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Langmuir 2008, 24, 302-309
Two-Dimensional Molecular Space with Regular Molecular Structure Ken Yao,* Xiaoqing You, Liyi Shi, Wen Wan, Futao Yu, and Jianming Chen Department of Chemistry, Shanghai UniVersity, Shanghai 200444, People’s Republic of China ReceiVed August 31, 2007. In Final Form: October 10, 2007 A novel two-dimensional molecular space (layered carboxylpropylamidephenylsilica, CPAPhS) with regular carboxyl groups was successfully synthesized through grafting carboxyl groups in the structure of layered (aminophenyl)silica using butanedioic anhydride. The carboxyl groups regularly arranged in the layered CPAPhS can react with various organic molecules with amino and hydroxyl groups through formation of reactive intermediate with catalyzers, such as SOCl2. In this research, an example was used to prove the reaction properties of regular carboxyl groups in layered CPAPhS. The layered CPAPhS was reacted with SOCl2 to form layered acyl chloridepropylamidephenylsilica (ACPAPhS) and then reacted with n-butylamine and n-butyl alcohol to form layered n-butylamidepropylamidephenylsilica (BAPAPhS) and n-butylesterpropylamidephenylsilica (BEPAPhS) with regular molecular structures. Layered CPAPhS showed the potential as a starting material for formation of a series of novel two-dimensional molecular space with various regular molecular structures, and as a solid acceptor for chemical reagent with amino and hydroxyl groups for chemical processes.
Introduction Two-dimensional layer spaces of layered materials, such as clay minerals and layered double hydroxides (LDHs), are expandable with the size of the intercalated molecules. The intercalated molecules can only form monolayers or bilayers in the interlayer space of layered materials independent of molecular size, due to the interaction between the host layer plate and guest molecules. The molecular reaction process probably can be influenced due to the geometrical and chemical limit of the interlayer space of the layered materials. Thus, two-dimensional layered materials are promising materials for influencing and controlling molecular reaction processes in the interlayer spaces by utilization of the interaction between the host layer plate and guest molecules, and a series of functional materials are probably formed utilizing two-dimensional layered materials.1-43 * To whom correspondence should be addressed. Phone: +86-21-66134857. Fax: +86-21-5638-8125. E-mail:
[email protected]. (1) Iyi, N.; Kurashima, K.; Fujita, T. Chem. Mater. 2002, 14, 583. (2) Beaudot, P.; De Roy, M. E.; Besse, J. P. Chem. Mater. 2004, 16, 935. (3) Xu, Z. P.; Stevenson, G. S.; Lu, C. Q.; Lu, G. Q.; Bartlett, P. F.; Gray, P. P. J. Am. Chem. Soc. 2006, 128, 36. (4) Gardner, E.; Huntoon, K. M.; Pinnavaia, T. J. AdV. Mater. 2001, 13, 1263. (5) Leroux, F.; Raymundo-Pinero, E.; Nedelec, J. M.; Beguin, F. J. Mater. Chem. 2006, 16, 2074. (6) Vakarin, E. V.; Badiali, J. P. J. Phys. Chem. B 2002, 106, 7721. (7) Feng, Y. J.; Williams, G. R.; Leroux, F.; Taviot-Gue´ho, C.; O’Hare, D. Chem. Mater. 2006, 18, 4312. (8) Williams, G. R.; O’Hare, D. Chem. Mater. 2005, 17, 2632. (9) Iyi, N.; Matsumoto, T.; Kaneko, Y.; Kitamura, K. Chem. Mater. 2004, 16, 2926. (10) Mu¨ller, R.; Hrobarikova, J.; Calberg, C.; Je´roˆme, R.; Grandjean, J. Langmuir 2004, 20, 2982. (11) Kooli, F.; Khimyak, Y. Z.; Alshahateet, S. F.; Chen, F. X. Langmuir 2005, 21, 8717. (12) Hu, G.; O’Hare, D. J. Am. Chem. Soc. 2005, 127, 17808. (13) Reinholdt, M. X.; Kirkpatrick, R. J.; Pinnavaia, T. J. J. Phys. Chem. B 2005, 109, 16296. (14) Yao, K.; Nishimura, S.; Imai, Y.; Wang, H. Z.; Ma, T. L.; Abe, E.; Tateyama, H.; Yamagishi, A. Langmuir 2003, 19, 321. (15) Yao, K.; Taniguchi, M.; Nakata, M.; Takahashi, M.; Yamagishi, A. Langmuir 1998, 14, 2410. (16) Yao, K.; Taniguchi, M.; Nakata, M.; Takahashi, M.; Yamagishi, A. Langmuir 1998, 14, 2890. (17) Allada, R. K.; Pless, J. D.; Nenoff, T. M.; Navrotsky, A. Chem. Mater. 2005, 17, 2455. (18) Fujita, S.; Sato, H.; Kakegawa, N.; Yamagishi, A. J. Phys. Chem. B 2006, 110, 2533. (19) Choy, J. H.; Jung, H.; Han, Y. S.; Yoon, J. B.; Shul, Y. G.; Kim, H. J. Chem. Mater. 2002, 14, 3823.
