Systematic investigation of the pore structure and surface properties of SBA-15 by water vapor physisorption

Accepted Manuscript Systematic investigation of the pore structure and surface properties of SBA-15 by water vapor physisorption Swaantje Maaz, Marcus Rose, Regina Palkovits PII:

S1387-1811(15)00482-5

DOI:

10.1016/j.micromeso.2015.09.005

Reference:

MICMAT 7287

To appear in:

Microporous and Mesoporous Materials

Received Date: 15 July 2015 Revised Date:

17 August 2015

Accepted Date: 1 September 2015

Please cite this article as: S. Maaz, M. Rose, R. Palkovits, Systematic investigation of the pore structure and surface properties of SBA-15 by water vapor physisorption, Microporous and Mesoporous Materials (2015), doi: 10.1016/j.micromeso.2015.09.005. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Systematic investigation of the pore structure and surface properties of SBA-15 by water vapor physisorption Swaantje Maaz,a Marcus Rosea,* and Regina Palkovitsa,* a

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Lehrstuhl für Heterogene Katalyse und Technische Chemie, ITMC, RWTH Aachen University, Worringerweg 2, 52064 Aachen, Germany. * [email protected], [email protected]

Abstract

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In order to establish a structure-property correlation in water vapor sorption, various sets of the ordered mesoporous silica SBA-15 with systematically varying properties

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were synthesized and characterized. General trends concerning the surface polarity, aging temperature during synthesis and micropore volume were observed. Calcining the materials with increasing temperatures of 300-800 °C decreases the performance in water vapor sorption which correlates mainly with the amount and type of silanol groups on the silica surface. Furthermore, the aging temperature during synthesis

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influences the water vapor sorption capacity of SBA-15 at low relative pressure. The best results in terms of an increased uptake of water over a broad range of relative pressure can be obtained for materials with high micropore volume and high surface

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polarity. They can be tailor-made by using a routine to remove the template, i.e., a

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combination of extraction with ethanol and subsequent calcination at 300 °C.

Keywords: ordered mesoporous silica, SBA-15, water vapor sorption, structure property relation, tailored adsorbent

ACCEPTED MANUSCRIPT 1. Introduction Increasing energy costs and concerns about the environment have led to a new interest in adsorption heating and cooling systems. Heating and cooling of buildings is an energyconsuming technology and makes up a large part of the final energy consumption all

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over the world providing a big potential to save energy.[1] Since adsorption heat transformers (AHT) can use heat as a main energy source instead of electricity, they are able to make use of low temperature heat sources like industrial waste heat, geothermal

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energy or even ambient temperature.[2] The big drawback is that AHT are not yet able to compete with conventional air-conditioning systems due to their low efficiency.[3] So

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far, mostly industrially available materials such as zeolites and silica gels are used in combination with water. They have, however, never been systematically optimized for applications in this field.[4]

In recent years, many new promising adsorbent materials have been synthesized and tested in water vapor sorption.[5] Nonetheless, systematic studies focusing on structure-

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performance correlations are limited. However, in order to tailor adsorbents for different AHT processes, it is necessary to know about the influence of different material properties on the water vapor sorption performance. The important material properties at

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this point are the physical properties, e.g., surface area, pore volume and pore diameter, and the chemical properties such as the surface polarity.[5] For a systematic investigation

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of the material properties influence ideally the properties can be varied independently from each other. This approach will allow to assign the reason for changes in water sorption behavior to either physical or chemical properties. In the end, it will give insights into the influence of specific material characteristics which may be useful in the preparation of new adsorbent materials for water sorption and AHT. Herein, SBA-15 is depicted as a perfectly suited model material for water vapor sorption even though it is not an efficient adsorbent for use in AHT. The synthesis of SBA-15 is well-known and different synthetic and post-synthetic routes can be used for the adjustment of the material properties.[6-8] The typical SBA-15 material is

ACCEPTED MANUSCRIPT synthesized in a template-assisted approach. The template is typically removed by calcination at 550 °C. It is well-known that calcination at high temperatures leads to condensation of silanol groups on the surface of the material.[9, 10] Thus, SBA-15 is reported to be rather hydrophobic and only adsorbs high amounts of water at high

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relative pressure.[11-13] Since for applications in AHT a steep uptake of water at rather low relative pressure is essential, SBA-15 is not suitable for the list of potential candidates for AHT.[5, 14] Nevertheless, the different synthetic approaches allow to purposefully modify specific material properties rendering SBA-15 an interesting model

