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Smart Adsorbents with Photoregulated Molecular Gates for Both Selective Adsorption and Efficient Regeneration Lei Cheng, Yao Jiang, Ni Yan, Shu-Feng Shan, Xiao-Qin Liu, and Lin-Bing Sun* Jiangsu National Synergetic Innovation Center for Advanced Materials (SICAM), State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing 210009, China S Supporting Information *
ABSTRACT: Selective adsorption and efficient regeneration are two crucial issues for adsorption processes; unfortunately, only one of them instead of both is favored by traditional adsorbents with fixed pore orifices. Herein, we fabricated a new generation of smart adsorbents through grafting photoresponsive molecules, namely, 4-(3-triethoxysilylpropyl-ureido)azobenzene (AB-TPI), onto pore orifices of the support mesoporous silica. The azobenzene (AB) derivatives serve as the molecular gates of mesopores and are reversibly opened and closed upon light irradiation. Irradiation with visible light (450 nm) causes AB molecules to isomerize from cis to trans configuration, and the molecular gates are closed. It is easy for smaller adsorbates to enter while difficult for the larger ones, and the selective adsorption is consequently facilitated. Upon irradiation with UV light (365 nm), the AB molecules are transformed from trans to cis isomers, promoting the desorption of adsorbates due to the opened molecular gates. The present smart adsorbents can consequently benefit not only selective adsorption but also efficient desorption, which are exceedingly desirable for adsorptive separation but impossible for traditional adsorbents with fixed pore orifices. KEYWORDS: selective adsorption, efficient regeneration, molecular gates, smart adsorbents, photoresponsive property
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INTRODUCTION Separation plays an important role in the chemical industry. Nevertheless, the predominant technique (e.g., distillation) is high energy consumption that accounts for 30−80% of the total production energy.1,2 To reduce energy consumption, distillation is attempted to be replaced by some alternatives such as adsorption, due to some evident merits such as easy operation and high energy efficiency.3,4 The fabrication of efficient adsorbents is crucial for an adsorptive separation unit.5−8 The predominant pore systems for traditional adsorbents are micropores or mesopores.9−16 For microporous adsorbents such as zeolite, the steric effect makes them excellent in selective adsorption,17−19 while the small pore orifices show relatively inefficient performance during desorption (Figure 1A). For mesoporous adsorbents, the large pore orifices exhibit an excellent performance in desorption but fail in adsorption selectivity (Figure 1B).20−25 Owing to practical requirements for adsorption processes, it is expected that an ideal adsorbent will be designed and fabricated, which benefits not only selectivity during the adsorption process with a small pore orifice but also efficient desorption during regeneration possessing an amplified pore orifice. Nevertheless, it is unlikely for traditional adsorbents with fixed pore orifices because the demands of adsorption/desorption are inherently contradictory. Although it remains a great challenge, a new generation of adsorbents needs to be designed and fabricated with pore orifices tailorable for adsorption and desorption. © XXXX American Chemical Society
Living systems always adjust to changeable environments from the molecular to the macroscopic level in order to preserve life and the living function.26−31 Motivated by complicated biology systems, the implementation of changeable molecules in artificial systems results in kinds of developed stimuli-responsive characteristics.32−39 The rule of the behavior of switchable molecules upon external stimuli (such as light, temperature, and pH) has been applied to both biological supramolecular machines and materials science.40−42 Among these stimuli, light is especially useful because it is a rapid and remote stimulus with great precision.43−48 Moreover, irradiation with light does not generate any undesired byproducts.49−51 The reversible conformation transition of photoresponsive molecules is likely to produce adsorbents with pore orifices tailorable as needed during adsorption/ desorption. Here, a new generation of adsorbents is fabricated by anchoring photoresponsive molecules 4-(3-triethoxysilylpropylureido)azobenzene (AB-TPI) onto the pore orifices of mesoporous silica (MS). The azobenzene (AB) derivatives serve as the molecular gates of mesopores and are reversibly opened and closed upon light irradiation (Figure 1C). Irradiation with visible light (450 nm) causes AB molecules Received: June 28, 2016 Accepted: August 17, 2016
A
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces
