CO2 Adsorption. The four MOFs were tested as CO2 adsorbents at T = 0 and 25 °C and pCO2 up to 1.2 bar. The corresponding isotherms at ambient temperature are reported in Figure , where the amounts of CO2 adsorbed are reported as mmol(CO2) adsorbed per mmol(MOF) in order to account for the materials density variation upon fluorinated linker insertion. The more conventional mmol g -1 unit is reported in Table and Figure . To quantify the strength of the host-guest interactions, the isosteric heat of adsorption (Qst) of CO2 was evaluated from the isotherms recorded at T = 0 and 25 °C applying a variant of the Clausius-Clapeyron equation (Figure ). The isosteric heat of adsorption reflects the interaction strength between CO2 and the inner pore walls of the MOFs. Finally, we estimated the CO2/N2 selectivity using the ratio of the initial slopes in the Henry region of the (CO2 and N2) adsorption isotherms measured at 25 °C (Figure ). From the critical and comparative analysis of the results, we can state that the good performance in CO2 adsorption depends on two factors: BET area and fluorinated linker content. The former is predominant in MOF-801, where the absence of F atoms is compensated by the high SSA value. Consequently, MOF-801 shows the best performance among the MOFs considered in this study in terms of CO2 loading on a gravimetric basis: 2.42 (10.6 wt.%) and 3.51 (15.4 wt.%) mmol g -1 at T = 25 and 0 °C, respectively. On the other hand, the introduction of TFS 2-partially reduces the accessible surface area (and the related CO2 loading) but considerably improves the thermodynamic affinity of the material for CO2 and its CO2/N2 selectivity. The latter is particularly important in the purification of post-combustion industrial flue gases, where the amount of CO2 is very low (4 -30%). The high Henry and IAST selectivity achieved by PF-MOF2 and ZrTFS in particular may be ascribed to the presence of fluorinedecorated ultramicropores that hamper N2 diffusion (because of its large kinetic diameter) but favor CO2 adsorption through the beneficial gas-fluorine interaction. On this basis, the best compromise can be found in the PF-MOF2, with a good CO2 loading of 2.1 mmol g -1 (9.3 wt.%) at ambient temperature and 1 bar, a Qst value of almost 30 kJ mol -1 and the good CO2/N2 selectivity of 95 (Henry)/41 (IAST). The same conclusion can be drawn from the isotherms reported in Figure , where PF-MOF2 shows the highest CO2 uptake: 3.7 mmolCO2 mmolMOF -1 at p = 1 bar. In comparison with other PF-MOFs reported in the literature, at ambient (T,p) conditions (25 °C, 1 bar) PF-MOF2 outperforms F4-UiO-66(Ce) (1.5 mmol g -1 ), but it is less efficient than F4-MIL-140A(Ce) (2.4 mmol g -1 ), AlFFIVE / NbOFFIVE (2.7 / 2.2 mmol g -1 , respectively) published by the team of Eddaoudi in 2016 or than SIFSIX-18-Ni (3.0 mmol g -1 ), reported by Zaworotko and co-workers in 2019.