## 3 Results  
### Characterization of IFA and FA  
The compounds obtained by O, L and Ln intercalation were characterized by XRPD patterns and TGA. The solvent used in the synthetic procedure, water or water/ethanol mixture, did not dramatically affect the X-ray diffraction patterns and the thermal profile of the intercalated compounds; thus, the data related to the samples obtained from water/ethanol will be discussed. The powder diffraction data provide information about the interlayer distance and thereby indirectly gives information about the arrangement of chains in the interlayer region. Figure 1 reports the XRPD of the LDH intercalated with O, L and Ln compared with the pristine LDH-NO\({}_{3}\). The interlayer distance of the LDH increases markedly upon intercalation of the organic anions with respect to that of LDH-NO\({}_{3}\), which is 8.8 A. Note that the pattern of LDH-NO\({}_{3}\) shows two reflections at low 2 theta angles ascribable to the diffraction of the reticular planes (_003_) and (_006_); the first, related to LDH metal atomic planes, gives the interlayer distance between the layers. Conversely, the first and the second peaks of the XRPD patterns of the intercalated LDH correspond to the (_006_) and (_009_) reticular planes, respectively. The interlayer distance in these compounds may be obtained by multiplying the distance of (_006_) planes by two; thus, interlayer distances of 30.8 A, 30.0 A, 30.0 A for MgAl-O, MgAl-L and MgAl-Ln, respectively, were obtained. The patterns of MgAl-O and MgAl-L showed a small reflection at 9.9 2 theta, corresponding to the nitrate phase, suggesting that nitrate anions are not completely exchanged by the organic anions. This reflection is lacking in the MgAl-Ln X-ray pattern, attesting that in this compound, a more efficient exchange occurred. However, the presence of residual nitrate anions cannot be excluded due to the formation of solid solution in which the nitrate phase is solubilized in the Ln phase [27]. The interlayer distances of the LDH intercalated with anions deriving from FA are close to that of the LDH intercalated with stearate (30.6 A) [17; 28], the corresponding saturate anion. The simulation of the arrangement of the stearate anions between the LDH sheets suggested the formation of a partially interdigitated monolayer. It can be supposed that this arrangement is also adopted from O, L and Ln. In order to study the thermal behavior of the intercalation compounds, TGA of the samples prepared in H\({}_{2}\)O/EtOH were performed and reported in Figure 2. The results were similar for all the considered samples (MgAl-O; MgAl-L; MgAl-Ln). The first weight loss, ranging from 20 \({}^{\circ}\)C to 150 \({}^{\circ}\)C, was due to the loss of the hydration water. After this, a series of processes occurred: exothermic degradation of the organic moieties prevailed and took place concomitantly with the de-hydroxylation of the brucite layers and the decomposition of residual nitrate anions, leading to the formation of mixed metal oxides [29; 30; 31; 32]. Notably, the position of the TGA curve, and the curves of MgAl-L and MgAl-Ln shifted towards high temperature, suggesting that the combustion of organic anions is delayed with respect to that of O in MgAl-O. The DTA curves are also different; the exothermic events in MgAl-L and MgAl-Ln occurred in a broader temperature range because the LDH lamellae produced a barrier effect to oxygen diffusion, protecting the organic species from the degradation. Moreover, it can be assumed that the packing of L and Ln into the interlayer region is more efficient to hinder the oxygen diffusion. The water contents obtained in MgAl-O, MgAl-L and MgAl-Ln were 5.7%, 4.0% and 4.6%, respectively. [PERSON] et al. (2009) prepared MgAl-LDH containing oleate, and the water content of this compound, calculated by TGA, was 7.1% (air, 20 \({}^{\circ}\)C/min, 50-800 \({}^{\circ}\)C).