Comprehensive Study of Pore Evolution, Mesostructural Stability, and

Apr 14, 2010 - Zhangxiong Wu,†,‡ Paul A. Webley,‡ and Dongyuan Zhao*,†,‡. †Department of Chemistry, Shanghai Key Laboratory of Molecular C...
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Comprehensive Study of Pore Evolution, Mesostructural Stability, and Simultaneous Surface Functionalization of Ordered Mesoporous Carbon (FDU-15) by Wet Oxidation as a Promising Adsorbent Zhangxiong Wu,†,‡ Paul A. Webley,‡ and Dongyuan Zhao*,†,‡ † Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Laboratory of Advanced Materials, Fudan University, Shanghai 200433, P. R. China, and ‡Department of Chemical Engineering, Monash University, Clayton, VIC 3800, Australia

Received January 30, 2010. Revised Manuscript Received March 31, 2010 Fuctionalization of porous carbon materials through chemical methods orientates the development of new hybrid materials with specific functions. In this paper, a comprehensive study of pore evolution, mesostructural oxidation resistance, and simultaneous surface functionalization of ordered mesoporous carbon FDU-15 under various oxidation conditions is presented for the first time. The mesostructure and pore evolution with increasing oxidative strength are retrieved from XRD, TEM, and N2 sorption techniques. The textural properties can be conveniently manipulated by changing the oxidation parameters, including different oxidative solution, temperature, and duration. It is revealed that the mesoporous carbon FDU-15 shows excellent structural stability under severe oxidation treatments by acidic (NH4)2S2O8, HNO3, and H2O2 solutions, much more stable than the mesostructural analogue CMK-3 carbon prepared by the nanocasting method. The surface area and porosity deteriorate to a large extent compared to the pristine carbon, with the micropores/small mesopores as the major contribution to the deterioration. The micropore/small mesopore can be blocked by the attached surface oxides under mild oxidation, while reopened with more carbon layer dissolution under more severe conditions. Simultaneously, high densities of surface oxygen complexes, especially carboxylic groups, can be generated. The contents and properties of the surface oxygen-containing groups are extensively studied by FTIR, TG, elemental analyses, and water and ammonia adsorption techniques. Such surface-functionalized mesoporous carbons can be used as a highly efficient adsorbent for immobilization of heavy metal ions as well as functional organic and biomolecules, with high capacities and excellent binding capabilities. Thus, we believe that the functionalized mesoporous carbon materials can be utilized as a promising solid and stable support for water treatment and organic/ biomolecules immobilization and may be applicable in drug delivery, separation, adsorption technology, and columns for GC and HPLC systems in the near future.

1. Introduction Porous carbon materials have been contributing to many areas of modern science and technology, including water and air purification, separation, catalysis, chromatography, and energy storage because of their high specific surface area, large pore volume, good electric and thermal conductivity, and mechanical and chemical stability.1-3 Recently, the emergence of ordered mesoporous carbon materials from hard and soft templating methods have further trigged enormous research activities because of their large and ordered mesopores and the properties mentioned above.4,5 Thus, they are more promising materials for adsorption, separation, and catalytic processes of large molecules compared to conventional activated carbon materials. Unfortunately, the inert and hydrophobic nature with poor wettability and dispersibility in polar solvents (water in particular) of pristine mesoporous carbon materials is unfavorable for many applications because their *Corresponding author: Tel þ86 21 5163 0205, Fax þ86 21 5163 0307, e-mail [email protected], [email protected]. (1) (a) Stein, A.; Wang, Z.; Fierke, M. A. Adv. Mater. 2008, 20, 1. (b) Wan, Y.; Shi, Y. F.; Zhao, D. Y. Chem. Commun. 2007, 897. (2) You, C. P.; Yan, X. W.; Wang, Y.; Zhang, S.; Kong, J. L.; Zhao, D. Y.; Liu, B. H. Electrochem. Commun. 2009, 11, 227. (3) Li, L.; Yao, X. D.; Sun, C. H.; Du, A. J.; Cheng, L. N.; Zhu, Z. H.; Yu, C. Z.; Zou, J.; Smith, S. C.; Wang, P.; Cheng, H. M.; Frost, R. L.; Lu, G. Q. Adv. Funct. Mater. 2008, 18, 1. (4) Ryoo, R.; Joo, S. H.; Kruk, M.; Jaroniec, M. Adv. Mater. 2001, 13, 677. (5) (a) Wan, Y.; Shi, Y. F.; Zhao, D. Y. Chem. Mater. 2008, 20, 932. (b) Wan, Y.; Yang, H. F.; Zhao, D. Y. Acc. Chem. Rec. 2007, 39, 423.

