Scientists Discover a New Cousin of Diamond That Was Thought To Exist Only in Theory

A shimmering diamond represents one of carbon’s most familiar forms. Scientists have now created a new, porous, diamond-like structure that reveals another surprising way carbon atoms can arrange themselves.
Diamond and graphite have a new carbon cousin called diamondiyne, with a crystal structure confirmed so far only in microscopic patches.
A carbon structure proposed 35 years ago has finally taken shape in a thin film where two liquids meet. Using relatively inexpensive equipment, researchers at the University of Gothenburg have created diamondiyne for the first time, adding a new three-dimensional structure to the forms carbon can take.
Diamondiyne is a carbon allotrope, a form of the element distinguished by how its atoms are arranged. Diamond and graphite are familiar examples. To create diamondiyne, the researchers joined carbon atoms through triple bonds. The material crystallizes into a network of tetrahedra, shapes with four triangular faces, connected corner to corner in all three dimensions.

“The structure creates voids between the tetrahedra. The carbon allotrope can therefore be compared to a porous diamond. But unlike diamonds, diamondiyne does not require high pressure to make the carbon atoms bond to one another,” says Karl Börjesson, professor of physical chemistry at the University of Gothenburg, who leads the research team.

Crystal patterns confirmed in tiny patches

Electron microscopy at Stockholm University confirmed the crystal structure, although only in patches on the film’s surface. Many things can go wrong during formation and prevent the carbon atoms from assembling into diamondiyne.
“We have at least managed to produce repeating patterns of diamondiyne in a volume measuring 10 nanometers on each side, 10 × 10⁻⁹ meters, and the images of the patterns correspond well with the theoretical models,” says Börjesson.

Carbon frameworks without metal ions

The discovery grew out of the team’s longstanding effort to create porous materials in which carbon-based molecules bind together without metal ions. These materials are called covalent organic frameworks, or COFs. They differ from metal-organic frameworks, or MOFs, which combine carbon-based molecules with metal ions and whose development earned the 2025 Nobel Prize in Chemistry.

A colleague told Börjesson about a website where theoretical chemists had compiled an almost endless list of carbon allotropes that should be possible to create. Diamondiyne’s tetrahedral structure had been described theoretically decades before the team succeeded in making it.
“It has taken us an incredibly long time, but we finally succeeded. I am very pleased,” says Börjesson.

For many years, known carbon allotropes were limited to diamond, graphite, and three artificially produced forms: fullerenes, carbon nanotubes, and graphene. The development of fullerenes and graphene was recognized with Nobel Prizes, largely because the idea that these materials could exist was itself new. Researchers have created many additional allotropes in recent years, with diamondiyne the first of this newer group to have a three-dimensional structure.

“We will now investigate the properties of diamondiyne and how it might be used. One exciting aspect of the porous structure is that several diamondiyne structures could potentially be interwoven through each other’s voids,” says Börjesson.