## 3 Results
### Characterization of rGO/CeO\({}_{2}\)/Polymer Monoliths
#### 3.2.4 CO\({}_{2}\) Adsorption  
The monoliths prepared were tested for CO\({}_{2}\) adsorption. In Figure 12, the adsorption isotherms can be seen. The adsorption capacities of all materials ranged from 0.50 mmol/g to 0.64 mmol/g. It can be seen that the highest adsorption was for the GCePN monolith (the one with PNVCL) and was 0.64 mmol/g, while the lower adsorption could be found for GCePM (0.50 mmol/g). The trend in the adsorption corresponded to the trend of the total pore volume, which in this case showed the most important factor affecting the adsorption capacity. The adsorption capacity of the pure monolith (rGO) had a value of 0.5 mmol/g (results not shown here), as has been studied in previous work [15]. It can be seen that almost all monoliths with CeO\({}_{2}\) particles showed better adsorption than the pure monolith, except for GCePM. Figure 10: Adsorption-desorption isotherms of all monoliths: GCe (black), GCePA (red), GCePN (blue), and GCePM (green). The materials presented different adsorption capacities at a lower pressure, which is also crucial for applications with low CO2 pressure (Figure 12b). Different parameters should be taken into account apart from their porous properties by analyzing the gas adsorption data. It is imperative to mention that CO2 is an acidic gas and that each monolith is inside an acidic environment. The monoliths with different polymer brushes will have different behavior inside the acidic CO2, since acidity affects the conformation of the brushes. These conformations will impact the CeO2, which has different polymers on its surface. Inside the monoliths, the particles can have its surface exposed less or more, due to the presence of the acidic gas and its effect on the brushes. Finally, the different functional groups of the polymer brushes and their affinity with the gas should be considered. The presence of polymer brushes will offer extra functionalities for the oxygen groups (of different chemical bonding) and extra heteroatoms. The nature of the solid surface and the specific surface area strongly influences the adsorption capacity [45]. Depending on the character of the solid surface (alkaline or acidic),  
Figure 11: (**a**) Determination of the microporous and mesoporous material based on t-plots for GCe (black), GCePA (red), GCePN (blue), and GCePM (green). (**b**) Incremental pore volume vs. pore width for GCe (black), GCePA (red), GCePN (blue) and GCePM (green). Figure 12: (**a**) Adsorption of CO2 for all monoliths at room temperature and (**b**) comparison of CO2 adsorption values for 760- (1 atm) and 100-mm Hg pressure, as long as the total pore volume is less than 7.5 Å in diameter at P/P\({}_{\rm o}\) = 0.016.  
the specific surface area can have more or less influence, helping with the adsorption of CO\({}_{2}\). Someone will expect that alkaline material will give an extra boost to the adsorption [45]. The presence of CeO\({}_{2}\) inside the graphitic monolith and the level of exposure of the surface of the CeO\({}_{2}\) is also noteworthy. These particles are used in catalysis, since they show a unique oxygen storage capacity and can store and release oxygen reversibly (switching the following Ce\({}^{4+}\) to Ce\({}^{3+}\)). The degree of high oxygen ion mobility is strongly associated with the size, dispersion, and abundancy of oxygen vacancy defects [46]. Dispersion of particles is strongly connected with their aggregation, due to polymer brushes that also affect the abundance of the oxygen defects. The different densities of the polymer brushes on the ceria will lead to more or less active positions for catalysis. The CeO\({}_{2}\) surface is known for adsorbing CO\({}_{2}\) and creating different types of carbonates [47]. These carbonates are hydrogen carbonate, bidentate carbonate, monodentate carbonate, and bridged carbonate [48]. Another important aspect is the affinity of specific chemical groups toward CO\({}_{2}\). In general, the introduction of oxygen atoms facilitates hydrogen bonding with the CO\({}_{2}\)[49].