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potential in adsorption, separation, electronics, and sensing applications require a functionalized carbon surface with specific affinity and/or reactivity. Thus, surface functionalization of mesoporous carbon materials is crucial for the development of new hybrid materials for specific applications. Significant efforts have been devoted to the surface functionalization of porous carbon materials in recent years. A series of functional groups can be attached onto the carbon surface through surface oxidation and/or activation,6-8 halogenation,9,10 sulfonation,11,12 grafting through diazonium chemistry,13,14 etc. Among them, surface oxidation is one of the most convenient and simplest methods for modifying the carbon surface, with not only attachment of oxygen-containing groups but also alteration of the surface hydrophobic/hydrophilic balance. It generally includes dry and wet oxidation plus a few reports using plasma treatment15 and (6) Xia, K.; Gao, Q.; Wu, C.; Song, S.; Ruan, M. Carbon 2007, 45, 1989. (7) Chen, X.; Farber, M.; Gao, Y.; Kulaots, I.; Suuberg, E. M.; Hurt, R. H. Carbon 2003, 41, 1489. (8) Choi, M.; Ryoo, R. J. Mater. Chem. 2007, 17, 4204. (9) Li, Z.; Del Cul, G. D.; Yan, W.; Liang, C.; Dai, S. J. Am. Chem. Soc. 2004, 126, 12782. (10) Wang, L.; Zhao, Y.; Lin, K.; Zhao, X.; Shan, Z.; Di, Y.; Sun, Z.; Cao, X.; Zou, Y.; Jiang, D.; Jiang, L.; Xiao, F. S. Carbon 2006, 44, 1336. (11) Wang, X.; Liu, R.; Waje, M. M.; Chen, Z.; Yan, Y.; Bozhilov, K. N.; Feng, P. Chem. Mater. 2007, 19, 2395. (12) Xing, R.; Liu, Y.; Wang, Y.; Chen, L.; Wu, H.; Jiang, Y.; He, M.; Wu, P. Microporous Mesoporous Mater. 2007, 105, 41. (13) Li, Z.; Yan, W.; Dai, S. Langmuir 2005, 21, 11999. (14) Li, Z.; Dai, S. Chem. Mater. 2005, 17, 1717. (15) Wu, G. M. Mater. Chem. Phys. 2004, 85, 81.

