## 3 Results and Discussion  
### Adsorbents Characteristics  
#### 3.1.1 Porosity Characteristics by Low-Temperature N\({}_{2}\) Adsorption/Desorption  
The structural properties of the synthesized adsorbents (C1-C4 and P1, P2) were determined based on standard measurement methods of low-temperature nitrogen adsorption/desorption isotherms. Figures 4 and 5 show the measured isotherms and the pore distributions calculated with the Barrett-Joyner-Halenda (BJH) method for all tested materials. The analysis of nitrogen adsorption isotherms for mesoporous carbon materials (C1-C4) (Figure 4A) revealed two types of adsorbent structures, namely a mixed type with the participation of micro- and mesopores (the carbons C1 and C3) and a borderline type characterized by the presence of almost exclusively mesopores (C2 and C4). According to the IUPAC classification, the isotherms are hybrids of type I and type IV with a hysteresis loop of type H4 (the carbons C1 and C3) and the typical type IV with a hysteresis loop of type H3 (the carbons C2 and C4). Compared to the others, the carbons C2 and C4 have a better-developed porous structure and a larger pore volume, which is reflected in much higher adsorption values at a relative pressure close to unity. In addition, adsorption on these materials systematically increases with increasing pressure, indicating a significant change in pore size in which subsequent batches of adsorbate condense. The types of hysteresis loops observed in the course of the adsorption and desorption curves indicate that the carbons are characterized by the presence of pores in the form of slits (the carbons C2 and C4) or narrow slits (the carbons C1 and C3) formed between two planes. Figure 4: Nitrogen adsorption/desorption isotherms on activated carbons (**A**) and polymers (**B**). Solid symbols indicate the adsorption branch, empty symbols indicate the desorption branch. Figure 5: Comparison of pore volume distributions in relation to their sizes determined from the adsorption and desorption branches of gas isotherms for activated carbons (**A**,**B**) and polymers (**C**,**D**). The nitrogen adsorption/desorption isotherms on the polymeric materials (Figure 4B) show a similar pattern, although the polymer P1 exhibits higher adsorption, especially in the high relative pressure region. The mesoporous nature of the tested polymers is evidenced by the presence of a well-defined hysteresis loop in the nitrogen adsorption/desorption isotherms. It should also be noted that for these materials at relatively high relative pressures (p/p\({}_{0}\) > 0.8), a significant increase in adsorption corresponding to condensation in mesopores is observed, indicating the presence of large pores. The isotherms for both polymers belong to type IV with a hysteresis loop of type H3 (slotted pore shape). Analysing the pore size distribution functions for the carbon materials (Figure 5A,B), it is observed that they represent a bimodal type with two significant maximum pore diameters. The distributions corresponding to the carbons C2 and C4 are broader at the base in terms of larger values of pore diameters compared to the others, indicating some variation in the sizes of the mesopores. Higher maximum values on the difference curves indicate that these carbons have a larger pore volume. The pore distribution functions for polymeric materials determined from the desorption branch of the isotherm (Figure 5C,D) are of the homogeneous (Gaussian) type (polymer P1) and the bimodal type (polymer P2). For both materials, the main peak is located in the region of large pore diameters (mesopore), while in the case of the polymer P2 there is also a population of smaller mesopores.