Biphenylene network zipped together

In the world of flat carbon allotropes, graphene gets most of the attention. But there are other ways of assembling sp²-hydridized carbon frameworks; they’re just challenging because of this type of carbon’s tendency to form benzenoids, structures formed exclusively from benzene rings. Scientists led by J. Michael Gottfried of Philipps University of Marburg and Peter Liljeroth of Aalto University, now report the synthesis of a biphenylene network—a planar structure composed of sp²-hybridized carbons in 4-, 6-, and 8-membered rings (Science 2021, DOI: 10.1126/science.abg4509). The researchers created the biphenylene network (shown) by zipping together strings of 2,5-difluoro-para-phenylene on a gold surface using a dehydrofluorination reaction. This hydrogen-fluorine (HF)-zipping strategy, they note, could be used to assemble other nonbenzenoid carbon allotropes. Theoreticians had disagreed about the possible properties of a biphenylene network: some argued that it would be metallic, while others postulated it would be dielectric. Scanning probe studies of the allotrope indicate that it is metallic. This means that it could be used to make wires for carbon-based circuits in the future, the scientists say.