trimethylammonium bromide (CTAB; Sigma-Aldrich, 99%), tetraethylorthosilicate (TEOS; Sigma-Aldrich, 98%), methanol (Aladdin, ≥99.9%), and hexane (Aladdin, 97%) have been used directly as purchased. Deionized water was manufactured from a Milli-Q water purification system. Materials Synthesis. The gate molecule 4-(3-triethoxysilylpropylureido)azobenzene (AB-TPI) was prepared by use of the reported method.23,54,55 TPI (2.05 g, 8.12 mmol) and 4-phenylazoaniline (1.58 g, 7.85 mmol) were added into dried THF (12 mL). The obtained solution was heated under reflux and an atmosphere of N2 overnight. Hexane (40 mL) was used to manufacture the crystallization of ABTPI at −20 °C overnight. The mixture was then filtered, washed with excessive hexane, and dried under vacuum. Shining needle-like orange samples can be dried under vacuum. Finally, shining needle-like orange samples can be obtained. The support mesoporous silica (MS) was prepared following the reported method.56 The template CTAB (1.0 g, 2.74 mmol) was added in a mixture solution of NaOH (2 M, 3.5 mL) and H2O (480 mL). After heating the obtained solution to 80 °C, TEOS (5.0 mL, 23.0 mmol) was added to the solution dropwise within several minutes. After stirring vigorously at 80 °C for 2 h, a white silica colloidal suspension was formed. The suspension was filtered, and the resultant solid was washed with deionized H2O and methanol. Finally, the sample was dried overnight under vacuum, and the as-synthesized MS was obtained, whose pores were occluded by template. The smart adsorbents azobenzene-functionalized mesoporous silica (AM) were synthesized as follows. As-synthesized MS nanoparticles (500 mg) were added to anhydrous toluene (80 mL) in a round bottle flask, followed by the addition of AB-TPI (10−50 mg). After being refluxed under N2 for 12 h, the resultant solution was filtrated and the obtained solid washed with a copious amount of methanol and dried under vacuum to obtain as-synthesized AM. The template CTAB was removed by extraction with HCl (2 M, 1.0 mL) and methanol (100 mL) at 80 °C for 24 h. The obtained solid from extraction was rinsed extensively using H2O and methanol and vacuum dried overnight, yielding the AM samples. The samples were denoted as AM-x (where x varies from 1 to 5) corresponding to the AB content ranging from 4.1 to 10.9 wt %, respectively (Table 1). Materials Characterization. 1H nuclear magnetic resonance (1H NMR) characterization of crystals was performed on a Bruker Avance 400 spectrometer (400 MHz). The peak frequencies were versus an internal standard (TMS) shift at 0 ppm. UV−vis spectra were performed using the SHIMADZU UV-2600 in the region of 200−800 nm. X-ray diffraction (XRD) patterns of materials were performed by an X-ray diffractometer (Japan Rigaku D/MAX-γA) with Cu Kα radiation. The microstructural analysis was verified by an FEI Tecnai G2 F20 electron microscope operated at 200 kV for transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) analyses. Scanning electron microscope (SEM) images were obtained using a Hitachi New Generation SU8010 field emission scanning electron microscope. N2 adsorption−desorption isotherms were carried out using an ASAP 2020 analyzer at −196 °C. Before analysis, the samples were under deaeration treatment at 100 °C overnight. The adsorption data was utilized to determine the Brunauer−Emmett−
Figure 1. (A) Schematic illustration of traditional microporous adsorbents possessing excellent performance in selective adsorption but inefficient during desorption, (B) schematic illustration of traditional mesoporous adsorbents possessing excellent performance in desorption but at a cost in adsorption selectivity, (C) after anchoring photoregulated molecular gates, smart adsorbents with the benefit of selective adsorption and efficient regeneration, (D) schematic illustration of molecular gates realizing reversibly closed/ opened owing to photoisomerization of AB.
to isomerize from cis to trans configuration,52,53 which blocks the pore orifices partially (Figure 1D). With the dimension of the pore orifices decreased, the smaller adsorbates can easily enter the pores but the bigger ones cannot, thus realizing the selective optional adsorption of the two molecules with different sizes. Consequent UV light (365 nm) irradiation converts AB molecules from trans to cis form,52,53 which expedites desorption of adsorbates, with the molecular gates open. Such smart adsorbents exhibit the properties of both selective adsorption and efficient separation and enable us to challenge the traditional adsorbents with fixed pore orifices.
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EXPERIMENTAL SECTION
Chemicals. Toluene (Adamas-beta, 99%) and tetrahydrofuran (THF; Aladdin, 99%) were dried before use using the molecular sieve 4A. Other chemicals including 4-aminoazobenzene (TCI, 98%), 3(triethoxysilyl)propyl isocyanate (TPI; Sigma-Aldrich, 95%), cetyl-
Table 1. Physicochemical Parameters and Elemental Composition of Different Samples elemental composition (wt %) sample MS AM-1 AM-2 AM-3 AM-4 AM-5
SBETa
−1
(m ·g ) 2
1110 1093 1080 1075 1064 1055
Vpb
−1
(cm ·g ) 3
1.14 1.14 1.12 1.12 1.10 1.08
C
H
N
grafted amount of ABc (wt %)
5.57 7.30 8.27 9.26 9.98 10.83
3.54 3.68 3.73 3.79 3.84 3.91
0.07 0.59 0.95 1.17 1.30 1.44
0 4.1 7.0 8.7 9.8 10.9
a The adsorption data was utilized to determine the BET surface area at p/p0 of 0.04−0.20. bThe pore volume was obtained at p/p0 = 0.99. cThe grafted amount of AB was calculated according to elemental analysis.
