## 3 Results and Discussion  
### Univariate Analysis  
In order to investigate the relationship of CO\({}_{2}\) adsorption and diffusion properties in N\({}_{2}\)+O\({}_{2}\) with the MOF structure during static adsorption and kinetic adsorption, we first analyzed the relationship among adsorption selectivity \(S_{\text{ads}}\), diffusion selective \(S_{\text{diff}}\), and the LCD of CO\({}_{2}\)/N\({}_{2}\)+O\({}_{2}\), as shown in Figure 1. Obviously, most MOFs with large adsorption selectivity and diffusion selectivity have relatively small LCDs. Figure 1a indicates that when the LCD is 2.8-6.5 A, the adsorption selectivity of CO\({}_{2}\)/N\({}_{2}\)+O\({}_{2}\) decreases, and when the LCD is \(>\)15 A, the adsorption selectivity gradually becomes stable, tending to 5, as depicted by the red line in Figure 1 This is because CO\({}_{2}\) has a strong quadrupole moment, and even in infinitely large pores it is preferentially adsorbed compared to N\({}_{2}\) and O\({}_{2}\). The trend of gas separation is consistent with the trends of previous reports [49; 50]. Figure 1b presents the relationship between \(S_{\text{diff}}\) and LCD. Similar to \(S_{\text{ads}}\), the larger diffusion selectivity (\(S_{\text{diff}}\) \(>\)1) only occurs in the LCDs ranging from 2.4-5 A, since the kinetic diameter of CO\({}_{2}\) is less than the kinetic diameters of O\({}_{2}\) and N\({}_{2}\) (the kinetic diameters of CO\({}_{2}\), O\({}_{2}\), and N\({}_{2}\) are 3.3, 3.46, and 3.64 A, respectively). When the LCD of an MOF is small, the CO\({}_{2}\) molecules with smaller diameters diffuse faster, so the diffusion selectivity \(S_{\text{diff (CO2/N2+O2)}}\) is larger. As the LCD increases, the diffusion selectivity gradually decreases. When the LCD is \(>\)15 A, the diffusion selectivity tends to be stable and fluctuates at around 0.36. Comparison of Figure 1a,b reveals that the adsorption selectivity is generally \(>\)1, while it is rare for the diffusion selectivity to be \(>\)1. Because CO\({}_{2}\) has a strong quadrupole distance, it has a strong interaction force with MOF molecules, thus hindering the diffusion of CO\({}_{2}\) and resulting in a slower diffusion rate, which may be even smaller than the diffusion rates of N\({}_{2}\) and O\({}_{2}\). Figure 1c,d show the relationships of \(S_{\text{ads}}\) and \(S_{\text{diff}}\) to the PLD, respectively. Comparing the panels in Figure 1 reveals that the PLD and LCD display the same trend in their relationships to the \(S_{\text{ads}}\) and \(S_{\text{diff}}\) of CO\({}_{2}\)/N\({}_{2}\)+O\({}_{2}\). Larger \(S_{\text{ads}}\) and \(S_{\text{diff}}\) values appear when the LCD and PLD are small, and \(S_{\text{ads}}\) and \(S_{\text{diff}}\) both decrease with increasing PLD or LCD, eventually tending toward stability. Therefore, there is a greater possibility of finding MOFs with simultaneously high \(S_{\text{ads}}\) and \(S_{\text{diff}}\) among MOFs with small PLDs and LCDs. Figure 2a shows that \(S_{\text{ads}}\) (CO2/N2+O2) increases monotonically with increasing \(Q_{\text{st}}\), indicating that \(Q_{\text{st}}\) may be the main parameter during the adsorption process. Since the concentration of CO2 in the atmosphere is low, it is close to the infinite dilution state. Hence, the selectivity is strongly dependent on the isosteric heat of adsorption of CO2 in the infinite dilution state. The larger \(S_{\text{diff}}\) (CO2/N2+O2) in Figure 2b occurs when the VSA is close to zero. As the VSA continues to increase, \(S_{\text{diff}}\) (CO2/N2+O2) gradually decreases, and eventually stabilizes. This is because when the VSA is close to zero, the MOF molecule either cannot pass any or only passes a small amount of CO2 molecules. When the VSA is large, all the gas molecules can pass through the MOF molecule. Therefore, the separation of CO2 cannot be achieved, i.e., the diffusion selectivity is substantially unchanged. Figure S11b,c indicate the relationship of adsorption selectivity with porosity and VSA, respectively.