By carefully controlling how nitrogen atoms are arranged, scientists have found certain structures capture CO2 better and release it using far less heat.
One version works at temperatures below 60 °C, meaning it could run on waste heat instead of costly energy. The discovery offers a powerful new blueprint for next-generation climate technology.
Stopping carbon dioxide (CO2) before it enters the atmosphere is a critical way to cut greenhouse gas emissions. While carbon capture has been around for many years, it has not been widely adopted because most systems are costly and inefficient.
A common industrial approach, aqueous amine scrubbing, requires heating large amounts of liquid to temperatures above 100°C to release the captured CO2 and reuse the solution. This high energy demand drives up operating costs and makes large-scale use difficult.
Solid carbon materials have gained attention as a more practical option. These materials are relatively inexpensive and have a large surface area that allows them to trap CO2.
They can also release the gas using less heat, especially when they contain nitrogen-based functional groups.
However, there has been a key limitation. Traditional manufacturing methods place these nitrogen groups randomly across the material, making it hard to pinpoint which specific arrangements lead to better performance.
To address this challenge, a research team led by Associate Professor Yasuhiro Yamada and Associate Professor Tomonori Ohba at Chiba University, Japan, developed a new type of carbon material called 'viciazites’.
These materials are designed with nitrogen groups positioned next to each other in a controlled way.
Building viciazites with controlled nitrogen pairing
The researchers created three different versions of viciazites, each with a unique type of neighbouring nitrogen configuration.
To produce adjacent primary amine groups (-NH2 groups), they first heated a compound called coronene, then treated it with bromine, followed by ammonia gas.
This three-step method achieved 76 per cent selectivity, meaning most of the nitrogen atoms were placed in the intended positions.
Two additional materials were produced using different starting compounds. One featured adjacent pyrrolic nitrogen with 82 per cent selectivity, while the other contained adjacent pyridinic nitrogen with 60 per cent selectivity.
Verifying structure and testing performance
Each material was applied to activated carbon fibres to create usable samples. The team confirmed the precise placement of nitrogen groups using techniques such as nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and computational modelling.
These methods verified that the nitrogen atoms were positioned side by side rather than randomly distributed.
When tested, the materials showed clear performance differences. Samples with adjacent -NH2 groups and pyrrolic nitrogen captured more CO2 than untreated carbon fibres. In contrast, the pyridinic nitrogen configuration offered little improvement.
Low-temperature CO2 release could cut energy use
The most notable finding involved how easily the materials released CO2. "Performance evaluation revealed that in carbon materials where NH2 groups are introduced adjacently, most of the adsorbed CO2 desorbs at temperatures below 60°C,” highlights Dr Yamada.
“By combining this property with industrial waste heat, it may be possible to achieve efficient CO2 capture processes with substantially reduced operating costs.”
The material containing pyrrolic nitrogen required higher temperatures to release CO2, but it may offer better long-term stability due to its stronger chemical structure.
A new path toward cost-effective carbon capture
This work shows that arranging nitrogen groups in specific adjacent patterns can be done reliably, providing a clear strategy for designing improved carbon capture materials.
"Our motivation is to contribute to the future society and to utilise our recently developed carbon materials with controlled structures,” concludes Dr Yamada.
“This work provides validated pathways to synthesise designer nitrogen-doped carbon materials, offering the molecular-level control essential for developing next-generation, cost-effective, and advanced CO2 capture technologies.”
Beyond capturing CO2, these viciazite materials could also be used for other applications, including removing metal ions or serving as catalysts, thanks to their customisable surface properties.