B
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces Teller (BET) surface area at p/p0 of 0.04−0.20. The pore volume was obtained at p/p0 = 0.99. The pore diameter was calculated from the adsorption branch of the isotherms by the Barrett−Joyner−Halenda (BJH) methods. Fourier transform infrared (IR) spectra in the range of 500−4500 cm−1 were measured from the use of a Nicolet Nexus 470 spectrometer with a KBr pellet. UV−vis spectra were collected on the PerkinElmer Lambda 35 in the region of 200−800 nm. AB-TPI was dissolved in ethanol to test the reversible photoisomerization behavior; the AM materials (40 mg) were dispersed in dry toluene (3 mL) for measurement. The elemental analysis (C, H, and N) was recorded on a Vario Micro Cube elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany). Thermogravimetric (TG) curves were obtained by a thermobalance (STA-499C, NETZSCH), where the temperature was heated from 25 to 1000 °C at a heating rate 20 °C min−1 under air atmosphere. Adsorption Experiments. Before the adsorption tests, standard curves of absorbance vs concentration of aqueous methylene blue (MB) and brilliant blue (BB) solutions were plotted using the Beer− Lambert law, from which two linear equations were obtained. The equations were then applied to determine the amount of dye molecules adsorbed from the solutions. Prior to the addition of dye solution (MB and BB), an adsorbent was weighted precisely and added to a cuvette. A UV−vis spectrophotometer was used to measure the adsorption curves after exposure to various irradiation conditions. The dye concentration was determined at appropriate time intervals, and adsorption amount (Qe) was calculated using formula 1
Qe =
(c i − ce)V m
Figure 2. Low-angle XRD patterns of the samples in the presence or absence of molecular gates.
noticeable diffraction peaks were detected after grafting of AB, suggesting that the arrangement of modificated molecules lacks long-range order. N2 adsorption−desorption isotherms of both AM and MS samples exhibit typical type IV isotherms (Figure 3A), which is characteristic of mesoporous construction. From the pore size distributions, the AM samples have a slightly lower pore size than MS (Figure 3B). Such a relatively insignificant change in the pore size reflects that the majority of AB molecules are anchored onto the orifices of mesopores instead of the pore channels. This can be confirmed by the slight change in pore volume and surface area after introduction of AB molecules (Table 1). The morphologies of samples are investigated by TEM and SEM (Figures 4 and S4). For both MS and AM samples, it is clear to observe a spherical morphology possessing a small particle diameter of 120 nm. Furthermore, the TEM images show particles with uniform and straight pores. These results confirm that the fixed pore periodicity is maintained after modification. Also, the straight and short channels are important for the absorption of guest molecules. The presence of C, N, O, and Si in the AM samples can be observed from the EDX spectrum (Figure S5). After the mapping analysis of the elemental distribution, a homogeneous distribution of C, N, O, and Si can be demonstrated (Figure 4C). The successful introduction of AB molecules to MS was examined by various methods. IR spectra of different samples were first recorded and are shown in Figure 5. Besides the characteristic vibrational bands for silica, a collection of new bands were detected including the band at 1540 cm−1 corresponding to the −NH−CO−NH− stretching vibration, the band at 1500 cm−1 derived from the N−H stretching vibration, and the band at 700 cm−1 stemmed from the aromatic amine vibration.60 These results reveal the modification of AB-TPI on the support MS successfully. With increasing AB content in the samples, the characteristic IR bands become stronger. In addition, no bands related to CTAB are present, which means the absolute withdrawal of the template. TG analysis gives a minor weight loss at temperatures up to ca. 100 °C (Figure S6), which is attributed to the withdrawal of physically adsorbed water within the materials. Another subsequent weight loss after 125 °C is observed and extended up to 300 °C; this is due to the dehydration of silanol condensation at elevated temperatures. The decomposition of AB derivatives takes place from 300 to 700 °C. In addition, elemental analysis shows an obvious growth of the N element content with the increase of AB loading (Table 1).
(1)
where ci and ce represent the initial concentration and the equilibrium concentration, respectively, V represents the volume of solution, and m represents the mass of adsorbent. Desorption experiments were performed by using saturated adsorbents in ethanol under various irradiation conditions. The dye concentration was measured at appropriate time intervals by a UV−vis spectrophotometer, and the desorption amount (Qd) was calculated according to formula 2
Qd =
cdV × 100% mQ e
(2)
where cd represents the desorption equilibrium concentration.
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RESULTS AND DISCUSSION Synthesis and Characterization. The gate molecule ABTPI was first synthesized and characterized using 1H NMR (Figure S1), which reveals the high purity of obtained AB-TPI. As-synthesized mesoporous silica was utilized for grafting, with pore channels full of the template, aiming at grafting sufficient AB molecules onto the pore orifices. After grafting, the template in the pore channels was removed by extraction with an acidic alcohol solution (Figure S2). The resultant materials were denoted as AM-1, AM-2, AM-3, AM-4, and AM5, representing grafted amounts of 4.1, 7.0, 8.7, 9.8, and 10.9 wt %, respectively (Table 1). The grafting of AB molecules on MS can be qualitatively discerned from the color change of samples from white to yellow (the characteristic color of AB derivatives). Various techniques were done to obtain structural characterization of the materials. The low-angle XRD patterns (Figure 2) of AM samples show a strong diffraction peak as well as two weak peaks, which are assigned to the d100, d110, and d200 reflections, consistent with a 2D hexagonal pore regularity p6mm space group.57,58 This indicates that the regulated mesoporous structure of materials is well maintained after chemical modification. Only one broad diffraction peak around 23° ascribed to amorphous silica walls was observed by the wide-angle XRD patterns of materials (Figure S3).59 No C
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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Figure 3. (A) N2 adsorption−desorption isotherms and (B) pore size distributions of the samples in the presence or absence of molecular gates. For clarity, curves are offset on the y axis.