However, the lack of functional properties and unchangeable layer structure makes the influencing and controlling of molecular reaction processes in the interlayer space by utilizing current layered materials difficult. If we can fabricate the two-dimensional molecular spaces with regular functional organic molecules, and simultaneously it is stable during the chemical reaction course, it would be valuable for the investigation on influencing and controlling molecular reaction processes in the two-dimensional (20) Greenwell, H. C.; Stackhouse, S.; Coveney, P. V.; Jones, W. J. Phys. Chem. B 2003, 107, 3476. (21) Choudary, B. M.; Madhi, S.; Chowdari, N. S.; Kantam, M. L.; Sreedhar, B. J. Am. Chem. Soc. 2002, 124, 14127. (22) Vaysse, C.; Guerlou-Demourgues, L.; Delmas, C.; Duguet, E. Macromolecules 2004, 37, 45. (23) Vaysse, C.; Guerlou-Demourgues, L.; Duguet, E.; Delmas, C. Inorg. Chem. 2003, 42, 4559. (24) O’Leary, S.; O’Hare, D.; Seeley, G. Chem. Commun. (Cambridge) 2002, 14, 1506. (25) Vieille, L.; Taviot-Gue´ho, C.; Besse, J. P.; Leroux, F. Chem. Mater. 2003, 15, 4369. (26) Vieille, L.; Moujahid, E. M.; Taviot-Gue´ho, C.; Cellier, J.; Besse, J. P.; Leroux, F. J. Phys. Chem. Solids 2004, 65, 385. (27) Leroux, F.; Besse, J. P. Chem. Mater. 2001, 13, 3507. (28) Roland-Swanson, C.; Besse, J. P.; Leroux, F. Chem. Mater. 2004, 16, 5512. (29) Liu, Z. P.; Ma, R. Z.; Osada, M.; Iyi, N.; Ebina, Y.; Takada, K.; Sasaki, T. J. Am. Chem. Soc. 2006, 128, 4872. (30) Triantafillidis, C. S.; LeBaron, P. C.; Pinnavaia, T. J. Chem. Mater. 2002, 14, 4088. (31) Xue, S. Q.; Reinholdt, M.; Pinnavaia, T. J. Polymer 2006, 47, 3344. (32) Moujahid, E. M.; Dubois, M.; Besse, J.; Leroux, F. Chem. Mater. 2002, 14, 3799. (33) Moujahid, E. M.; Dubois, M.; Besse, J. P.; Leroux, F. Chem. Mater. 2005, 17, 373. (34) Darder, M.; Lo´pez-Blanco, M.; Aranda, P.; Leroux, F.; Ruiz-Hitzky, E. Chem. Mater. 2005, 17, 1969. (35) Whilton, N. T.; Vickers, P. J.; Mann, S. J. Mater. Chem. 1997, 7, 1623. (36) Yuan, Q.; Wei, M.; Evans, D. G.; Duan, X. J. Phys. Chem. B 2004, 108, 12381. (37) Frey, G. L.; Reynolds, K. J.; Friend, R. H.; Cohen, H.; Feldman, Y. J. Am. Chem. Soc. 2003, 125, 5998. (38) Zhong, Z. H.; Ding, W. P.; Hou, W. H.; Chen, Y. Chem. Mater. 2001, 13, 538. (39) So, H.; Jung, H.; Choy, J.; Belford, R. L. J. Phys. Chem. B 2005, 109, 3324. (40) Matsumoto, Y.; Unal, U.; Kimura, Y.; Ohashi, S.; Izawa, K. K. J. Phys. Chem. B 2005, 109, 12748. (41) Tong, Z. W.; Shichi, T.; Takagi, K. J. Phys. Chem. B 2002, 106, 13306. (42) Sasai, R.; Iyi, N.; Fujita, T.; Arbeloa, F. L.; Martı´nez, V. M.; Takagi, K.; Itoh, H. Langmuir 2004, 20, 4715. (43) Hagerman, M. E.; Salamone, S. J.; Herbst, R. W.; Payeur, A. L. Chem. Mater. 2003, 15, 443.
