## 3 Results and Discussion  
### Adsorbent Characterization  
Elemental analysis does not provide enough information to determine the presence of phenyl groups. The residual surfactant and the alcohol adsorbed used in the extraction procedure can interfere in the carbon content (%C). Therefore, the phenyl incorporation cannot be determined by CHN elemental analysis. However, the increasing %C when phenyl groups are grafted was observed. Thus, for the extracted materials in which the amount of surfactant present is residual, the observed differences in the %C are remarkable, being this C % higher for material \(\Phi_{5}\)-PPH (9.04%) and reduced for \(\Phi_{50}\)-PPH (2.62%), as displayed in Table 1.  
The concentration of phenyl groups in the synthesized material was determined by UV-VIS spectroscopy at \(\lambda\) = 210 nm in hexane. As seen in the UV-VIS spectra (Figure 1), the absorption due to the phenyl groups decreases with the TEOS/\(\Phi\) molar ratio. A calibration curve was performed by hydrolysis of different amounts of phenyl triethoxysilane and the amount of phenyl groups incorporated in each material was determined (Table 2). As expected, the highest observed incorporation of phenyl groups occurred with sample \(\Phi_{5}\)-PPH, although the found value (0.047 mmol/g) was below the theoretical one if all the phenyl groups added were incorporated to the structure. This fact may be due to steric effects and to the non-polar character of phenyl groups which prevents their presence in large amounts in the interlayer space, giving a low incorporation when the silica galleries are formed upon hydrolysis and condensation of PTES, together with the TEOS. This also justifies the found number of functional groups incorporated into the material \(\Phi_{25}\)-PPH that is only slightly lower than that found for \(\Phi_{5}\)-PPH, despite the fact that the amount of functionalized alkoxide added to the latter was five times the added amount in the case of \(\Phi_{25}\)-PPH. However, in spite of the increase in the number of phenyl groups incorporated, the final absorbance remained constant. Finally, as expected, in the case of material \(\Phi_{50}\)-PPH, the incorporation of phenyl groups in this material is very low. After removing the surfactant used as a template, the inner silica galleries are free and a porous material is obtained. For hybrid \(\Phi_{\times}\)-PPH, the surface phenyl groups are directed to the inner porous material. This is true if the inorganic framework is preserved after surfactant removal. This fact can be determined by studying the corresponding XRD diffractograms. The results show a single broad signal at a low angle corresponding to the d\({}_{001}\) reflection, showing the separation of the layers of zirconium phosphate (Figure 2A). This confirms the presence of silica galleries in the interlayer region of zirconium phosphate, which keep these layers separate when the surfactant has been removed. In \(\Phi_{5}\)-PPH, the diffraction peak appears at a slightly lower angle so that the basal spacing is 32.9 A, the intensity is weak and the definition of the peak poor. This indicates that the presence of phenyl groups hinders the arrangement of the internal phase material. This low crystallinity can be justified by the steric hindrance of the phenyl groups, due to their non-polar character, since the  
Figure 2: (**A**) XRD pattern of \(\Phi_{5}\)-PPH, \(\Phi_{25}\)-PPH and \(\Phi_{50}\)-PPH; (**B**) N\({}_{2}\) adsorption-desorption isotherms at 77 K of \(\Phi_{5}\)-PPH. surfactant micelles which act as structural elements of the silica galleries present a polar end placed in this environment which hinders the correct formation of the inorganic structure, mainly for the precursors which contain the phenyl group. This fact is reflected, as discussed in the previous section, in the incorporation of organic groups where the amount of phenyl groups is lower than the other functionalized PPH studied [35].