Exceptional Gas Adsorption Properties by Nitrogen-Doped Porous Carbons Derived from Benzimidazole-Linked Polymers Babak Ashourirad, Ali Kemal Sekizkardes, Suha Altarawneh, † and Hani M. El-Kaderi* † Department of Chemistry, Virginia Commonwealth University, Richmond, Virginia 23284-2006, United States * S Supporting Information ABSTRACT: Heteroatom-doped porous carbons are emerging as platforms for use in a wide range of applications including catalysis, energy storage, and gas separation or storage, among others. The use of high activation temperatures and heteroatom multiple-source precursors remain great challenges, and this study aims to addresses both issues. A series of highly porous N- doped carbon (CPC) materials was successfully synthesized by chemical activation of benzimidazole-linked polymers (BILPs) followed by thermolysis under argon. The high temperature synthesized CPC-700 reaches surface area and pore volume as high as 3240 m 2 g -1 and 1.51 cm 3 g -1 , respectively, while low temperature activated CPC-550 exhibits the highest ultramicropore volume of 0.35 cm 3 g -1 . The controlled activation process endows CPCs with diverse textural properties, adjustable nitrogen content (1-8 wt %), and remarkable gas sorption properties. In particular, exceptionally high CO 2 uptake capacities of 5.8 mmol g -1 (1.0 bar) and 2.1 mmol g -1 (0.15 bar) at ambient temperature were obtained for materials prepared at 550 °C due to a combination of a high level of N-doping and ultramicroporosity. Furthermore, CPCs prepared at higher temperatures exhibit remarkable total uptake for CO 2 (25.7 mmol g -1 at 298 K and 30 bar) and CH 4 (20.5 mmol g -1 at 298 K and 65 bar) as a result of higher total micropores and small mesopores volume. Interestingly, the N sites within the imidazole rings of BILPs are intrinsically located in pyrrolic/pyridinic positions typically found in N-doped carbons. Therefore, the chemical and physical transformation of BILPs into CPCs is thermodynamically favored and saves significant amounts of energy that would otherwise be consumed during carbonization processes. 1. INTRODUCTION The increasing concentration of anthropogenic carbon dioxide in the atmosphere in recent decades is believed to be the main cause of global warming and climate change. 1,2 Therefore, carbon dioxide (CO 2 ) capture and sequestration (CCS) is regarded as a short-term solution until fossil fuels are replaced by renewable clean energy sources. The conventional approach for CCS, absorption by aqueous amine solutions, suffers from serious drawbacks such as corrosion of equipment, solvent evaporation and toxicity, and most importantly substantial energy cost for regeneration. 3 For cyclic CCS from the postcombustion flue gas mixtures, physisorption of CO 2 is preferred because the moderate CO 2 /adsorbent interaction facilitates regeneration of sorbent. To this end, a wide spectrum of porous adsorbents including zeolites, 4,5 metal organic frameworks (MOFs), 6,7 porous organic polymers (POPs), 8,9 functionalized porous silica, 10,11 and porous carbons 12-14 have been developed for use in the CCS. Among these, MOFs and porous carbons have attracted considerable attention. MOFs can exhibit high CO 2 adsorption capacity at both low and high pressures because of their tunable physical and chemical nature. 15,16 However, some MOFs are water sensitive and made of metal ions. As such, finding alternative adsorbents that are green (metal-free) and chemically robust like porous carbons is highly desirable for gas storage and separation applications. Porous carbons exhibit multifaceted desirable features such as high thermal and chemical stability, tunable textural properties, lightweight and metal-free framework, and ease of regeneration, and most importantly they can be prepared from renewable sources. 17,18 In addition to these properties, the Received: December 2, 2014 Revised: January 21, 2015 Article pubs.acs.org/cm © XXXX American Chemical Society A DOI: 10.1021/cm504435m Chem. Mater. XXXX, XXX, XXX-XXX