(AEDPH3)·(8-OQH)·(H2O): A yellow supramolecular plaster with ammonia adsorption and ammonia-induced discoloration properties

Article abstract of DOI:10.1039/c3ce41940a

A novel supramolecular plaster, namely (AEDPH₃)·(8-OQH) ·(H₂O) (1), is synthesized and characterized. This plaster is an organic acid-base compound, which shows a three-dimensional (3D) sandwich-type supramolecular network. It is a yellow gelling material with excellent mechanical properties superior to that of gypsum plaster. Moreover, the plaster can adsorb ammonia (NH₃) effectively, and exhibits an interesting ammonia-induced discoloration property.

Full text of DOI:10.1039/c3ce41940a

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(AEDPH3)·(8-OQH)·(H2O): a yellow supramolecular
plaster with ammonia adsorption and
Cite this: CrystEngComm, 2014, 16,
ammonia-induced discoloration properties†
2732
a
a
a
b
a
*
Di Tian, Juan Xiong, Xi-chao Liang, Jing Deng, Liang-jie Yuan
b
*
and Shuo-ping Chen
Received 25th September 2013,
Accepted 28th December 2013
A novel supramolecular plaster, namely (AEDPH3)·(8-OQH)·(H2O) (1), is synthesized and characterized.
This plaster is an organic acid–base compound, which shows a three-dimensional (3D) sandwich-type
supramolecular network. It is a yellow gelling material with excellent mechanical properties superior to
that of gypsum plaster. Moreover, the plaster can adsorb ammonia (NH3) effectively, and exhibits an
interesting ammonia-induced discoloration property.
DOI: 10.1039/c3ce41940a
www.rsc.org/crystengcomm
(AEDPH4) and corresponding organic bases, for instance,
Introduction
bactericidal supramolecular plaster (AEDPH3)·(1,2,4-tzH)·(H2O)
In recent decades, the hydrogen-bonded assembly of organic
acid and base molecular building blocks has become an
attractive research area in supramolecular chemistry.1 Various
kinds of organic acid–base compounds have been synthesized
and characterized, which may provide interesting supramo-
lecular architectures2 and functional materials.3 The plaster-
like supramolecular gelling materials (i.e. supramolecular
plasters) are a kind of novel functional materials constructed
by hydrogen-bonded assemblies of small organic molecules.4
Similar to general gypsum plaster, such plasters can display
good mechanical properties. Moreover, they exhibit special
behaviors that common gypsum plaster does not possess. By
choosing or varying different structural units, the structures
and properties of the supramolecular plasters can be modified,
which allows them to be widely used in various application
fields. Our previous studies provided a series of supramolecular
plasters constructed by 1-aminoethylidenediphosphonic acid
(1,2,4-tz = 1,2,4-triazole),4a gas absorption supramolecular plaster
(AEDPH3)·(ureaH)·(H2O),4b etc.
On the other hand, more and more attention has been
focused on indoor air pollution in the past two decades.5
Among various indoor air contaminants, ammonia (NH3) is a
colorless alkali gas, which can strongly stimulate the mucosa
and corrode the skin. Ammonia is also considered as an
important cause of several diseases like pneumonedema and
respiratory distress syndrome.6 Taghizadeh-Toosi et al. and
Soto-Garrido et al. reported that some solid sorbents (such as
activated carbon or biochar) can absorb ammonia effectively.7
Some ammonia sensors based on different chemical interfaces,
including metal, metal–oxide, and polymer films,8 have also
been developed.
The supramolecular plaster has been proven to be a new
kind of decorative material for indoor air pollution control.
Compared with common solid sorbents, supramolecular plaster
combines attractive mechanical properties and excellent
adsorption/detection performance for indoor air pollutants,
without any additive. For example, a novel supramolecular
plaster (AEDPH3)·(BtaH) was synthesized and reported in our
recent work.9 This plaster can adsorb and eliminate formaldehyde
effectively, and can detect formaldehyde by interesting
formaldehyde/ultraviolet ray-induced luminescence switching.
Based on our previous studies, we focused on designing a
supramolecular plaster that can adsorb and detect ammonia.
As one major component of the supramolecular plaster,
AEDPH4 is an organic acid which can react with ammonia
and endow the plaster with ammonia adsorption performance.
However, the detection of ammonia needs some kind of color
change or fluorescence switching. In addition, all the supramo-
lecular plasters that were reported previously are white,4,9 and
a College of Chemistry and Molecular Sciences, Wuhan University, Wuhan 430072,
PR China. E-mail: ljyuan@whu.edu.cn; Tel: +86 27 6875 2800
b Key Lab of New Processing Technology for Nonferrous Metals & Materials,
Ministry of Education, Guangxi Scientific Experiment Center of Mining,
Metallurgy and Environment, College of Materials Science and Engineering,
Guilin University of technology, Guilin 541004, PR China.