10.1021/la702700s CCC: $40.75 © 2008 American Chemical Society Published on Web 11/28/2007
Two-Dimensional CPAPhS Molecular Space
molecular spaces. Otherwise, the regular molecular structures are the basis of designing and controlling material properties. The novel hybrid materials with various attractive physical and chemical properties could be formed utilizing two-dimensional molecular spaces with regular molecular structures. Previously, we developed novel two-dimensional molecular spaces (layered (aminophenyl)silica, APhTMS-DS, and (aminopropyl)silica, ATMS-DS)44,45 with regular ammonium groups in the structure, using organosilanes with amino groups templated with anionic surfactant (sodium dodecyl sulfate, SDS) under acidic conditions. Kaneko et al. have reported the formation of layered polysiloxane by direct concentration of aminoalkyltrialkoxysilane.46 We also have developed a novel two-dimensional molecular space with regular double bonds (layered acrylamidephenylsilica, AAPhS) by hybridizing the layered aminophenylsilica with acrylic acid.47 The regular arrangement of functional groups is the basis for influencing and controlling molecular reaction processes in the two-dimensional molecular space. The regular arrangement of functional groups in the twodimensional structure forms a controllable molecular reaction space by utilization of the interaction between the regular functional groups and the molecules. The potential of twodimensional molecular space with regular ammonium groups on influencing and controlling molecular reaction processes was also investigated using the polymerization process of acrylic acid.48 The acrylic acid regularly fixed in layered aminopropylsilica was completely polymerized to form a novel organicinorganic nanocomposite material named as layered polyacrylamidepropylsilica (ATMS-PAA) with monolayers of polyacrylamide in the layer space of layered aminopropylsilica without initiator. But deep into the investigation, we find that though the twodimensional molecular space with regular ammonium groups has shown the potential to influence molecular reaction processes and form novel hybrid materials with regular molecular structures, the reactive properties of regular ammonium groups in twodimensional molecular space were limited as ionic groups. Therefore, in order to broaden the research on influencing and controlling the molecular reaction processes in the twodimensional molecular space and form novel hybrid materials with regular molecular structures, it is very important to synthesize a series of novel two-dimensional molecular space with other regular functional groups in the structure. A series of novel composite materials can be obtained and a series of novel chemical and physical properties will be found by utilization of the twodimensional molecular space with various regular functional groups. Here, we report the fabrication and investigation of reaction properties of a novel two-dimensional molecular space with regular carboxyl groups (layered carboxylpropylamidephenylsilica, CPAPhS), which grafted carboxyl groups in the twodimensional structure of layered aminophenylsilica (APhTMSDS) using butanedioic anhydrid. The layered aminophenylsilica was synthesized using (p-aminophenyl)trimethoxysilane (APhTMS) templated with sodium dodecyl sulfate under acidic conditions.45 The (p-aminophenyl)trimethoxysilane with three (44) Yao, K.; Imai, Y.; Shi, L. Y.; Dong, A. M.; Abe, E.; Adachi, Y.; Nishikubo, K.; Tateyama, H. J. Colloid Interface Sci. 2005, 285, 259. (45) Yao, K.; Imai, Y.; Shi, L. Y.; Abe, E.; Adachi, Y.; Nishikubo, K.; Tateyama, H. Chem. Lett. 2004, 33, 1112. (46) Kaneko, Y.; Iyi, N.; Matsumoto, T.; Fujii, K.; Kurashima, K.; Fujita, T. J. Mater. Chem., 2003, 13, 2058. (47) Yu, F. T.; Yao, K.; Shi, L. Y.; Wang, H. Z.; Fu, Y.; You, X. Q. Chem. Mater. 2007, 19, 335. (48) Yu, F. T.; Yao, K.; Shi, L. Y.; Wan, W.; Zhong, Q. D.; Fu, Y.; You, X. Q. Chem. Mater. 2007, 19, 3412.
Langmuir, Vol. 24, No. 1, 2008 303 Scheme 1. Schematic Illustrations of the Layered Aminophenylsilica: (a) Top View of Si-O Hexagonal Sheet; (b) Vertical Cross-Section View of APhTMS-DS
sol-gel reaction points tends to form a two-dimensional lamellar structure along with the surface of a surfactant micelle of dodecyl sulfate. The host part of the layered APhTMS-DS was a highly crystalline Si-O hexagonal sheet, as illustrated in Scheme 1a. The lattice parameters of the a- and b-axes were found to be 0.52 and 0.90 nm, respectively. The ammonium groups were alternately arranged on both sides of the sheet, as illustrated in Scheme 1b. The layered structure of layered (aminophenyl)silica was retained after the removal of the surfactant using other molecules.45,47 The layered APhTMS-DS with regular ammonium groups exhibited a stable layer structure and better intercalation response. The better X-ray diffraction (XRD) responses of various intercalation precipitates of layered (aminophenyl)silica were obtained, and they demonstrated the high regular arrangement of phenylsilica in the layer structure of layered (aminophenyl)silica. We all know that carboxyl groups are important functional groups in organic chemistry and biochemistry. The carboxyl groups regularly arranged in the layer structure of layered CPAPhS can react with various organic molecules with amino and hydroxyl groups through formation of reactive intermediate with catalyzers, such as SOCl2. The layered CPAPhS with regular carboxyl groups would become an important starting material for preparing a series of functional two-dimensional molecular space with various regular functional molecules, especially biological molecules, and it would have tremendous potential study value both in material science and biological application. Experimental Section All the reagents were purchased from the Aldrich Chemical Co. and used as received. Layered APhTMS-DS was synthesized by the slow titration of HCl into a mixture of APhTMS (2.78 mmol) and SDS (2.92 mmol) in aqueous solution, and the suspension was stirred at room temperature for 2 weeks (pH 2-3). APhTMS-DS was obtained as a light pink precipitate.45
304 Langmuir, Vol. 24, No. 1, 2008 The two-dimensional molecular space material with regular carboxyl groups (layered CPAPhS) was synthesized by mixing 0.18 g of butanedioic anhydride and 0.15 g of APhTMS-DS in 30 mL of THF solution, and the suspension was stirred at 50 °C for 10 or 24 h. The precipitate was filtered, washed with deionized water and ethanol, and then dried under vacuum. The cation exchange precipitate (CPAPhS-CTA) of layered CPAPhS was obtained by mixing 0.84 g of cetyltrimethylammonium bromide (CTAB) and 0.056 g of CPAPhS in 100 mL of deionized water, and then the suspension was stirred at 50 °C for 6 h. The intercalation precipitate was filtered, washed with deionized water and ethanol, and then dried under vacuum. Layered ACPAPhS was synthesized by mixing 0.01 g of CTAPhS and 0.06 mmol of SOCl2 in 30 mL of toluene, and then the suspension was stirred at 50 °C for 3 h. The residual SOCl2 was removed under vacuum. Layered n-butylamidepropylamidephenylsilica (BAPAPhS) and layered n-butylesterpropylamidephenylsilica (BEPAPhS) were synthesized by mixing 0.01 g of ACTAPhS and 3.8 mmol of n-butylamine or 3.8 mmol of n-butyl alcohol in 30 mL of toluene, and then the suspension was stirred at 50 °C for 3 h. The precipitates were filtered, washed with dichloromethane, and then dried under vacuum. The reactions of ACTAPhS with a mixture were carried out by mixing 0.01 g of ACTAPhS with 2 mL of butanal, 2 mL of acetone, 2 mL of THF, 2 mL of ethyl acetate, and 2 mL of n-butylamines or 2 mL of butanal, 2 mL of acetone, 2 mL of THF, 2 mL of ethyl acetate, and 2 mL of n-butyl alcohol at room temperature for 4 h, respectively. Then, the precipitates were filtered, washed with dichloromethane, and then dried under vacuum. The 29Si high-power dipole decoupling (HPDEC) MAS NMR and 13C cross-polarization/magic angle spinning (CP/MAS) NMR spectra were recorded on a Bruker MSL-500WB spectrometer at 59.62 MHz for 29Si and 75.47 MHz for 13C. Chemical shifts for both 29Si and 13C NMR were referenced to tetramethylsilane (TMS) at 0 ppm. FTIR spectra were obtained by using an “Avatar 370” spectrophotometer of Nicolet, the preparation of the samples consisted of dispersing and gently grinding the powder in KBr. XRD data on the powder samples were recorded with an X-ray diffractometer (Rigaku, D\max-2550) using Cu KR radiation (λ ) 0.1541 nm) under the conditions of 40 kV and 30 mA. Chemical analyses were performed by elementary organic microanalysis for C, N, and S in a “VerioEL III” element analyzer. The TEM image was recorded by JEM-4000EX with an acceleration voltage of 400 kV.
Results and Discussion The two-dimensional molecular space (layered CPAPhS) with regular carboxyl groups was synthesized through grafting carboxyl groups in the layer structure of layered APhTMS-DS using butanedioic anhydride. First, the IR spectra were used to probe the formation process of CPAPhS. Figure 1 showed the IR spectra of layered APhTMS-DS and the reactive precipitates between (aminophenyl)silica and butanedioic anhydride. Spectral assignments for the IR spectrum of APhTMS-DS shown in Figure 1a are made as follows. The peaks at 2800 to 3000 cm-1 are assigned to the stretch vibration of methyl and methylenes of DS; the peaks at 1600 and 1507 cm-1 were assigned to the vibration peaks of the benzene ring; the peak at 1638 cm-1 corresponded to the vibrations of water molecules adsorbed in layered APhTMS-DS. In the IR spectrum of reactive precipitates between (aminophenyl)silica and butanedioic anhydride after heating at 50 °C for 10 h appeared two new peaks at 1706 and 1670 cm-1 compared with layered APhTMS-DS, which were assigned to carbonyl in amide and carboxylic acid, respectively (Figure 1b). It is considered that the ammonium groups in layered APhTMS-DS reacted with one carbonyl of butanedioic anhydride to form amide, and another carbonyl of butanedioic anhydride was translated to carboxylic acid. The vibration peaks of benzene ring at 1600 cm-1 and 1524 cm-1also appeared, and the vibration
Yao et al.
