Synthesis and characterization of aminophosphonates zirconium as new mesoporous materials

Article abstract of DOI:10.1155/2012/640317

A serial of aminophosphonates zirconium with the different arm lengths of -(CH₂)n- organic chains (n=2-6) was synthesized for the first time. These compounds are characterized by FT-IR, SEM, TEM, TG and nitrogen adsorption-desorption. And based on the experimental data, these materials not only have layer structure mesoporous and good thermal stability such as zirconium phosphate, but also can be adjusted the layer distance, pore size and pore volume. So aminophosphonates zirconium posses special excellent properties and will have potential prospect applications.

Full text of DOI:10.1155/2012/640317

ISSN: 0973-4945; CODEN ECJHAO
E-Journal of Chemistry
http://www.ejchem.net
2012, 9(3), 1320-1326
Synthesis and Characterization of
Aminophosphonates Zirconium as New Mesoporous
Materials
LIANG ZHOU
College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715,
P.R. China
cosa007cosa007@126.com
Received 13 November 2011; Accepted 15 January 2012
Abstract: A serial of aminophosphonates zirconium with the different arm
lengths of –(CH2)n– organic chains (n=2–6) was synthesized for the first time.
These compounds are characterized by FT-IR, SEM, TEM, TG and nitrogen
adsorption-desorption. And based on the experimental data, these materials not
only have layer structure mesoporous and good thermal stability such as
zirconium phosphate, but also can be adjusted the layer distance, pore size and
pore volume. So aminophosphonates zirconium posses special excellent
properties and will have potential prospect applications.
Keywords: Mesoporous materials; Aminophosphonates Zirconium; Synthesis and Characterization.
Introduction
Zirconium phosphonate and its derivatives are very important compounds to use in the field
of catalysis, adsorption, ion exchange and/or functional materials. If the P-OH bonds in the
molecule of zirconium phosphonate are whole or part changed to the P-R, the compounds
become organic zirconium phosphonates or their derivatives [1-3]. The common inorganic
materials such as mesoporous, macroporous silica gel and molecular sieve with surface of
single hydroxyl have difficult to be further modified [4-6]. A variety of functional groups of

Synthesis and Characterization of Aminophosphonates Zirconium 1321
zirconium phosphonates can overcome this problem. By controlling the synthesis conditions,
zirconium phosphonates with different groups and spacing of layers can be prepared.
Zirconium phosphonates as supports in catalysis have recently been highlighted as a new
option for the immobilization of homogeneous catalysts [7-8]
.
They generally have amorphous structure with high specific surface area that let
reactive sites fully expanded. And the container effects of micropores and mesopores of
zirconium phosphonates are benefit to chemical reaction sufficient occurring.
In this paper, a serial of aminophosphonates zirconium with the different arm lengths of
–(CH2)n– organic chains (n=2–6) was synthesized for the first time. These compounds are
characterized by FT-IR, SEM, TEM, TG and nitrogen adsorption-desorption.
Experimental
Material and Methods:
FT-IR spectra were recorded on Bruker RFS100/S spectrophotometer (USA) using KBr
pellets in the 400–4000 cm-1 range. 1H, 13C and 31P NMR spectra were recorded by using an
av-300 NMR instrument at 300, 75 and 121 MHz, respectively. TG analyses were performed
on a SBTQ600 Thermal Analyzer (USA) with the heating rate of 20oC/min in the
temperature range of 30–1200oC under flowing N2 (100 mL/min). N2 adsorption–desorption
isotherms carried out at 77 K on Autosorb-1 apparatus (Quantachrome). The surface areas
were determined by using the BET equation, and the average pore size was estimated
according to the BJH model. Scanning electron microscopy (SEM) analysis was performed
on S-4800 FE-SEM instrument (Hitachi). Transmission electron microscopy (TEM) analysis
was recoded on a TECNAI10 (PHILIPS, Holland) apparatus.
Phthalimide was purchased from Alfa Aesar. Other commercially available chemicals
were laboratory-grade reagents from local suppliers.
Synthesis of Aminophosphonates Zirconium:
O
C
O
C
NH
O
P
C
O
O
P
OEt
OEt
reflux
5h
OEt
OEt
(CH )n
N
P(OEt) + Br(CH2)nBr
Br (CH )n
2
3
2
C
O
K2CO3,MeCN
1a-e (n=2-6)
2a-e (n=2-6)
O
0.5molL-1NaOH
ZrOCl2
8H2O
O Zr
O Zr
HCl
100oC
H N (CH )n P
2
2
3a-e (n=2-6)
Figure 1. The synthese route of aminophosphonates zirconium.
(1) In the dried three-necked flask (250 mL) was charged ω-alkane dibromide (n=2–6)
(237mmol) and followed by dropwise addition of triethyl phosphate (13.11g, 79 mmol)