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electrochemical modification.16 Dry oxidation involves reactions with oxidizing gases (such as steam, CO2, and O3) at high temperatures (>700 °C).17,18 However, the surface oxygen complexes, especially carboxyl, hydroxyl, and carbonyl, are unstable and decompose at high temperature. Wet oxidation is widely adopted and involves reactions between the carbon surface and oxidizing solutions, such as HNO3, H2O2, NaClO, and (NH4)2S2O8, under relatively mild reaction conditions (20-150 °C).19-25 HNO3 is often used since its oxidizing properties can be readily controlled by adjusting the concentration and temperature.19 However, HNO3 can bring about some problems: (1) reducing the specific surface area and porosity significantly and considerably damaging the mesostructure at ∼80 °C even with low concentrations;21,23,26 (2) liberating toxic NOx gas during the reactions. H2O2 can also be used to generate surface oxides, but it is very toxic and can damage the mesostructure severely.22 In contrast, acidic ammonia persulfate (APS, (NH4)2S2O8) solution is a gentle and less-toxic oxidant, with a good capability of generating surface oxides without obvious damage to the porous structure.25 Moreover, recent studies showed that the treatment of microporous activated carbons with APS would give more COOH groups on the surface than treatment with HNO3 or H2SO4.25,27,28 Until now, the wet oxidation and mesostructural stability of ordered mesoporous carbon replica CMK-n materials in HNO3, H2O2, and (NH4)2S2O8 solutions have been well reported.21-25 However, for the ordered mesoporous carbon materials obtained from the facile and simple organic-organic self-assembly,29-31 their pore evolution and stability in strong wet oxidative conditions are still unknown. Moreover, given their great potential and ease of industry-scale production, it is desirable to generate surface functional groups, especially carboxylic groups (COOH), in such novel carbon materials for specific applications. It has been expected that COOH-functionalized mesoporous carbons, combined with their high surface area, could have great potential for adsorption, immobilization, and separation of metal ions/ complexes, organic compounds, and biomolecules. In this paper, we comprehensively investigated the mesostructural stability, pore evolution, and surface functionalization of ordered mesoporous carbon materials obtained from organicorganic self-assembly under various wet oxidation conditions. We choose the mesoporous carbon FDU-15 as a model and acidic (16) Yue, Z. R.; Jiang, W.; Wang, L.; Gardner, S. D.; Pittman, C. U. Carbon 1999, 37, 1785. (17) Leboda, R.; Zieba, J. S.; Bogillo, V. I. Langmuir 1997, 13, 1211. (18) Yan, Y.; Wei, J.; Zhang, F. Q.; Meng, Y.; Tu, B.; Zhao, D. Y. Microporous Mesoporous Mater. 2008, 113, 305. (19) Boehm, H. P. Carbon 2002, 40, 145. (20) Chingombe, P.; Saha, B.; Wakeman, R. J. Carbon 2005, 43, 3132. (21) Jun, S.; Choi, M.; Ryu, S.; Lee, H. Y.; Ryoo, R. Stud. Surf. Sci. Catal. 2003, 146, 37. (22) Lu, A. H.; Li, W. C.; Muratova, N.; Spliethoff, B.; Sch€uth, F. Chem. Commun. 2005, 5184. (23) Bazuza, P. A.; Lu, A. H.; Nitz, J. J.; Sch€uth, F. Microporous Mesoporous Mater. 2008, 108, 266. (24) Li, H. F.; Xi, H. A.; Zhu, S. M.; Wen, Z. Y.; Wang, R. D. Microporous Mesoporous Mater. 2006, 96, 357. (25) Vinu, A.; Hossian, K. Z.; Srinivasu, P.; Miyahara, M.; Anandan, S.; Gokulakrishnan, N.; Mori, T.; Ariga, K.; Balasubramanianc, V. V. J. Mater. Chem. 2007, 17, 1819. (26) Gil, A.; de la Puente, G.; Grange, P. Microporous Mater. 1997, 12, 51. (27) Moreno-Castilla, C.; Carrasco-Marı´ n, F.; Mueden, A. Carbon 1997, 35, 1619. (28) Moreno-Castilla, C.; Ferro-Garcı´ a, M. A.; Joly, J. P.; Bautista-Toledo, I.; Carrasco-Marı´ n, F.; Rivera-Utrilla, J. Langmuir 1995, 11, 4386. (29) Meng, Y.; Gu, D.; Zhang, F. Q.; Shi, Y. F.; Yang, H. F.; Li, Z.; Yu, C. Z.; Tu, B.; Zhao, D. Y. Angew. Chem., Int. Ed. 2005, 44, 7053. (30) Zhang, F. Q.; Meng, Y.; Gu, D.; Yan, Y.; Yu, C. Z.; Tu, B.; Zhao, D. Y. J. Am. Chem. Soc. 2005, 127, 13508. (31) Huang, Y.; Cai, H. Q.; Feng, D.; Gu, D.; Deng, Y. H.; Tu, B.; Wang, H. T.; Webley, P. A.; Zhao, D. Y. Chem. Commun. 2008, 2641.

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APS and HNO3 solutions as the gentle and strong oxidants, respectively. The functionalization is controlled by using different oxidant concentrations, different temperatures, and various treatment times. It is found that FDU-15 shows excellent mesostructural stability under strong oxidation conditions. The mesostructure, pore evolution, and the texture properties can be conveniently manipulated and are studied in detail. Meanwhile, a large number of surface oxygen complexes, especially carboxylic groups, can be successfully generated, and their contents and properties are determined. Moreover, the functionalized mesoporous carbon are used as a highly efficient adsorbent for trapping a variety of guest species, including heavy metal ions, functional dyes, and biomaterials, with highly promising adsorption, separation, and immobilization efficiency.