Figure 1. IR spectra of (a) APhTMS-DS, (b) CPAPhS formed at 50 °C for 10 h, and (c) CPAPhS formed at 50 °C for 24 h.
peaks (2800-3000 cm-1) of methyl and methylenes of dodecyl sulfate, which are strong in Figure 1a, became weak but do not disappear in the IR spectrum of reactive precipitates heated at 50 °C for 10 h. Apparently, the DS in the two-dimensional molecular space of APhTMS-DS was not completely displaced by the butanedioic anhydride because ammonium groups in the layered APhTMS-DS were not completely reacted with butanedioic anhydride. To make the reaction perfect, the reaction time was increased. Figure 1c shows the IR spectrum of reactive precipitates between (aminophenyl)silica and butanedioic anhydride after heating at 50 °C for 24 h. Two peaks at 1706 and 1670 cm-1, corresponding to stretch vibrations of carbonyl in amide and carboxylic acid, grew stronger, and vibration peaks at 2800-3000 cm-1 became very weak. But all these were not sufficient to conclude that the ammonium groups in layered APhTMS-DS were completely reacted with butanedioic anhydride and the DS in the two-dimensional molecular space of APhTMS-DS was completely displaced by the butanedioic anhydride, although butanedioic anhydride grafted in layered (aminopropyl)silica also can arouse the stretch vibrations at 28003000 cm-1 in the IR spectra. To further affirm the result, the reactive precipitate (CPAPhS) between APhTMS-DS and butanedioic anhydride heated at 50 °C for 24 h was characterized by 13C CP/MAS NMR spectra. The 13C CP/MAS NMR spectra of APhTMS-DS and CPAPhS are shown in Figure 2. The resonance peaks at 125 and 135 ppm observed in the 13C CP/ MAS NMR spectrum of APhTMS-DS (Figure 2a) were attributed to the superposition of resonances of carbon species in the aromatic rings of (aminophenyl)silica due to the aromatic rings fixed in the framework of silica as a layer plate.45,47 The resonance peaks during 5-70 ppm observed in the 13C CP/MAS NMR spectrum of APhTMS-DS (Figure 1a) were attributed to the methyl and methylenes of DS existing in the layer space of APhTMS-DS. The 13C CP/MAS NMR spectrum of CPAPhS was clearly different from that of APhTMS-DS. Two new similar height resonance peaks were observed at 177.8 and 172.6 ppm assigned
Two-Dimensional CPAPhS Molecular Space
Langmuir, Vol. 24, No. 1, 2008 305 Scheme 2. Schematic Illustrations of (a) Layered CPAPhS and (b) Layered CPAPhS-CTA
Figure 2. 13C CP/MAS NMR spectra of (a) layered APhTMS-DS and (b) layered CPAPhS.
Figure 3. Powder XRD patterns of (a) layered APhTMS-DS, (b) layered CPAPhS, (c) layered CPAPhS-CTA, (d) layered BAPAPhS, and (e) layered BEPAPhS.
to carbon species of carbonyl in amide -C(dO)-NH- and carboxylic acid -C(dO)OH, respectively (Figure 2b). It is considered that the ammonium groups in layered APhTMS-DS reacted with one carbonyl of butanedioic anhydride to form amide and another carbonyl of butanedioic anhydride was translated to carboxylic acid, as shown in Scheme 2a. The resonance peaks of carbon species in the aromatic rings of CPAPhS were observed during 110-150 ppm (Figure 2b). The complex resonance peaks attributed to the methyl and methylenes of DS in APhTMS-DS (Figure 1a) were not observed in the 13C CP/MAS NMR spectrum of CPAPhS. Only one resonance peak was obtained at 29.3 ppm assigned to the two methylenes of butanedioic anhydride. The result of the 13C CP/MAS NMR spectrum of CPAPhS indicated that the dodecyl sulfate completely disappeared in CPAPhS because the ammonium groups in layered APhTMS-DS were completely reacted with one carbonyl of butanedioic anhydride
to form amide and that the carboxyl groups were successfully grafted in layered (aminophenyl)silica to form carboxylpropylamidephenylsilica. The X-ray diffraction spectra were used to examine the twodimensional structure of CPAPhS. The XRD pattern of APhTMSDS and CPAPhS were shown in Figure 3. The X-ray diffraction peak of CPAPhS assigned to the 001 reflection was shifted from 2θ ) 2.2° in APhTMS-DS (Figure 3a) to 2θ ) 3.8° (Figure 3b). The interlayer distance shifted from 4 nm in APhTMS-DS to 2.3 nm in CPAPhS. The change of the interlayer distance was consistent with the change in the molecular length from APhTMSDS to CPAPhS, as shown in Scheme 2a. The reason for the broadness of the XRD patterns of CPAPhS was considered to be due to the turbulence of stacked structure and the decrease of the crystalline size. The shape of the XRD pattern of APhTMSDS apparently was attributed to the template effect of the surfactant micelle of DS. The better XRD responses indicated that the layer structure had been retained during the formation processes of layered CPAPhS by the liquid-solid reaction between layered APhTMS-DS and butanedioic anhydride, and
306 Langmuir, Vol. 24, No. 1, 2008
Figure 4.
