fluorescent emission. J. Mol. Struct. 2005, 750,
3
5–38.
(
(
(
(
29) Matsuzaki, T.; Iitaka, Y. The crystal structure of calcium terephthalate trihydrate. Acta
Crystallogr. Sect. B Struct. Crystallogr. Cryst. Chem. 1972, 28 (7), 1977–1981.
30) Groeneman, R. H.; Atwood, J. L. Terephthlate bridged coordination polymers based upon
group two metals. Cryst. Eng. 1999, 2 (4), 241–249.
31) Dale, S. H.; Elsegood, M. R. J. catena-Poly-[[di-aqua-calcium(II)]-[mu]3-terephthalato-
[
mu]2-aqua] at 150 K. Acta Crystallogr. E 2003, 59, m586–m587.
32) Scholz, G.; Abdulkader, A.; Kemnitz, E. Mechanochemical Synthesis and Characterization
of Alkaline Earth Metal Terephthalates: M(C8H4O4)·nH2O (M = Ca, Sr, Ba). Z. Anorg. Allg.
1
8

Page 19 of 50
CrystEngComm
View Article Online
DOI: 10.1039/C7CE01906H
Chem. 2014, 640 (2), 317–324.
(
33) Mazaj, M.; Mali, G.; Rangus, M.; Žunkovič, E.; Kaučič, V.; Logar, N. Z. Spectroscopic
Studies of Structural Dynamics Induced by Heating and Hydration A Case of Calcium
Terephthalate Metal Organic Framework. J. Phys. Chem. C 2013, 117 (15), 7552–7564.
34) Al-Terkawi, A.-A.; Scholz, G.; Emmerling, F.; Kemnitz, E. Mechanochemical Synthesis,
Characterization, and Structure Determination of New Alkaline Earth Metal-
Tetrafluoroterephthalate Frameworks: Ca(pBDC-F4)·4H2O, Sr(pBDC-F4)·4H2O, and
Ba(pBDC-F4). Cryst. Growth Des. 2016, 16 (4), 1923–1933.
(
(
35) Al-Terkawi, A.-A.; Scholz, G.; Buzanich, A. G.; Reinsch, S.; Emmerling, F.; Kemnitz, E. Ca-
and Sr-tetrafluoroisophthalates: mechanochemical synthesis, characterization, and ab
initio structure determination. Dalt. Trans. 2017, 46, 6003–6012.
(36) JCPDS-ICDD, International Centre for Diffraction Data: PDF-2 Database (Sets 1–51 plus
7
0–89). International Centre for Diffraction Data: PA 19073–3273 USA 2001.
(
37) David, W. I. F.; Shankland, K.; Van De Streek, J.; Pidcock, E.; Motherwell, W. D. S.; Cole, J.
C. DASH: A program for crystal structure determination from powder diffraction data. J.
Appl. Crystallogr. 2006, 39 (6), 910–915.
(
(
(
38) Cheary, R. W.; Coelho, a. a.; Cline, J. P. Fundamental parameters line profile fitting in
laboratory diffractometers. J. Res. Natl. Inst. Stand. Technol. 2004, 109 (1), 1.
39) Le Bail, A.; Duroy, H.; Fourquet, J. L. Ab initio structure determination of LiSbWO6 by X-
ray powder diffraction. Mater. Res. Bull. 1998, 23 (3), 447–452.
40) Le Bail, A. Whole powder pattern decomposition methods and applications: A
retrospection. Powder Diffr. 2005, 20 (4), 316–326.
(
(
41) Langford, J. I.; Louër, D. Powder diffraction. Rep. Prog. Phys. 1996, 59 (2), 131–234.
42) Brunauer, S.; Emmett, P. H.; Teller, E. Adsorption of Gases in Multimolecular Layers. J.
Am. Chem. Soc. 1938, 60 (2), 309–319.
(
(
(
(
(
(
43) Fagerlund, G. Determination of specific surface by the BET method. Matériaux Constr.
1
973, 6 (3), 239–245.
44) ISO 9277. Determination of the specific surface area of solids by gas adsorption — BET
method; 2010; Vol. E.
45) Ravel, B.; Newville, M. ATHENA, ARTEMIS, HEPHAESTUS: Data analysis for X-ray
absorption spectroscopy using IFEFFIT. J. Synchrotron Radiat. 2005, 12 (4), 537–541.
46) Rehr, J. J.; Kas, J. J.; Vila, F. D.; Prange, M. P.; Jorissen, K. Parameter-free calculations of X-
ray spectra with FEFF9. Phys. Chem. Chem. Phys. 2010, 12 (21), 5503–5513.
47) Chiari, G. On Metal-Oxygen Coordination . A Statistical Method to Determine
Coordination. Acta Crystallogr. B 1990, B46, 717–723.
48) Murugavel, R.; Banerjee, S. First alkaline earth metal 3-aminobenzoate (3-aba) complex:
1
8
-D polymeric [Ca(3-aba)2(H2O)2]n assembly. Inorg. Chem. Commun. 2003, 6 (7), 810–
14.
(
49) Deacon, G. B.; Phillips, R. J. Relationships between the carbon-oxygen stretching
frequencies of carboxylato complexes and the type of carboxylate coordination. Coord.
Chem. Rev 1980, 33, 227–250.
(50) Al-Terkawi, A.-A.; Scholz, G.; Emmerling, F.; Kemnitz, E. Strontium-Coordination Polymers
based on Tetrafluorophthalic and Phthalic acids: Mechanochemical Synthesis, ab initio
1
9

