Influence of Porous Texture and Surface Chemistry on the CO₂ Adsorption Capacity of Porous Carbons: Acidic and Basic Site Interactions

Abstract

Doped porous carbons exhibiting highly developed porosity and rich surface chemistry have been prepared and subsequently applied to clarify the influence of both factors on carbon dioxide capture. Nanocasting was selected as synthetic route, in which a polyaramide precursor (3-aminobenzoic acid) was thermally polymerized inside the porosity of an SBA-15 template in the presence of different H3PO4 concentrations. The surface chemistry and the porous texture of the carbons could be easily modulated by varying the H3PO4 concentration and carbonization temperature. Porous texture was found to be the determinant factor on carbon dioxide adsorption at 0 °C, while surface chemistry played an important role at higher adsorption temperatures. We proved that nitrogen functionalities acted as basic sites and oxygen and phosphorus groups as acidic ones toward adsorption of CO2 molecules. Among the nitrogen functional groups, pyrrolic groups exhibited the highest influence, while the positive effect of pyridinic and quaternary functionalities was smaller. Finally, some of these N-doped carbons exhibit CO2 heats of adsorption higher than 42 kJ/mol, which make them excellent candidates for CO2 capture.

Effect of activating agents on the development of microporosity in polymeric-based carbon for CO2 adsorption

“…The purpose of this study was to examine the efficiency of different activating agents toward creation of micropores, especially those with sizes <1 nm, which are essential for enhancing the CO 2 uptake at ambient conditions [8]. The PSD curves for the carbons studied show that the C-KOH and C-CO 2 carbons feature one significant peak in the range up to 1 nm and the second one in the range between 1 and 2.5 nm.…”

“…These materials already serve in the industry as adsorbents for other gases and vapors [5,6] and offer tunable structure, easy regeneration, and inexpensive disposal [7]. Especially, microporous carbons possess large surface areas and pore sizes <1 nm for efficient CO 2 capture [8,9]. In addition, these features can be further improved by either chemical or physical activation.…”

Effect of Heat Treatment on the Nitrogen Content and Its Role on the Carbon Dioxide Adsorption Capacity of Highly Ordered Mesoporous Carbon Nitride

“…[4] An umber of advanced and cost-effective technologiesa re being developed for capture, storage, and utilization of atmos-phericC O 2 .C oncurrently,t echnologiesa re also being developed to convert captured CO 2 into value-added chemicals. [6,7] Membrane separation processes are also used for CO 2 capture,but their high costs make the overall process economically untenable, andt herefore, unappealing. Industrially, aqueous amine scrubbing processes are the most commonly used methods to capture CO 2 from flue gases.…”

“…[8] [a] K. S. Lakhi Among the solid-baseda dsorbents,p orous materials are excellent candidates for CO 2 adsorption because of their inherent properties, such as high surfacea rea, pore volume (PV), [7] and the presence of free surface functional groups that can be used to tune the structural and textural properties and facilitate easy chemical modification. [2,12] However,t he adsorption capacityo fc arbon materials is lowo wing to weaker adsorbent-adsorbate interactions that are ascribed to the hydrophobic nature and lack of surfacec harges. [9][10][11] However,e ach of these materials has their own advantages and disadvantages.…”

“…[8] Severalp orous materials, such as activated carbons, porousc arbons, zeolites, mesoporous silica, and metal-organic frameworks, have been investigated as potential solid adsorbents for CO 2 . [2,13] It has been suggested in an umber of reports that the incorporationo fb asic functionalities, such as nitrogen or free ÀNH or ÀNH 2 groups could enhancet he CO 2 adsorption capacity of carbon-based adsorbents because nitrogen atoms can interactt hrough their lone pairs with the mildly acidic CO 2 molecule. For example, zeolites offer large surface areas andh ave specific sites suitable for adsorption, but the small pore system poses diffusional problems.…”