Graphyne-based two-dimensional (2D) carbon allotropes feature extraordinary physical properties; however, their synthesis as crystalline single-layered materials has remained challenging. We report on the fabrication of large-area organometallic Ag−bis-acetylide networks and their structural and electronic properties on Ag(111) using low-temperature scanning tunneling microscopy combined with density functional theory (DFT) calculations. The metalated graphyne-based networks are robust at room temperature and assembled in a bottom-up approach via surface-assisted dehalogenative homocoupling of terminal alkynyl bromides. Large-area networks of several hundred nanometers with topological defects at domain boundaries are obtained due to the Ag–acetylide bonds’ reversible nature. The thermodynamically controlled growth mechanism is explained through the direct observation of intermediates, which differ on Ag(111) and Au(111). Scanning tunneling spectroscopy resolved unoccupied states delocalized across the network. The energy of these states can be shifted locally by the attachment of a different number of Br atoms within the network. DFT revealed that free-standing metal−bis-acetylide networks are semimetals with a linear band dispersion around several high-symmetry points, which suggest the presence of Weyl points. These results demonstrate that the organometallic Ag−bis-acetylide networks feature the typical 2D material properties, which make them of great interest for fundamental studies and electronic materials in devices.

中文翻译：

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基于金属石墨烯的网络作为二维材料：结晶，拓扑缺陷，离域电子态和特定于位置的掺杂

基于石墨烯的二维（2D）碳同素异形体具有非凡的物理特性；然而，它们作为晶体单层材料的合成仍然具有挑战性。我们报告使用低温扫描隧道显微镜结合密度泛函理论（DFT）计算的大面积有机金属Ag-双乙炔网络的制造及其在Ag（111）上的结构和电子性能。基于金属化石墨烯的网络在室温下很坚固，并通过自下而上的方法通过末端炔基溴化物的表面辅助脱卤均偶联。由于银乙炔键的可逆性质，获得了具有纳米结构域边界缺陷的数百纳米大面积网络。通过对中间体的直接观察来解释热力学控制的生长机理，这些中间体在Ag（111）和Au（111）上有所不同。扫描隧道光谱学解决了在网络上散布的未占用状态。这些状态的能量可以通过网络中不同数量的Br原子的附着而局部移动。DFT显示，独立的金属双乙炔化物网络是半金属，在几个高对称点周围呈线性带状色散，表明存在Weyl点。