The significance of the achievement lies in the chemistry it replaces. Conventional polyurethanes, found in everything from furniture foam to automotive clearcoats, are formed when isocyanates react with polyols. Isocyanates are potent respiratory sensitizers, and their production depends on the equally hazardous and fossil-derived phosgene. NIPU chemistry sidesteps both hazards by coupling cyclic carbonates with amines, a polyaddition reaction that produces polyhydroxyurethanes bearing hydroxyl groups along the backbone. Those pendant hydroxyls form additional hydrogen bonds, which can enhance adhesion and cohesion, but the field has struggled to match the mechanical performance of conventional systems, particularly in crosslinked coatings.

The Turkish team’s strategy began with two complementary bio-based epoxides. The first was epoxidized linseed oil, a triglyceride derived from flax seeds whose long, flexible fatty acid chains are prized for imparting elasticity. The second was Cardolite NC514S, a cardanol-based epoxy derived from cashew nut shell liquid, an agricultural byproduct rich in phenolic lipids. Cardanol brings a rigid aromatic structure and a long C15 alkyl side chain, a combination that can simultaneously stiffen a network and provide hydrophobic character. By converting both epoxides into cyclic carbonates and then blending them in varying ratios, the researchers created a tunable platform in which flexibility and rigidity could be dialled in at will.

The conversion of epoxide to cyclic carbonate is where the carbon dioxide enters the story. The researchers bubbled CO2 through the epoxidized oils in the presence of tetrabutylammonium bromide, a quaternary ammonium salt that catalyzes the insertion of carbon dioxide into the strained epoxide rings. Each epoxide ring thus becomes a five-membered cyclic carbonate, chemically locking atmospheric carbon into the monomer itself. This CO2 fixation step, performed catalytically and without solvents, transforms a greenhouse gas into a structural building block, a strategy that aligns with the broader push toward carbon capture and utilization across the chemical industry.

With the cyclic carbonates in hand, the team carried out a solvent-free polyaddition with Priamine 1071, a renewable diamine derived from dimerized fatty acids. The amine groups ring-open the carbonate rings, forming urethane linkages and generating secondary hydroxyls that hydrogen-bond throughout the growing network. Because both the carbonate monomers and the diamine hardener are bio-based, the resulting thermoset coatings are fully renewable in origin. The crosslinking reaction proceeds without added catalysts or volatile solvents, an important consideration for coatings manufacturers seeking to reduce volatile organic compound emissions and simplify regulatory compliance.

To verify that the networks had formed properly, the researchers measured gel content, the fraction of the material insoluble in a good solvent, which serves as a proxy for crosslink density. The hybrid coatings achieved gel fractions of 83 to 85 percent, remarkably consistent across the range of linseed-to-cardanol ratios tested. This indicated that well-developed three-dimensional networks formed regardless of formulation, giving manufacturers a wide processing window. The consistency suggests that the two carbonated monomers, despite their very different architectures, participate cooperatively in the amine-carbonate reaction rather than one dominating the cure chemistry.

Thermal analysis told an encouraging story about durability. Thermogravimetric experiments showed a single-step degradation profile between 300 and 500 degrees Celsius, with degradation onset and mid-point temperatures spanning 270 to 455 degrees Celsius depending on composition. For coatings that must survive baking ovens, sunlight, and abrasive service, this level of thermal robustness is competitive with petrochemical benchmarks. The char yields were low, between 0.22 and 0.31 percent, which the authors attributed to residual inorganic components from the catalyst rather than to the polymer itself. Differential scanning calorimetry revealed glass transition temperatures rising from minus 17.2 to minus 11.2 degrees Celsius as the cardanol content increased, confirming that the aromatic cardanol segments stiffen the network even in these elastomeric formulations.

Mechanical testing showed the trade-offs the formulation ratio makes possible. As the cardanol-derived carbonate fraction grew, the elastic modulus climbed from 0.26 to 0.39 megapascals and yield strength rose from 0.31 to 0.42 megapascals, while toughness improved from 24.6 to 29.3 joules. Elongation at break decreased moderately, as expected when rigid aromatic units replace flexible fatty acid chains. In practical terms, the linseed-rich formulations behave as soft, extensible films suited to substrates that flex, while cardanol-rich versions deliver harder, stronger, and tougher coatings for demanding protective applications. The ability to engineer this spectrum from just two renewable monomers is precisely what industrial formulators need.

