•A general strategy for synthesizing negatively curved molecular nanocarbons •Remarkably curved π-backbones containing multiple heptagons •π-Backbones interlocked through both edge-to-face and face-to-face π-π interactions Embedding heptagons in polycyclic aromatic frameworks gives rise to negatively curved molecular nanocarbons, which not only are key fragments of long-sought-after carbon schwarzites but also bring new opportunities to explore unprecedented nanocarbons with interesting properties. This study demonstrates the Scholl reactions of macrocyclic precursors as a general strategy for synthesizing negatively curved molecular nanocarbons containing different numbers of heptagons. The π-backbones containing multiple heptagons are significantly curved and rigid, as revealed by density functional theory calculations and X-ray crystallography. Some of these negatively curved π-backbones are interlocked through both face-to-face and edge-to-face π-π interactions in the crystals. Such unusual π-π interactions have enabled a p-type organic semiconductor, although its hole mobility in the field effect transistors is limited by the amorphous nature of the vacuum-deposited films. Embedding heptagons in polycyclic aromatic frameworks gives rise to negatively curved molecular nanocarbons, which not only are key fragments of long-sought-after carbon schwarzites but also bring new opportunities to explore unprecedented nanocarbons with interesting properties. This study demonstrates the Scholl reactions of macrocyclic precursors as a general strategy for synthesizing negatively curved molecular nanocarbons containing different numbers of heptagons. The π-backbones containing multiple heptagons are significantly curved and rigid, as revealed by density functional theory calculations and X-ray crystallography. Some of these negatively curved π-backbones are interlocked through both face-to-face and edge-to-face π-π interactions in the crystals. Such unusual π-π interactions have enabled a p-type organic semiconductor, although its hole mobility in the field effect transistors is limited by the amorphous nature of the vacuum-deposited films.