CrystEngComm
Page 20 of 50
View Article Online
DOI: 10.1039/C7CE01906H
Structures Determination, and Spectroscopic Characterization. Dalt. Trans. 2017, 46 (37),
2574–12587.
1
(
(
(
51) Scholz, G.; Emmerling, F.; Dreger, M.; Kemnitz, E. Mechanochemical Synthesis and
Characterization of Hydrated and Dehydrated Crystalline Strontium Terephtalates. Z.
Anorg. Allg. Chem. 2013, 639 (5), 689–693.
52) Hulvey, Z.; Furman, J. D.; Turner, S. a.; Tang, M.; Cheetham, A. K. Dimensionality trends in
metal-organic
frameworks
containing
perfluorinated
or
nonfluorinated
benzenedicarboxylates. Cryst. Growth Des. 2010, 10 (5), 2041–2043.
53) Cheetham, A. K.; Rao, C. N. R.; Feller, R. K. Structural diversity and chemical trends in
hybrid inorganic-organic framework materials. Chem. Commun. (Camb). 2006, No. 46,
4
780–4795.
List of Figures and Tables captions
Figure 1. The mechanochemical synthesis and PXRD patterns of reactants, compound (1), and
compound (1-H O).
2
(a) PXRD patterns of the reactants H oBDC and Ca(OH) .
2 2
(
b) The hydrated CP [Ca(oBDC)(H O)] (1) was mechanochemically synthesized by milling
2
H oBDC with Ca(OH) and 130 µL H O for 30 min, 1h, and 4h. In the absence of water,
2
2
2
the same compound was also obtained after milling H oBDC with Ca(OH) for 4h. The
2
2
molar ratio between organic and inorganic reactants was retained as 1:1. The inorganic
chains are crosslinked via the organic linkers to form 2D-polymeric chains. Parts of the
organic linkers are hidden for clarity.
(
c) The dehydrated CP [Ca(oBDC)] (1-H O) was obtained by the thermal annealing of 1 at
2
2
2
90 °C. The inorganic chains are connected via the carboxylate-oxygen atoms to form a
D-CP. Parts of organic linkers are hidden for clarity.
*
Color codes: calcium atoms (yellow), carbon atoms (gray), hydrogen atoms (light gray),
carboxylate-oxygen atoms (red), water-oxygen atoms (aqua).
Figure 2. Rietveld refinement of the crystal structures of (a) [Ca(oBDC)(H O)] (1), (b) [{Ca(oBDC)]
2
(
1-H O), (c) [Ca(mBDC)(H O)] (2) and (d) [Ca(pBDC)(H O) ] (3). Scattered X-ray intensity at
2 2 2 3
ambient conditions is shown as a function of diffraction angle 2θ. The observed pattern
black circles), the best Rietveld fit profile (red line), the reflection positions (blue tick
(
marks), and the difference curve (gray line) between observed and calculated profiles are
shown. The refinement factors are given in Table 1.
Figure 3. The local coordination environment and the crystal structure of compound 1.
II
(
(
(
a) The local coordination of the Ca O polyhedron and bond lengths in Å.
7
II
b) The bridged Ca -ions via the carboxylate-oxygen atoms from four organic anions.
c) The coordination mode of the organic linker oBDC (each linker coordinates to four Ca
atoms)
2
-
(d) Parallel polymeric chains formed in the crystal structures of 1 along the crystallographic
2
0