Surface performance, the ultimate test for any coating, proved equally compelling. Water contact angles between 72 and 88 degrees indicated moderately hydrophilic surfaces, while gloss values exceeding 100 gloss units signaled the smooth, mirror-like finishes demanded by architectural and consumer products. Hardness and adhesion both improved with cardanol content, and in accelerated salt-spray corrosion testing the cardanol-rich formulations delivered superior protection of the underlying metal. The long alkyl side chains of cardanol likely contribute to this barrier effect, packing densely at the surface and slowing the ingress of chloride-laden water toward the substrate, a mechanism consistent with cardanol’s established reputation in anticorrosive coating research.

The study, partially funded by the Scientific and Technological Research Council of Türkiye under grant number 222O017, with analytical support from Kordsa Teknik Tekstil, arrives at a moment of intense interest in isocyanate-free polyurethanes. Recent literature has explored NIPUs from carbonated soybean oil, lignin, vanillin, tannins, and terpenes, but few reports combine fully bio-based monomers, solvent-free processing, CO2 utilization, and a complete thermo-mechanical and protective characterization in a single coating platform. By demonstrating that a simple two-monomer blend of carbonated linseed oil and carbonated cardanol can span soft to stiff, elastic to corrosion-resistant, the Marmara University team has provided a practical blueprint for greener coatings. If such systems can be scaled from the laboratory bench to industrial application lines, the humble flax seed and the cashew shell, with a helping of recycled carbon dioxide, may soon be protecting bridges, appliances, and vehicles alike.

Subject of Research: Fully bio-based non-isocyanate polyurethane coatings synthesized from carbonated linseed oil and cardanol

Article Title: Sustainable NIPU coatings based on carbonated linseed oil and cardanol: synthesis and thermo-mechanical performance

Article References: Atılal, E., & Apohan, N. K. (2026). Sustainable NIPU coatings based on carbonated linseed oil and cardanol: synthesis and thermo-mechanical performance. Polymer Bulletin, 83(12), Article 670. https://doi.org/10.1007/s00289-026-06715-9

Image Credits: AI Generated

DOI: 10.1007/s00289-026-06715-9

Keywords: non-isocyanate polyurethane, NIPU, linseed oil, cardanol, cyclic carbonates, CO2 utilization, bio-based polymers, protective coatings, corrosion resistance, thermal stability, green chemistry, solvent-free synthesis

The chemicals at the heart of the work matter far beyond the laboratory. Dimethyl carbonate, or DMC, is a low-toxicity, biodegradable solvent with a growing role as an electrolyte component in lithium-ion batteries, whose demand is rising in step with global electrification. It is also the key intermediate for phosgene-free polycarbonate synthesis. Diphenyl carbonate, or DPC, is the canonical carbonate donor for making polycarbonate from bisphenol-A without the phosgene chemistry that has long plagued the industry with toxicity concerns and chlorinated waste streams. If captured CO2 can be converted into these molecules at scale, hard-to-abate sectors such as cement and steel, whose process emissions are largely unavoidable, would gain one of the few credible pathways toward deep emission reductions.

The research team, led by Namgyu Son and Sukyong Jung of the Research Institute of Industrial Science and Technology together with colleagues from Soulbrain, attacked the problem in two linked stages. In the first, urea itself is made from CO2 and ammonia, and the urea is then reacted with methanol over a zirconium-based catalyst to produce DMC. In the second stage, DMC is transesterified with phenol to make DPC. Both routes share a fundamental thermodynamic obstacle: they generate by-products, ammonia in one case and methanol in the other, that push the reactions backward. The entire process design therefore revolves around reaction-separation coupling, continuously stripping the by-products out of the reaction zone so the equilibrium must keep marching forward.

A crucial and often overlooked discovery concerned the catalyst itself. The researchers prepared zirconium precursors from three different commercial suppliers and found that, after identical drying treatments, the materials evolved into different crystallographic phases. Precursors from two suppliers converged to an amorphous, poorly crystalline Zr(OH)2(NO3)2-like network rich in accessible catalytic sites, achieving roughly 85 to 88 percent conversion in batch tests. A third supplier’s material retained a more highly hydrated crystalline phase and delivered only about 52 percent conversion. The lesson is stark: the hydration state and short-range order of the zirconium precursor, governed by supplier lot and drying history, directly determine catalytic performance, and controlling that drying protocol is essential for reproducible industrial operation.

