Dicyclopentadiene, commonly abbreviated as DCPD, is an important industrial olefin used in the production of specialty polymers, resins, fuels and high-performance materials. Its molecule contains two carbon–carbon double bonds arranged within a rigid bicyclic structure, making complete hydrogenation chemically demanding. Hydrogenation must proceed efficiently while avoiding excessive reaction temperatures, over-hydrogenation, skeletal rearrangement or the formation of undesired by-products. Conventional noble-metal catalysts can provide high activity, but their performance often depends strongly on particle size, metal dispersion, electronic structure and the nature of the support. The researchers’ strategy addresses all of these factors simultaneously by creating a catalytic environment in which ruthenium, nickel and the cerium-containing framework cooperate at the atomic and nanoscale levels.

At the heart of the system is UiO-66(Ce), a metal–organic framework constructed from cerium-oxo clusters connected by organic linkers. MOFs are crystalline porous materials whose internal channels can concentrate reactant molecules near catalytic sites, while their inorganic nodes can influence the electronic properties of supported metals. In this work, the researchers introduced structural defects into UiO-66(Ce) using cyanuric acid, which acted as molecular “etching scissors.” Rather than simply damaging the framework, controlled etching removed or disrupted selected linker connections and generated a more chemically open and reactive support. These defects exposed additional cerium-oxo environments, modified the local pore structure and created anchoring points capable of interacting strongly with metal species.

The defect-rich framework was then used to stabilize highly dispersed ruthenium–nickel nanoparticles. Ruthenium is well known for its ability to activate molecular hydrogen and catalyze carbon–carbon double-bond hydrogenation, but isolated or very small Ru particles can exhibit electronic characteristics that differ substantially from bulk ruthenium. Nickel was introduced as a promoter rather than merely as a second catalytic component. The researchers found that the Ni species altered the chemical environment of ruthenium and formed Ni–Ru bonds, while interactions between the metals and the cerium-oxo clusters generated Ce–O–Ru/Ni interfaces. These interconnected junctions created pathways for electron redistribution across the support and the bimetallic particles.

Electron transfer is central to the catalyst’s performance. In a conventional metal catalyst, hydrogen must adsorb, dissociate and subsequently react with an olefin at an appropriate balance of bond strength. If hydrogen binds too weakly, activation becomes slow; if it binds too strongly, the surface can become saturated with hydrogen or release reaction products inefficiently. The same principle applies to the carbon–carbon double bond. The Ru₁Ni₁.₅@UiO-66(Ce)-12 h catalyst was designed to make ruthenium electron-rich through the combined influence of defective cerium-oxo clusters and nickel. According to the study, electrons can migrate from the Ce-based nodes and Ni-containing species toward Ru⁰ sites, changing the orbital occupancy and adsorption behavior of the active metal.

The defects and nickel promoter therefore perform complementary functions. Defect engineering changes the microenvironment around the nanoparticles, increases the accessibility of support-bound metal sites and exposes cerium centers that can participate in interfacial bonding. Nickel provides an additional electronic and geometric lever through Ni–Ru interactions. Together, these effects regulate the abundance, distribution and electronic state of metallic Ru⁰ sites. The researchers report that the modified sites have an enhanced ability to adsorb and activate both H–H bonds in hydrogen and C=C bonds in dicyclopentadiene. A plausible catalytic sequence begins with hydrogen adsorption and dissociation at the Ru–Ni or metal–support interface, followed by transfer of hydrogen atoms to the two unsaturated bonds of DCPD. The porous framework helps bring the reactant into contact with these sites and may also limit uncontrolled aggregation of the nanoparticles.

