Scientists Create 'Cage of Cages' Material to Trap Greenhouse Gases

Researchers in the United Kingdom and China have synthesized a new material with an unusual molecular architecture—what they call a 'cage of cages'—that shows promise for trapping two of the most damaging greenhouse gases. The material is built in two steps: simple triangular prism structures assemble themselves into larger, symmetrical tetrahedral cages, creating the first molecular structure of its kind, according to the team's claims. What makes it effective is the abundance of polar molecules throughout its porous structure, which attract and hold carbon dioxide and other gases with strong affinity. The material also proved stable in water, a critical property for industrial use where gases are often wet or humid.

Marc Little, a materials scientist at Heriot-Watt University in Edinburgh and senior author of the study, called it an exciting discovery because the world needs new porous materials to address major challenges like capturing and storing greenhouse gases. In laboratory experiments, the cage material showed high uptake of sulfur hexafluoride, a gas far more destructive than carbon dioxide. While CO2 persists in the atmosphere for 5 to 200 years, sulfur hexafluoride lingers for 800 to 3,200 years. Although atmospheric concentrations of sulfur hexafluoride are much lower than CO2, its extreme longevity gives it a global warming potential roughly 23,500 times greater than carbon dioxide when measured over a century.

The scale of the problem the material might help address is staggering. Scientists estimate that removing around 20 billion tons of CO2 annually would be necessary to offset current emissions, which continue to rise. Today, carbon removal strategies extract about 2 billion tons per year, but the vast majority of that comes from natural processes—trees and soils doing what they have always done. Only about 0.1 percent of carbon removal, approximately 2.3 million tons yearly, comes from new technologies like direct air capture, which uses porous materials to pull CO2 directly from the air. The new cage material could potentially improve the efficiency and reduce the energy demands of these emerging technologies, though it has not yet been tested at industrial scale.

Creating a material with such intricate molecular complexity required careful work. The researchers used a strategy called supramolecular self-assembly, where simpler building blocks chemically interlock to form more complex structures. The challenge lies in finding the right reaction conditions—what works is often not obvious. The more complex the final molecule, the harder it becomes to synthesize, and unwanted molecular scrambling can occur during reactions. To navigate these invisible molecular interactions, the team used computer simulations to predict how their starter molecules would assemble into the new porous material, considering the geometry of precursor molecules and the chemical stability and rigidity of the final product.

Beyond capturing greenhouse gases, the researchers suggest the material could remove other toxic fumes from air, including volatile organic compounds that easily vaporize from surfaces like the interiors of new cars. Little emphasized that the study represents an important step toward unlocking such applications in the future. The work was published in Nature Synthesis. While the material shows genuine promise in the laboratory, the gap between what it can do on a bench and what it might accomplish at scale remains wide. To avert the worst impacts of climate change, emissions reductions must accelerate faster than these nascent technologies currently allow. Nevertheless, researchers are pursuing every avenue available, and this new material represents one more tool in an urgent effort to slow atmospheric warming.