## 3 Results
### Physical Characteristic Analysis after CO\({}_{2}\) Sorption  
The results of the XRD analysis of PZI30 and PAI10-40 sorbents conducted to identify the structural changes before and after CO\({}_{2}\) sorption are shown in Figure 3. The XRD patterns of PZI30 in the fresh state show the sharp peaks of ZrO\({}_{2}\) (JCPDS No. 83-0940) and small peaks of K\({}_{2}\)CO\({}_{3}\) (JCPDS No. 16-0820). For PAI10-40 sorbents before CO\({}_{2}\) sorption, only K\({}_{2}\)CO\({}_{3}\), and y-Al\({}_{2}\)O\({}_{3}\) (JCPDS No. 10-0425) phases were observed. In the case of PAI10-40 sorbents, the peak intensity of K\({}_{2}\)CO\({}_{3}\) increased with increasing K\({}_{2}\)CO\({}_{3}\) loading. For PZI30 sorbent, the KHCO\({}_{3}\) phase could not be detected after CO\({}_{2}\) sorption in the presence of water vapor at 200 \({}^{\circ}\)C and 20 atm, as shown in Figure 3 II. After CO\({}_{2}\) sorption, on the other hand, the XRD patterns of PAI10-40 sorbents showed two phases: Al\({}_{2}\)O\({}_{3}\), and KAl(CO\({}_{3}\))(OH)\({}_{2}\) (JCPDS No. 15-3303). XRD patterns of PAI10-40 sorbents showed no KHCO\({}_{3}\) phase after CO\({}_{2}\) sorption regardless of the K\({}_{2}\)CO\({}_{3}\) loading. Based on the XRD results, the KAl(CO\({}_{3}\))(OH)\({}_{2}\) phase formed from K\({}_{2}\)CO\({}_{3}\) and y-Al\({}_{2}\)O\({}_{3}\) over PAlx sorbents during CO\({}_{2}\) sorption in the presence of 10 vol\(\%\) CO\({}_{2}\) and 10 vol\(\%\) H\({}_{2}\)O at 200 \({}^{\circ}\)C and 20 atm. Figure 1: CO\({}_{2}\) breakthrough curves (**a**) and CO\({}_{2}\) capture capacities (**b**) of PZI30 and PAI10–40 sorbents according to K\({}_{2}\)CO\({}_{3}\) loading at 20 atm. Figure 2: CO\({}_{2}\) capture capacities per 1 g of K\({}_{2}\)CO\({}_{3}\) as a function of the amount of K\({}_{2}\)CO\({}_{3}\) for PZI30 and PAI10–40 sorbents after CO\({}_{2}\) sorption in the presence of 10 vol\(\%\) CO\({}_{2}\), 10 vol\(\%\) H\({}_{2}\)O, N\({}_{2}\) balance at 200 \({}^{\circ}\)C and 20 atm. FTIR analysis of PZI30, PAI10-40 sorbents, and pure KHCO\({}_{3}\) reagent (Sigma-Aldrich, CAS No. 298-14-6) was conducted to confirm the formation of the KHCO\({}_{3}\) structure after CO\({}_{2}\) sorption in the range of 400 to 4000 cm\({}^{-1}\). These results are shown in Figure 4. In all PZI30 and PAI10-40 sorbents, the broad peaks at a wavenumber of 3400 cm\({}^{-1}\) (the expected bond is O-H) are attributed to H\({}_{2}\)O on the surface. In the case of PAI-\(x\) and PZI30 sorbents after CO\({}_{2}\) sorption, the weak peaks at wavenumber 662 cm\({}^{-1}\) (the expected bond is O\({}_{1}\)CO\({}_{2}\)), and 840 cm\({}^{-1}\) (the expected bond is CO\({}_{3}\)) are attributed to carbonate. In addition, the strong peaks at wavenumber 1007 cm\({}^{-1}\) (the expected bond is C-O+C\(\cdots\)-O), 1402 cm\({}^{-1}\) (the expected bond is O-H\(\cdots\)O), and 1630 cm\({}^{-1}\) (the expected bond is C=O) are attributed to bicarbonate species [17, 24, 27, 31]. These results are in agreement with pure KHCO\({}_{3}\) analysis. The weak peaks at 1100 cm\({}^{-1}\) of PAI10-40 sorbents are due to Al-O stretching and Al-O-H bending vibration, and the broad peaks at 1500 cm\({}^{-1}\) of PAI10-40 sorbents are attributed to the H-O-H bend of absorbed H\({}_{2}\)O [32]. The FTIR results show that for the K\({}_{2}\)CO\({}_{3}\) loaded alumina-based CO\({}_{2}\) sorbent, the KHCO\({}_{3}\) structure was formed during CO\({}_{2}\) sorption in the presence of 10 vol% CO\({}_{2}\) and 10 vol% H\({}_{2}\)O at 200 \({}^{\circ}\)C and 20 atm. We suggest that the KHCO\({}_{3}\) structure is formed during CO\({}_{2}\) sorption in the presence of water vapor at 200 \({}^{\circ}\)C and 20 atm [24, 25, 26].