Nat. Commun.: Dynamic stretching beyond electron transfer enhances Fenton-like reactivity in homopyrrolmic MOFs by Professor Wang Chongchen's research group at Beijing University of Civil Engineering and Architecture.

First Authors: Wang Fei, Li Yuhang, Wang Fuxue

Corresponding Authors: Wang Chongchen, Ji Haodong, Liu Wen

DOI: 10.1038/s41467-026-68917-z

In January 2026, Nature Communications published online the latest research results of Professor Wang Chongchen's team at Beijing University of Civil Engineering and Architecture in the field of MOF for water pollution control. This work reports a novel interpenetrating MOF material (BUC-95) with a flexible dynamic tensile structure.

Experiments and DFT calculations show that the dynamic stretching effect of this material can effectively reduce the energy barrier for electron transfer from Fe-Fe² active sites to PDS, significantly improving the Fenton-like reaction activity compared to the structural analog BUC-96. This achievement provides a theoretical and technical basis for the design of dynamically stretched MOF structures and also expands a new direction for Fenton-like water purification technology. The first authors of the paper are: Wang Fei, Li Yuhang, and Wang Fuxue; the corresponding authors are: Wang Chongchen, Ji Haodong, and Liu Wen. Researchers have conducted extensive studies on the design of heterogeneous catalyst structures, aiming to improve electron transfer kinetics by regulating the microenvironment of active sites. However, the often-overlooked dynamic phenomenon of transient structural evolution of catalysts in interfacial reactions may profoundly affect the catalytic oxidation mechanism and urgently needs to be explored. At present, this field mainly faces two limitations: (1) the structural adaptability of traditional catalysts is insufficient, and there is an inherent bottleneck in improving catalytic performance by relying on metal-oxygen bond stretching vibrations; (2) in advanced oxidation processes, there is a lack of effective synthesis strategies for dynamically stretched catalysts. In particular, the structure-activity relationship between the dynamic stretching behavior of catalysts and catalytic activity has not yet been clarified, which is a core scientific problem that urgently needs to be solved. Interpenetrating metal-organic frameworks (MOFs) have entangled and non-covalently bonded identical frameworks. Their intrinsic structural flexibility provides a potential way to solve the above challenges, and they can undergo reversible stretching deformation in response to external stimuli (such as chemical stimuli). Compared with the "breathing" effect of traditional MOF channels and other flexible MOFs, the large-scale dynamic stretching behavior of interpenetrating MOFs makes them an ideal model for studying the overall framework dynamics in Fenton-like systems. This study is the first to synthesize a novel homo-interpenetrating MOF (BUC-95, CCDC: 2352385), which exhibits flexible dynamic stretching behavior. The mechanism of this behavior in the activation of persulfate (PDS) to generate high-valent iron species (Fe(IV)=O) and subsequently degrade ofloxacin (OFC) was systematically elucidated.

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Figure 1. Figures appearing in the paper

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Micro-ED resolved the atomic structure of BUC-95, with the molecular formula Fe_sub>4(bpy)₄(bdc)₄ (Figure 1a). BUC-95 exhibits a homo-interpenetrating structure composed of a pair of identical three-dimensional frameworks. SEM and HR-TEM showed that BUC-95 exhibits a rod-like morphology (Figures 1b and 1d). PXRD showed that its characteristic peaks corresponded well with the simulation card, proving the successful preparation of BUC-95 (Figure 1e). Replacing H₂bdc with H₄dhtp synthesized a structural analog (BUC-96), and its dynamic stretching effect was compared with that of BUC-95. Single-crystal X-ray diffraction data showed that BUC-96 is a homo-interpenetrating three-dimensional framework structure with the same coordination mode as BUC-95 (SI, Figure 10). However, IGM visualization analysis revealed that the DMF molecule was encapsulated within the channels of BUC-96, with its O atoms forming hydrogen bonds with the H atoms of the bpy ligand (2.509 Å). These hydrogen bond interactions almost completely constrained the inherent dynamic stretching behavior of the homo-interpenetrating framework (SI, Figure 11 and Video 1). X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses revealed the local coordination environment and electronic structure properties of Fe in BUC-95 and BUC-96. Figures 1f and 1g show that the near-edge of BUC-95 is shifted to higher energy levels compared to BUC-96, and its FT-EXAFS spectral intensity is lower than that of BUC-96, indicating a lower electron density at the Fe center in BUC-95. Furthermore, wavelet transform (WT) results for BUC-95 showed the absence of Fe-Fe bonds in the sample (Figure 1h), indicating the absence of Fe clusters in the structure of BUC-95.