E-mail: chenshuoping_777@163.com; Tel: +86 773 5896290
† Electronic supplementary information (ESI) available: Fig. S-1: the schematic
diagram of the color change between neutral 8-OQ molecule and protonated
8-OQH+ cation; Fig. S-2: PXRD patterns of the plaster 1 and compound 1 which
is calculated by the single crystal data; Fig. S-3: the TG and DSC curves of
plaster 1; Fig. S-4: IR spectrum of plaster 1; Fig. S-5 and 6: 1H NMR and
13C NMR spectra of 8-OQ extracted from the equimolar mixture of plaster 1
and ammonia; Table S-7: hydrogen bonds of plaster 1; cif file of 1. CCDC 873343.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c3ce41940a
2732 | CrystEngComm, 2014, 16, 2732–2737
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it is expected that a chromatic plaster is more suitable for an
advanced decoration material. It is noted that 8-hydroxyquinoline
(8-OQ) can show a distinct color change (from gray white to
yellow) when it is protonated (see Fig. S-1 in ESI†). Thus, 8-OQ
and AEDPH4 were chosen as the acid–base pair to synthesize a
novel chromatic supramolecular plaster. It is a yellow plaster
with excellent mechanical properties that can adsorb/eliminate
ammonia and detect ammonia by changing its color.
acid–base compound, namely (AEDPH3)·(8-OQH)·(H2O) (1).
Combined with the results of powder X-ray diffraction (PXRD)
of the supramolecular plaster, it is proven that the structure
of the plaster is exactly the same as 1 (see Fig. S-2 in ESI†). In
the plaster 1, i.e. (AEDPH3)·(8-OQH)·(H2O), each AEDPH4
molecule deprotonates one proton and transfers the proton to
−
the amino-nitrogen atom, forming an AEDPH3 anion itself.
Meanwhile, the neutral 8-OQ molecule is protonated to form
an 8-OQH+ cation. In addition, there is one lattice water
molecule in each asymmetric unit of the plaster (see Fig. 2a).
Synthesis
−
As shown in Fig. 2b, the AEDPH3 anions in plaster 1 form
Similar to the other supramolecular plasters reported previ-
ously,4,9 this yellow plaster is easy to synthesize and process
at room temperature: first, a mixture of AEDPH4 and 8-OQ
with 1 : 1 mole ratio was ground for 30 s to form a kind of
yellow powder. Then with strong agitation, 0.57 times amount
(mass ratio) of distilled water was added to the mixture. The
mixture began to coagulate after 10 s and became plastic and
easily figurable. At this time, it could be shaped into any
form by a mould or just by handwork without any additional
pressure. After figuration, the plaster lost its plasticity and
indurated gradually, and then turned into a yellow solid after
adding the distilled water for 30 s. By using the above
method, the plaster could be made into a board, artwork,
coating, chalk, and so on (see Fig. 1).
a stable two-dimensional (2D) supramolecular network. At
the beginning, two AEDPH3 anions are self-assembled to
−
form a dimer by a very strong hydrogen bond O3–H3A⋯O4#4
(2.584(8) Å) with a cyclic motif R22(8). Then each amino group
−
of the AEDPH3 anion can form three hydrogen bonds close
to neighboring phosphonic oxygen atoms (N1–H1A⋯O1#1 =
2.753(8) Å, N1–H1B⋯O4#5 = 2.839(7) Å, N1–H1C⋯O6#1 =
2.854(8) Å), which connect the adjacent dimers and generate
a one-dimensional (1D) linear double supramolecular chain
along the c axis. Finally, the 1D supramolecular chains are
Crystal structure
In order to obtain an accurate structure of the supramolecular
plaster, a yellow single crystal constructed by AEDPH4 and
8-OQ was synthesized (see experimental section). X-ray crystal-
lographic analysis shows that the crystal is a new organic
Fig. 2 Structure of plaster 1. (a) The Oak Ridge Thermal Ellipsoid Plot
(ORTEP) of the asymmetric unit of plaster 1 with thermal ellipsoids at
the 30% probability; (b) 2D supramolecular layers constructed by
−
AEDPH3− anions; (c) 3D supramolecular network constructed by
Fig. 1 (a) Bricks of the supramolecular plaster which are shaped by
molds. (b) A chicken-like statue made by the supramolecular plaster.