With the high-activity catalyst in hand, the DMC pilot train ran three continuous campaigns totaling 211 hours. Two shorter campaigns focused on start-up stabilization and operating-window optimization, while the third delivered an extended 150-hour run. The reactors, two jacketed stirred packed vessels in series maintained at roughly 190 degrees Celsius and 3 to 5 bar, converted methyl carbamate intermediate into DMC while venting ammonia continuously. Across all three campaigns the plant produced 570.5 kilograms of DMC from 442.3 kilograms of urea, an overall yield of 85.9 percent relative to the 663.9-kilogram theoretical maximum. Productivity was remarkably consistent, averaging 2.70 kilograms per hour with campaign-to-campaign variation of less than six percent.

The product quality was the showstopper. Gas chromatography confirmed 99.93 percent purity, and the water content of 30 to 50 parts per million sits just above the battery-electrolyte specification but is easily removed by routine drying. Most remarkably, when the pilot DMC was formulated into a 1.2 M LiPF6 electrolyte and cycled 400 times in R2032 coin cells with NCM811 cathodes and graphite anodes at 45 degrees Celsius, capacity retention was 85.1 percent versus 84.9 percent for commercial battery-grade DMC. Coulombic efficiency, impedance, and initial efficiency showed no statistically significant differences. In plain terms, a solvent made from captured carbon dioxide performed indistinguishably from the fossil-derived benchmark in one of the most demanding commercial applications.

The second train tackled an even harder equilibrium problem. In batch testing at 200 degrees Celsius with lead oxide catalyst, phenol and DMC reached only about 45 percent phenol conversion, because the intermediate phenyl methyl carbonate accumulates and the second transesterification step is thermodynamically unfavorable. When the team added continuous methanol removal using a reflux configuration, a single batch test leapt to 86 percent conversion and roughly 85 percent DPC yield. That insight drove the pilot design: a fixed-bed PbO reactor at 195 to 200 degrees Celsius coupled directly to a distillation column that strips methanol overhead while recycled phenol returns to the feed, with a pressure step-down helping vaporize the methanol as it forms.

The DPC pilot then ran for roughly 180 hours of steady production following a 20-hour stabilization period, consuming 180.2 kilograms of phenol and 201.8 kilograms of DMC. Phenol conversion remained essentially quantitative throughout, a direct consequence of feeding phenol as the limiting reactant while continuously removing methanol to pull the equilibrium toward product. The final DPC yield, however, was 32.1 percent of the 204.98-kilogram theoretical limit, with 65.8 kilograms collected including an estimated 10.5 kilograms of in-equipment hold-up. Post-run inspection revealed the culprit: substantial quantities of the intermediate phenyl methyl carbonate and polymeric high-boiling residues trapped within the reactor and piping rather than appearing in the product stream. Recovering and reworking these hold-ups is identified as the clearest lever for yield intensification, alongside stronger methanol-removal driving forces and additional reaction stages dedicated to converting PMC into DPC.

The DPC product itself met polymer-grade requirements. Gas chromatography found no residual DMC and no distinct impurity peaks, and trial polymerization with bisphenol-A yielded polycarbonate with a relative viscosity of at least 0.5, comparable to material made from commercial phosgene-route DPC. A caveat remains on the catalyst: lead oxide is toxic, and although no bed plugging or pressure-drop anomalies occurred during the campaign, polymeric films on catalyst surfaces are known to progressively block active sites over longer horizons. Because in-situ regeneration risks lead leaching and creates hazardous waste streams, the team is already developing low-lead PbO-MgO formulations containing only 5 to 10 percent PbO, and in parallel pursuing entirely lead-free alternatives such as Mo-MgO and other non-toxic metal-oxide and solid-acid systems.

Taken together, the two trains sketch out something approaching a blueprint for sustainable carbonate manufacturing. Stable temperature and pressure profiles, controlled reflux ratios, column pressure drops within target bounds, and closed material balances over hundreds of hours demonstrate that this is not a laboratory curiosity but a technically feasible process architecture. The researchers frame the next phase clearly: integrate the DMC and DPC trains with polycarbonate production to realize a fully non-phosgene CO2-to-DMC-to-DPC-to-PC chain, valorize the ammonia by-product from the DMC route, and extend catalyst lifetimes through lower-toxicity formulations. For a chemical industry searching for practical ways to turn its largest liability into feedstock, this pilot-scale demonstration provides exactly the kind of long-duration, specification-compliant evidence that scale-up decisions demand.

