## 1 Introduction  
The increase in the atmospheric carbon dioxide (CO\({}_{2}\)) level has been almost guaranteed as being responsible for global warming and climate change. According to statistical data, the emission of CO\({}_{2}\) has mostly occurred from anthropogenic activities. In order to mitigate the increasing concentration of CO\({}_{2}\), several CO\({}_{2}\) capture technologies have been widely studied. Among them, adsorption techniques are effective processes to separate CO\({}_{2}\) from exhaust. Based on this, selecting appropriate adsorbents is very important, and many porous materials have been considered as potential candidates for CO\({}_{2}\) capture [1; 2; 3; 4; 5]. The affinity of the adsorbent surface to CO\({}_{2}\) molecules determines the adsorption capacities of CO\({}_{2}\) on the adsorbents. Several studies have shown that the CO\({}_{2}\) adsorption performance arises from the synergetic effect of the micropores and the surface nitrogen functionalities [6; 7]. The porosity of activated carbons was highly associated with the activation temperature, rather than the activation time [8]. It was found that the adsorption capacity of gas at a lower pressure was controlled by ultramicropores, but micropores and mesopores became dominant at a higher pressure [8; 9]. Nevertheless, [PERSON] et al. [10] observed that in addition to the micropore volume and specific surface area of the carbons, the CO\({}_{2}\) uptake was dependent on other properties of the carbons. [PERSON] et al. [11] reported that the CO\({}_{2}\) adsorption capacity was positively associated with the microporovosity of the carbons. They suggested that only pore sizes of less than 1.0 nm were effective in CO\({}_{2}\) adsorption at atmospheric pressure,based on the molecular size of CO\({}_{2}\) being 0.209 nm. At present, a value of 0.33 nm is usually used as the kinetic diameter of CO\({}_{2}\) molecules [12; 13; 14]. Referring to the study of [PERSON] et al. [15], the hydrogen adsorption capacity was primarily subject to the pore volume, with a width of about 0.6-0.7 nm. Accordingly, several studies have found that high CO\({}_{2}\) capacity can mainly be attributed to the presence of small micropores (<0.8 nm) [16] or ultramicropores (<0.7 nm) [13], because the adsorption potential in the pores was enhanced. A high CO\({}_{2}\) capacity of 8.9 mmole/g at 0 \({}^{\circ}\)C and 1 bar on activated phenolic resin-derived carbon spheres has been obtained [16]. As a general rule, doping a Lewis-base onto the surface of adsorbents could improve their CO\({}_{2}\) adsorption capacities, because CO\({}_{2}\) is regarded as a weak Lewis acidic gas. Reacting with N-containing compounds was commonly a useful and effective method for providing Lewis-base active sites on the surface of adsorbents. The electron-donor properties induced by these N-functionalities could go towards CO\({}_{2}\) capture [17; 18]. The CO\({}_{2}\) adsorption capacities on the polyetherimide impregnated activated carbons positively depend on the adsorption temperature, which is indicative of chemical adsorption [11]. The activated carbons modified at a high temperature with ammonium gas exhibited lower CO\({}_{2}\) capacities, which could be ascribed to the total or partial blinding of micropores by N-functionalities [11]. [PERSON] et al. [19] also found that alkylamine coating increased the nitrogen content and basic sites on the activated carbons, but the microporous volumes and the CO\({}_{2}\) adsorption capacities of the activated carbons were significantly decreased. Tetraethylenepentamine (TETPA) has been grafted onto the surface of carboxyl-rich porous carbons, and a nitrogen content of 11.56 wt% was obtained [20]. Although the CO\({}_{2}\) uptake achieved was about 3.2 mmole/g at 25 \({}^{\circ}\)C and 1 bar, the N-rich adsorbents were not heat-treated such that the N-functionalities might be unstable, and would probably be released under desorption with high temperatures.