MOF-based systems enable detection and removal of diuron pesticide

Metal–organic frameworks, the endlessly tunable class of crystalline porous materials built from metal ions linked by organic struts, are stepping into one of agriculture’s most stubborn environmental problems: the herbicide diuron. A new review published in Environmental Geochemistry and Health by Mukaddes Saklan, Elif Ozyilmaz and Mustafa Yilmaz of Selcuk University in Konya, Turkey, assembles, for the first time, a comprehensive picture of how these framework materials can be used across the entire lifecycle of diuron — not merely to mop it up after it has leaked into water, but to deliver it in a controlled fashion in the first place, to sense it at vanishingly small concentrations, and to strip it back out of contaminated matrices once its work is done. The authors argue that this integrated, three-pronged approach is precisely what the literature has been missing, and their synthesis of existing data suggests the field is closer to practical deployment than many researchers realize.

Diuron, a phenylurea herbicide used worldwide to control a broad spectrum of weeds in crops, along roadsides and around industrial sites, has become a textbook case of a beneficial agrochemical turning into a persistent pollutant. Because it is designed to inhibit photosynthesis by blocking electron transport in Photosystem II, it is inherently toxic to algae, aquatic plants and, at sufficient concentrations, a wide range of non-target organisms. The review draws on ecotoxicological studies documenting diuron’s effects on marine diatoms, Nile tilapia, Javanese medaka, zebrafish embryos and human cell lines, including evidence that its metabolites can act as endocrine disruptors and that the compound can cross the human placenta. Overuse and its moderate persistence in soil and water mean that diuron is now routinely detected in surface waters, groundwater, drinking water reservoirs and agricultural soils across Europe and beyond, with surveys of European agricultural soils revealing pesticide residues as a hidden but widespread reality.

Conventional remediation strategies, from activated carbon derived from biomass to biochars, carbon nanotubes, ozonation and photocatalytic degradation with metal oxide nanorods, have all been applied to diuron with varying degrees of success, but each carries trade-offs in cost, regenerability, selectivity or secondary waste. This is where metal–organic frameworks offer a structurally rational alternative. MOFs are assembled from metal nodes — zinc, zirconium, titanium, iron, chromium, cobalt — coordinated to organic linkers, producing frameworks with extraordinarily high surface areas, adjustable pore sizes and chemically addressable internal surfaces. Because the pore environment can be functionalized with amines, fluorinated groups, aromatic walls or polymer coatings, the interaction between the framework and a small aromatic molecule like diuron can be engineered deliberately, exploiting hydrogen bonding, hydrophobic effects and, crucially, π–π stacking between the herbicide’s phenyl ring and the aromatic linkers lining the pores.

The quantitative picture assembled by the Turkish team is striking. For adsorptive removal, composite and functionalized frameworks emerge as the clear front-runners. A titanium-MOF encapsulated in a chitosan–epichlorohydrin matrix, analyzed with the aid of density functional theory calculations and optimized through Box–Behnken experimental design, and derivatives of the chromium-based framework Cr-MIL-101, achieve maximum adsorption capacities of up to 441.8 milligrams of diuron per gram of material. That figure places MOF-based sorbents at or beyond the top of the range reported for activated carbons, biochars and polymeric adsorbents in the same application. The review attributes this performance to the combination of high porosity and tailored surface chemistry, which allows diuron molecules to be captured both on external surfaces and deep within the framework’s channels, with π–π interactions and hydrogen bonding to functionalized linkers providing the dominant binding mechanisms.

On the delivery side, the review highlights work from the authors’ own laboratory on magnetic ZIF-8 nanocomposites, designated KMP-2, in which diuron is encapsulated within a zeolitic imidazolate framework built from zinc ions and imidazolate linkers and rendered magnetically retrievable. The numbers here address two chronic weaknesses of herbicide application: waste and mobility. Loading efficiencies of the herbicide into the framework reached up to 73 percent, meaning far less active ingredient is lost during formulation. Once applied to soil, the encapsulated diuron reduced soil permeability to the compound by a factor of eight, dramatically slowing its leaching through the soil profile and lowering the environmental load that escapes the target zone. Perhaps most practically, the magnetic character of the nanocomposite allowed recovery rates of up to 88 percent, opening the door to reclaiming both the carrier and its residual payload after application rather than abandoning them to the environment.

