Investigation of carbon dioxide adsorption by nitrogen-doped carbons synthesized from cubic MCM-48 mesoporous silica

Copyright © Korean Carbon Society http://carbonlett.org Carbon dioxide (CO2) is a component of the flue gas of power plants and automobile emissions. This gas is recognized as a primary greenhouse gas and is a presumed agent of climate change [1,2]. The drawbacks of the traditional MEA liquid method that is used for CO2 capture include the requirement for heavy equipment, and the toxic, flammable, corrosive, and volatile nature of the process [3]. Therefore, CO2 capture by means of adsorption in porous materials has received increasing attention because this method has proven to be superior than the conventional technologies in terms of the advantages associated with it. Compared to traditional processes, the convenient reversibility of adsorption on porous solid materials based on physisorption for the capture and release of CO2 makes this technique a greener and more cost-efficient method. To date, a variety of solid-based materials have been intensively studied for gas adsorption, especially CO2 capture, such as metal organic frameworks, covalent organic frameworks, zeolites, activated carbons, functionalized graphene, carbon molecular sieves, chemically modified mesoporous materials, etc [4-13]. Furthermore, the low concentration of CO2 in flue gas (ca. 15%) requires selective separation from the large volume of other component gases, mainly N2 [14]. Ideally, solid sorbents designed for CO2 capture should offer reduced energy consumption for regeneration, greater capture capacity, stability, selectivity, ease of handling, reduced environmental impact, etc. Currently, there is significant interest in the development of solid carbon adsorbents that are capable of selectively adsorbing CO2, because of their large surface area, porosity, abundance, cost efficiency, low density, fast adsorption kinetics, and high chemical and thermal stability [15-18]. Furthermore, these materials offer some advantages in terms of ease of handing, pore structure, and surface characteristics, as well as low-regeneration energy [19]. Therefore, carbon materials are currently considered attractive candidate sorbents for CO2 capture in the development of alternate clean and sustainable energy technologies. Based on these strengths, increasing efforts have recently been devoted to the synthesis of element-doped porous carbons that combine the high porosity and unique properties of doped carbon frameworks. The MCM-48 templated carbons have a high porosity without activation usually required to develop an accessible porous structure. Nitrogen doping has earned particular distinction because of the enhanced surface polarity, electrical conductivity, and electron-donor tendency conferred to the mesoporous carbons by nitrogen incorporation, which enables their application in CO2 capture, electric double-layer capacitors, fuel cells, catalysis, etc [20,21]. In the present study, we describe an alternate approach for the production of nitrogen-containing carbon materials with a cubic structure that facilitates CO2 diffusion and capture. Fig. 1a presents the low angle X-ray diffraction (XRD) pattern of MCM-48.The pattern exhibits several well-resolved peaks in the low-angle range of 2θ = 2°–6°, which can be indexed as the (211), (220), (420), and (332) diffraction peaks; this pattern corresponds to the cubic Ia3d space group [2,22]. In Fig. 1b high-angle XRD patterns, the synthesized carbon materials show two apparent peaks at around 2θ = 25° and 44°, which correspond to the (002) and (101) diffractions of the graphite structure, involving the hexagonal graphitic site and rhombohedral graphitic site, respectively [23]. Low-angle XRD patterns of the carbons synthesized with various amounts of pyrrole were acquired, as shown in Fig. DOI: http://dx.doi. org/ DOI:10.5714/CL.2016. 18.062