29Si
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HPDEC/MAS NMR spectrum of CPAPhS. Table 1. Elemental Analytical Results of CPAPhS
Figure 5. TEM micrograph of layered CPAPhS.
the carboxyl groups were regularly arranged in the layer structure of layered CPAPhS. The 29Si HPDEC/MAS NMR spectrum of CPAPhS shows two peaks at -72.5 and -80.0 ppm (Figure 4) similar to the spectrum of APhTMS-DS. The peak at -80 ppm was assigned to the Si species covalently bonded to an carbon and three -OSi groups in the RSi(OSi)3, and the peak at -70 ppm was assigned to the Si species in the RSi(OH)(OSi)2 (the edge part of the silica layer), as shown in Scheme 2a.49 Only two peaks of RSi(OSi)3 and RSi(OH)(OSi)2 observed in the 29Si HPDEC/MAS NMR spectrum of CPAPhS demonstrated that the two-dimensional network structure like Scheme 1a has remained stable during the formation process of CPAPhS. The TEM micrograph of CPAPhS was shown in Figure 5. Stacked layerlike materials can be confirmed in the TEM micrograph of CPAPhS similar to that of APhTMS-DS.45 The TEM micrograph further indicated that CPAPhS retained the layer structure after the graft reaction.46 The elemental analytical results of layered CPAPhS were shown in Table 1. No sulfur atom was observed in CPAPhS. The (49) Inagaki, S.; Guan, S.; Fukushima, Y.; Ohsuna, T.; Terasaki, O. J. Am. Chem. Soc. 1999, 121, 9611.
sample
C (wt %)
N (wt %)
S (wt %)
attempted formula
CPAPhS
48.19
5.637
0
SiO1.5C6H4NHCOC2H4 COOH‚0.24H2O
result of no sulfur element in the CPAPhS further indicated that DS in the two-dimensional molecular space of APhTMS-DS was completely replaced by the butanedioic anhydride in CPAPhS. The elemental analytical results of layered CPAPhS also indicated that almost 100% of the amino groups in layered APhTMS-DS reacted with one carbonyl in butanedioic anhydride to form amide, and another carbonyl in butanedioic anhydride was translated to carbonyl groups. Higher liquid-solid reactive efficiency between layered APhTMS-DS and butanedioic anhydride further confirmed that the carboxyl groups were regularly arranged in the layer structure of layered CPAPhS. The results of 13C CP/MAS NMR, IR, X-ray diffraction spectra, and elemental analysis of CPAPhS indicated that the ammonium groups in layered APhTMS-DS completely reacted with one carbonyl of butanedioic anhydride to form amide, and another carbonyl of butanedioic anhydride was translated to carboxylic acid. The carboxyl groups were successfully grafted in layered (aminophenyl)silica to form a novel two-dimensional molecular space with regular carboxyl groups (carboxylpropylamidephenylsilica). To further examine the carboxyl groups regularly arranged in the two-dimensional molecular space of CPAPhS, a cation exchange reaction was demonstrated. Cetyltrimethylammonium (CTA) cations were used for the intercalation reaction of layered CPAPhS. The IR spectrum of the intercalated precipitates (CPAPhS-CTA) showed that a series of stronger vibration peaks appeared from 3000 to 2800 cm-1 (Figure 6b) compared with layered CPAPhS (Figure 6a). The vibration peaks from 3000 to 2800 cm-1 were assigned to stretch vibrations of methyl and methylenes in CTA. The vibration peaks of carbonyl in amide and carboxylic acid were also observed at 1706 and 1670 cm-1 in the IR spectrum of CPAPhS-CTA, respectively. The result of X-ray diffraction of CPAPhS-CTA was shown in Figure 3c. The
Two-Dimensional CPAPhS Molecular Space
Langmuir, Vol. 24, No. 1, 2008 307
Figure 6. IR spectra of (a) layered CPAPhS, (b) layered CPAPhS-CTA, (c) layered ACPAPhS, (d) layered BAPAPhS, and (e) layered BEPAPhS.