2. Experimental Section 2.1. Chemicals and Carbon Materials. Triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) Pluronic F127 (Mw = 12 600, EO106PO70EO106) was purchased from Acros Corp. Phenol, formaldehyde solution (37 wt %), hydrochloric acid, sodium hydroxide (NaOH), ammonium persulfate [(NH4)2S2O8, APS], sulfuric acid (H2SO4), nitric acid (HNO3), ferric nitrate [Fe(NO3)3 3 9H2O], copper nitrate [Cu(NO3)2 3 2.5H2O], cadmium nitrate [Cd(NO3)2 3 4H2O], lead nitrate [Pb(NO3)2], the organic dye fuchsin, and the drug ibuprofen were purchased from Shanghai Chemical Corp. All chemicals were used as received. Deionized water was used in all the experiments. The mesoporous carbon FDU-15 was prepared by using Pluronic F127 as a template and phenolic resin with low molecular weight as a carbon precursor and carbonizing at 900 °C.29 For control experiments, mesoporous carbon replica CMK-3 was also synthesized by using the hard templating method according to the reported procedures.32,33 2.2. Wet Oxidation and Surface Functionalization. The pristine mesoporous carbon FDU-15 was treated under various wet oxidation conditions to investigate the structure evolution and generate surface functionalities (Scheme 1a,b). The carbon material was treated with the mild oxidant of a 1.0 M APS solution (prepared in 2 M H2SO4). Different temperatures (30-120 °C) and durations (0.5-24 h) were adopted to achieve different levels of texture and surface modification as well as to determine the oxidation resistance of the carbon materials. To check the upper limit of the wet oxidation resistance, a stronger oxidant, HNO3, was also adopted for the modification under different conditions. For a typical treatment, 0.5 g of mesoporous carbon FDU-15 calcined at 900 °C and 30 mL of freshly prepared 1.0 M acidic APS solution were added into a round flask, which was air-proofed by a liquid seal setup. The mixture was stirred and refluxed at 60 °C for 12 h. Then, the solids were filtered, washed with copious amounts of water and then ethanol, and dried under vacuum at 60 °C overnight. The functionalized samples were denoted as FDU-15-APS-x-y, where x stands for temperature (°C) and y for the treatment time (h), respectively. Also, mesoporous carbon replica CMK-3 was treated in certain conditions for comparison.

2.3. Adsorption Experiments. 2.3.1. Measurement of Surface Acidity and Hydrophilicity. Adsorption of ammonia by pristine and several functionalized carbon samples was investigated by the thermogravimetric method to evaluate the density of the surface acidic groups. The sorption was conducted at 50 °C to highlight the adsorption through the weak acid sites by eliminating the weak physisorption. In order to evaluate the (32) Jun, S.; Joo, S. H.; Ryoo, R.; Kruk, M.; Jaroniec, M.; Liu, Z.; Ohsuna, T.; Terasaki, O. J. Am. Chem. Soc. 2000, 122, 10712. (33) (a) Wan, Y.; Zhao, D. Y. Chem. Rev. 2007, 107, 2821. (b) Zhao, D. Y.; Feng, J. L.; Huo, Q. S.; Melosh, N.; Fredrickson, G. H.; Chmelka, B. F.; Stucky, G. D. Science 1998, 279, 548.