Detection, the third pillar of the review, is where the analytical chemistry becomes most eye-catching. Electrochemical sensors built on MOF-derived and MOF-composite architectures have pushed detection limits for diuron down to 2.52 nanomolar — deep enough to monitor environmentally relevant concentrations in real water and food samples. Two systems stand out in the compiled data: a cobalt–zinc phosphide/oxide core-shell heterostructure, Co1Zn0.5-P/CoO/ZnO, synthesized by template-assisted methods for the simultaneous electrochemical detection of carbofuran and diuron, and a hybrid architecture in which gold nanorods are embedded in microporous ZIF-8 and wrapped in graphene oxide, AuNRs@ZIF-8@GO. The gold nanorods boost electron transfer while the ZIF-8 shell provides molecular sieving and the graphene oxide layer adds conductivity and surface area. In complex agri-food and water matrices, these sensors delivered high selectivity against interferents and recovery values reaching 107.8 percent, indicating that the measurements remain reliable even in the messy real-world samples that defeat many laboratory-grade methods.

The authors underscore that their survey of the Web of Science, Scopus and Google Scholar databases found no prior review that treats diuron–MOF interactions comprehensively across adsorption, controlled release and detection simultaneously. Most existing reviews have addressed either pollutant removal by MOFs in general, or pesticide sensing in isolation, or agricultural delivery platforms without tying them to a specific contaminant’s chemistry. By consolidating the fragmented literature into a single framework-centered narrative, the review exposes design principles that cut across all three functions: the importance of aromatic surface density for π–π binding, the value of polymer encapsulation for aqueous stability and processability, the utility of magnetic components for recovery and reuse, and the synergy between hierarchical porosity and conductive additives for electrochemical sensing.

The reusability question, often the Achilles heel of nanomaterial-based water treatment, receives particular attention. Frameworks that can be regenerated and cycled repeatedly without significant capacity loss transform the economics of adsorption, since a single batch of sorbent can treat many volumes of contaminated water. Magnetic composites simplify this further by allowing the spent sorbent to be collected with a simple external magnet rather than by filtration or centrifugation, a feature that scales far more gracefully toward field deployment in rural or resource-limited settings. The 88 percent recovery rate reported for the KMP-2 system, combined with the strong adsorption capacities of the chromium- and titanium-based composites, suggests that a genuinely circular materials economy around diuron management is technically within reach, even if the review is candid that direct evidence linking MOF-mediated removal to a measured reduction in human health risk remains limited and represents an important research gap.

What makes the review timely is the convergence of regulatory pressure and materials progress. Pesticide residues in European agricultural soils have been described as a hidden reality, monitoring studies of rivers and drinking water reservoirs continue to flag diuron and its transformation products, and ecotoxicity thresholds for diuron in fresh and marine waters are frequently exceeded in agricultural catchments. Meanwhile, the MOF literature has matured from proof-of-concept synthesis to engineered systems with pH-responsive release, improved leaf affinity, ultrahigh loading capacities and biodegradable polymer composites designed explicitly for sustainable pesticide delivery. The same chemistry that lets a Zr-based framework deliver a pesticide with pH-triggered precision can be inverted to capture that pesticide from a drainage stream, and the review makes that duality explicit for the first time.

The Selcuk University team, whose work was supported in part by the university’s Research Foundation and grew out of Saklan’s master’s thesis, positions MOFs as highly efficient, reusable and selective platforms for what they call diuron lifecycle management. The implication extends well beyond a single herbicide: the design rules extracted here — aromatic-functionalized pores for phenylurea capture, magnetic ZIF-8 carriers for precision agriculture, and conductive MOF hybrids for parts-per-trillion sensing — are transferable to the wider family of phenylurea and triazine herbicides that share diuron’s chemistry and its environmental stubbornness. If the field can now close the remaining gap between laboratory adsorption isotherms and demonstrated reductions in human and ecological exposure, metal–organic frameworks may move from the pages of chemistry journals into the water treatment plants and farm supply chains where the diuron problem actually lives.