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a-axis. The hydrogen bonds are represented by dashed green lines.
e) the layered 2D crystal structure (along b-axis).
(
*
Color codes: Metal (yellow), carbon atoms (gray), carboxyl-oxygen atoms (red), water-oxygen
atoms (aqua), and hydrogen atoms (light gray).
Figure 4. The local coordination environment and the crystal structure of compound [Ca(oBDC)]
1-H O).
(
2
II
(
(
(
a) The local coordination of the Ca O polyhedron and bond lengths in Å.
b) The bridged Ca ions via the carboxylate-oxygen atoms from six organic anions.
c) The coordination mode of the organic linker oBDC (each linker anion coordinates to six
8
II
2
-
Ca atoms)
(d) The linked polymeric chains formed in the crystal structures along the crystallographic a-
axis.
(e) the 2D layered crystal structure along crystallographic c-axis.
*
Color codes: Metal (yellow), carbon atoms (gray), carboxyl-oxygen atoms (red), and hydrogen
atoms (light gray).
Figure 5. The mechanochemical synthesis and PXRD pattern of compound 2.
(a) PXRD patterns of the reactants H mBDC and Ca(OH)
2 2.
(
b) [Ca(mBDC)(H O) ] (2) was mechanochemically synthesized by milling H mBDC with
2
3.4
2
Ca(OH) and 130 µL H O for 1h. The molar ratio between organic and inorganic
2
2
reactants was 1:1. The crystal structure of 2 consists of helical chains which are
connected via intensive network of hydrogen bonds. A 1D helical chain is shown.
*
Color codes: calcium atoms (yellow), carbon atoms (gray), hydrogen atoms (light gray),
carboxylate-oxygen atoms (red), water-oxygen atoms (aqua).
Figure 6. The local coordination environment and the crystal structure of [Ca(mBDC)(H O) ]
2
3.4
(2).
(
a) The local coordination of the divalent metal cation Ca1 (bond lengths in Å). Ca1 is eight-
fold coordinated to six oxygen-carboxyl (from four ligand anions) and two water
molecules.
(
(
(
b) The local coordination of Ca2 (bond lengths in Å). Ca2 is eight-fold coordinated to six
oxygen-carboxyl (from four ligand anions) and two water molecules.
c) The local coordination of Ca3 comprising nine oxygen atoms, four oxygen-carboxyl (from
four ligand anions) and three coordinating water molecules.
d) The coordination modes of the organic anions. Each carboxylate group chelates one
metal and bridge another.
(
(
(
(
e) The bridged metals via carboxyl- and water-oxygen atoms within a 1D-chain.
f) A helical 1D-polymeric chain along b-axis.
g) Helical strands along b-axis (side view), carbon and hydrogen are omitted for simplicity.
h) Layers along c-axis (top view), carbon and hydrogen are omitted for simplicity.
*
Colors codes: Metal (yellow), water-oxygen atoms (aqua), carboxyl-oxygen-(red), carbon
gray), and hydrogen (light gray).
(
2
1

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DOI: 10.1039/C7CE01906H
Figure 7. The local coordination environment and the crystal structure of [Ca(pBDC)(H O) ] (3).
2
3
(
a) The local coordination of the divalent metal cation Ca1. Ca1 is eight-fold coordinated to
four carboxylate oxygen atoms (from three ligand anions) and three water molecules.
b) The bridged metals via carboxylate oxygen atoms and water molecules.
c) The reaction mode of the organic anions. One carboxyl group chelates one metal and
bridge another two. The second carboxyl group is free of coordination.
(
(
(d) The parallel 1D zig-zag chains (along c-axis).
(e) π-π stacking and hydrogen bonds among the polymeric chains (along c-axis) forming the
3
D-supermolecular arrays.
Colors codes: Metal (yellow), water-oxygen atoms (aqua), carboxyl-oxygen (red), carbon (gray),
and hydrogen (light gray).
Figure 8. The thermoanalytical curves of compounds 1 and 2.
1
1
13
Figure 9. (a) H MAS NMR spectra (ν = 10 KHz) and (b) H→ C CP MAS NMR spectra (ν = 10
rot
rot
KHz, the applied contact time (P15) = 10 ms.) for the organic linkers H oBDC (black spectra) and
2
H mBDC (red spectra), compound 1 (blue spectra), compound (1-H O) (green spectra), and
2
2
compound 2 (magenta spectra).
Figure 10. (a) Isotherm curves for the dynamic vapor sorption of water on a sample of
compound 1-H O. (b) PXRD patterns of compound 1 (blue PXRD pattern), compound 1-
2
H O (black PXRD pattern), and the sample after controlled rehydration (red PXRD
2
pattern).
Table 1. Coordination, crystal data, and refinement parameters for compounds 1, (1-H O), 2,
2
and 3.
Table 2. Structural properties and thermal stabilities of Ca-CPs based on benzene-dicarboxylic
acids and their fluorinated analogues. All compounds were synthesized via
mechanochemical reactions. (HB: hydrogen bonds).
n
m
*
Footnote: according to the I O terminology by Cheetham et al., where n = the degree of inorganic connectivity
5
3
between metal centers and m = the degree of organic connectivity between metal centers.
Associated Content
Supplementary Information is available as a pdf file (a) and four cif files (b).
(
a) Supplementary Information: Powder X-ray diffraction data, ATR-Infrared spectra, EXAFS
spectra, EXAFS data, SEM images, adsorption isotherms, and crystal data.
2
2