Figure 4. TEM images of the samples (A) MS, (B) AM-3, and (C) EDX-mapping images of C, N, O, and Si elements.
associates with the characteristic feature of the cis isomer. A π−π* transition appears with higher energies at about 350 nm corresponding to the trans isomer.61,62Upon irradiation with UV light, the absorption around 350 nm decreased; meanwhile, the absorption around 450 nm increased. After irradiation for 2 min, a photostationary state was obtained. Further increasing the irradiation time the UV−vis spectrum hardly changed. Irradiation with visible light or heating (80 °C) recovered the absorption band at 350 nm (Figure S8). It is worthy of note that the band intensity even exceeds that of the initial sample slightly. This is due to the fact that a certain amount of AB derivatives is in the cis configuration in the initial sample. After further treatment by altering UV and visible light, the photoisomerization change of AB-TPI is steadily reversible for many cycles. These results demonstrate the excellent photoisomerization characteristic of the gate molecule. The photoresponsive property of the AM materials was then examined. The absorption band at 358 nm ascribed to AB molecules can be observed by the UV−vis spectra of AM materials (Figures 6 and S9). After UV light irradiation, the band at 358 nm became weakened, and a photostationary state was obtained within 2 min of irradiation. By increasing the UV light irradiation to 5 min, the intensity of the 358 nm band was close to that irradiated for 2 min. When the photostationary state was reached, the trans configuration can be restored by either visible light irradiation or heating (Figure S10). Moreover, the trans−cis isomerization process is totally
Figure 5. IR spectra of the samples in the presence or absence of molecular gates.
On the basis of the aforementioned results above, we can confirm that the gate molecules (AB derivatives with different contents) are successfully grafted onto the orifices of MS. Meanwhile, the spherical morphology and ordered mesostructure are well preserved regardless of the AB content in AM samples. Photoresponsive Properties. The photoresponsive property of the gate molecule AB-TPI was first tested. In the UV− vis spectrum AB-TPI shows two individual characteristic absorption bands (Figure S7). From the absorption band around 450 nm, which belongs to an n−π*-like transition, it D
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces
Figure 6. (A) Alteration in the UV−vis spectra of AM-3 upon UV light and then visible light irradiation. (B) Reversible changes in absorbance at 358 nm as a function of cycles for AM-3.
Figure 7. Dynamic adsorption curves of (A) MB and (B) BB on MS before and after UV light irradiation as well as (C) MB and (D) BB on AM-3 with and without UV light irradiation. Profiles for the initial BB solution before and after adsorption by AM-3 is inserted in D in the presence or absence of irradiation.
is visibly demonstrated after light irradiation. Taking AM-3 for example, for the small molecule MB, no noticeable difference is observed in the adsorption amount of MB before and after UV light irradiation (from 29.9 to 30.7 mg g−1, Figure 7C). Nevertheless, for the large molecule BB, the adsorption amount shows a sharp growth of 86.4% after irradiation with UV light (from 10.3 to 18.9 mg g−1, Figure 7D). This leads to a high selectivity of MB over BB on AM-3 after irradiation (2.9), which is much higher than that before irradiation (1.6). The molecular gates onto the orifices of mesopores endow adsorption behavior with an enormous difference. Before UV light irradiation, the AB molecules in AM-3 show a trans configuration, with the molecular gates closed, which blocks the pore orifices partially. The adsorption of large guest molecules is obstructed, while small guest molecules can be absorbed freely. In this case, selective adsorption of two molecules can be achieved. On the contrary, upon irradiation with UV light the AB molecules exhibit a cis configuration, which enables the molecular gates to change to opened. As a result, the absorption
reversible through periodic alternation of UV and visible light irradiation (Figure 6B). On the basis of these results above, clearly, the photoresponsive property of AB molecules is maintained after the modification. The molecular gates are able to be reversibly opened and closed upon UV and visible light irradiation, respectively, which is attributed to the photoresponsive molecules anchored onto the orifices of mesopores. Also, the photoresponsive property shows interesting performance in adsorptive separation as described below. Adsorption Performance. The adsorption properties of the materials were checked from the equilibrium isotherms of two probing molecules with different diameters, which is MB (1.26 nm) and BB (1.98 nm) (Figure S11). The adsorption behavior of two dye molecules over the support MS was first examined (Figures 7A and 7B). Exposure of MS nanoparticles to UV light results in no change in the adsorption amount of both MB and BB, demonstrating that the support MS has no photoresponsive property. Unlike the support MS, the fascinating adsorption behavior of the AB-containing materials E
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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ACS Applied Materials & Interfaces
in Figure 10, the adsorption of BB over the original adsorbent was first conducted. After saturation, desorption was performed
of large guest molecules is greatly facilitated, resulting in a big increase in the adsorption amount. From the perspective of desorption, after UV light irradiation the amplified pore orifices are pretty beneficial as discussed later. The effect of AB loading on the change of adsorption capacity was explored. In spite of the AB loading, the adsorption amount of MB with a small diameter is barely influenced (Figures 8 and S12−S15). Among the adsorbents
Figure 10. Adsorption/desorption cycles of BB over AM-3 under UV light and visible light irradiation.