X-ray diffraction peak of the CPAPhS-CTA assigned to the 001 reflection was shifted from 2θ ) 3.8° in the CPAPhS (Figure 3b) to 2θ ) 1.7° (Figure 3c). The interlayer distance shifted from 2.3 nm in CPAPhS to 5.2 nm in CPAPhS-CTA. The change of the interlayer distance was consistent with the change in the molecular length from CPAPhS to CPAPhS-CTA, as shown in Scheme 2b. The results of IR and XRD spectra of CPAPhS-CTA indicated that CTA cations were successfully intercalated in the two-dimensional molecular space of CPAPhS. The better intercalation behavior of CPAPhS further confirmed that the carboxyl groups were successfully grafted in layered (aminophenyl)silica to form a novel two-dimensional molecular space with regular carboxyl groups (carboxylpropylamidephenylsilica). The hydrogen ions of carboxyl groups regularly arranged in CPAPhS can be exchanged by other cations, and the layer structure of CPAPhS was stable during the intercalation process. We all know that carboxyl groups are important functional groups in organic chemistry and biochemistry. Esterification and amidation are the two important properties of carboxyl groups, which can react with various organic molecules with amino and hydroxyl groups through formation of reactive intermediate with catalyzers, such as SOCl2. If the carboxyl groups regularly arranged in the layered CPAPhS can react with various organic molecules with amino and hydroxyl groups, the layered CPAPhS with regular carboxyl groups will become an important starting material for synthesizing a series of two-dimensional molecular spaces with various regular molecular structures. Therefore, it
is important to investigate the reactive behaviors of carboxyl groups regularly arranged in the layered CPAPhS with catalyzeres to form a reactive intermediate. Here, the reaction of carboxyl groups regularly arranged in the layered CPAPhS with thionyl chloride SOCl2 was investigated. The layered CPAPhS was reacted with thionyl chloride SOCl2 to form ACPAPhS. The IR spectrum of ACPAPhS shows that the vibration peak at 1670 cm-1 (Figure 6c), which was assigned to the stretch vibration of the carbonyl in carboxylic acid, completely disappeared compared with layered CPAPhS (Figure 6a). The disappearance of the vibration peak at 1670 cm-1 indicated that carboxyl groups were completely reacted with SOCl2 to form acyl chloride. A new vibration peak that appeared at 1777 cm-1 in the IR spectrum of ACPAPhS was considered to be the stretch vibration of the carbonyl in acyl chloride. The vibration peaks of the benzene ring were also observed at 1600 and 1525 cm-1. The IR spectrum of ACPAPhS indicated that SOCl2 was successfully reacted with carboxyl groups regularly arranged in the layered CPAPhS to form a novel two-dimensional molecular space ACPAPhS with regular acyl chloride groups as illustrated in Scheme 3a. The acyl chloride groups regularly arranged in ACPAPhS showed a stable property during the treatment process for IR spectral analysis. ACPAPhS can be easily translated to CPAPhS, and the similar IR, 13C CP/MAS NMR, and XRD spectra with layered CPAPhS can be obtained after treatment with water. To demonstrate the reactive potential of ACPAPhS, which possesses regularly arranged carboxyl groups, n-butylamine and
308 Langmuir, Vol. 24, No. 1, 2008 Scheme 3. Schematic Illustrations of (a) Layered ACPAPhS, (b) Layered BAPAPhS, and (c) Layered BEPAPhS
n-butyl alcohol were introduced to react with ACPAPhS, respectively. First, the ACPAPhS was reacted with n-butylamine to form layered BAPAPhS. The IR spectrum of BAPAPhS showed stronger vibration peaks at 2800-3000 cm-1, which was attributed to the methyl and methylenes in n-butylamine (Figure 6d). The vibration peaks of the carboxyl group at 1670 cm-1 was not observed in the IR spectrum of BAPAPhS. It was considered that acyl chloride groups regularly arranged in the two-dimensional molecular space of ACPAPhS completely reacted with amino groups of n-butylamine to form amide. The vibration peak of amide formed between n-butylamine and ACPAPhS was observed at 1774 cm-1 in the IR spectrum of BAPAPhS (Figure 6d). The vibration peaks of the benzene ring were also obtained at 1600 and 1522 cm-1. A vibration peak of water molecules absorbed in BAPAPhS was observed at 1638 cm-1. The X-ray diffraction peak of the BAPAPhS assigned to the 001 reflection was shifted from 2θ ) 3.8° in the CPAPhS to 2θ ) 3° (Figure 3d). The interlayer distance shifted from 2.3 nm in CPAPhS to 2.94 nm in BAPAPhS. The change of the interlayer distance was consistent with the change in the molecular length from CPAPhS to BAPAPhS, as illustrated in Scheme 3b. The better XRD response of BAPAPhS confirmed that the layered structure was retained during the formation process of BAPAPhS, and butylamide was regularly arranged in the two-dimensional nanospace of layered BAPAPhS. Then, ACPAPhS was reacted with n-butyl alcohol to form layered BEPAPhS. The acyl chloride groups were considered to be completely reacted with hydroxide groups in n-butyl alcohol to form an ester, because the vibration peak of the carboxyl group at 1670 cm-1 did not appear in the IR spectrum of BEPAPhS (Figure 6e). The IR spectrum of
Yao et al.