AEDPH3 anions (green), 8-OQH+ cations (blue) and water molecules.
Dashed lines represent hydrogen bonds.
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further extended to form a 2D zigzag supramolecular layer by
hydrogen bond O6–H6A⋯O5#3 (2.549 (7) Å).
The 8-OQH+ cations and water molecules lie in the interlayer,
connecting neighboring 2D supramolecular layers to
a
stable three-dimensional (3D) sandwich-type supramolecular
network by strong hydrogen bonds (O8–H8⋯O7#2 = 2.410(12) Å,
N2–H2⋯O2
=
2.662(18) Å, O7–H7A⋯O2
= 2.760(11) Å,
O7–H7A⋯O8 = 3.46(2) Å, O7–H7B⋯O1#1 = 2.790(11) Å). In
addition, very strong π–π stacking interactions are found
among the 8-OQH+ cations, with a face to face distance of
2.57–2.65 Å, and a center to center distance of 2.81–2.98 Å,
which make the 3D supramolecular network more stable
(see Fig. 2c).
Fig.
3 The ammonia adsorption performance of plaster 1 and
gypsum plaster.
Mechanical properties
As shown in Table 1, plaster 1 shows excellent mechanical
properties: the bending strength, compressive strength and
Moh's hardness are 30.93 MPa, 27.17 MPa and 3.5, respectively,
which are superior to that of the gypsum plaster and other
supramolecular plasters reported previously.4,9 The excellent
mechanical properties of plaster 1 may be due to its stronger
hydrogen bonds among the supramolecular network and
strong π–π stacking interactions between the 8-OQH+ cations.
It is expected that plaster 1 is suitable for creating substantial
plaster products, such as those for carving, building, painting,
and coating.
In addition, plaster 1 displays an interesting discoloration
performance when in contact with ammonia. The solid-state
visible diffuse spectra of plaster 1 placed in ammonia
atmosphere for different times are given in Fig. 4a. At first,
plaster 1 displays stable yellow color at room temperature,
corresponding to an obvious absorption in the region of
400–500 nm. When it contacts with ammonia, the absorption
of 1 in the visible region is weakened and undergoes a
blue-shift gradually with the increasing of contacting time.
After 1 h contacting, there is almost no absorption in the
region of 450–800 nm. Visually, the surface color of plaster 1
gradually changes from yellow to gray white, which can be
used for detecting indoor ammonia (see Fig. 4b). In addition,
the gray white color of the ammonia-treated plaster block can
Ammonia adsorption and ammonia-
induced discoloration performance
Fig. 3 shows the adsorption capacities of plaster 1 and
gypsum plaster in ammonia atmosphere. It can be observed
that, compared with gypsum plaster, plaster 1 can absorb
ammonia with high efficiency: when the initial ammonia
concentration is 6.1 ppm, plaster 1 can absorb 8.4 wt%
ammonia after 0.5 h and 45.5 wt% ammonia after 48 h, while
the mass fractions of the ammonia adsorption of gypsum
plaster are only 2.4 wt% after 0.5 h and 12.2 wt% after 48 h,
respectively. The results indicate that plaster 1 is very suitable
as an environmental decorative material. In addition, the
adsorption of ammonia may weaken the mechanical strength
of plaster 1. After adsorbing ammonia for 24 h, its bending
strength, compressive strength and Moh's hardness are
6.16 MPa, 1.84 MPa and 2.5, respectively.
Table 1 Mechanical properties and concreting times of plaster 1 and
self-made gypsum plaster sample. The gypsum plaster blocks used for
comparison were produced by the reaction of hemihydrate gypsum
and water with a water–gypsum ratio of 0.75
Contents
Plaster 1
Gypsum plaster
Fig. 4 (a) The solid-state visible diffuse spectra of plaster 1 placed in
ammonia atmosphere for different lengths of time: 0 h (magenta),
0.5 h (green), 1 h (black), 6 h (red), 12 h (blue); (b) photo of the
ammonia-induced discoloration: color change of plaster 1 in contact
with ammonia for 1 h.
Bend strength/MPa
Tensile strength/MPa
Moh's hardness
Initial concreting time (s)
Final concreting time (s)
30.93
27.17
3.5
10
30
3.15
6.97
2
402
1050
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be maintained and remains stable if it is removed from the
ammonia atmosphere, which indicates that the ammonia
adsorption and ammonia-induced coloration of plaster 1
is irreversible.
neutral 8-OQ is formed when plaster
1
contacts with
ammonia. Thus, the mechanism of ammonia adsorption and
ammonia-induced discoloration performance of plaster 1 may
be explained as follows: the AEDPH3− anion reacts with ammo-
nia to form organic salt, meanwhile, plaster 1 undergoes phase
disengagement, yellow 8-OQH+ cation transfers a proton to
ammonia, forming free, neutral 8-OQ molecule with gray white
color. So the plaster discolors with a change from yellow to
gray white.