in ethanol for sufficient time to ensure the release of all adsorbed dye molecules. The recovered adsorbent was used for adsorption again after irradiation with UV light. Then desorption was performed, yielding the recovered adsorbent for adsorption after visible light irradiation. In each cycle, similar adsorption amount can be obtained over the adsorbent subjected to either UV light or visible light irradiation. It is worthy of note that upon visible irradiation the adsorption capacity is even lower than the initial value slightly. This is due to the fact that a certain amount of AB derivatives is in the cis configuration in the initial sample. Irradiation with visible light (450 nm) causes all AB derivatives to isomerize from cis to trans configuration.52,63 This demonstrates that the opened/ closed state of molecular gates upon light irradiation is totally reversible. On the basis of results above, we can confirm that the photoregulated molecular gates show extreme performance for adsorptive separation. The properties of both selective adsorption and efficient desorption endow the smart adsorbents with enthralling adsorption performance. It is impossible to realize by conventional adsorbents with fixed pore orifices. The molecular gates of the pore orifices transform closed under visible light irradiation. It is easy for smaller diameter guest molecules to enter but difficult for the larger ones, as a result, achieving selective adsorption. The molecular gates transform open after UV light irradiation, with the size of pore orifices increased in the meantime, thus promoting efficient desorption.
Figure 8. Change in the adsorption capacity on MB and BB over different adsorbents in the presence or absence of UV light irradiation.
with various AB loadings, AM-3 illustrates the biggest distinction in the adsorption amount of BB before and after irradiation with UV light. For the adsorbents with a low density of AB molecules, the photoisomerization of gate molecules can hardly affect the size of pore orifices. In contrast, for the adsorbents with too high density of AB molecules, the change in the adsorption capacity of BB decreases. This is because excessive AB molecules disturb each other during conformation transition. Hence, to realize high adsorption selectivity the optimal loading of AB derivatives is around 8.7 wt % (namely, the sample AM-3). After saturation, the desorption was executed using the adsorbent AM-3 with the guest molecule BB. For the adsorbent before UV light irradiation, the gate molecules are in the trans configuration. The pore orifices are partially blocked, and about 60% of the guest molecules are desorbed (Figure 9). After UV
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CONCLUSIONS In summary, the smart adsorbents were fabricated based on photoregulated molecular gates after anchoring AB derivatives onto the orifices of mesopores successfully. The reversible photoisomerization of AB moieties under the irradiation conditions realizes the molecular gates closed/opened. Smart adsorbents are able to benefit not only selective adsorption but also efficient desorption in adsorptive separation. We can also confirm that the density of AB molecules plays an important role in adsorption, and the optimum AB loading is 8.7 wt %. Our strategy enables us to challenge the tradition that adsorbents contain fixed pore orifices naturally, leading to the creation of a new generation of adsorbents possessing smart function. We envision that the adsorptive separation will value this concept to design and fabricate smart adsorbents with other multiple stimuli-responsive systems (such as temperature,
Figure 9. Desorption curves of BB on AM-3 in the presence or absence of UV light irradiation.
light irradiation, the gate molecules are transformed to the cis configuration; as a result, almost 100% of the adsorbed molecules are desorbed. This demonstrated that the opened molecular gates provide great convenience for desorption. The reversibility of molecular gates is believed to be one of the most important issues for smart adsorbents. Reversible adsorption behavior over AM-3 was thus examined. As shown F
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
