# Intelligent Prediction of Nitro Oxide Capture in Designable Ionic Liquids
## 4 Results and Discussion
### Effect of the Thermodynamic and Molecular Properties of Ionic Liquids  
Based on the most accurate and validated model trained by the TLFFNN algorithm, the solubility of N\({}_{2}\)O in seven different ionic liquids was predicted over a large range of temperature and pressure values. As shown in Figure 10a,b, when the pressure was under 10 bar, the [(OH)\({}_{2}\)IM][Tf\({}_{2}\)N], [BMIM][Tf\({}_{2}\)N], and [BMIM][AC] ionic liquids performed better than other ionic liquids in absorbing N\({}_{2}\)O, but when the pressure was over 40 bar, the [(ETO)\({}_{2}\)IM][Tf\({}_{2}\)N] ionic liquid demonstrated an excellent ability to absorb N\({}_{2}\)O. The solubility of N\({}_{2}\)O in [(ETO)\({}_{2}\)IM][Tf\({}_{2}\)N] continued to grow as the pressure increased, while for other ionic liquids, after reaching their maximal values, the solubility did not increase with the pressure. The effects of the anions and cations of the ionic liquids were also analyzed. As shown in Figure 10c,d, four ionic liquids had the same cations ([BMIM]) but different anions. As the pressure increased, the solubility curve of [BMIM][AC] first reached a peak and then remained unchanged; then, the curves of [BMIM][Tf\({}_{2}\)N] and [BMIM][BF\({}_{4}\)] reached a higher peak. Additionally, the curve of [BMIM][SCN] was stable at the highest peak. From these figures, we can see that anions of ionic liquids play an important role in capturing N\({}_{2}\)O, and the performance of anions in absorbing N\({}_{2}\)O was [AC] \(>\) [Tf\({}_{2}\)N] \(>\) [BF\({}_{4}\)] \(>\) [SCN] when the pressure was below 10 bar. However, when the pressure was over 80 bar, the results were reversed, and performance of anions became [SCN] \(>\) [Tf\({}_{2}\)N] \(>\) [BF\({}_{4}\)] \(>\) [AC]. Cations also play an important role in N\({}_{2}\)O capture. The solubility levels of N\({}_{2}\)O in three different ionic liquids with the same anion ([Tf\({}_{2}\)N]) are presented in Figure 10e,f. When the pressure was low, i.e., 10 bar, and performances of cations in absorbing N\({}_{2}\)O were [(OH)\({}_{2}\)IM] \(>\) [BMIM] \(>\) [(ETO)\({}_{2}\)IM]. However, as the pressure increased, the situation reversed; when the pressure was higher than 40 bar, and performance of the cations was [(ETO)\({}_{2}\)IM] \(>\) [(OH)\({}_{2}\)IM] \(>\) [BMIM]. According to our examination of thermodynamic and molecular properties, the solubility of N\({}_{2}\)O in ionic liquids will not always grow as the pressure increases. In most cases, it will be stable at a peak value and no longer increase. The question is how high the pressure should be raised to reach the peak solubility. In our case, in the low-pressure zone (under 10 bar), the cation [(OH)\({}_{2}\)IM] and anion [AC] were the best at absorbing N\({}_{2}\)O; in the high-pressure zone (over 80 bar), the best absorbents were the cation [(ETO)\({}_{2}\)IM] and anion [SCN]. Due to their enormous capacity for N\({}_{2}\)O capture with rising pressure, the [(ETO)\({}_{2}\)IM] cation and [SCN] anion are favored when synthesizing new ILs. Our model can also be used to estimate the solubility of N\({}_{2}\)O in a new IL at various pressures and temperatures so that its potential capability can be assessed before it is synthesized. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Method** & **Dataset** & **MSE** & **RMSE** & **R2** \\ \hline LSSVM [33] & & – & 0.0120 & 0.9959 \\ SVM [33] & & – & 0.0104 & 0.9970 \\ ANN [33] & & – & 0.0115 & 0.9963 \\ MLP-ANN [33] & & 0.0003 & – & 0.9945 \\ Hybrid-ANFIS [33] & & 0.0020 & – & 0.9590 \\ PSO-ANFIS [34] & Test & 0.0026 & – & 0.9473 \\ CSA-LSSVM & & 0.0006 & – & 0.9888 \\ CFNN-LM [35] & & – & 0.0074 & 0.9985 \\ RBFNN-PSO [35] & & – & 0.0095 & 0.9978 \\ GEP [35] & & – & 0.0179 & 0.991 \\ TLFFNN [This work] & & 0.00002 & 0.0045 & 0.9981 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Comparison of the performance of different models. Figure 10: The solubility of N\({}_{2}\)O varies in various ionic liquids under various pressures and temperatures.