On-surface synthesis has revealed remarkable potential in the fabrication of atomically precise nanographenes. However, surface-assisted synthesis often involves multiple-step cascade reactions with competing pathways, leading to a limited yield of target nanographene products. Here, we devise a strategy for the ultrahigh-yield synthesis of circumcoronene molecules on Cu(111) via surface-assisted intramolecular dehydrogenation of the rationally designed precursor, followed by methyl radical-radical coupling and aromatization. An elegant electrostatic interaction between circumcoronenes and metallic surface drives their self-organization into an extended superlattice, as revealed by bond-resolved scanning probe microscopy measurements. Density functional theory and tight-binding calculations reveal that unique hexagonal zigzag topology of circumcoronenes, along with their periodic electrostatic landscape, confines two-dimensional electron gas in Cu(111) into a chiral electronic Kagome-honeycomb lattice with two emergent electronic flat bands. Our findings open up a new route for the high-yield fabrication of elusive nanographenes with zigzag topologies and their superlattices with possible nontrivial electronic properties.

表面合成已显示出在制造原子精确的纳米石墨烯方面的巨大潜力。然而，表面辅助合成通常涉及具有竞争性途径的多步级联反应，导致目标纳米石墨烯产物的产量有限。在这里，我们设计了一种策略，用于通过合理设计的前体的表面辅助分子内脱氢，然后进行甲基自由基-自由基偶联和芳构化，在Cu（111）上超高产率合成环丁烯分子。正如键分辨扫描探针显微镜测量所揭示的，环酮与金属表面之间的优雅的静电相互作用驱使它们的自组织成扩展的超晶格。密度泛函理论和紧密结合计算表明，环己烯酮的独特六边形之字形拓扑结构及其周期性的静电态势将Cu（111）中的二维电子气限制为具有两个出现的电子平带的手性电子Kagome-蜂窝状晶格。我们的发现为具有锯齿形拓扑结构及其超晶格（可能具有非平凡的电子特性）的高产量纳米石墨烯的制备开辟了一条新途径。