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material to explore structure-property correlations. It offers the unique opportunity to control various structural and chemical parameters and thus, bridges a materials gap

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between typically applied amorphous silica and structurally well-defined zeolites. There are different possibilities to affect the structural properties in the scope of wellknown synthetic procedures. The mesopore size and micropore volume can be controlled by the aging temperature during synthesis.[6] Moreover, there are other methods besides

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calcination to remove the template from the pores. The template can be extracted with an acidic ethanol solution which does not involve any high temperature treatment and thus, results in less shrinkage and less condensation of silanol groups.[15, 16] Another

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possibility is to cleave the ether bonds in the template with sulfuric acid, followed by calcination at 300 °C. This rather gentle procedure yields materials with large mesopores

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that are also more stable than the typical SBA-15.[8] In this work, different aging temperatures and combinations of template removal methods were used to create a variety of SBA-15 materials with either similar structural parameters and differing surface polarity or vice versa. Using different aging temperatures, materials with an increasing mesopore diameter are synthesized. Then, the materials are calcined at 550 °C in order to remove the template. For SBA-15 materials prepared in the same manner, Palkovits et al. found that the silanol number is higher for SBA-15 aged at 100 °C than for SBA-15 aged at 60 °C.[17] Thus, an increase in water uptake would be expected with increasing aging temperature.

ACCEPTED MANUSCRIPT In order to vary the surface polarity by calcination while maintaining the pore structure, the starting material has to be thermally stable. Therefore, SBA-15 is synthesized using the sulfuric acid route and calcined at 300 °C which produces a very stable intermediate. It may then be calcined again at temperatures between 300 and

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800 °C for variation of the surface polarity without loss of structure. In addition, the micropore volume can be modified. Using a combination of extraction and calcination, materials with extraordinarily high micropore volume for an SBA-15 are available and show a very good water uptake.

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The insights gained in this first systematic study on structure property relations for water vapor sorption provide a basis to tailor suitable adsorbents for applications such as

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AHT and enable an improvement of efficiency.

2. Experimental

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2.1 Materials

All reagents and solvents used were analytical grade and used as received. Triblock copolymer Pluronic P123 (EO)20(PO)70(EO)20 and tetraethyl orthosilicate (TEOS, >99 %) were purchased

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from Aldrich. Concentrated hydrochloric acid (HCl, 35-38 %) and sulfuric acid (H2SO4, 95 %) were purchased from Chemsolute. Ethanol and distilled water were technical grade.

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2.2 Syntheses

2.2.1 Preparation of SBA-15 samples SBA-15 was synthesized according to literature.[6] In a typical synthesis, 6 g of Pluronic P123 [(EO)20(PO)70(EO)20] were dissolved in 90 g of water and 180 g of 2 M aqueous HCl solution with stirring (400 rpm) at 35 °C. When P123 was completely dissolved, 2.1 g of TEOS were added to the solution and stirring was continued for 24 hours. This mixture was hydrothermally treated under static conditions for 24 hours at either 60, 80, 100 or 120 °C. Afterwards, the product was separated by filtration while the solution was still hot. Then, the solids were washed with acetone, except for materials synthesized at

ACCEPTED MANUSCRIPT 60 °C which proceeded without washing since better material properties were observed when the materials aged at 60 °C were not washed. The obtained materials were then dried at 80 °C for 48 hours.

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2.2.2. Template removal In order to remove the template, one part of the as-made material was calcined at 550 °C for 6 hours (heating rate 1 K min-1).[6] Another part was treated with sulfuric acid and calcined at a lower temperature as described elsewhere.[8] 3.5 g of as-made SBA-15

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were stirred (500 rpm) in a solution of 150 ml of ethanol and 5 drops of conc. HCl for 30 min at room temperature. The solid was recovered by filtration and dried without

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washing at 80 °C over night. 1 g of the extracted SBA-15 material was then stirred (400 rpm) in 60 ml of 48 % H2SO4 solution at 90 °C for 24 hours. The mixture was cooled down, decanted twice and filtered. The solid was washed with water until the eluent was neutral, then washed again with acetone and dried at 80 °C over night. To remove the

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remaining template, the solid was calcined at 300 °C for 3 hours (heating rate 2 K min-1). In order to obtain different concentrations of silanol groups in these materials, 0.2 g of the material were then calcined a second time at temperatures between 300 and 800 °C

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for 6 hours (heating rate 2 K min-1).

