The material at the heart of the study is a bimetallic version of MOF-74, a well-known metal-organic framework built from metal ions linked by organic ligands into a porous crystalline lattice. MOF-74 is prized for its one-dimensional channels lined with open metal sites, the unsaturated coordination positions that can grab passing molecules or ions. By combining two metals, copper and zinc, in a single framework, researchers can tune the density and variety of these active sites, often improving adsorption performance beyond what either monometallic version achieves alone. The challenge has been manufacturing: conventional solvothermal synthesis of MOF-74 typically requires organic solvents, sealed reactors, elevated temperatures, and reaction times stretching over hours or even days, which limits scalability and generates solvent waste.

The Chinese team, led by Lihan Wen, Juan Shen, Shuangxian Wu, and Bo Jin, sidestepped those constraints entirely. Writing in the Journal of Materials Science, they describe a solvent-free mechanochemical strategy based on what they call a spiral gas-solid flow method, abbreviated S-GSF. In mechanochemistry, mechanical force rather than heat or solvent drives chemical reactions; grinding or milling solid precursors together can generate the intimate mixing, local heating, and defect-rich interfaces needed for framework assembly. The spiral gas-solid flow variant accelerates this dramatically, allowing the solid metal salt and organic ligand precursors to react and crystallize into the bimetallic Cu/Zn-MOF-74, dubbed CZ-M74-11, in a single minute of processing. That is a synthesis timescale more reminiscent of flash chemistry than of the slow crystal growth usually associated with metal-organic frameworks.

The payoff shows up immediately in the adsorption data. When the material was tested against strontium ions in water, it removed 98.26 percent of the Sr2+ within just 15 minutes of contact. That ultrafast kinetics matters in practice, because in an emergency response scenario, such as a reactor accident releasing radionuclides into waterways, the ability to strip a dangerous isotope rapidly can determine whether contamination spreads or is contained. The maximum adsorption capacity, fitted with the Langmuir isotherm model, reached 295.13 milligrams of strontium per gram of adsorbent at 303.15 K, a figure that places the material among the high-performing strontium scavengers reported to date and reflects the abundance of accessible binding sites created by the bimetallic composition and the mechanochemical route.

Thermodynamic analysis added an important nuance: the adsorption process is spontaneous and exothermic, meaning it releases heat as it proceeds and is favored at lower temperatures. That behavior is consistent with a physisorption-dominated capture mechanism rather than a process requiring thermal activation. For deployment scenarios, exothermic spontaneous uptake is advantageous because it requires no external energy input to drive the binding; the ions are captured simply because the thermodynamics favor it at ambient conditions.

To understand exactly how the strontium ions bind, the researchers turned to X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy, complemented by cyclic desorption experiments. The combined evidence indicates that the dominant uptake pathway is outer-sphere complexation, in which the strontium ions associate with the framework surface without directly displacing or bonding to the coordinating atoms, typically through electrostatic attraction and hydrogen-bonded water layers at the interface. A minor contribution comes from inner-sphere coordination involving carboxylate groups, where the strontium forms direct chemical bonds with the ligand’s carboxylate oxygen atoms. This mechanistic picture is significant because outer-sphere complexes are generally easier to reverse, and indeed the cyclic desorption data confirmed that the material can release its captured strontium and be regenerated for repeated use, a critical property for any adsorbent intended for real wastewater treatment rather than single-use disposal.

The regeneration capability also has implications for waste management economics. An adsorbent that can be cycled through multiple adsorption-desorption rounds reduces both the volume of secondary radioactive waste and the cost per liter of treated water. Concentrating the strontium onto a small mass of regenerable material, rather than dispersing it through large volumes of ion-exchange resin or coagulant sludge, simplifies the downstream handling of the radioactive concentrate, which is often the most expensive part of remediation.

