Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template

• Published in: Nature (London) 2016-07, Vol.535 (7610), p.131-135
• Main Authors: Kim, Kyoungsoo, Lee, Taekyoung, Kwon, Yonghyun, Seo, Yongbeom, Song, Jongchan, Park, Jung Ki, Lee, Hyunsoo, Park, Jeong Young, Ihee, Hyotcherl, Cho, Sung June, Ryoo, Ryong
• Format: Article
• Language: English
• Subjects: 140/131; 639/301/299/1013; 639/301/357/918; 639/638/298/918; Alcohol; Carbon; Carbon compounds; Catalysis; Chemical properties; Chemical synthesis; Crystal structure; Crystals; High temperature; Humanities and Social Sciences; Hydrocarbons; Lanthanum; letter; Lithium; Methods; Morphology; multidisciplinary; Pores; Production processes; Science; Spectrum analysis; Temperature; X-ray diffraction; Yttrium; Zeolites
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature18284

A long-sought three-dimensional graphene-like carbon structure that resembles periodically networked carbon nanotubes is now readily available through lanthanum-catalysed carbon synthesis using a zeolite template. Caged graphene-like frameworks This paper demonstrates that graphene-like carbon frameworks can be selectively formed inside inorganic zeolite micropore templates at relatively low temperatures, without carbon deposition at the external surfaces, by incorporating lanthanum or other carbide-forming metal ions as a carbonization catalyst in zeolite pores. Ryong Ryoo and colleagues go on to show that the synthesis can be readily scaled up, an important requirement for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports. Three-dimensional graphene architectures with periodic nanopores—reminiscent of zeolite frameworks—are of topical interest because of the possibility of combining the characteristics of graphene with a three-dimensional porous structure 1 , 2 , 3 , 4 , 5 , 6 . Lately, the synthesis of such carbons has been approached by using zeolites as templates and small hydrocarbon molecules that can enter the narrow pore apertures 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 . However, pyrolytic carbonization of the hydrocarbons (a necessary step in generating pure carbon) requires high temperatures and results in non-selective carbon deposition outside the pores. Here, we demonstrate that lanthanum ions embedded in zeolite pores can lower the temperature required for the carbonization of ethylene or acetylene. In this way, a graphene-like carbon structure can be selectively formed inside the zeolite template, without carbon being deposited at the external surfaces. X-ray diffraction data from zeolite single crystals after carbonization indicate that electron densities corresponding to carbon atoms are generated along the walls of the zeolite pores. After the zeolite template is removed, the carbon framework exhibits an electrical conductivity that is two orders of magnitude higher than that of amorphous mesoporous carbon. Lanthanum catalysis allows a carbon framework to form in zeolite pores with diameters of less than 1 nanometre; as such, microporous carbon nanostructures can be reproduced with various topologies corresponding to different zeolite pore sizes and shapes. We demonstrate carbon synthesis for large-pore zeolites (FAU, EMT and beta), a one-dimensional medium-pore zeolite (LTL), and