Moreover, the template can be removed by extraction and calcination. 1 g of as-made

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SBA-15 was stirred (400 rpm) in a solution of 150 ml ethanol and 15 drops of conc. HCl under reflux for 24 hours. The solid was recovered by centrifugation and dried at 80 °C over night. In order to remove the remaining template, the material was calcined at 300 °C for 3 hours (heating rate 2 K min-1). The samples are labelled as follows: calcined materials (C) and extracted materials (E) with aging temperature of 60 to 120 °C, e.g. C-60 or E-120, acid-treated materials (A) with temperature of the second calcination step 300 up to 800 °C, e.g. A-500. A comprehensive overview on all prepared samples with the respective synthesis conditions is given in Table S1.

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2.3 Characterization Powder XRD patterns were measured on a Siemens D5000 instrument using Cu-Kα radiation (λ = 0.154 nm). The nitrogen adsorption/desorption isotherms were measured

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on a Quadrasorb SI (Quantachrome Instruments). Prior to the measurement, the samples were degassed at 120 °C for at least 12 hours. In order to calculate the specific surface area, the BET model was applied in the range of 0.05 ≤ p/p0 ≤ 0.2. The total pore volume

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was calculated from the amount of nitrogen adsorbed according to Gurvich at a relative pressure of 0.98. The pore size distribution and the average pore sizes were determined

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using the NLDFT-model for nitrogen at -196 °C on cylindrical silica pores. For analysis of the micropores, the t-plot model by Harkin and Jura was used. Water vapor adsorption/desorption isotherms were measured at 20 °C on an Autosorb iQ (Quantachrome Instruments). Before the measurement, the samples were degassed at 120 °C until they passed the degassing test (21 millitorr min-1). The pore volume was

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calculated at relative pressures of 0.1 and 0.9. In order to relate the pore volume occupied by adsorbed water at high relative pressure to the total pore volume in the sample, the pore filling degree (PFD) was calculated as quotient of the pore volume from

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physisorption.

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water adsorption at p/p0=0.9 and the total pore volume determined from nitrogen

3. Results and discussion

3.1 Adsorbent synthesis and general characterization In order to obtain materials with varying structural properties, SBA-15 was synthesized at four different aging temperatures, namely 60, 80, 100 and 120 °C. The syntheses were successful, as proven by X-ray diffraction of the four materials which were calcined at 550 °C (Fig. 1). The patterns show the three distinct reflections of SBA-15 corresponding to the (100), (110) and (200) reflections. With increasing synthesis

ACCEPTED MANUSCRIPT temperature, the (100) reflection is shifted to lower 2θ-values as expected for an increasing size of the unit cell.[6] To vary surface polarity, the as-made starting materials were used in three different approaches of template removal known from literature, namely calcination at 550 °C (C)[7], a combination of acid-treatment and calcination at

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300 °C (A)[8] and extraction with ethanol (E)[15] (Fig. 3). Since extraction with ethanol is known to only incompletely remove the template,[15, 16] the materials were calcined at 300 °C after extraction. Thermogravimetric analysis shows that the template was successfully removed (Fig. S1). A broad library of materials with different structural and

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chemical properties was produced. The nitrogen physisorption data in Tab. 1 demonstrate the structural variety of the different samples.

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In addition, Fig. 2 shows the nitrogen physisorption isotherms of three exemplary SBA-15 materials pointing at the differences in micropore volume, mesopore diameter, surface area and total pore volume. As expected, the acid treated material A-300 shows a larger pore diameter and pore volume than the calcined analogue C-100. A second

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calcination step at higher temperatures does not destroy the structure. Only small shrinkage can be observed even after a treatment at 800 °C. Furthermore, the extracted materials E generally show higher surface areas, pore volumes and micropore volumes

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than their calcined analogues which is probably due to the more gentle method of

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template removal.

