Bilayer nanographene reveals halide permeation through a benzene hole

Supplemental data to report https://doi.org/10.1038/s41586-024-08299-8:

Graphene is a single-layered sp2-hybridized carbon allotrope, which is impermeable to all atomic entities other than hydrogen. The introduction of defects allows selective gas permeation; efforts have been made to control the size of these defects for higher selectivity. Permeation of entities other than gases, such as ions, is of fundamental scientific interest because of its potential application in desalination, detection and purification. However, a precise experimental observation of halide permeation has so far remained unknown. Here we show halide permeation through a single benzene-sized defect in a molecular nanographene. Using supramolecular principles of self-aggregation, we created a stable bilayer of the nanographene. As the cavity in the bilayer nanographene could be accessed only by two angstrom-sized windows, any halide that gets trapped inside the cavity has to permeate through the single benzene hole. Our experiments reveal the permeability of fluoride, chloride and bromide through a single benzene hole, whereas iodide is impermeable. Evidence for high permeation of chloride across single-layer nanographene and selective halide binding in a bilayer nanographene provides promise for the use of single benzene defects in graphene for artificial halide receptors, as filtration membranes and further to create multilayer artificial chloride channels.

用于补充报道https://doi.org/10.1038/s41586-024-08299-8的补充数据：
石墨烯（graphene）是一种单层sp²杂化碳同素异形体，除氢气外可阻隔所有原子实体。引入缺陷可实现选择性气体渗透；学界已开展诸多工作以调控此类缺陷的尺寸，从而获得更高的渗透选择性。除气体外的其他实体（如离子）的渗透行为具有重要的基础科学研究价值，因其在海水淡化、检测与纯化领域存在潜在应用前景。然而，截至目前，学界尚未实现对卤化物渗透过程的精准实验观测。本研究通过分子纳米石墨烯（molecular nanographene）中单个苯环尺寸的缺陷，实现了卤化物渗透行为的观测。我们借助自聚集的超分子原理，构建了稳定的纳米石墨烯双层结构。由于该纳米石墨烯双层的空腔仅能通过两个埃级尺寸的窗口进行存取，因此被困于空腔内的卤化物必须穿过单个苯环孔洞才能完成渗透。实验结果表明，氟离子、氯离子与溴离子可通过单个苯环孔洞实现渗透，而碘离子则无法渗透。单层纳米石墨烯对氯离子的高渗透特性，以及双层纳米石墨烯对卤化物的选择性结合特性，为利用石墨烯中的单个苯环缺陷构建人工卤化物受体、过滤膜，乃至进一步开发多层人工氯离子通道提供了可行性依据。