## 1 Introduction
It has been shown repeatedly that nitrogen atoms, possessing a pair of lone electrons, can act as a Lewis base and are able to facilitate the adsorption of CO\({}_{2}\) through the interactions between the quadrupole moment of CO\({}_{2}\) molecules and the polar N-species [6]. Specifically, the nitrogen groups on the adsorbents that have a basic character were amine groups and imine groups, so the presence of these groups would lead to higher CO\({}_{2}\) capacities, probably partially from chemisorption [11]. [PERSON] et al. [21] also reported that pyrrolic N might function as polar sites for CO\({}_{2}\) capture. As for pyridonic N, its nitrogen atom is positioned just next to the \(-\)OH group, such that this nitrogen atom is surrounded with a higher electron density and behaves as a strong Lewis base [22], promoting a high CO\({}_{2}\) adsorption capacity. Even though most studies have utilized acid-base interactions to interpret the high CO\({}_{2}\) adsorption capacities of N-rich carbons, [PERSON] et al. [10] proposed another point of view. They thought that the importance of the hydrogen-bonding interactions between the CO\({}_{2}\) molecules and the hydrogen atoms on the N-doped carbons should be taken seriously, as they may override the effects of acid-base interactions. [PERSON] et al. [22] believed that the pyridonic N groups play an important role in CO\({}_{2}\) adsorption because the position of the N atom enhances its Lewis basicity, and the pole-pole interactions between the CO\({}_{2}\) molecules and the carbon surface. [PERSON] et al. [23] suggested that, besides the nitrogen functionalities, the hydrogen bonding or polar interactions of CO\({}_{2}\) within the confined pores of carbonaceous adsorbents may originate from other heteroatomic functional groups. If these chemical interactions were inevitable, the adsorption phenomena would be complicated and the performance of the adsorbents in long-term applications could be unpredictable. Among the known adsorbents, activated carbon fibers (ACFs) have unique characteristics compared with powder or granular activated carbons. A small fiber diameter ensures fast intraparticle adsorption kinetics, and the fibrous form is favored because of ease in handling when it is used in fabric or felt forms [24]. Recently, several special structures of carbon materials have been studied to serve as CO\({}_{2}\) adsorbents [25]. However, some have complicated manufacturing processes, some were expensive, and there was often a challenge in realizing mass production and commercialization. In terms of practical applications, ACFs should be a feasible adsorbent, and how to improve their CO\({}_{2}\) uptake is a relevant question. The studies regarding the CO\({}_{2}\) uptake of ACFs published in literature have almost always focused on the discussion of capacities and porosity. Only a few studies have talked about the effect of the chemical properties of ACFs on CO\({}_{2}\) adsorption, and almost no studies have investigated the role of surface functional groups on CO\({}_{2}\) adsorption performance. Therefore, this paper is intended to investigate the material properties of ACFs modified with potassium hydroxide (KOH) or TEPA, determine their adsorption capacities of CO\({}_{2}\), and discuss the dependence of CO\({}_{2}\) uptake on the primary parameters.