BEPAPhS also showed two vibration peaks at 2962 and 2933 cm-1, corresponding to the methyl and methylenes in n-butyl alcohol (Figure 6e). The vibration peak of the ester formed between n-butyl alcohol and ACPAPhS was observed at 1775 cm-1 in the IR spectrum of BEPAPhS (Figure 6e). The vibration peaks of C-O-C bonds were obtained at 1249 and 1204 cm-1 as shown in the IR spectrum of BEPAPhS. A vibration peak of water molecules absorbed in BEPAPhS was observed at 1638 cm-1. The X-ray diffraction peak of the BEPAPhS assigned to the 001 reflection was shifted from 2θ ) 3.8° in the CPAPhS to 2θ ) 3.05° (Figure 3e). The interlayer distance shifted from 2.3 nm in CPAPhS to 2.9 nm in BEPAPhS. The change of the interlayer distance was consistent with the change in the molecular length from CPAPhS to BEPAPhS, as shown in Scheme 3c. The better XRD response of BEPAPhS also indicated that the layered structure was retained during the formation process of BEPAPhS, and butyl ester was regularly arranged in the two-dimensional nanospace of layered BEPAPhS. These successful esterification and amidation reactions showed the tremendous potential of layered ACPAPhS as a starting material for synthesizing a series of two-dimensional molecular space with various regular molecular structures through esterification and amidation reactions. Various functional molecules with amino and hydroxyl groups can be regularly fixed in two-dimensional molecular space to form a series of novel two-dimensional functional molecular space. ACPAPhS as a powder sample represents the better behaviors of esterification and amidation reactions. This behaviors also imply the potential of ACPAPhS as an acceptor of chemistry reagents with amino and hydroxyl groups. The esterification and amidation reactions of ACPAPhS provide a selective reactive capability for chemistry reagents with amino and hydroxyl groups during chemical processes. ACPAPhS as a powder sample can fix chemistry reagents with amino and hydroxyl groups in the two-dimensional molecular space, and no reactions occur with other chemistry reagents, such as aldehyde, ketone, ether, and ester. Here, we demonstrated the selective reactions of ACPAPhS using a mixture of butanal, acetone, THF, ethyl acetate, and n-butylamines and a mixture of butanal, acetone, THF, ethyl acetate, and n-butyl alcohol, respectively. The IR spectra of reactive precipitates between ACPAPhS and the mixture were shown in Figure 7. The IR spectra of reactive precipitates showed that stronger vibration peaks were obtained at 2800-3000 cm-1 (Figure 7b,c) compared with the IR spectrum of ACPAPhS (Figure 7a), which is attributed to the methyl and methylenes in n-butylamine and n-butyl alcohol, respectively, similar to the IR spectra of BAPAPhS and BEPAPhS as shown in Figure 6d,e. The vibration peaks of amide (1774 cm-1) and ester (1775 cm-1) formed between n-butylamine and ACPAPhS, and between n-butyl alcohol and ACPAPhS were also observed in the IR spectra of reactive precipitate (Figure 7b,c), respectively, similar to those of BAPAPhS and BEPAPhS as shown in Figure 6. The smaller vibration peaks of carboxyl groups at 1670 cm-1 were observed in the IR spectra of reactive precipitates, as shown in Figure 7b,c, different from those of BAPAPhS and BEPAPhS shown in Figure 6. It was considered that acyl chloride groups in ACPAPhS have not completely reacted with amino groups of n-butylamine and hydroxyl groups of n-butyl alcohol, and a part of the acyl chloride groups in ACPAPhS reacted with water molecules contained in a mixture to form carboxyl groups again at room temperature. The vibration peaks of C-O-C bonds were observed at 1249 and 1204 cm-1 (Figure 7c), similar to the IR spectrum of BEPAPhS (Figure 6e). The vibration peaks (1638 cm-1) of adsorbed water molecules also appeared in the IR spectra
Two-Dimensional CPAPhS Molecular Space
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for chemistry reagents with amino and hydroxyl groups during any chemical processes. This selectivity is governed by the inherent properties of ACPAPhS, such as esterification and amidation, and its state also determines that it is easy to be separated from other liquid compounds, so it would have a broad range of important applications in chemical processes.
Conclusions
Figure 7. IR spectra of (a) layered ACPAPhS; (b) reactive precipitates between ACPAPhS and mixture of butanal, acetone, THF, ethyl acetate, and n-butylamines; and (c) reactive precipitates between ACPAPhS and butanal, acetone, THF, ethyl acetate, and n-butyl alcohol.
of reactive precipitates. The results of the IR spectra of reactive precipitates between ACPAPhS and a mixture showed the better chemical selectivity of ACPAPhS for chemistry reagents with amino and hydroxyl groups as a powder sample even at room temperature. The ACPAPhS showed a potential as solid accepter
A novel two-dimensional molecular space (layered carboxylpropylamidephenylsilica, CPAPhS) with regular carboxyl groups was successfully synthesized through grafting carboxyl groups in the structure of layered (aminophenyl)silica. The better cation exchange and chemical reaction behaviors of layered CPAPhS were observed. The layered CPAPhS showed a great potential as a starting material for formation of a series of novel twodimensional molecular spaces with various regular molecular structures. The carboxyl groups regularly arranged in the layer structure of layered CPAPhS can react with catalyzers to form a reactive intermediate. In this research, an example was used to prove the reaction properties of regular carboxyl groups in layered CPAPhS. A novel two-dimensional molecular space (acylchloridepropylamidephenylsilica, ACPAPhS) with regular acyl chloride groups was obtained through reaction between layered CPAPhS and thionyl chloride SOCl2. ACPAPhS can react with various organic molecules with amino and hydroxyl groups to form a series of novel two-dimensional molecular space with regular molecular structures. Otherwise, ACPAPhS showed better chemical selectivity for chemistry reagents with amino and hydroxyl groups even at room temperature. The solid ACPAPhS can be an accepter of chemistry reagents with amino and hydroxyl groups during chemical processes. Acknowledgment. This work was financially supported by Technical Innovation Team Project of Shanghai Science and Technology Committee (06DZ05902). LA702700S
