This journal is c The Royal Society of Chemistry 2012 Chem. Commun., 2012, 48, 7259–7261 7259 Cite this: Chem. Commun., 2012, 48, 7259–7261 Nanoporous carbons through direct carbonization of a zeolitic imidazolate framework for supercapacitor electrodesw Watcharop Chaikittisilp, a Ming Hu, a Hongjing Wang, ab Hou-Sheng Huang, c Taketoshi Fujita, a Kevin C.-W. Wu, d Lin-Chi Chen, c Yusuke Yamauchi* abe and Katsuhiko Ariga* ae Received 12th May 2012, Accepted 31st May 2012 DOI: 10.1039/c2cc33433j Nanoporous carbons with high surface area are achieved through direct carbonization of a commercially available zeolitic imidazolate framework (ZIF-8) without any additional carbon sources. The resultant nanoporous carbons exhibit high electrochemical capacitances in an acidic aqueous electrolyte. Porous carbons possessing high surface area have been one of the most important and conventional porous materials studied so far. 1 They have been widely utilized in many practical applica- tions ranging from adsorbents and catalytic supports, through electrode materials for batteries, fuel cells, and supercapacitors, to drug delivery carriers. Highly porous carbons can be achieved via several methods, e.g., pyrolysis followed by physical or chemical activation of organic precursors, carbonization of polymeric aerogels, and nanocasting with hard-templates. 2 In particular, nanocasting is a powerful tool for creating ordered microporous and mesoporous carbons using zeolites and mesoporous silicas, respectively, as sacrificial solid templates, although it is slightly complex and unfavourable for large-scale production. 3 As a novel class of porous materials, metal–organic frame- works (MOFs) or porous coordination polymers (PCPs) have gained particular attention, because they can be modularly synthesized by self-assembly of transition-metal clusters and organic molecules, leading to designed framework structures and diverse function. 4 Motivated by their high surface area and large pore volume, several MOFs, such as MOF-5, Al-PCP, and ZIF-8, have recently been demonstrated as promising templates to construct microporous carbons. 5–7 In this synthetic protocol, a primary carbon precursor, typically furfuryl alcohol, is impregnated and subsequently polymerized inside the micro- pores of MOFs. Upon thermal carbonization, the formation of porous carbon networks and the decomposition of MOFs occur simultaneously; therefore, MOFs function as both a sacrificial template and a secondary carbon precursor. Considering the large carbon content in MOFs or PCPs, we and other groups have recently reported that highly nanoporous carbon can also be achieved by direct carbonization of Al-PCP and MOF-5, respectively, without the need of additional carbon precursors. 8 This method has a privilege over the conventional nanocasting technique with several steps, because it is a facile and single-step procedure. However, such reported carbon materials possessed broad pore size distributions and the carbo- nization conditions were not studied in detail. Herein we report nanoporous carbons prepared by direct carbonization of a commercially available zeolitic imidazolate framework (ZIF-8) as a singular precursor without any additional carbon sources (Fig. 1). The obtained nanoporous carbons show superior electrochemical performance as supercapacitor electrodes. ZIF-8, which is constructed from zinc and methylimidazole possessing the sodalite structure, 9 is selected because of its Fig. 1 Schematic representation of preparation of nanoporous carbons via direct carbonization of ZIF-8. The SEM images are taken from the Z-900 sample. a World Premier International (WPI) Research Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan. E-mail: Yamauchi.Yusuke@nims.go.jp, Ariga.Katsuhiko@nims.go.jp b Faculty of Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan c Department of Bio-Industrial Mechatronics Engineering, National Taiwan University, No. 1, Sec. 4, Roosevelt Rd., Taipei 10617, Taiwan d Department of Chemical Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan e Precursory Research for Embryonic Science and Technology(PRESTO) & Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), 1-1 Namiki, Tsukuba 305-0044, Japan w Electronic supplementary information (ESI) available: Experimental details, SEM images and Raman spectra of the obtained nanoporous carbons, TG-DTA result of ZIF-8, and N 2 sorption isotherms of the samples before acid treatments. See DOI: 10.1039/c2cc33433j ChemComm Dynamic Article Links www.rsc.org/chemcomm COMMUNICATION Published on 18 June 2012. Downloaded by Monash University on 16/12/2014 08:32:31. View Article Online / Journal Homepage / Table of Contents for this issue