## 2 Materials and Methods
### Dynamic Breakthrough Experiments  
Cyclic adsorption-desorption measurements were conducted in a custom-built device, whose schematic diagram is given in Figure 1. The adsorption column consisted of an AISI 316-L tubular reactor (250 mm length; 20.9 mm ID), which was heated by a PID controlled electric furnace. A K-type thermocouple was placed in the center of the packed bed. Experiments were performed using an initial mass of adsorbent that corresponded to a bed height of 220 mm. Small particle sizes (i.e., below 0.212 mm) were discarded to avoid excessive pressure drop. A small portion of fused quartz wool was placed at both ends of the column to prevent the loss of adsorbent.  
The feed flow rates of pure N\({}_{2}\), CO\({}_{2}\), and helium were adjusted using mass flow controllers (Brooks, USA). A mass flow meter (Omega Engineering, UK) was used to measure the outlet gas flow rate. CO\({}_{2}\) concentrations were measured using a continuous gas analyzer (ABB model EL3020, Germany). During the adsorption step, the absolute pressure was kept constant at a value of 110-115 kPa. The desorption step was conducted under vacuum (VSA) using an oil rotary vane vacuum pump (Busch, Germany), which assured an absolute pressure of 10 kPa at suction flow rate up to 0.33 m\({}^{3}\) s\({}^{-1}\) STP.  
In a typical cyclic experiment under dry conditions, the adsorbent was initially outgassed by purging with helium at 150 \({}^{\circ}\)C for 4 h. Afterwards, the bed was cooled down to the desired temperature (25 or 50 \({}^{\circ}\)C). Adsorption was then started by switching the feeding gas from helium to a dry mixture of N\({}_{2}\) and CO\({}_{2}\) (with a CO\({}_{2}\) composition of 13.75-14.25 vol. %) at a total flow rate of 3.67 cm\({}^{3}\) s\({}^{-1}\) STP. Under these operating conditions and assuming a void fraction of 0.65-0.75 (estimated from the  
Figure 1: Schematic diagram of the packed-bed setup used for dynamic breakthrough tests.  
measured pressure drop across the bed, which ranged from 165 to 430 Pa, and the Ergun equation), the gas residence time within the packed bed was \(13.2\pm 1.3\) and \(12.2\pm 1.2\) s at 25 and 50 \({}^{\circ}\)C, respectively. Once saturation was reached, the feeding gas was turned off and the column outlet was connected to the vacuum pump. During the desorption step, the temperature of the packed bed was kept at the same value than for the preceding adsorption step.  
For the dynamic adsorption measurements under humid conditions (at a temperature of 50 \({}^{\circ}\)C), 0.0226 cm\({}^{3}\) min\({}^{-1}\) of water was added to the dry feeding gas (at the same flow rate as mentioned above) using a HPLC pump (model 521 from Analytical Scientific Instruments, USA). The amount of added water corresponded to a relative humidity (RH) of the wet gas of approximately 100% at the operating conditions of the column. The water content of the wet feeding gas was 11.2 vol. %.  
Since the dead volume of the system was relatively large, especially for the experiments conducted under humid conditions (in which the moisture trap and measurement chamber were also used), blank adsorption tests were carried out to estimate the time required to displace the dead volume. The blank tests were conducted in both dry and humid conditions for an empty and filled (with glass beads of 1.0 mm OD) adsorption column.