1322 Liang Zhou
refluxed for 5 h with the tracking of TLC. The reaction mixture was chromatographed on a
silica gel column eluted with petroleum ether (60–90oC)/ethyl acetate (10:1 in volume) to
give 1a–e [10], respectively in 75–85% yield.
(2) In the dried three-necked flask (250 mL) was charged anhydrous K2CO3 (5.5g, 40
mmol) and phthalimide (5.88g, 40mmol), flushed three times with nitrogen at room
temperature, added dropwise 100mL acetonitrile solution of 1a–e (n=2–6) (40mmol) then
refluxed for 48 h with the tracking of TLC. The reaction mixture was concentrated under
reduced pressure. After removal of the solvent, the residue was diluted with CHCl3 (100 mL)
and then was washed with brine (30 mL×3), dried over anhydrous Na2SO4 and concentrated
under reduced pressure to give the pale yellow liquid. The crude product was purified by
silica gel column chromatography using petroleum ether (60–90oC)/CHCl3 (4:1 in volume)
to give 2a–e, respectively in 58–64% yield.
(3) A mixture of 2a–e (n=2–6) (2 mmol), 15 mL of hydrochloric acid (36%) was stirred
at 100oC for 24 h and concentrated under reduced pressure. Zirconium oxychloride (1.7g, 6
mmol) in 15 mL of deionized water was added dropwise and stirred at room temperature for
another 16 h. The white solid was filtered, dispersed in 50 mL of water, adjusted to pH= 6–7
by using sodium carbonate (0.5mol/L) and filtered again. The mud cake was washed with
deionized water till chloride ion was not detected by using ion chromatography, and then
dried at 60oC for 24 h under reduced pressure to afford aminophosphonates zirconium 3a-e,
respectively in 52–63% yield.
Results and Discussion
Infrared Spectroscopy:
Figure 2. IR spectra of 3a-e.
The FT-IR spectra of the parent supports 3a–e had the similar infrared spectroscopy in
the 4000–500cm-1 range. The 3a-e exhibited bands at 3600-3200cm-1 assigned to the

Synthesis and Characterization of Aminophosphonates Zirconium 1323
characteristic vibration of the –NH groups. The several absorption peaks in the scan range
1686-1650cm-1 for 3a–e were attributed to the N–H vibrations of the appended organic
moieties. Therefore, based on IR spectra of 3a-e, it was demonstrated that
aminophosphonates zirconium were successfully prepared.
Surface Morphology:
Scanning electron micrograph (SEM) was recorded to understand morphology of the
surface of aminophosphonates zirconium in solid state. From the SEM images shown in Fig.
3(a), 3a were conglomerated with the globular aggregates with the diameters of about
0.1–0.2 um, which indicated that the diameter of the particles of the material was in
submicron. Also, it showed that the material was loose, and had various caves, holes and
porous. Interestingly, 3a in the organic solvents were easily swollen, which could be verified
by the TEM images. After the samples 4a–e were dispersed in cyclohexane and stirred for
2h, their morphologies of the filiform structure with thickness about 20–50 nm and length
about several micrometers was observed in Fig. 3(b). The similar SEM and TEM images and
results were obtained for the other four compounds 3b–e.
Figure 3. (a) SEM image of aminophosphonates zirconium 3a
and (b) TEM image of aminophosphonates zirconium 3a.
Thermal Gravimetric Analysis:
On heating the samples of aminophosphonates zirconium 3a, the thermolysis over a
broad temperature range of 40–1200oC with three steps of weight loss were observed (Fig.
4). The first slope curve was due to the desorption of the surface-bound or intercalated water
from the pore channels at 50-100oC. In the 100-200oC, the thermal gravimetric curve is
relatively flat. The sharp weight loss in the temperature range of 200–500oC, accompanied
by endothermic peaks in the DSC curves at 250oC, corresponded to the decomposition of the

1324 Liang Zhou
appended organic fragments. Finally, in the temperature range of 600–1200oC, the third
slope curve was attributed to the dehydrolysis of Zr(HPO4)2 to ZrP2O7. The similar thermal
gravimetric curves and results were obtained for the other four compounds 3b–e.
Figure 4. The thermal gravimetric curves of 3a.
Nitrogen Adsorption–Desorption Isotherms:
The materials 3a-e all have the similar nitrogen adsorption-desorption isotherms (Fig.
5). The textural parameters of 3a–e calculated by N2 adsorption and desorption isotherms at
77 K were presented in Table 1. As expected, it was shown that 4a–e (n = 2–6) were porous
solid materials with the surface areas of 22.12–88.98 m2/g, pore volumes of 0.072–0.445cc/g
and average pore sizes of 13.95–99.49 Å. With the increase in arm chain lengths n from 2 to
6, it was observed that the surface areas of 3a–e increased and average pore sizes decreased
respectively.
Figure 5. The nitrogen adsorption-desorption isotherms of 3a.

Synthesis and Characterization of Aminophosphonates Zirconium 1325
Table 1. The surface area, pore diameter and pore volume of 3a-e.
Samples[a] SBET (m2/g) [b] Pore Size (Å) [c] Pore Volume [cc/g] [d]
3a
3b
3c
3d
3e
22.12
48.57
53.44
73.31
88.98
99.49
40.08
25.61
21.73
13.95
0.445
0.147
0.095
0.089
0.072
[a] The samples were degassed at 100oC for 5 h.
[b] Surface based on multipoint BET method.
[c] Pore size based on the desorption data using BJH method.
[d] Pore volume based on the desorption data of BJH method.
A reasonable and plausible explanation of this change in surface area and average pore
size was that the longer arm chain lengths n from 2 to 6 made the inorganic zirconium layers
more expanded and amorphous, and then the more surface areas were obtained. In the other
hand, the organic moieties with the arm chain lengths n from 2 to 6 between the neighbor
zirconium layers tended to be more close packing in the interlayer region, which caused the
less free pores and the decrease in the average pore sizes from 99.49 to 13.95 Å.
Conclusions
In summary, the materials of aminophosphonates zirconium were successfully prepared for
the first time. Owing to their layered mesoporous structures, these aminophosphonates
zirconium could act as catalyst supports, enabling one to take advantage of the rigid frame,
the confinement effect and the cooperation effect, and bridging the gap between
heterogeneous catalysts and homogeneous catalysts.
Acknowledgments
Author is grateful to Southwest University of China for financial support.
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