Subject of Research: Pilot-scale continuous production of CO2-derived dimethyl carbonate and diphenyl carbonate via integrated reaction-separation coupling

Article Title: CO₂-to-carbonates via reaction–separation coupling: pilot performance of continuous DMC/DPC

Article References: Son, N., Jung, S., Jung, W., Lee, G. M., Kim, J., Yun, J. C., & Lee, S. H. (2025). CO₂-to-carbonates via reaction–separation coupling: pilot performance of continuous DMC/DPC. Advances in Industrial and Engineering Chemistry, 1(1), Article 39. https://doi.org/10.1007/s44405-025-00039-4

Image Credits: AI Generated

DOI: 10.1007/s44405-025-00039-4

Keywords: carbon capture and utilization, dimethyl carbonate, diphenyl carbonate, urea methanolysis, transesterification, zirconium catalyst, lead oxide catalyst, reactive distillation, lithium-ion battery electrolyte, polycarbonate, pilot plant, non-phosgene process

The answer that MES offers is deceptively simple in concept. A typical system consists of two chambers separated by an ion-exchange membrane. In the anodic compartment, water or organic substrates are oxidized to release electrons. In the cathodic compartment, electroactive microorganisms intercept those electrons either directly from the cathode surface, where they form biofilms, or indirectly via hydrogen gas and redox mediators generated at the electrode. Once inside the cell, the electrons enter microbial metabolism and serve as reducing power for fixing carbon dioxide. Because the microbial catalysts are alive, they replicate themselves, operate under mild near-ambient conditions, and tolerate feedstock variability in a way that expensive metal catalysts cannot. And because microbial metabolism is enormously diverse, MES can in principle reach C3 and longer-chain molecules that remain stubbornly out of reach for conventional electrochemistry.

The contrast with existing CO2 conversion technologies is stark. Thermocatalytic routes such as the Sabatier reaction and reverse water-gas shift chemistry require high temperatures, high-purity hydrogen as a reductant, and durable metal catalysts that suffer from carbon deposition and poisoning. Electrochemical CO2 reduction on copper and other catalysts can make carbon monoxide, formate, and C2 products under ambient conditions, but selectivity for C3 and more complex molecules remains poor, catalysts deactivate, and long-term stability is inadequate. Meanwhile, green hydrogen produced by water electrolysis currently costs between 4.5 and 6.0 US dollars per kilogram, meaning that simply reducing CO2 with hydrogen often yields chemicals worth less than the hydrogen consumed. Microbial catalysts sidestep many of these constraints, using self-assembled enzymatic pathways such as the Wood-Ljungdahl route to weave carbon dioxide into multi-carbon products with remarkable specificity.

The performance numbers reported in recent studies are striking. Acetate, the workhorse product of MES, is routinely produced with coulombic efficiencies exceeding 90 percent, meaning that more than nine out of every ten electrons supplied by the circuit end up stored in the target molecule. Most impressively, a continuous thermophilic hydrogen-mediated system using the acetogenic bacterium Thermoanaerobacter kivui has achieved acetate concentrations of up to 29.4 grams per liter, roughly 490 millimolar, from carbon dioxide. That is an order of magnitude beyond typical laboratory titers and begins to approach concentrations relevant to industrial separation. For context, commercial acetic acid is produced today by methanol carbonylation in plants rated at 200,000 to 650,000 tonnes per year, so MES still has far to travel in scale, current density, and process intensification, but the trajectory of improvement is unmistakable.

Beyond acetate, the product spectrum widens considerably. When acetate and ethanol accumulate in the reactor, chain-elongating microbes take over, running reverse beta-oxidation pathways that stitch short-chain intermediates into C4 through C8 medium-chain fatty acids such as butyrate and caproate, which command far higher market prices as feed and chemical precursors. Solventogenic metabolism can be triggered by tuning reactor operating conditions, reducing accumulated organic acids to ethanol, butanol, and 2,3-butanediol. Reductive branches of the tricarboxylic acid cycle yield lactate and succinate. Photo-bioelectrochemical systems using the purple bacterium Rhodobacter sphaeroides go further still, simultaneously converting CO2 into biomass and hydrogen gas, while MES-integrated setups direct CO2-derived carbon into intracellular polyhydroxybutyrate, a biodegradable plastic. In each case, the electron source is the electrode rather than sugar, decoupling production from agricultural feedstocks.