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(13) Jones, C. W. Zeolites Go Organic. Science 2003, 300, 439−440. (14) Jiang, Y.; Tan, P.; Kang, Y. H.; Xing, Z. M.; Cheng, L.; Zhu, L.; Liu, X. Q.; Sun, L. B. Fabrication of Adsorbents with Thermocontrolled Molecular Gates for Both Selective Adsorption and Efficient Regeneration. Adv. Mater. Interfaces 2016, 3, 1500829. (15) Jiang, Y.; Tan, P.; Cheng, L.; Shan, S.-F.; Liu, X.-Q.; Sun, L.-B. Selective Adsorption and Efficient Regeneration Via Smart Adsorbents Possessing Thermo-Controlled Molecular Switches. Phys. Chem. Chem. Phys. 2016, 18, 9883−9887. (16) Zhu, J.; Ding, J.-J.; Liu, X.-Q.; Tan, P.; Sun, L.-B. Realizing Both Selective Adsorption and Efficient Regeneration Using Adsorbents with Photo-Regulated Molecular Gates. Chem. Commun. 2016, 52, 4006−4009. (17) Qian, D.; Lei, C.; Wang, E. M.; Li, W. C.; Lu, A. H. A Method for Creating Microporous Carbon Materials with Excellent CO2Adsorption Capacity and Selectivity. ChemSusChem 2014, 7, 291−298. (18) Brochard, L.; Vandamme, M.; Pellenq, R. J.-M.; Fen-Chong, T. Adsorption-Induced Deformation of Microporous Materials: Coal Swelling Induced by CO2−CH4 Competitive Adsorption. Langmuir 2012, 28, 2659−2670. (19) Kondo, M.; Shimamura, M.; Noro, S.-i.; Minakoshi, S.; Asami, A.; Seki, K.; Kitagawa, S. Microporous Materials Constructed from the Interpenetrated Coordination Networks. Structures and Methane Adsorption Properties. Chem. Mater. 2000, 12, 1288−1299. (20) Awala, H.; Gilson, J.-P.; Retoux, R.; Boullay, P.; Goupil, J.-M.; Valtchev, V.; Mintova, S. Template-Free Nanosized Faujasite-Type Zeolites. Nat. Mater. 2015, 14, 447−451. (21) Gibson, L. Mesosilica Materials and Organic Pollutant Adsorption: Part A Removal from Air. Chem. Soc. Rev. 2014, 43, 5163−5172. (22) Li, W.; Zhao, D. An Overview of the Synthesis of Ordered Mesoporous Materials. Chem. Commun. 2013, 49, 943−946. (23) Hoffmann, F.; Cornelius, M.; Morell, J.; Froba, M. Silica-Based Mesoporous Organic-Inorganic Hybrid Materials. Angew. Chem., Int. Ed. 2006, 45, 3216−3251. (24) Schuth, F. Endo- and Exotemplating to Create High-SurfaceArea Inorganic Materials. Angew. Chem., Int. Ed. 2003, 42, 3604−3622. (25) Ukmar, T.; Planinsek, O. Ordered Mesoporous Silicates as Matrices for Controlled Release of Drugs. Acta Pharm. 2010, 60, 373− 385. (26) Zhou, J.; Yin, P.; Chen, X.; Hu, L.; Liu, T. Temperature-and Salt-Responsive Polyoxometalate−Poly (N-Isopropylacrylamide) Hybrid Macromolecules in Aqueous Solution. Chem. Commun. 2015, 51, 15982−15985. (27) Roy, D.; Brooks, W. L.; Sumerlin, B. S. New Directions in Thermoresponsive Polymers. Chem. Soc. Rev. 2013, 42, 7214−7243. (28) Xiao, W.; Zeng, X.; Lin, H.; Han, K.; Jia, H.-Z.; Zhang, X.-Z. Dual Stimuli-Responsive Multi-Drug Delivery System for the Individually Controlled Release of Anti-Cancer Drugs. Chem. Commun. 2015, 51, 1475−1478. (29) Nishikawa, M.; Kume, S.; Nishihara, H. Stimuli-Responsive Pyrimidine Ring Rotation in Copper Complexes for Switching Their Physical Properties. Phys. Chem. Chem. Phys. 2013, 15, 10549−10565. (30) Wang, Y.; Hosta-Rigau, L.; Lomas, H.; Caruso, F. Nanostructured Polymer Assemblies Formed at Interfaces: Applications from Immobilization and Encapsulation to Stimuli-Responsive Release. Phys. Chem. Chem. Phys. 2011, 13, 4782−4801. (31) Brugger, B.; Vermant, J.; Richtering, W. Interfacial Layers of Stimuli-Responsive Poly-(N-Isopropylacrylamide-Co-Methacrylicacid) (PNIPAM-co-MAA) Microgels Characterized by Interfacial Rheology and Compression Isotherms. Phys. Chem. Chem. Phys. 2010, 12, 14573−14578. (32) Aznar, E.; Oroval, M.; Pascual, L.; Murguía, J. R. n.; MartínezMáñez, R. n.; Sancenón, F. l. Gated Materials for on-Command Release of Guest Molecules. Chem. Rev. 2016, 116, 561−718. (33) Qu, D.-H.; Wang, Q.-C.; Zhang, Q.-W.; Ma, X.; Tian, H. Photoresponsive Host−Guest Functional Systems. Chem. Rev. 2015, 115, 7543−7588.
magnet, and pH), achieving high efficiency and low energy consumption during separation processes.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.6b07853. XRD, IR, SEM, TEM, N2 adsorption/desorption isotherms, EDX spectrum, TG, UV−vis absorption, and dynamic adsorption curves of different samples (PDF)
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AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the Distinguished Youth Foundation of the Jiangsu Province (BK20130045), the National Natural Science Foundation of China (21576137), the Fok Ying-Tong Education Foundation (141069), and the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions.
