One-Minute Solvent-Free Synthesis Yields MOF That Strips Radioactive Strontium from Water in Minutes

Radioactive strontium-90 has long been one of the most feared contaminants in nuclear wastewater. With a half-life of roughly 29 years, a strong tendency to mimic calcium and accumulate in bone, and high mobility through soil and groundwater, it can persist in ecosystems for generations and pose serious risks to public health. Cleaning it out of contaminated water has traditionally required adsorbents that are slow to synthesize, slow to act, or both. Now, a team at Southwest University of Science and Technology in Mianyang, China, reports a strikingly fast and sustainable way to make an adsorbent that tackles strontium with exceptional speed and capacity, and the synthesis itself takes just one minute.

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