Key Takeaways
- Researchers at Chiba University developed a new material called viciazites, optimizing nitrogen atom positions for better carbon capture efficiency.
- Viciazites use adjacent nitrogen pairs to capture CO2 at lower temperatures, significantly reducing energy costs compared to traditional methods.
- Testing showed that adjacent NH2 and pyrrolic nitrogen variants perform well in CO2 uptake and desorption, with potential applications in low-temperature industrial settings.
- The study emphasizes the importance of precision in nitrogen doping, challenging previous assumptions about control at the atomic level.
- Further testing is needed to assess durability and performance in realistic industrial conditions, as the materials exhibited varying stability.
Two nitrogen atoms, sitting next to each other on the jagged edge of a carbon surface. That arrangement, which sounds almost comically simple, turns out to govern whether a carbon capture material needs water close to boiling to regenerate, or can release everything it has caught at temperatures a factory already throws away as waste. The difference between those two scenarios is roughly the difference between carbon capture that is economically marginal and carbon capture that might actually scale. A team of researchers at Chiba University in Japan has spent years working out how to put nitrogen atoms precisely where they need to go, and their answer, published in the journal Carbon in February 2026, is a new category of designed material they have named viciazites.
Carbon capture has been around long enough that its limitations are well understood. The most common industrial method involves passing flue gases through an aqueous amine solution, which grabs carbon dioxide and holds it until the liquid is heated above 100 degrees Celsius to drive the gas back out and reset the system. That heating step is expensive. It consumes energy proportional to the amount of liquid involved, and industrial operations involve a lot of liquid. Solid carbon-based adsorbents are, broadly speaking, a cheaper and less energy-intensive alternative: the material binds CO2 without requiring large volumes of solvent, and it can be regenerated with less heat. The problem is that nobody has been entirely sure why some configurations of nitrogen-doped carbon work better than others, because standard synthesis methods deposit nitrogen groups randomly, making it hard to isolate which arrangement is actually doing the useful chemistry.
That is the specific problem Yasuhiro Yamada and Tomonori Ohba set out to solve. Both associate professors at Chiba University, they approached it by finding ways to introduce nitrogen groups into carbon materials not randomly but next to each other, in controlled adjacent pairs. The word “viciazite” is their coinage for this new class of material: “vici” from the Latin for adjacent, “azite” from nitrogen-containing carbon material. There are three distinct variants, each carrying a different type of adjacent nitrogen pairing: primary amine groups (NH2), pyrrolic nitrogen, and pyridinic nitrogen.
When two nitrogen atoms sit next to each other on the carbon edge, they can interact with a captured CO2 molecule from two directions at once, forming a more efficient bond that is still easy enough to break at low temperatures. Nitrogen atoms scattered randomly across the surface work less cooperatively, either grabbing CO2 too weakly to be useful or too strongly to release without significant heating. The geometry, in other words, determines the energy cost of the whole cycle.
The Chiba team tested their material against air at realistic CO2 concentrations and found it did capture meaningful amounts, even in the presence of nitrogen, oxygen, and moisture. That is an encouraging result, though dilute-stream capture at atmospheric CO2 levels is considerably harder than capturing from concentrated industrial flue gas. The low regeneration temperature, potentially achievable using waste heat alone, is the property that would matter most for making the economics work at scale.
The main problem is the energy required to regenerate them. Aqueous amine systems require heating large volumes of liquid above 100 degrees Celsius to drive captured CO2 back out, and the energy cost of that step is a major reason carbon capture has remained expensive. Solid adsorbents like viciazites sidestep the liquid volume problem entirely, and the adjacent NH2 variant releases its CO2 at temperatures below 60 degrees Celsius, which potentially means using heat that an industrial facility would otherwise vent as waste.
That remains an open question. Accelerated moisture testing showed that the adjacent pyrrolic nitrogen variant lost roughly 38 percent of its nitrogen content after soaking in hot water, while the adjacent NH2 material lost about 30 percent. The amine groups appear more stable, partly because they are embedded within micropores where water access is limited. Long-term performance under repeated cycling and variable gas conditions has not yet been tested, which is one of the main gaps between this laboratory result and any industrial application.