One of the most commercially mature applications is biogas upgrading. Anaerobic digestion plants in Germany, Denmark, and the Netherlands already supply 10 to 20 percent of renewable power in parts of the European Union, but raw biogas contains only 50 to 70 percent methane, with the remainder mostly CO2 plus troublesome impurities such as siloxanes and sulfur compounds. Conventional pressure swing adsorption can polish biogas to roughly 97 percent methane for pipeline injection, but contaminants foul the adsorbents and raise costs. MES offers an elegant pre-treatment: raw biogas is sparged into the cathode chamber, where methanogenic archaea electrochemically reduce the CO2 fraction to additional methane. Recent work with biogas from an operating anaerobic digestion plant achieved 95 percent methane in the upgraded gas at a methane production rate of 8.8 liters of CH4 per square meter of catalyst per day. Because gaseous impurities dissolve into the liquid phase during this step, the downstream PSA unit faces a lighter, cleaner load, and the captured CO2 is not merely discarded but converted into fuel.

The review also highlights an emerging application with obvious public appeal: power-to-protein. In these schemes, renewable electricity splits water to generate hydrogen, formate, or methanol, which feed bioreactors cultivating protein-rich microorganisms for food and feed. Single-cell protein is not new; companies such as Unibio and Calysta have commercialized fermentation-based production, but their processes traditionally rely on sugar substrates that compete with food supply. A techno-economic assessment of solar-driven microbial protein production found that photovoltaic-powered systems could achieve protein yields per unit of land up to an order of magnitude higher than conventional agriculture, and that estimate assumed conservative solar-to-electricity and power-to-chemical conversion efficiencies of 5 percent or less. Because electricity delivers reducing power to microbes far more efficiently than photosynthesis delivers it to crops, the land-use arithmetic of protein production could be transformed, freeing farmland while feeding a growing population.

None of this means MES is ready for prime time, and the authors are candid about the obstacles. Most laboratory studies still rely on small H-type reactors whose distant electrodes and ion-exchange membranes impose severe ohmic resistance and overpotentials, often pushing cell voltages above 3 volts and crushing energy efficiency. The oxygen evolution reaction at the anode is kinetically sluggish, particularly on carbon-based electrodes, and acts as a bottleneck for the entire system. Mixed microbial consortia, while robust, tend to foul membranes and default to acetate rather than more valuable products, whereas pure cultures of Shewanella, Sporomusa, Geobacter, or Rhodobacter offer precision but demand sterility. The field is responding with nanostructured and conductive-polymer-coated cathodes such as polyaniline-deposited graphite felt, synthetic-biology strains with engineered electron-transfer and metabolic pathways, artificial redox mediators like neutral red, and scalable reactor geometries including bubble columns and 3D-printed electrodes designed to improve hydrogen delivery.

The most pragmatic near-term strategy may be integration rather than replacement. Because MES alone is unlikely to reach commercial viability at current productivities, the authors describe two-stage processes in which MES first converts CO2 to acetate, which is then recovered and fed to a second, optimized bioprocess that converts it into long-chain alkyl esters or high-value isoprenoids. Such hybrid configurations sidestep the selectivity limits of mixed-culture MES while still exploiting its unique ability to fix carbon with electricity. Coupled with direct air capture and low-carbon power, an integrated MES platform could even operate as a carbon-negative factory, drawing down atmospheric CO2 while selling chemicals, fuel, and protein. The remaining challenges, from current density to product recovery costs, are formidable but increasingly quantified, and for the first time the road from laboratory biofilm to industrial biorefinery looks less like a leap of faith and more like an engineering schedule.

Subject of Research: Microbial electrosynthesis using renewable electricity to convert CO2 into value-added chemicals, biogas, and protein

Article Title: Renewable electricity–driven microbial electrosynthesis for high-value CO2 valorization: recent trends

Article References: Lee, C. H., Kim, M., Kong, D. S., Son, H., & Kim, J. R. (2026). Renewable electricity–driven microbial electrosynthesis for high-value CO2 valorization: recent trends. Advances in Industrial and Engineering Chemistry, 2(1), Article 4. https://doi.org/10.1007/s44405-026-00044-1

Image Credits: AI Generated

DOI: 10.1007/s44405-026-00044-1

Keywords: microbial electrosynthesis, CO2 valorization, renewable electricity, acetate production, biogas upgrading, single-cell protein, polyhydroxybutyrate, bioelectrochemical systems, Wood-Ljungdahl pathway, power-to-protein, carbon capture and utilization, electroactive bacteria