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REFERENCES
(1) Karan, S.; Jiang, Z.; Livingston, A. G. Sub-10 nm Polyamide Nanofilms with Ultrafast Solvent Transport for Molecular Separation. Science 2015, 348, 1347−1351. (2) Motkuri, R. K.; Thallapally, P. K.; Annapureddy, H. V.; Dang, L. X.; Krishna, R.; Nune, S. K.; Fernandez, C. A.; Liu, J.; McGrail, B. P. Separation of Polar Compounds Using a Flexible Metal-Organic Framework. Chem. Commun. 2015, 51, 8421−8424. (3) Peng, X.; Wang, W.; Xue, R.; Shen, Z. Adsorption Separation of CH4/CO2 on Mesocarbon Microbeads: Experiment and Modeling. AIChE J. 2006, 52, 994−1003. (4) McDonald, T. M.; Mason, J. A.; Kong, X.; Bloch, E. D.; Gygi, D.; Dani, A.; Crocellà, V.; Giordanino, F.; Odoh, S. O.; Drisdell, W. S. Cooperative Insertion of CO2 in Diamine-Appended Metal-Organic Frameworks. Nature 2015, 519, 303−308. (5) Flytzani-Stephanopoulos, M.; Sakbodin, M.; Wang, Z. Regenerative Adsorption and Removal of H2S from Hot Fuel Gas Streams by Rare Earth Oxides. Science 2006, 312, 1508−1510. (6) Sun, L.-B.; Li, J.-R.; Lu, W.; Gu, Z.-Y.; Luo, Z.; Zhou, H.-C. Confinement of Metal−Organic Polyhedra in Silica Nanopores. J. Am. Chem. Soc. 2012, 134, 15923−15928. (7) Kang, Y. H.; Liu, X. D.; Yan, N.; Jiang, Y.; Liu, X. Q.; Sun, L. B.; Li, J. R. Fabrication of Isolated Metal-Organic Polyhedra in Confined Cavities: Adsorbents/Catalysts with Unusual Dispersity and Activity. J. Am. Chem. Soc. 2016, 138, 6099−6102. (8) Jiang, W.-J.; Yin, Y.; Liu, X.-Q.; Yin, X.-Q.; Shi, Y.-Q.; Sun, L.-B. Fabrication of Supported Cuprous Sites at Low Temperatures: An Efficient, Controllable Strategy Using Vapor-Induced Reduction. J. Am. Chem. Soc. 2013, 135, 8137−8140. (9) Pérez-Ramírez, J. Zeolite Nanosystems: Imagination Has No Limits. Nat. Chem. 2012, 4, 250−251. (10) Li, J.-R.; Yu, J.; Lu, W.; Sun, L.-B.; Sculley, J.; Balbuena, P. B.; Zhou, H.-C. Porous Materials with Pre-Designed Single-Molecule Traps for CO2 Selective Adsorption. Nat. Commun. 2013, 4, 1538. (11) Choi, M.; Cho, H. S.; Srivastava, R.; Venkatesan, C.; Choi, D.H.; Ryoo, R. Amphiphilic Organosilane-Directed Synthesis of Crystalline Zeolite with Tunable Mesoporosity. Nat. Mater. 2006, 5, 718−723. (12) Gies, H. Materials Science: Pore Show. Nature 2005, 437, 633− 633. G
DOI: 10.1021/acsami.6b07853 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX
Research Article
ACS Applied Materials & Interfaces
alities in the Framework of Mesoporous Silica. Chem. Commun. 2011, 47, 9024−9035. (56) Tan, S. Y.; Ang, C. Y.; Li, P.; Yap, Q. M.; Zhao, Y. Drug Encapsulation and Release by Mesoporous Silica Nanoparticles: The Effect of Surface Functional Groups. Chem. - Eur. J. 2014, 20, 11276− 11282. (57) Yin, Y.; Jiang, W.-J.; Liu, X.-Q.; Li, Y.-H.; Sun, L.-B. Dispersion of Copper Species in a Confined Space and Their Application in Thiophene Capture. J. Mater. Chem. 2012, 22, 18514−18521. (58) Kresge, C.; Leonowicz, M.; Roth, W.; Vartuli, J.; Beck, J. Ordered Mesoporous Molecular Sieves Synthesized by a LiquidCrystal Template Mechanism. Nature 1992, 359, 710−712. (59) Yin, Y.; Tan, P.; Liu, X.-Q.; Zhu, J.; Sun, L.-B. Constructing a Confined Space in Silica Nanopores: An Ideal Platform for the Formation and Dispersion of Cuprous Sites. J. Mater. Chem. A 2014, 2, 3399−3406. (60) Chen, T.; Chen, R.; Jin, Z.; Liu, J. Engineering Hollow Mesoporous Silica Nanocontainers with Molecular Switches for Continuous Self-Healing Anticorrosion Coating. J. Mater. Chem. A 2015, 3, 9510−9516. (61) Tanaka, T.; Ogino, H.; Iwamoto, M. Photochange in Pore Diameters of Azobenzene-Planted Mesoporous Silica Materials. Langmuir 2007, 23, 11417−11420. (62) Zhu, Y. C.; Fujiwara, M. Installing Dynamic Molecular Photomechanics in Mesopores: A Multifunctional Controlled-Release Nanosystem. Angew. Chem., Int. Ed. 2007, 46, 2241−2244. (63) Park, J.; Sun, L. B.; Chen, Y. P.; Perry, Z.; Zhou, H. C. Azobenzene-Functionalized Metal-Organic Polyhedra for the Optically Responsive Capture and Release of Guest Molecules. Angew. Chem., Int. Ed. 2014, 53, 5842−5846.