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Scheme 1. Possible Models for Surface Structures of (a) Pristine Mesoporous Carbon FDU-15, (b) the Oxidized Surface and the Illustration of the Micropore/Small Mesopore Blocking and Reopening with Increasing Oxidation Temperature and Duration, and (c) the Metal Ion Immobilized Surface

surface hydrophilicity, water adsorption isotherms at 25 °C of the pristine and typical functionalized carbon samples were obtained by using a digital microbalance with a high weight precision of micrograms. Typical procedures for the adsorption of NH3 and water can be found in the Supporting Information. 2.3.2. Evaluation of Adsorption Performance. In order to develop a promising carbon-based adsorbent, we chose several adsorbates, including heavy metal ions, a functional dye, and a drug to evaluate the adsorption performances of the typical functionalized carbon materials. First, the pristine and typical functionalized carbon samples were adopted for immobilizing metal ions (Fe3þ, Cu2þ, Cd2þ, and Pb2þ) (Scheme 1c) in aqueous solutions at 25 °C. The immobilized amounts after filtration and washing were retrieved from TG analysis. Then, adsorption isotherms of fuchsin (dye) and ibuprofen (drug) were conducted at 25 °C for the same materials. The adsorption amounts at different concentrations of adsorbates were determined by using a UV/vis spectrophotometer. Detailed procedures for the adsorption and methods for the calculation of all the above adsorbates can be found in the Supporting Information. 2.4. Characterization. Small-angle X-ray diffraction (XRD) patterns were reordered with a Bruker D4 X-ray diffractometer (Germany) with Ni-filtered Cu KR radiation (40 kV, 40 mA). Transmission electron microscopy (TEM) experiments were conducted on a Philips CM200 (Netherlands) microscope operated at 200 kV. The samples for TEM measurements were suspended in ethanol and dropped onto a holey carbon film supported on a Cu grid. Nitrogen adsorption/desorption isotherms were measured at -196 °C with a Micromeritics Tristar 3000 analyzer. Before the measurements, the samples were degassed in vacuum at 120 °C for at least 8 h. The BET and BJH methods were utilized to calculate the specific surface area (SBET) and derive the pore size distribution (PSD), respectively. The total pore volume (Vt) was estimated from the adsorbed amount at p/p0 of 0.995. The micropore Langmuir 2010, 26(12), 10277–10286

volume (Vmic) and micropore surface area (Smic) were calculated from the t-plot method. Fourier transform infrared (FTIR) spectra were collected on Nicolet Fourier spectrophotometer using KBr pellets of the solid samples. The C, H, and O contents of the samples were measured on a Vario EL III elemental analyzer (Germany). Thermogravimetric (TG) analysis was conducted on a Mettler Toledo TGA/SDTA851 analyzer from 25 to 900 °C under N2 or air (20 mL min-1) with a ramp rate of 5 °C min-1. The concentrations of fuchsin and ibuprofen solutions were measured by a JASCO UV-vis (V-550) adsorption spectroscopy at 544 and 273 nm with predetermined work curves for both of the adsorbates.

3. Results and Discussion 3.1. Structural and Textural Properties of Mesoporous Carbon FDU-15. Small-angle XRD pattern (Figure 1A, a) shows typical diffractions with a strong 10 reflection and weak 11 and 20 peaks based on a 2-D hexagonal (space group p6mm) symmetry.29,34 N2 sorption isotherms (Figure 1B, a) show a combination of type I and IV curves, with an obvious condensation step at p/p0 range of 0.4-0.6, a H2 hysteresis loop, and large amount of N2 adsorption at very low p/p0 value, indicating typical mesoporous materials with narrow PSD (centered at ∼3.8 nm) and a lot of micropores in the framework. The BET surface area and total pore volume are calculated to be 996 m2/g and 0.67 cm3/g, respectively, with a large contribution from micropores of 600 m2/g and 0.27 cm3/g, respectively (Table 1). The TEM image (Figure 2a) further confirms the 2-D hexagonal mesostructure in large domains. (34) Meng, Y.; Gu, D.; Zhang, F. Q.; Shi, Y. F.; Cheng, L.; Feng, D.; Wu, Z. X.; Chen, Z. X.; Wan, Y.; Stein, A.; Zhao, D. Y. Chem. Mater. 2006, 18, 4447.

