Professor Sarah S. Park's team at KAIST in Daejeon has cracked a problem that has stumped materials scientists for decades: how to keep two-dimensional conductors performing at their best when you stack them together. The answer lies in a simple but elegant twist—literally.
For years, two-dimensional materials have seemed like a miracle waiting to happen. Atomically thin—thinner than a single sheet of paper—these materials let electrons move at ultrahigh speeds, making them ideal candidates for next-generation semiconductors and quantum computers. But there was a catch. The moment you stacked multiple layers together for practical applications, the performance collapsed. Interlayer interactions would obstruct electron movement, like cars suddenly hitting traffic congestion when speeding along separate roads finally intersect.
Two-dimensional conductive metal-organic frameworks, or MOFs, were particularly frustrating. In their single-layer state, they showed outstanding promise. But stack them up, and their electronic properties weakened dramatically. It seemed impossible to get the best of both worlds: the performance of a single layer with the practicality of bulk material.
Park's team, working with collaborator Christopher H. Hendon from the University of Oregon, focused on one key insight: the angle of alignment. Rather than letting layers sit perfectly flat against each other, they designed a structure where each layer would be arranged at a specific angle, minimizing direct face-to-face contact. The principle is simple—imagine stacking a deck of cards with a slight twist rather than aligning them perfectly. The cards don't stick together; interference vanishes.
To achieve this structure, the researchers designed a triptycene-based molecule and used it to synthesize a new material they named Ni3(HITrip)2. The results, published in the Journal of the American Chemical Society, were striking. The material preserved an electronic structure highly similar to a single layer, even when arranged in multiple layers. Crucially, it retained a unique electronic structure known as the Dirac band structure of a Kagome lattice—a configuration that allows electrons to move rapidly and efficiently, as if traveling on a frictionless highway without obstacles.
The real proof came in the numbers. Ni3(HITrip)2 exhibited electrical conductivity of 0.58 S/cm without any additional doping—the process of introducing impurities to boost performance. This demonstrated that exceptional electrical properties could be maintained while eliminating interlayer interference. Through computational modeling and spectroscopic analysis, the team confirmed the mechanism at work: molecules and metal atoms within the material cooperate to facilitate electron transport, creating a stable environment for movement.
The implications ripple outward from this Daejeon laboratory. This finding resolves a decades-old fundamental challenge that has blocked the path from laboratory discovery to commercial application. By proving that superior electronic properties previously locked into single layers can now be realized in bulk materials, the work opens new doors. Researchers anticipate widespread applications in high-performance electronic devices and next-generation energy materials. Perhaps more significantly, this breakthrough creates new possibilities for quantum materials and topological materials—next-generation functional materials with unique electron transport properties—pointing toward advances in future semiconductor and quantum information technologies.