The performance reported for the optimized material is striking because it is achieved under comparatively gentle conditions. At 35 °C and 1 MPa, the catalyst completed DCPD hydrogenation in about 25 minutes, producing tetrahydrodicyclopentadiene with essentially complete selectivity. The product is valuable because hydrogenating the unsaturated bonds changes the reactivity and physical properties of DCPD while preserving the carbon skeleton. High selectivity is particularly important in industrial processing, where separation and purification of side products can add substantial energy and cost. By reducing the need for elevated temperatures, the catalyst could also lower energy consumption, although broader process evaluations would be required before judging its commercial advantages.

The study emphasizes that the best performance did not arise simply from adding more ruthenium or nickel. Instead, catalytic activity depended on matching the defect concentration of the UiO-66(Ce) support with the amount of nickel promoter. Too few defects would provide insufficiently accessible interfacial sites, while excessive structural disruption could compromise the framework’s porosity, stability or ability to anchor nanoparticles. Similarly, the nickel content had to be controlled so that Ni–Ru interactions improved hydrogen and olefin activation without blocking ruthenium sites or producing less selective metal ensembles. The designation “12 h” in the catalyst name refers to the defect-engineering treatment time used in the preparation, highlighting how synthesis conditions were used to tune the final catalytic microenvironment.

Durability is another important feature of the result. The optimized catalyst retained its structure and catalytic performance after six reaction cycles, according to the researchers. This stability suggests that the defective UiO-66(Ce) framework can confine and anchor the Ru–Ni nanoparticles strongly enough to resist severe sintering or metal loss during repeated hydrogenation. For practical catalysis, stability is as important as initial activity: a catalyst that performs rapidly but deactivates after one reaction offers little industrial value. The reported recycling result does not by itself establish long-term operation, resistance to impurities or performance at larger scale, but it provides evidence that defect-engineered MOF supports can serve as robust hosts for bimetallic hydrogenation catalysts.

The work offers a broader blueprint for designing noble-metal catalysts with lower precious-metal requirements and more precisely controlled active sites. Rather than treating the support as an inert scaffold, the researchers use the cerium-oxo framework as an electronic participant, the defects as chemical access points and nickel as a promoter that reshapes ruthenium’s behavior. This coordinated approach could be extended to other selective hydrogenation reactions involving olefins, alkynes, carbonyl compounds or biomass-derived molecules. The central lesson is that catalytic performance can emerge from a carefully engineered network of charge-transfer channels and confined interfaces, not from the isolated properties of any single element. If the material can be produced reproducibly and tested under continuous-flow and industrially relevant conditions, it may help move MOF-supported bimetallic catalysts closer to real-world applications in low-temperature hydrogenation.

Subject of Research: Defect-engineered cerium-based metal–organic framework catalysts and Ni-promoted Ru nanoparticles for mild-condition dicyclopentadiene hydrogenation

Article Title: Defect engineering and Ni promoter synergistically accelerating electron transfer to Ru⁰ sites in UiO-66(Ce) for dicyclopentadiene hydrogenation under mild condition

Article References: Li, R., Ban, T., Zhao, D. et al. “Defect engineering and Ni promoter synergistically accelerating electron transfer to Ru⁰ sites in UiO-66(Ce) for dicyclopentadiene hydrogenation under mild condition.” Nano Research 17, 9550–9563 (2024).

Image Credits: AI Generated

DOI: 10.1007/s12274-024-6954-1

Keywords: metal–organic frameworks; defect engineering; Ni promoter; electron-rich Ru⁰ active sites; dicyclopentadiene hydrogenation; bimetallic catalysis; electron transfer; UiO-66(Ce)

At the forefront of this advancement is a groundbreaking team of researchers led by Prof. Gao and Prof. Wang from the University of Science and Technology Beijing. They have pioneered an innovative strategy that aims to overcome the current hurdles faced in the field of FLP catalysis through the design of cerium-based metal-organic frameworks (Ce-MOFs). By utilizing cerium’s unique redox properties and structural adaptability, the researchers engineered a series of defect-rich MOF-808 materials doped with functional groups, such as -NH2, -OH, -Br, and -NO2. This approach employs a competitive coordination strategy involving functionalized monocarboxylate ligands, leading to the formation of MOFs that exhibit a diverse array of catalytic properties.