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Figure 1. Small-angle XRD patterns (A), N2 sorption isotherms (B), and the inset corresponding pore size distribution curves of (a) the pristine mesoporous carbon FDU-15 material and the products after the treatment in a 1.0 M acidic APS solution at (b) 30, (c) 60, (d) 90, and (e) 120 °C for 6 h. Table 1. Structural and Textural Parameters of the Pristine Mesoporous Carbon FDU-15 and the Products after the Treatments by a 1.0 M Acidic APS Solution under Various Conditions samplea

a0b (nm)

SBETc (m2/g)

Smice (m2/g)

Vtd (cm3/g)

Vmicf (cm3/g)

Dg (nm)

pristine FDU-15 10.3 996 600 0.67 0.27 3.8 FDU-15-APS-30-6 10.3 533 273 0.38 0.12 3.7 FDU-15-APS-60-6 10.4 649 352 0.45 0.16 3.7 FDU-15-APS-90-6 10.4 662 363 0.44 0.16 3.8 FDU-15-APS-120-6 10.5 709 388 0.47 0.17 3.8 FDU-15-APS-60-0.5 10.3 537 282 0.37 0.13 3.7 FDU-15-APS-60-3 10.3 645 358 0.43 0.16 3.7 FDU-15-APS-60-12 10.4 546 286 0.38 0.13 3.8 FDU-15-APS-60-24 10.5 622 332 0.42 0.15 3.8 a The samples after the functionalization were denoted as FDU-15-APS-x-y, where x stands for the treatment temperature in °C while y for the treatment time in hours. b The cell parameters calculated from XRD patterns. c The BET specific surface areas evaluated from N2 adsorption data at -196 °C in p/p0 from 0.04 to 0.2. d The total pore volumes estimated on the basis of the volume adsorbed at p/p0 ∼ 0.995. e The micropore surface areas calculated through the t-plot method. f The pore volumes calculated through the t-plot method. g The pore sizes derived from the adsorption branches of the isotherms by using the BJH method.

3.2. Wet Oxidation by Acidic APS Solution. 3.2.1. Structural and Textural Evolution under Various Conditions. Acidic APS solution is shown to be a gentle oxidant with less destruction of the carbon support than other strong oxidants.25 After treatments with a 1.0 M acidic APS solution at 30-120 °C for 6 h, the small-angle XRD patterns (Figure 1A, b-e) show that the mesostructural regularity can be well retained. They all present a distinct and strong 10 diffraction peak and a weak 11 peak, which are quite similar to the pristine carbon. The cell parameters increase very slightly with increasing temperature (Table 1), suggesting that the oxidation can probably remove several layers of carbon from the mesopore walls. Moreover, we found that the mesostructure could be still partially maintained even if the temperature was up to 200 °C (data not shown), suggesting excellent oxidation resistance of FDU-15 carbon in acidic APS solution. TEM images further reveal the mesostructural stability and structural evolution after wet oxidation by the 1.0 M acidic APS solution at 30-120 °C for 6 h (Figure 2b-e). Generally, the 2-D hexagonal regularity can be clearly observed regardless of the treatment conditions. Specifically, after treatment at a low temperature of 30-60 °C for 6 h, the carbon samples still exhibit a high-quality hexagonal mesostructure (Figure 2b,c). The tiny structural changes under such mild conditions are not observable. 10280 DOI: 10.1021/la100455w

After treatment at 90 and 120 °C for 6 h, the mesostructural regularity is still well preserved (Figure 2d,e). Interestingly in this case, the carbon species are partially dissolved, with many “cavities” and/or “holes” on the surface of the sample. At 90 °C, the TEM image (Figure 2d) shows that some carbon layers are removed from the carbon particles, leading to uneven surface and many “cavities”. At 120 °C, while part of the “cavities” are still visible, some of them are completely dissolved, leaving large holes in the whole particle (Figure 2e). It further suggests that some carbon species can be removed by the oxidation, possibly due to the cleavage of carbon-carbon bonds on the outside layers. Such behavior becomes more dramatic at higher temperature. As a result, although the mesostructure is retained, the sample loses about 15 wt % of its original weight at 120 °C. Although the mesostructural regularity of the products is retained after the oxidation, their textural properties deteriorate considerably compared to the pristine carbon. N2 sorption isotherms (Figure 1B, b-e) show that after treated by APS at 30-120 °C for 6 h all the samples still have typical type IV curves and H2 hysteresis loops with very small change of the mesopore size. However, the surface areas and total pore volumes decrease dramatically after the treatment, a drawback always present with wet oxidation.25 At a low temperature of 30 °C, the surface area and pore volume of the treated sample decrease significantly from Langmuir 2010, 26(12), 10277–10286

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Figure 2. TEM images of (a) the pristine mesoporous carbon FDU-15 material and the products after the treatments in a 1.0 M acidic APS solution at (b) 30, (c) 60, (d) 90, and (e) 120 °C for 6 h and at 60 °C for (f) 0.5, (g) 3.0, (h) 12, and (i) 24 h.

