Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template
Lanthanum-catalysed synthesis of microporous 3D graphene-like carbons in a zeolite template
复制标题
DOI：
10.1038/nature18284
复制
发表时间：
2016-07-07
期刊：
影响因子：
64.8
通讯作者：
Ryoo, Ryong
中科院分区：
文献类型：
--
作者：
Kim, Kyoungsoo;Lee, Taekyoung;Ryoo, Ryong
具有周期性纳米孔的三维石墨烯结构——让人联想到沸石框架——由于将石墨烯的特性与三维多孔结构相结合的可能性而备受关注（1-6）。最近，用沸石作为模板和可以进入窄孔的小碳氢化合物分子来合成这种碳（7-15）。然而，碳氢化合物的热解碳化（生成纯碳的必要步骤）需要高温，并导致孔隙外的非选择性碳沉积。在这里，我们证明了嵌入在沸石孔中的镧离子可以降低乙烯或乙炔碳化所需的温度。通过这种方式，可以选择性地在沸石模板内部形成类似石墨烯的碳结构，而不会在外表面沉积碳。碳化后的沸石单晶x射线衍射数据表明，沿沸石孔壁产生了与碳原子相对应的电子密度。除去沸石模板后，碳骨架的电导率比非晶介孔碳高出两个数量级。镧催化可以使碳骨架在直径小于1纳米的沸石孔中形成；因此，微孔碳纳米结构可以与不同的沸石孔径和形状相对应，具有不同的拓扑结构。我们展示了大孔沸石（FAU， EMT和beta），一维中孔沸石（LTL），甚至小孔沸石（MFI和LTA）的碳合成。催化作用是镧、钇和钙的共同特征，它们都是形成碳化物的金属元素。我们还表明，合成可以很容易地扩大规模，这将是重要的实际应用，如生产锂离子电池和沸石样催化剂载体。
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(1-6). 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(7-15). 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 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.