## 3 Results and Discussion
### Gas Adsorption and Selectivity  
The adsorption isotherms of gases (CO\({}_{2}\), CH\({}_{4}\), N\({}_{2}\), H\({}_{2}\), and O\({}_{2}\)) were measured using a simple volumetric sorption apparatus designed in our laboratory (the scheme is given in Figure 2). All sorption measurements were performed at a constant, actively controlled temperature of 25 \({}^{\circ}\)C.  
Table 3 presents a comparison of the adsorption capacities of the unmodified and modified polymers for pure gases, determined from the measured isotherms at a pressure of 100 kPa. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **C** & **CI** & **N** & **S** & **Si** \\  & **(\%)** & **(\%)** & **(\%)** & **(\%)** & **(\%)** \\ \hline HCLPP & 97.79 & 0.42 & 1.74 & - & 0.05 \\ HCLPP-EDA & 90.62 & 0.08 & 9.21 & - & 0.10 \\ HCLPP-DETA & 90.55 & 0.05 & 9.32 & - & 0.07 \\ HCLPP-DENDRIMER & 99.93 & 0.30 & 5.37 & 0.20 & 0.21 \\ \hline \end{tabular}
\end{table} 
Table 2: EDX analysis of pure and functionalized porous polymers HCLPPs. Figure 4: TGA curves of synthesized polystyrene based HCLPPs. The results demonstrated that polymer modification by amines led to a decrease in the amount of adsorbed gas, with the exception of oxygen. This could be attributed to the reduced surface area of the amine-functionalized forms of the polymer. However, the decrease in the adsorption capacity was not as significant as the decrease in the specific surface area or pore volume of the modified materials. [PERSON] et al. (2016) reported similar trends in CO\({}_{2}\) and N\({}_{2}\) capacities at 25 \({}^{\circ}\)C for the porous polymer network synthesized by solvothermal polymerization of DVB and VBC, see Table 6.  
In contrast, in the case of the material modified with a dendrimer containing amino groups, an increase in the adsorption performance of CO\({}_{2}\) and oxygen was observed, despite the fact that, similar to other modified forms of the polymer, the specific surface area also decreased, but to a lesser extent. However, if the adsorption capacities of the materials were normalized to the specific surface area, the efficiency of CO\({}_{2}\) capture was significantly improved, thus confirming the positive effect of functionalization (Table 4). While the gas-uptake ability of the porous material decreased after functionalization, the selectivity increased in all cases. In particular, the CO\({}_{2}\)/N\({}_{2}\) and O\({}_{2}\)/N\({}_{2}\) separation efficiencies of the HCLPPs after amination were improved. Table 5 shows the selectivity values for different gas pairs obtained from the adsorption isotherms of pure gases at 100 kPa. To verify the precision of the measurements using the simple apparatus constructed in our laboratory, we also performed control measurements of CO\({}_{2}\) adsorption using the automated commercial apparatus ASAP 2050 (Micromerities, Norcross, GA, USA). As shown in Figure 5, the agreement of the results was excellent; therefore, the apparatus provided the correct results. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Sample**} & \multicolumn{2}{c}{**CO\({}_{2}\)**} & \multicolumn{2}{c}{**CH\({}_{4}\)**} & \multicolumn{2}{c}{**N\({}_{2}\)**} & \multicolumn{2}{c}{**H\({}_{2}\)**} & \multicolumn{2}{c}{**O\({}_{2}\)**} \\  & **(\(\mu\)mol m\({}^{2}\))** & **(\(\mu\)mol m\({}^{2}\))** & **(\(\mu\)mol m\({}^{2}\))** & **(\(\mu\)mol m\({}^{2}\))** & **(\(\mu\)mol m\({}^{2}\))** \\ \hline HCLPP & 1.33 & 0.41 & 0.12 & 0.03 & 0.02 \\ HCLPP-EDA & 3.22 & 0.46 & 0.12 & 0.05 & 0.17 \\ HCLPP-DETA & 2.96 & 0.47 & 0.10 & 0.04 & 0.15 \\ HCLPP-DENDRIMER & 1.79 & 0.39 & 0.10 & 0.03 & 0.14 \\ \hline \hline \end{tabular}  
* at temperature 25 \({}^{\circ}\)C and pressure 100 kPa.  
\end{table} 
Table 4: Gas adsorption capacity of pure and functionalized porous HCLPP based on VBC *.