In order to investigate the mechanism of ammonia
adsorption and ammonia-induced discoloration, an equimolar
mixture of plaster 1 and ammonia was placed at room temper-
ature for 24 h. The resulting powders were fully dried and
then characterized using PXRD and infrared (IR) spectra. As
shown in Fig. 5a, after adsorbing equimolar ammonia, the
structure of plaster 1 is completely destroyed, and a crystalline
phase of neutral 8-OQ is observed (characteristic diffraction
peak: 2θ = 9.475°, 14.219°, 15.517°, 18.882°, 19.899°, 23.439°,
24.699°, 28.457°, 28.698°, 31.161°, 31.982°); on the other
hand, a series of characteristic infrared absorption peaks of
protonated 8-OQH+ cations in plaster 1 (1622, 1600, 1552,
1534 cm−1) disappear after ammonia adsorption, while
corresponding characteristic peaks of neutral 8-OQ molecule
(1624, 1619, 1542 cm−1) appear (see Fig. 5b). Furthermore, we
added excess distilled water to the powders of equimolar
mixtures of plaster 1 and ammonia, and then filtered, washed
and dried the precipitate. Pure, gray white powders of 8-OQ
Experiment section
General materials and measurements
The AEDPH4 was prepared according to DE Patent 2625767.10
The 8-hydroxyquinoline (8-OQ, 99.5% purity), hemihydrate
gypsum (CaSO4·0.5H2O, 97% purity), and ammonia (25%
ammonia water solution) were purchased from Sinopharm
Chemical Reagent Co., Ltd. The elemental analysis data
(C, H, N) were obtained from a Perkin-Elmer 240B elemental
analyzer. Infrared (IR) spectra were recorded as KBr pellets
in the range of 400–4000 cm−1 on a Nicolet 5700 FT-IR
spectrometer with a spectral resolution of 4.00 cm−1. H and
1
1
were obtained and characterized by H and 13C NMR spectra
13C NMR spectra were recorded on a Bruker Avance DRX-400
spectrometer. Thermogravimetric analysis (TGA) was carried
out with a NETZSCH STA 449 °C at a heating rate of
10 K min−1 in N2. The powder X-ray diffraction (PXRD) patterns
were obtained with a Bruker D8 advanced diffractometer with
Cu Kα radiation (λ = 1.54056 Å) at 40 kV and 40 mA at the scan
speed of 4° min−1 (2θ).
(see Experiment section, Fig. S-5 and 6 in ESI†). It is clear that
Example of the synthesis of plaster 1
A mixture of 20.50 g AEDPH4 (0.1 mol) and 14.50 g 8-OQ
(0.1 mol) was ground in a miller for 30 s. Then 20 mL
distilled water was added to the mixture with strong agitation
to form a suspension. The suspension was poured in 1 × 1.5 ×
10.5 cm and 2 × 2 × 2 cm moulds as quickly as possible, and
could be completely coagulated after 30 s. The samples
produced by this method were preserved in the laboratory
conditions for 24 h. After this period, they were demoulded
and deposited at room temperature for 7 days, and then
tested for flexion and compression.
Synthesis of single crystal of (AEDPH3)·(8-OQH)·(H2O) (1)
A mixture of 0.0513 g AEDPH4 (0.25 mmol), 0.0363 g 8-OQ
(0.25 mmol) and 3 mL distilled water was sealed in a small
glass vial and heated at 80 °C for 10 h, and then taken out
and placed at 40 °C for 3 days. Bright yellow sheet-like
crystals for X-ray crystallographic analysis were obtained and
filtrated immediately as they were hot. X-ray crystallographic
analysis shows that the crystal is a new organic acid–base
compound, namely (AEDPH3)·(8-OQH)·(H2O) (1). Elemental
analysis (%): found: C 32.16, H 4.90, N 7.34; calculated (%)
for C11H18N2O8P2: C 35.88, H 4.93, N 7.61.
Fig. 5 (a) PXRD patterns of pure 8-OQ (blue), equimolar mixture of
plaster 1 and ammonia (black) and original plaster 1 (red); (b) IR spectra
of pure 8-OQ (blue), equimolar mixture of plaster 1 and ammonia
(black) and original plaster 1 (red). The * symbol represents the characteristic
peak of pure 8-OQ.
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CrystEngComm, 2014, 16, 2732–2737 | 2735