title: Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template.
abstract: 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. 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. 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 even small-pore zeolites (MFI and LTA). The catalytic effect is a common feature of lanthanum, yttrium and calcium, which are all carbide-forming metal elements. We also show that the synthesis can be readily scaled up, which will be important for practical applications such as the production of lithium-ion batteries and zeolite-like catalyst supports.
authors.forename: Kyoungsoo
authors.initials: K
authors.lastname: Kim
authors.forename: Taekyoung
authors.initials: T
authors.lastname: Lee
authors.forename: Yonghyun
authors.initials: Y
authors.lastname: Kwon
authors.forename: Yongbeom
authors.initials: Y
authors.lastname: Seo
authors.forename: Jongchan
authors.initials: J
authors.lastname: Song
authors.forename: Jung Ki
authors.initials: JK
authors.lastname: Park
authors.forename: Hyunsoo
authors.initials: H
authors.lastname: Lee
authors.forename: Jeong Young
authors.initials: JY
authors.lastname: Park
authors.forename: Hyotcherl
authors.initials: H
authors.lastname: Ihee
authors.forename: Sung June
authors.initials: SJ
authors.lastname: Cho
authors.forename: Ryong
authors.initials: R
authors.lastname: Ryoo