(34) Cobo, I.; Li, M.; Sumerlin, B. S.; Perrier, S. Smart Hybrid Materials by Conjugation of Responsive Polymers to Biomacromolecules. Nat. Mater. 2015, 14, 143−159. (35) Mura, S.; Nicolas, J.; Couvreur, P. Stimuli-Responsive Nanocarriers for Drug Delivery. Nat. Mater. 2013, 12, 991−1003. (36) Yanai, N.; Uemura, T.; Inoue, M.; Matsuda, R.; Fukushima, T.; Tsujimoto, M.; Isoda, S.; Kitagawa, S. Guest-to-Host Transmission of Structural Changes for Stimuli-Responsive Adsorption Property. J. Am. Chem. Soc. 2012, 134, 4501−4504. (37) Coskun, A.; Banaszak, M.; Astumian, R. D.; Stoddart, J. F.; Grzybowski, B. A. Great Expectations: Can Artificial Molecular Machines Deliver on Their Promise? Chem. Soc. Rev. 2012, 41, 19−30. (38) Stuart, M. A. C.; Huck, W. T.; Genzer, J.; Müller, M.; Ober, C.; Stamm, M.; Sukhorukov, G. B.; Szleifer, I.; Tsukruk, V. V.; Urban, M. Emerging Applications of Stimuli-Responsive Polymer Materials. Nat. Mater. 2010, 9, 101−113. (39) Kume, S.; Nomoto, K.; Kusamoto, T.; Nishihara, H. Intramolecular Electron Arrangement with a Rotative Trigger. J. Am. Chem. Soc. 2009, 131, 14198−14199. (40) Zhang, J.; Zou, Q.; Tian, H. Photochromic Materials: More Than Meets the Eye. Adv. Mater. 2013, 25, 378−399. (41) Muraoka, T.; Kinbara, K.; Aida, T. A Self-Locking Molecule Operative with a Photoresponsive Key. J. Am. Chem. Soc. 2006, 128, 11600−11605. (42) Vallet-Regi, M.; Balas, F.; Arcos, D. Mesoporous Materials for Drug Delivery. Angew. Chem., Int. Ed. 2007, 46, 7548−7558. (43) Kundu, P. K.; Samanta, D.; Leizrowice, R.; Margulis, B.; Zhao, H.; Börner, M.; Udayabhaskararao, T.; Manna, D.; Klajn, R. LightControlled Self-Assembly of Non-Photoresponsive Nanoparticles. Nat. Chem. 2015, 7, 646−652. (44) Park, J.; Yuan, D.; Pham, K. T.; Li, J.-R.; Yakovenko, A.; Zhou, H.-C. Reversible Alteration of CO2 Adsorption Upon Photochemical or Thermal Treatment in a Metal-Organic Framework. J. Am. Chem. Soc. 2012, 134, 99−102. (45) Lyndon, R.; Konstas, K.; Ladewig, B. P.; Southon, P. D.; Kepert, P. C. J.; Hill, M. R. Dynamic Photo-Switching in Metal−Organic Frameworks as a Route to Low-Energy Carbon Dioxide Capture and Release. Angew. Chem., Int. Ed. 2013, 52, 3695−3698. (46) Borah, P.; Sreejith, S.; Anees, P.; Menon, N. V.; Kang, Y.; Ajayaghosh, A.; Zhao, Y. Near-IR Squaraine Dye−Loaded Gated Periodic Mesoporous Organosilica for Photo-Oxidation of Phenol in a Continuous-Flow Device. Sci. Adv. 2015, 1, e1500390. (47) Timm, J.; Stoltenberg, C.; Senker, J.; Bensch, W. AzobenzeneFunctionalized SBA-15 Material for Application in Selective Separation. Z. Anorg. Allg. Chem. 2014, 640, 595−603. (48) Lim, H. S.; Han, J. T.; Kwak, D.; Jin, M. H.; Cho, K. Photoreversibly Switchable Superhydrophobic Surface with Erasable and Rewritable Pattern. J. Am. Chem. Soc. 2006, 128, 14458−14459. (49) Huang, N.; Ding, X.; Kim, J.; Ihee, H.; Jiang, D. A Photoresponsive Smart Covalent Organic Framework. Angew. Chem. 2015, 127, 8828−8831. (50) Brühwiler, D. Postsynthetic Functionalization of Mesoporous Silica. Nanoscale 2010, 2, 887−892. (51) Zhao, L.; Loy, D. A.; Shea, K. J. Photodeformable Spherical Hybrid Nanoparticles. J. Am. Chem. Soc. 2006, 128, 14250−14251. (52) Liu, N. G.; Dunphy, D. R.; Rodriguez, M. A.; Singer, S.; Brinker, J. Synthesis and Crystallographic Structure of A Novel Photoresponsive Azobenzene-Containing Organosilane. Chem. Commun. 2003, 42, 1144−1145. (53) Kojima, M.; Nebashi, S.; Ogawa, K.; Kurita, N. Effect of Solvent on Cis-to-Trans Isomerization of 4-Hydroxyazobenzene Aggregated through Intermolecular Hydrogen Bonds. J. Phys. Org. Chem. 2005, 18, 994−1000. (54) Liu, N.; Chen, Z.; Dunphy, D. R.; Jiang, Y. B.; Assink, R. A.; Brinker, C. J. Photoresponsive Nanocomposite Formed by SelfAssembly of An Azobenzene-Modified Silane. Angew. Chem., Int. Ed. 2003, 42, 1731−1734. (55) Linares, N.; Serrano, E.; Rico, M.; Balu, A. M.; Losada, E.; Luque, R.; Garcia-Martinez, J. Incorporation of Chemical FunctionH
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