The study situates itself within a crowded field of strontium-capture materials. Previous approaches have included porous zirconium phosphates, layered metal sulfides that act as ion exchangers, carboxylated covalent organic frameworks, crown-ether-based metal-organic frameworks, manganese dioxide core-shell nanocomposites, thiol-rich ion-imprinted hydrogel membranes, and Prussian blue coatings on polymer foams. Each has its strengths, but many suffer from slow kinetics, modest capacity, complex multistep synthesis, or poor recyclability. Metal-organic frameworks have repeatedly shown promise in this space, including anionic interpenetrated frameworks and hierarchical mesoporous zinc MOFs, but the synthesis bottleneck has been persistent. The one-minute, solvent-free route reported here directly addresses that gap, and it builds on a growing body of mechanochemical MOF research, including prior work on scalable mechanochemical amorphization of bimetallic Cu-Zn MOF-74 catalysts and mechanochemical synthesis of high-entropy MOF-74 for carbon dioxide capture.

What makes the bimetallic composition particularly interesting mechanistically is the interplay between the two metals. Copper and zinc occupy the same framework nodes in MOF-74 but bring different electronic properties and coordination preferences, creating a heterogeneous landscape of active sites along the pore walls. In adsorption applications, this heterogeneity can enhance uptake by offering multiple binding geometries for the target ion, and it may also improve the framework’s structural resilience in aqueous environments, a known vulnerability of some MOF chemistries. The Langmuir fit of the capacity data suggests relatively homogeneous site energies across the material, consistent with a well-ordered bimetallic framework rather than a random mixture of separate copper and zinc phases.

The broader significance of the work lies in the demonstration that sustainable manufacturing and high performance need not be in tension. A solvent-free, one-minute synthesis eliminates the organic solvent burden and energy costs of solvothermal routes while producing a material that captures nearly all strontium from water within a quarter of an hour and can be regenerated. As nuclear power expands and legacy waste sites demand remediation, rapid, scalable production of high-capacity radionuclide scavengers could become a practical necessity. This study offers a template for how mechanochemical flow chemistry might deliver the next generation of environmental cleanup materials, not just for strontium but potentially for the wider family of radioactive and heavy-metal contaminants that threaten water supplies worldwide.

Subject of Research: Solvent-free mechanochemical synthesis of bimetallic Cu/Zn-MOF-74 for rapid strontium removal from radioactive wastewater

Article Title: One-minute mechanistical synthesis of bimetallic Cu/Zn-MOF-74 for rapid and high-capacity Sr2+ removal from radioactive wastewater

Article References: Wen, L., Shen, J., Wu, S., & Jin, B. (2026). One-minute mechanistical synthesis of bimetallic Cu/Zn-MOF-74 for rapid and high-capacity Sr2+ removal from radioactive wastewater. Journal of Materials Science. https://doi.org/10.1007/s10853-026-13770-0

Image Credits: AI Generated

DOI: 10.1007/s10853-026-13770-0

Keywords: metal-organic frameworks, MOF-74, strontium-90, radioactive wastewater, mechanochemistry, adsorption, water remediation, bimetallic materials, outer-sphere complexation, solvent-free synthesis, nuclear waste, environmental chemistry

The team, led by Nina Dyakova with colleagues Dmitry Lyubashevsky, Julia Shcherbina and Julia Lyubashevskaya, measured the specific activity of five radionuclides in paired samples of soil and plantain leaves collected across the Voronezh Region of Russia. Two of them, cesium-137 and strontium-90, are artificial isotopes that trace the legacy of twentieth-century nuclear activities and atmospheric fallout. The other three, potassium-40, thorium-232 and radium-226, are natural radionuclides that have always been present in the Earth’s crust. By analysing soil and leaf material from the same sampling points, the researchers could calculate how efficiently each isotope crosses the soil-to-plant boundary.

The headline result is reassuring for public health: every sample examined fell comfortably within radiological safety limits. The researchers computed an integral safety index for each sample, and all values ranged between 0.17 and 0.45, well below the threshold value of 1.0 that would signal a concern. In other words, the plantain leaves harvested in the region are radiologically safe as raw material for herbal preparations, a finding that matters because demand for wild-harvested medicinal plants has been rising steadily in the Russian pharmaceutical market and elsewhere.

Beneath that reassuring surface, however, the study uncovered a rich structure in how different radionuclides behave. Strong positive Pearson correlations between soil concentrations and leaf concentrations confirmed that the plant is genuinely taking these isotopes up from the ground rather than accumulating them from atmospheric deposition. The correlations were remarkably tight for strontium-90, cesium-137 and potassium-40, each with a coefficient of about 0.89, followed closely by radium-226 at 0.86. Thorium-232 showed a weaker but still meaningful correlation of 0.47, consistent with its well-known tendency to remain locked in soil minerals and resist root uptake.