The MOF-808 materials synthesized in this research exhibit a wealth of Ce-CUS (Lewis acid) and Ce-OH (Lewis base) sites that are spatially confined. These sites are effectively designed to form frustrated Lewis pairs within the framework, establishing unique environments that enable synergistic hydrogen cleavage. This arrangement allows for the activation of hydrogen molecules, employing a “push-pull” mechanism that could significantly enhance catalytic efficiency for hydrogenation reactions. The implications of this breakthrough are vast, particularly as the team reported that the optimized MOF-808-NH2 achieved complete conversion of substrates, styrene and dicyclopentadiene, under mild conditions of 100 °C and a hydrogen pressure of 2 MPa.

Delving deeper into the intricacies of their findings, the research team highlighted that the incorporation of electron-donating functional groups, such as -NH2, can elevate the strength of the Lewis base by redistributing electron density towards the Ce-OH sites. This electronic modulation is crucial as it lowers the activation barrier for the heterolytic cleavage of hydrogen. MOF-808-NH2 demonstrated remarkable performance by achieving a 100% conversion rate for the selected substrates, a feat that is not only impressive but also exceeds the performance of its unmodified counterpart, MOF-808, by a factor of three.

The study also employed sophisticated characterization techniques such as in-situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) and X-ray Photoelectron Spectroscopy (XPS) to affirm the formation of intermediates during the activation of hydrogen. The formation of Ce–Hδ⁻ and O–Hδ⁺ species during this activation process suggests a novel catalytic pathway, shedding light on the mechanistic aspects of hydrogen activation within the FLP framework. Additionally, Density Functional Theory (DFT) calculations provided valuable insights, revealing a remarkably low energy barrier of just 0.404 eV for hydrogen dissociation on the optimized framework.

This research fosters a deeper understanding of FLP catalysis by demonstrating that strategic engineering of the local environment around Lewis pairs can yield significant enhancements in catalytic activity. The implications extend beyond academic curiosities; they offer a solid foundation for the development of non-precious-metal hydrogenation catalysts, paving the way for a new generation of catalysts that could operate more efficiently and sustainably. The coupling of defect engineering with the functionalization of ligands creates a blueprint that may not only inspire further research within MOF systems but also be adapted for various catalytic processes, including fine chemical synthesis and renewable energy applications.

In summary, this innovative approach to FRP catalysis emphasizes the importance of optimizing the microenvironment surrounding catalytic sites to enhance chemical reactivity. The implications of this research are profound, suggesting that the precise tuning of electronic and spatial arrangements within catalyst frameworks may lead to breakthroughs that are essential for the transition towards sustainable chemical manufacturing.

Forward-looking insights indicate that the team’s findings could significantly influence how chemists design catalysts for multi-functional applications. Future studies may aim to combine these FLP frameworks with other materials—potentially integrating them into hybrid systems for enhanced catalytic performance. As the fields of energy and environmental sustainability continue to intertwine, the engineering of Ce-MOFs represents a pivotal step toward achieving practical solutions to some of the most pressing challenges in modern catalysis.

The discoveries made by this team not only enrich the fundamental understanding of FLP catalysis but also open new pathways for innovation in materials science. As research progresses, there may be potential applications that extend well beyond current horizons, leading to novel strategies for functionalizing hydrogenation catalysts and experiencing unprecedented transformations in the landscape of green chemistry.

Subject of Research: Engineering Frustrated Lewis Pairs in Cerium-Based Metal-Organic Frameworks
Article Title: Microenvironment modulation around frustrated Lewis pairs in Ce-based metal-organic frameworks for efficient catalytic hydrogenation
News Publication Date: 6-Aug-2025
Web References: Chinese Journal of Catalysis
References: DOI: 10.1016/S1872-2067(25)64695-X
Image Credits: Credit: Chinese Journal of Catalysis

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