## 3 Results and Discussion
### Sorption Behaviour
\begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Sample** & **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{0}\)** & **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{0}\)** & **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{1}\)** & **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{9}\)** \\
**Form** & **Power** & **Solid Gel Cube** & **Solid Gel Cube** & **Solid Gel Cube** \\ \hline \multicolumn{5}{l}{Particle radius (\(r_{\text{0.5}}\)) (eq.)\({}^{\text{a}}\), \(\mu\)m} & 25.4 & 3310 & 3090 & 2820 \\ Density (\(p\)), g cm\({}^{-3}\) & 1.542 & 1.448 & 1.494 & 1.619 \\ \hline \multirow{5}{*}{CO\({}_{2}\)\({}^{\text{b}}\)} & \(k_{\text{D}}\)\({}^{\text{c}}\), cm\({}^{3}\) (STP) cm\({}^{-3}\) bar\({}^{-1}\) & 1.12 & 1.78 & 1.84 & 1.79 \\  & \(C_{\mu}\), cm\({}^{3}\) (STP) cm\({}^{-3}\) & 5.31 & 0 & 0 & 1.08 \\  & \(b\), bar\({}^{-1}\) & 0.29 & 0 & 0 & 9.8 \\
20\({}^{\circ}\)C & \(S^{\prime}\), cm\({}^{3}\) (STP) cm\({}^{-3}\) bar\({}^{-1}\) & 2.31 & 1.78 & 1.84 & 2.77 \\  & \(\text{cm}^{2}\) s\({}^{-1}\) & \(7.60\cdot 10^{-9}\) & \(1.03\cdot 10^{-6}\) & \(9.08\cdot 10^{-7}\) & \(5.19\cdot 10^{-7}\) \\  & \(P^{\text{d}}\), Barrer & 2.32 & 245.5 & 222.7 & 191.6 \\ \hline \multirow{5}{*}{N\({}_{2}\)\({}^{\text{a}}\)} & \(k_{\text{D}}\)\({}^{\text{c}}\), cm\({}^{3}\) (STP) cm\({}^{-3}\) bar\({}^{-1}\) & 0.031 & 0.067 & 0.052 & 0.019 \\  & \(C_{\mu}^{\text{a}}\), cm\({}^{3}\) (STP) cm\({}^{-3}\) & 0 & 0 & 0 & 0 \\ \cline{1-1}  & \(b\), bar\({}^{-1}\) & 0 & 0 & 0 & 0 \\ \cline{1-1}
20\({}^{\circ}\)C & \(S^{\text{d}}\), cm\({}^{3}\) (STP) cm\({}^{-3}\) bar\({}^{-1}\) & 0.031 & 0.067 & 0.052 & 0.019 \\ \cline{1-1}  & \(D\), cm\({}^{2}\) s\({}^{-1}\) & 2.30 \(\cdot 10^{-8}\) & \(1.21\cdot 10^{-6}\) & \(8.90\cdot 10^{-7}\) & \(1.40\cdot 10^{-6}\) \\ \cline{1-1}  & \(P^{\text{e}}\), Barrer & 0.095 & 10.81 & 6.17 & 3.56 \\ \hline \multicolumn{5}{l}{\(P_{\text{CO}_{2}}\)/\(R_{\text{N}_{2}}\)\({}^{\text{d}}\)} & 24.4 & 22.7 & 36.1 & 53.8 \\ \hline \hline \end{tabular}  
* The composite materials were thick solid gel discs that were cut into squares varying in size from 4.43 mm to 5.39 mm with equivalent radii given in the table. Therefore, \(r_{\text{0.5}}\) refers only to the pure poly(ionic-liquid) (PIL) sample. \({}^{\text{b}}\) Average relative error of 4.7%. \({}^{\text{c}}\) As all experimental data points lay in the non-linear sorption region the accuracy in the determination of \(k_{D}\) may be compromised. \({}^{\text{d}}\) At 1 bar. \({}^{\text{e}}\) Permeability was calculated indirectly from solubility \(S_{i}\) and diffusion \(D_{i}\) as product \(P_{i}=S_{i}\cdot D_{i}\). Barrer = \(10^{-10}\) cm\({}^{-3}\) STP cm cm\({}^{-2}\) s\({}^{-1}\) cmHg\({}^{-1}\).  
\end{table} 
Table 2: Dual-mode model parameters and separation properties obtained at 20 \({}^{\circ}\)C  
Figure 3: CO\({}_{2}\) (**a**) and N\({}_{2}\) (**b**) sorption isotherms in composites at 20 \({}^{\circ}\)C measured directly by gravimetric apparatus. Filled and open symbols denote absorption and desorption runs, respectively. The corresponding coloured solid curves provide guides for the eyes. In the case of **(a)**, the curves are fitted with DMM. complex nature and ability to coordinate CO\({}_{2}\) molecules [44], might lead to longer desorption times due to CO\({}_{2}\) chemisorption in/from the material. The total N\({}_{2}\) sorption capacitywas very low (less than 0.1 wt % at 10 bar) in all samples investigated and decreased in the order **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{0}>\)P\({}_{9}\)IL\({}_{6}\)Zn\({}_{1}>\)P\({}_{9}\)IL\({}_{6}\)Zn\({}_{0}>\)P\({}_{9}\)IL\({}_{6}\)Zn\({}_{9}\)**. This difference in comparison to CO\({}_{2}\) is due to the far worse condensability of N\({}_{2}\) compared to CO\({}_{2}\)[72; 73]. Therefore, one would expect all N\({}_{2}\) isotherms to follow [PERSON]'s sorption model. However, this trend deviated for **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{0}\)** and **P\({}_{9}\)IL\({}_{6}\)Zn\({}_{1}\)** N\({}_{2}\) sorption isotherms, as strong hysteresis was observed in the lower pressure region (\(<9\) bar).