3.2 Water vapor sorption In order to investigate the adsorption behavior of the systematically synthesized SBA-15 samples, water vapor sorption was measured. Fig. 4A shows the full isotherms of the calcined materials C which can be assigned as type V according to the IUPAC definition, describing rather hydrophobic materials which adsorb reasonably high amounts of water only at high relative pressure.[11] The interaction between adsorbent and adsorptive can be observed at low relative pressure (0.1), since at higher relative pressure (0.9) the

ACCEPTED MANUSCRIPT uptake of water in these materials is mainly governed by water-water interactions.[11] Our results show that the uptake at high relative pressure (0.9) does not correlate with the chemical properties but rather with the total pore volume of the samples. Typically, samples show a pore filling degree of 0.55 – 0.70 without any connection to polarity or

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other differences due to the varying treatments (Tab. 1). Nonetheless, at low relative pressure, differences in water uptake are observed and ascribed to certain material properties such as surface polarity and micropore volume. Fig. 4B shows the pore volumes occupied by adsorbed water at low relative pressure for the calcined materials

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C. It is evident that the sample synthesized at 60 °C shows the highest uptake of water while the sample synthesized at 120 °C shows the lowest uptake of water in this region.

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This is rather surprising since Palkovits et al. were able to prove that SBA-15 aged at a lower temperature has a lower surface silanol concentration than SBA-15 aged at a higher temperature.[17] It is possible that for samples which do not differ significantly in the number of surface silanol groups another material property influences the uptake of

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water more significantly. A correlation with the mesopore diameter is not consistent with the results from water vapor sorption, since C-100 and C-100-2 from different synthesis batches with clear deviation of the pore diameters showed the same uptake of water at

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low relative pressure (Tab. 1). This suggests that the uptake at low relative pressure is governed by an influence of the aging temperature during synthesis of the material and

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not as much by structural properties. It is possible that a low aging temperature results in a lower amount of rather hydrophilic silanol groups while a high aging temperature leads to more isolated silanol groups and hence, renders the surface more hydrophobic. Nonetheless, the effect is reproducible in calcined materials C and can also be noticed for the extracted materials E as illustrated in Fig. 5. This indicates that the different behavior in water uptake is not just due to measurement uncertainty. It is interesting to note that the acid treated materials A do not show the same trend of a decreasing water uptake at low relative pressure with increasing aging temperature (Fig. S2). It is reported that the acid treatment leads to a higher degree of condensation in the structure.[15] Thus, it is

ACCEPTED MANUSCRIPT possible that a higher degree of condensation results in a higher amount of isolated silanol groups on the surface and therefore, renders the acid treated materials uniformly hydrophobic. However, there is no further evidence to support this theory yet. In addition to the influence of structural features, the influence of the surface polarity

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on water vapor sorption was also systematically investigated. At high temperatures, neighboring silanol groups start to condensate, leaving rather hydrophobic siloxy groups on the surface.[11] Thus, the surface polarity is decreased. Therefore, the samples A were calcined at different temperatures between 300 and 800 °C to vary the surface

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silanol concentration. As summarized in Tab. 1, the structural properties remained generally intact. The differences in water uptake at low relative pressure shown in Fig. 5

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can hence be connected to a decreasing surface polarity with increasing calcination temperature. The big gap between 400 and 600 °C is probably due to the fact that at temperatures higher than 400 °C mainly isolated silanol groups are left on the surface, which are known to be rather hydrophobic.[18, 19]

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Furthermore, the influence of micropore volume was examined. All extracted materials E exhibit very high micropore volumes and were tested in water vapor sorption. The isotherms show a significantly increased water uptake over a broad range

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of relative pressure and a substantially higher uptake at low relative pressure compared to all the other materials. In order to differentiate between high micropore volume and

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surface polarity as reason for the high uptake, one sample was calcined for a second time at 500 °C (E-100-2*) to decrease the surface polarity. The structural properties of the sample remain intact but the water uptake drops significantly though it is still higher than for the materials C and A (Fig. 6). Consequently, the high uptake in these materials is not only due to a high micropore volume but also due to the gentle method of template removal via extraction with ethanol and calcination at temperatures as low as 300 °C. This keeps more silanol groups on the surface intact during template removal. Moreover, the influence of surface polarity on the appearance of the hysteresis was observed. Fig. 7 shows the water sorption isotherms of three materials with different

ACCEPTED MANUSCRIPT hydrophilicity but the same pore diameter. It can be seen that the hysteresis is shifted to higher relative pressures with a decreasing surface polarity. The same effect can be observed when comparing A-300 to A-800 (Fig. S3). Even though A-800 has a smaller pore diameter than A-300 and the pore condensation is expected to occur at a lower

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relative pressure, the adsorption branch is shifted to higher relative pressures. We assign this effect to the lower surface polarity despite the smaller pore diameter.