Page 23 of 50
CrystEngComm
View Article Online
DOI: 10.1039/C7CE01906H
(
b) Crystallographic Information Files (CIF): Four files containing the crystal parameters of
compounds 1 (CCDC 1582672), (1-H O) (CCDC 1582673), 2 (CCDC 1582675), and 3 (CCDC
2
1
582674).
TOC-Synopsis / For Table of Contents Use Only
Manuscript title:
Hydrated and Dehydrated Ca-Coordination Polymers based on
Benzene-Dicarboxylates: Mechanochemical Synthesis, Structures
Refinement, and Spectroscopic Characterization.
Authors list:
1
, 2, 3
* 1
2
2
Abdal-Azim Al-Terkawi
, Gudrun Scholz , Carsten Prinz , Annett Zimathies , Franziska
*
2
* 1
Emmerling , Erhard Kemnitz
1
Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D – 12489
Berlin, Germany.
2
Federal Institute for Materials Research and Testing (BAM), Richard-Willstaetter- Str. 11, D –
1
2489 Berlin, Germany.
3
School of Analytical Sciences Adlershof (SALSA), Humboldt-Universität zu Berlin, Unter den
Linden 6, D – 10099 Berlin, Germany.
2
3

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DOI: 10.1039/C7CE01906H
TOC graphic:
Synopsis:
Hydrated calcium-based coordination polymers were successfully synthesized via a
mechanochemical synthesis route by milling calcium hydroxide with phthalic acid, isophthalic
acid, or terephthalic acid. Dehydrated coordination polymers were obtained, in reversible
phase transition processes, by thermal post-treatments of the hydrated samples. The
coordination polymers were systematically investigated using various spectroscopic methods
and compared to their fluorinated counterparts.
2
4

Page 25 of 50
CrystEngComm
View Article Online
DOI: 10.1039/C7CE01906H
Keywords:
Calcium, benzene-dicarboxylic acids, fluorine-free coordination polymers, fluorinated
coordination polymers, Green synthesis, mechanochemistry, Rietveld refinement.
2
5

CrystEngComm
Page 26 of 50
Hydrated and Dehydrated Ca-Coordination Polymers based on Benzene-Dicarboxylates: Mechanochemical
Synthesis, Structures Refinement, and Spectroscopic Characterization.
Abdal-Azim Al-Terkawi 1, 2, 3, Gudrun Scholz , Carsten Prinz , Annett Zimathies , Franziska Emmerling , Erhard Kemnitz
* 1
2
2
* 2
* 1
1
Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Str. 2, D – 12489 Berlin, Germany.
2
Federal Institute for Materials Research and Testing (BAM), Richard-Willstaetter- Str. 11, D – 12489 Berlin, Germany.
3
School of Analytical Sciences Adlershof (SALSA), Humboldt-Universität zu Berlin, Unter den Linden 6, D – 10099 Berlin, Germany.
Figures and Tables
1

Page 27 of 50
CrystEngComm
[
Ca(oBDC)(H O)] (1)
[Ca(oBDC)] (1- H O)
2
2
H oBDC (1a)
2
290 °C
+
Ca(OH) (1b)
2
+
130 µl H O
2
7
.9°
6
.8°
(1)
(1- H O)
4
h, no water
2
(
1b)
1a)
4
1
h
h
3
0 min
(
2
a
b
c

CrystEngComm
Page 28 of 50
Figure 1. The mechanochemical synthesis and PXRD patterns of reactants, compound (1), and compound (1-H O).
2
(
a) PXRD patterns of the reactants H oBDC and Ca(OH) .
2
2
(
b) The hydrated CP [Ca(oBDC)(H O)] (1) was mechanochemically synthesized by milling H oBDC with Ca(OH) and 130 µL H O for 30 min, 1h, and 4h. In the
2
2
2
2
absence of water, the same compound was also obtained after milling H oBDC with Ca(OH) for 4h. The molar ratio between organic and inorganic
2
2
reactants was retained as 1:1. The inorganic chains are crosslinked via the organic linkers to form 2D-polymeric chains. Parts of the organic linkers are
hidden for clarity.
(
c) The dehydrated CP [Ca(oBDC)] (1-H O) was obtained by the thermal annealing of 1 at 290 °C. The inorganic chains are connected via the carboxylate-
2
oxygen atoms to form 2D-CP. Parts of organic linkers are hidden for clarity.
*Color codes: calcium atoms (yellow), carbon atoms (gray), hydrogen atoms (light gray), carboxylate-oxygen atoms (red), water-oxygen atoms (aqua).
3

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a
b
Figure 2.
4