966 to 533 m2/g and 0.67 to 0.38 cm3/g, respectively (Table 1). Interestingly, the reduction of the surface area and total pore volume is attributed to a fairly larger extent by the micropores than the mesopores (Table 1). The N2 adsorbed amount at very low p/p0 value ( Fe3þ > Cd2þ). The complete carbon combustion temperature is 550 °C for the functionalized sample (Supporting Information Figure S1), but shifting to 465-350 °C for the corresponding metalimmobilized carbon samples (Figure S7). Moreover, the Fe3þimmobilized sample can be further used as an efficient matrix for selectively enriching phosphopeptides (Figure S8), which is very important for post-translational modifications in regulation of biological functions.48 3.5.2. Adsorption of Fushcin and Ibuprofen. The pristine and the functionalized carbon FDU-15 can be used as highly efficient adsorbents for the organic dye (fushcin). The functionalized FDU-15 from APS at 60 °C shows a larger adsorption capacity than that of the pristine carbon. The two adsorption isotherms can be well-fitted with the Langmuir model (Figure S9). The saturation adsorption capacity of fuchsin onto the pristine carbon and the functionalized FDU-15 is as high as 216.5 and 292.4 mg/g, respectively, which is larger than those of most conventional adsorbents. Moreover, the functionalized FDU-15 shows a larger adsorption affinity toward fuchsin compared to the pristine carbon, indicated by the Kb values (Table 2). This is because the surface carboxylic and phenolic groups can act as weak acid sites, favoring binding affinity toward the basic dye adsorbate. Furthermore, the functionalized mesoporous carbon sample can also be used as an efficient support to load ibuprofen, a common drug. The adsorption isotherms (Figure S9) show that functionalized FDU-15 has a high ibuprofen loading amount of ∼5.5 mg/g at 25 °C, larger than the pristine carbon (Table 2).

4. Conclusions The pore evolution, mesostructure oxidation resistance, and simultaneous surface functionalization of the ordered mesoporous carbon FDU-15 were investigated for the first time by wet oxidation with acidic APS and HNO3 solutions. Our results show that FDU-15 has excellent mesostructural stability under strong (42) Li, Y. H.; Ding, J.; Luan, Z. K.; Di, Z. C.; Zhu, Y. F.; Xu, C. L.; Wu, D. H.; Wei, B. Q. Carbon 2003, 41, 2787. (43) Bystrzejewski, M.; Pyrzynska, K.; Huczko, A.; Lange, H. Carbon 2009, 47, 1201. (44) Jiang, M. Q.; Wang, Q. P.; Jin, X. Y.; Chen, Z. L. J. Hazard. Mater. 2009, 170, 332. (45) Liu, A. M.; Hidajat, K.; Kawia, S.; Zhao, D. Y. Chem. Commun. 2000, 1145. (46) Algarra, M.; Jimenez, M. V.; Rodrı´ guez-Castellon, E.; Jimenez-Lopez, A.; Jimenez-Jimenez, J. Chemosphere 2005, 59, 779. (47) Kubilay, S-.; G€urkan, R.; Savran, A.; S-ahan, T. Adsorption 2007, 13, 41. (48) Pan, C.; Ye, M.; Liu, Y.; Feng, S.; Jiang, X.; Han, G.; Zhu, J.; Zou, H. J. Proteome Res. 2006, 5, 3114.

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Table 2. Metal Ions Immobilization and Fuchsin and Ibuprofen Adsorption Properties on the Pristine and the Functionalized FDU-15 Carbon Materialsa metal ions (mmol/g) sample

Fe3þ

Cu2þ

Cd2þ

fuchsin Pb2þ

Asb (mg/g)

Kbc (L/g)

ibuprofen (mg/g)

pristine carbon FDU-15