3.3 Uncertainty of measurement and stability of the materials in water vapor

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Since the investigated materials only adsorb very small amounts of water at low relative pressure, even a small measuring error is quite significant at those points. In order to

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determine the measuring error, one sample was measured at least three times, while always using a fresh amount of the sample. The results show different standard deviations for different samples, indicating that the measurement does not only depend on the device but also on the sample. Furthermore, the standard deviation at high relative pressure (0.9, around 5 %) is significantly lower than at low relative pressure (0.1,

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around 25 %) which is due to the fact that the water uptake at 0.9 is about one order of magnitude higher than at 0.1.

After a water vapor physisorption experiment, selected samples were measured again

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by nitrogen physisorption to examine possible loss of structure. A partial loss of structure

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was observed for all selected materials. However, the damage is most pronounced for the material E-60 and less pronounced for C-100, while A-300 stays mostly intact (Fig. S4).

4. Conclusion

A systematic investigation of the influence of structural and chemical properties on the water sorption behavior of the mesoporous silica SBA-15 was carried out. Structural and chemical properties were varied independently using different aging temperatures and methods of template removal. The results suggest that a lower aging temperature is beneficial for a high water uptake at low relative pressure. As expected, the surface

ACCEPTED MANUSCRIPT polarity of SBA-15 is significantly decreased by treatment at temperatures higher than 400 °C due to the condensation of silanol groups which can be observed by a decrease of the water uptake at low relative pressure. The highest water uptake was obtained for samples with both high micropore volume and high surface polarity. Those materials

even if they had been treated at temperatures as high as 500 °C.

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Appendix A. Supplementary data.

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showed a significantly higher uptake of water over a broad range of relative pressure

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Supplementary data related to this article can be found at …

Acknowledgments

Funded by the Excellence Initiative of the German federal and state governments within the

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Boost Fund project “CO2 -neutrale Klimatisierungstechnologie für Elektrobusse”.

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633-635.

[11] E.-P. Ng, S. Mintova, Microporous Mesoporous Mater. 114 (2008) 1-26. [12] J.S. Oh, W.G. Shim, J.W. Lee, J.H. Kim, H. Moon, G. Seo, J. Chem. Eng. Data 48

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ACCEPTED MANUSCRIPT Tables Tab. 1 Structural properties of the SBA-15 materials obtained by nitrogen physisorption at 196 °C.

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Sample Taging / SBET / Vp / Dp / Vp,micro / PFD(0.9)a Vp,H2O (0.1) / 2 -1 3 -1 3 -1 °C mg cm g nm cm g cm3g-1 C-60 60 637 0.69 4.2 0.08 0.66 3.91*10-2 C-80 80 633 0.78 6.3 0.03 0.69 3.86*10-2 C-100 100 725 1.08 7.9 0.00 0.64 3.07*10-2 680 1.24 8.8 0.00 0.67 1.97*10-2 C-120 120 A-300 100 597 1.26 9.1 0.03 0.67 3.11*10-2 A-400 100 597 1.21 9.1 0.04 0.54 2.78*10-2 A-600 100 513 1.11 8.8 0.02 0.51 4.35*10-3 410 0.83 8.1 0.01 0.31 1.66*10-3 A-800 100 E-60 60 1146 1.10 4.5 0.24 0.57 8.42*10-2 E-80 80 798 0.90 5.4 0.10 0.64 6.60*10-2 1.48 6.0 0.13 0.63 5.14*10-2 E-100 100 1009 E-120 120 959 1.46 8.8 0.10 0.65 4.48*10-2 E-100-2 100 912 1.28 8.1 0.11 0.60 5.18*10-2 880 1.22 8.1 0.11 0.42 3.37*10-2 E-100-2* 100 a The pore filling degree (PFD) is calculated as the quotient of the filled pore volume from water vapor physisorption at p/p0=0.9 and the total pore volume determined from nitrogen physisorption.

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Figure captions

Fig. 1 XRD patterns of SBA-15 aged at 60, 80, 100 and 120 °C and calcined at 550 °C Fig. 2 N2 sorption isotherms of SBA-15: aged at 60 °C and calcined at 550 °C (■), aged at 100 °C and acid treated (▲), aged at 100 °C and extracted with ethanol (●), adsorption: filled symbols, desorption: empty symbols.

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Fig. 3 Scheme of template removal: SBA-15 calcined at 550 °C (C), treated with H2SO4, calcined at 300 °C and calcined again at 300 – 800 °C (A), extracted with ethanol and calcined at 300°C (E).

