## 3 Results and Discussion
The reaction is summarized in Equation (3):  
\[\mathrm{Mg_{2}(OH)_{3}Br\text{-}4H_{2}O\to Mg_{2}(OH)_{3}Br\text{-}2H_{2}O+2H_{2 }O}. \tag{3}\] \begin{table}
\begin{tabular}{c c} \hline \hline
**Wavenumbers (cm\({}^{-1}\))** & **Assignment** \\ \hline
3648, 3623 & Stretching modes (\(\
u\)) of O-H in Mg(OH)\({}_{2}\) \\
3370 & Stretching modes (\(\
u\)) of H-O-H in H\({}_{2}\)O \\
2050 & Bending (\(\delta\)) and rocking (\(\rho\)) vibrations of H-O-H in H\({}_{2}\)O \\
1608 & Bending (\(\delta\)) vibration of H-O-H in MgBr\({}_{2}\)8H\({}_{2}\)O \\
1523, 1445 & Stretching modes (\(\
u\)) of Mg-O MgBr\({}_{2}\)8H\({}_{2}\)O \\
853 & Stretching vibration (\(\
u\)) of Mg-O cubic structure \\
574 & Deformation (\(\delta\)) and stretching (\(\
u\)) vibrations of Mg-Br \\
420 & Vibrational modes of the lattice showing the Mg-O/Mg\({}^{2+}\), O/O-Mg-O/O-Mg\({}^{2+}\)-O bonds \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Assignments of the major absorption bands of MOB. Figure 7: Collected FT-IR spectra of tested magnesium oxybromide phases. The next step was the second effect with a maximum at \(\sim\)250 \({}^{\circ}\)C, which could be attributed to a release of one molecule of water (see Equation (4)):  
\[\mathrm{Mg_{2}(OH)_{3}Br\cdot 2H_{2}O\to Mg_{2}(OH)_{3}Br\cdot H_{2}O+H_{2}O.} \tag{4}\]  
The third endothermic effect beginning at \(\sim\)380 \({}^{\circ}\)C was attributed to a release of two molecules of water, accompanied by a release of hydrobromic acid, which was evolving continuously at temperatures higher than 400 \({}^{\circ}\)C (see Equation (5)):  
\[\mathrm{Mg_{2}(OH)_{3}Br\cdot H_{2}O\to 2 MgO+HBr+2H_{2}O.} \tag{5}\]  
The thermal behavior of the sample MOB-518 is comparable to the thermal behavior of its chlorinated analogue, which has already been described in literature [34]. During the heating, five effects were detected from the heat flow signal (see Figure 9). The first endothermic effect was attributable to a release of three molecules of water (see Equation (6)) and its maximum was at \(\sim\)125 \({}^{\circ}\)C.  
\[\mathrm{Mg_{3}(OH)_{5}Br\cdot 4H_{2}O\to Mg_{3}(OH)_{5}Br\cdot H_{2}O+3H_{2}O} \tag{6}\]  
Figure 8: Simultaneous thermal analysis with mass spectroscopy of MOB-318 measured in an inert atmosphere. The next step of the heating showed another endothermic effect (with two local maxima at \(\sim\)340 \({}^{\circ}\)C and 370 \({}^{\circ}\)C, respectively) which was attributed to the release of two water molecules (Equation (7)). \[\mathrm{Mg_{3}(OH)_{5}Br\cdot H_{2}O\to Mg_{2}(OH)_{3}Br+2H_{2}O+MgO} \tag{7}\]  
The last effect (maximum at \(\sim\)420 \({}^{\circ}\)C) was attributed to a release of two crystalline water molecules and two hydrobromic acid molecules (see Equation (8)). After this step, only pure MgO was obtained. \[2\mathrm{Mg_{2}(OH)_{3}Br\to 2 HBr+4 MgO+2H_{2}O} \tag{8}\]  
We would like to note that during the heating of MOB-518, there was also a release of CO\({}_{2}\) around 350 \({}^{\circ}\)C caused by the decomposition of MgCO\({}_{3}\) that was formed on the sample surface. The process of formation of MgCO\({}_{3}\) on the surface of magnesia-based materials has previously been described in literature [35].