Building each variant required a different route. The most consequential, the adjacent NH2 version, began with a polycyclic hydrocarbon called coronene, which was carbonised at high temperature, then treated with bromine to introduce reactive leaving groups at specific edge positions, then exposed to ammonia gas at 723 Kelvin to substitute those bromine atoms with primary amine groups. The selectivity achieved at that temperature was 76 percent, meaning roughly three quarters of the introduced nitrogen ended up as adjacent NH2 pairs rather than other configurations. Computational simulations using a reactive force field confirmed why: the particular edge geometry of carbonised coronene, a type called DUO, is energetically favorable for stabilising two adjacent NH2 groups, minimising steric conflict between them. The other two variants followed different precursors; adjacent pyrrolic nitrogen was obtained at 82 percent selectivity from a compound called 11,12-dihydroindolo[2,3-a]carbazole, and adjacent pyridinic nitrogen at 60 percent selectivity from 1,10-phenanthroline.
All three materials were coated onto activated carbon fibers to produce practical adsorbent samples. The researchers then characterised each using nuclear magnetic resonance spectroscopy, X-ray photoelectron spectroscopy, and infrared analysis, confirming that the nitrogen groups were genuinely adjacent and not scattered. This was not a trivial step: the whole point of the exercise is controlling atomic position, so demonstrating that control was established matters as much as the performance data that follows it.
The performance data is, on the whole, quite striking. Materials carrying adjacent NH2 groups and adjacent pyrrolic nitrogen both outperformed untreated carbon fibers in CO2 uptake across a range of temperatures. Adjacent pyridinic nitrogen, by contrast, showed almost no benefit; pyridinic groups lack the N-H bonds that allow the other two types to form hydrogen bonds with adsorbed CO2. The more dramatic result, though, concerns desorption, which is the step where energy costs are actually incurred. For the adjacent NH2 material, most of the captured CO2 released at temperatures below 333 Kelvin, which is 60 degrees Celsius. For adjacent pyrrolic nitrogen, the corresponding temperature was 363 Kelvin. Those numbers may sound abstract, but 333 Kelvin sits well within the range of waste heat that large industrial facilities routinely generate and currently cannot put to productive use.
Yamada has noted that “by combining this property with industrial waste heat, it may be possible to achieve efficient CO2 capture processes with substantially reduced operating costs.” That framing is deliberately cautious, and probably right to be; the gap between laboratory demonstration and industrial deployment is not small, and the paper itself acknowledges it. The viciazites were tested under controlled conditions, not exposed to the variable gas mixtures, humidity swings, and contamination that characterise real flue gases. Accelerated moisture testing, which involved soaking samples in hot water at 353 Kelvin for five hours, revealed that adjacent pyrrolic nitrogen is more susceptible to hydrolysis than adjacent NH2, with nitrogen content dropping by about 38 percent compared to roughly 30 percent for the amine material. That’s not a disqualifying result, but it suggests the two variants have different long-term durability profiles that would need to be weighed against their respective performance advantages.
There is also the question of what the material can do beyond a pure CO2 atmosphere. The team ran a separate experiment using compressed air at realistic CO2 concentrations (350 parts per million, in the presence of nitrogen, oxygen, and moisture) and found that both the adjacent NH2 and adjacent pyrrolic nitrogen materials still captured meaningful amounts of CO2 and released most of it below 373 Kelvin. The selectivity for CO2 over nitrogen in real air is imperfect but evident, which at least suggests that dilute-stream capture is not entirely out of reach for this class of material.
The broader significance of the viciazite work is arguably as much about methodology as materials. Carbon-based adsorbents are not new, and the general utility of nitrogen doping has been known for years. What has been harder to establish is which specific nitrogen configurations are responsible for which specific effects, because you cannot learn much from a mixture. By developing routes to high-selectivity introduction of defined adjacent pairs, Yamada’s group has produced something closer to a controlled experiment than most previous work in this area: three materials with genuinely distinct structures that can be compared on a level footing. The hierarchy that emerges, adjacent NH2 outperforming adjacent pyrrolic nitrogen outperforming adjacent pyridinic nitrogen for low-temperature desorption, now has experimental grounding that earlier studies, working with poorly characterised mixtures, could not provide.
The Chiba team suggests that viciazites may prove useful beyond CO2 capture, perhaps as adsorbents for metal ions or as catalysts, given the precision of their surface chemistry. That is speculative at this stage, but not unreasonably so. The more immediate interest is whether the low-temperature desorption property holds up under the conditions that matter industrially, and whether the synthesis routes can be scaled without losing the selectivity that makes them useful. The 76 percent selectivity for adjacent NH2, achieved without any catalyst, is already competitive with the best previously reported figures in the literature. Whether that is good enough for an industrial process is a different question, and one that will take considerably more work to answer.
What the viciazites do, at minimum, is reframe what precision means in this field. For decades the assumption has been that controlling nitrogen doping at the atomic level was either not necessary or not achievable. The Chiba group has done something awkward to that assumption: demonstrated that both were wrong.
DOI / Source: 10.1016/j.carbon.2026.121405
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