The accumulation factor, defined as the ratio of the radionuclide concentration in leaves to its concentration in the corresponding soil, revealed a clear hierarchy of mobility. Cesium-137 proved the most readily accumulated isotope, with an accumulation factor of 2.55, meaning plantain leaves can concentrate this isotope to more than twice its soil level. Potassium-40 followed at 1.47, then strontium-90 at 1.12. Radium-226 hovered near parity at 0.93, while thorium-232 lagged far behind at just 0.37. This ordering makes chemical sense: cesium and potassium are alkali metals that travel through the same membrane transport channels in plant roots, while strontium mimics calcium, and thorium forms highly insoluble complexes that plants largely exclude.

Perhaps the most striking insight emerged when the researchers plotted accumulation factors against soil radionuclide concentrations. Across the dataset, they identified a universal inverse relationship: the more concentrated a given radionuclide is in the soil, the lower the accumulation factor measured in the plant. This pattern suggests active homeostatic regulation, a kind of internal control system by which the plant moderates its ion uptake. Rather than absorbing isotopes in strict proportion to their availability, plantain leaves appear to dampen accumulation as soil levels rise, a phenomenon with major implications for how transfer of radioactivity from environments to food and medicine chains is modelled.

This finding speaks to a long-standing debate in radioecology. Classic models of radionuclide transfer, including widely used handbooks of parameter values published by the International Atomic Energy Agency, rely on concentration ratios that assume a broadly linear relationship between soil and plant burdens. Earlier experimental work by researchers such as Sheppard and Evenden in the late 1980s had already questioned the linearity assumption, and subsequent studies on radium and thorium uptake by groups including Vandenhove and colleagues confirmed that soil properties and plant physiology can bend the transfer curve substantially. The new plantain dataset adds a medicinal-plant data point to that critical tradition, showing that the deviation from simple proportionality is systematic enough to be described with regression equations.

Those regression equations, together with the measured accumulation factors, are the study’s most practical product. By fitting linear models to the paired soil and leaf data, the authors produced predictive parameters that can be used to estimate radionuclide content in plantain leaves directly from soil measurements. For environmental monitoring agencies, this means soil surveys could become a screening tool for the safety of wild-harvested medicinal raw materials, reducing the need to analyse every batch of plant material. For pharmaceutical regulators, the derived transfer parameters offer a defensible basis for setting harvesting guidance, particularly in regions where residual contamination from historical fallout or industrial activity remains a concern.

The choice of study region is significant. The Voronezh Region sits within Russia’s Central Black Earth belt, famous for its fertile chernozem soils, and it hosts an active tradition of harvesting wild medicinal plants. Earlier work by the same research group had examined radionuclide accumulation in nettle leaves and in burdock roots, and the plantain study extends that programme into one of the most commonly gathered species. Because plantain is harvested for its leaves, which are used in expectorant and wound-healing preparations, the leaf-soil transfer parameters generated here apply directly to the part of the plant that enters commerce.

The authors conclude that the region enjoys a favourable radiation status and that plantain’s homeostatic mechanisms actively regulate isotope uptake in a predictable way. Beyond the immediate reassurance for consumers of herbal medicine, the study demonstrates how a humble, ubiquitous weed can serve as a bioindicator of environmental radioactivity. As demand for plant-based remedies grows worldwide, systematic soil-to-plant transfer measurements of this kind, grounded in paired sampling and quantitative modelling, provide exactly the kind of evidence base needed to keep natural products both trusted and safe.

Subject of Research: Soil-to-plant transfer of natural and technogenic radionuclides in the medicinal plant Plantago major L.

Article Title: Radionuclide accumulation in leaves of the medicinal plant Plantago major L

Article References: Radionuclide accumulation in leaves of the medicinal plant Plantago major L. (n.d.). https://doi.org/10.1007/s11104-026-08754-7

Image Credits: AI Generated

DOI: 10.1007/s11104-026-08754-7

Keywords: Plantago major, radionuclides, cesium-137, strontium-90, medicinal plants, soil-to-plant transfer, radiation safety, environmental monitoring, accumulation factor, Voronezh Region, radioecology, herbal medicine