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Fig. 4 A) Water vapor sorption isotherms at 20 °C of SBA-15 C-60 (●), C-80 (♦), C-100 (■) and C-120 (▲); B) Pore volume occupied by adsorbed water at relative pressure 0.1 of the respective materials. Fig. 5 Pore volume occupied by adsorbed water at relative pressure 0.1 for SBA-15 materials A, C and E. Fig. 6 Water vapor sorption isotherms of SBA-15 materials C-60 (▲), A-400 (♦), E-100-2 (●) and E-100-2* (■), adsorption: filled symbols, desorption: empty symbols. Fig. 7 Water sorption isotherms at 20 °C of SBA-15 materials with the same pore diameter and different surface polarity, C-120 (■), A-800 (▲) and E-120 (●), adsorption: filled symbols, desorption: empty symbols.

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Systematic investigation of material property influences on water vapor sorption. A broad library of SBA-15 materials with varying properties was produced. The materials were investigated by water vapor sorption at 20 °C. Low aging temperature during synthesis is beneficial for higher uptake at low p/p0. Gentle template removal, i.e. by extraction, leads generally to a high uptake.

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• • • • •

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Systematic investigation of the pore structure and surface properties of SBA-15 by water vapor physisorption S. Maaz,a M. Rosea and R. Palkovitsa*

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Lehrstuhl für Heterogene Katalyse und Technische Chemie, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany.

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Supporting Information

Template removal

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calcination at 550 °C in air calcination at 550 °C in air calcination at 550 °C in air calcination at 550 °C in air 1. sulfuric acid treatment, 2. calcination at 300 °C for 3 h, 3. calcination at 300 °C for 6 h 1. sulfuric acid treatment, 2. calcination at 300 °C for 3 h, 3. calcination at 400 °C for 6 h 1. sulfuric acid treatment, 2. calcination at 300 °C for 3 h, 3. calcination at 600 °C for 6 h 1. sulfuric acid treatment, 2. calcination at 300 °C for 3 h, 3. calcination at 800 °C for 6 h 1. extraction with acidic ethanol solution, 2. calcination at 300 °C for 3 h 1. extraction with acidic ethanol solution, 2. calcination at 300 °C for 3 h 1. extraction with acidic ethanol solution, 2. calcination at 300 °C for 3 h 1. extraction with acidic ethanol solution, 2. calcination at 300 °C for 3 h 1. extraction with acidic ethanol solution, 2. calcination at 300 °C for 3 h like E-100-2, then calcination at 500 °C for 6 h

EP

Taging / °C C-60 60 C-80 80 C-100 100 C-120 120 A-300 100 A-400 100 A-600 100 A-800 100 E-60 60 E-80 80 E-100 100 E-120 120 E-100-2 100 E-100-2* 100

AC C

Sample

M AN U

Table S1. Overview of all prepared SBA-15 samples regarding the synthesis conditions (aging temperature and method of template removal).

ACCEPTED MANUSCRIPT 100

60

E-120 E-100

40

E-80 E-60

20

0 100

200

300

400

500

600

700

800

SC

Temperature / °C

RI PT

Mass / %

80

M AN U TE D

0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01 0.00

EP

Vp H2O / cm3g-1

Figure S1. Thermogravimetric Analysis of SBA-15 materials E-60, E-80, E-100 and E-120.

AC C

A-60

A-80

A-100

A-120

Figure S2. Filled pore volume determined by water vapor sorption at relative pressure 0.1 for SBA-15 materials A-60, A-80, A-100, A-120 (aging temperature 60, 80, 100 and 120 °C, template removal by acid treatment and calcination at 300 °C followed by a second calcination step at 300 °C).

ACCEPTED MANUSCRIPT 1200

A-300 026-a-300-300 A-800 026-a-300-800

800

600

RI PT

Vads @ STP / cm3g-1

1000

400

200

0.0

0.2

0.4

0.6

0.8

p/p0

SC

0 1.0

M AN U

Figure S3. Adsorption desorption isotherms of water vapor sorption of SBA-15 materials A-300 and A-800 at 20 °C.

900

TE D

800

600

C-100 C-100-v

EP

500 400 300

A-100 A-100-v E-60

AC C

Vads @ STP / cm3 g-1

700

E-60-v

200 100

0

0.0

0.2

0.4

0.6

0.8

1.0

1.2

p/p0 Figure S4. Adsorption desorption isotherms of nitrogen physisorption of C-100, A-100 and E-60 before and after (v) the water vapor measurement.