Figure 2. Figure 2 appearing in the paper

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Selecting electron-rich ofloxacin (OFC) as the target pollutant, experiments show that BUC-95 catalyzes and activates PDS to degrade OFC with excellent performance, far superior to the BUC-95/H₂O₂ and BUC-95/PMS systems. This is presumably related to the most negative adsorption energy (-6.95 eV) and the maximum electron transfer number (1.6437 e⁻) of BUC-95 for PDS.

Compared to BUC-96 (kobs = 0.03 min⁻¹), the reaction rate of the BUC-95/PDS system (kobs = 5.52 min⁻¹) is increased by 2.3 orders of magnitude, and its unique flexible dynamic stretching structure is likely the key to the improved catalytic performance. This system can completely degrade various electron-rich pollutants such as TC and ENR within 10.0 min, exhibiting catalytic efficiency superior to previously reported catalysts. Cycling experiments confirm that BUC-95 has good water stability and recyclability. Capture experiments and ESR tests confirm that the main active species in this system is high-valence iron.

Figure 3. Figure 3 appearing in the paper

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PMSO experiments and BUC-95 Mössbauer spectroscopy (Figures 3a-c) confirm the presence of high-valence iron; Fe site masking experiments and Fe 2p XPS (Figure 3d) indicate that the species generating high-valence iron is Fe(II), and FB probe experiments exclude the SO₄ conversion pathway.

ERP testing showed that BUC-95 has oxygen vacancies, which can promote the adsorption of Fe-OH to form Fe-OH and activate PDS. After the reaction, the O 1s XPS showed a -OH peak at 532.2 eV, confirming this mechanism. DFT calculation (-OH to PDS adsorption energy -9.61 eV, Figure 3f) confirmed that the formation of high-valence iron was a spontaneous reaction. Bader charge analysis (Figure 3g) supported that -OH promoted charge transfer and high-valence iron formation. pCOHP analysis (Figure 3h) showed that the Fe‒O bond energy in the BUC-95-OH/PDS system was lower, which was conducive to PDS desorption. Orbital hybridization analysis (Figure 3i) showed that the transfer of two electrons from the Fe dz² orbital promoted the formation of Fe(IV)=O, which corresponds to the decrease in the area of ​​the OH-edge double peak from 14.21% to 9.14% (Figure 3j). DFT thermodynamics (Figure 3k) shows that the Gibbs free energy (-3.55 eV) of the rate-limiting step in the formation of Fe(IV)=O in the presence of -OH is much lower than that of BUC-95 (1.71 eV). In summary, combining multiple characterizations, probe experiments, and calculations, we confirm that Fe(IV)=O is the main reactive oxygen species in the system and propose a schematic diagram of its formation.

Figure 4. Figure 4 appearing in the paper

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CV and EIS tests show that BUC-96 has a larger electrochemical active area and a smaller EIS radius, resulting in superior electron transfer efficiency compared to BUC-95 (Figures 4a-c); differential charge density (Figure 4h) and Fe 3d orbital PDOS analysis (Figure 4i) further confirm that BUC-96 has a stronger electron transfer capability to PDS. However, BUC-96's activation of PDS for OFC degradation is poor. This negative correlation between electron transfer efficiency and reactivity highlights the crucial role of BUC-95's flexible dynamic stretching.

Multiple in-situ characterizations confirmed the dynamic stretching behavior of BUC-95: In-situ PXRD showed that the characteristic peaks of BUC-96 remained unchanged after the addition of H₂O and PDS, while the diffraction peaks of BUC-95 shifted significantly (Fig. 4d); in-situ XPS (SI, Fig. 54b), XAFS (Fig. 4e), FTIR (Fig. 4f), and Raman (Fig. 4g) further confirmed its reversible and flexible dynamic stretching. In-situ molecular dynamics simulations under different conditions (Fig. 4j, SI videos 2-3) showed that BUC-95 exhibited significant reversible dynamic stretching in the presence of H₂O and PDS, while BUC-96 showed no significant structural changes (SI, Fig. 65, videos 4-5). In summary, although the electron transfer ability of BUC-95 is weaker than that of BUC-96, its flexible dynamic stretching overcomes the dependence on electron transfer efficiency and significantly improves Fenton-like performance.

Figure 5. Figure 5 appearing in the paper

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To evaluate the practicality of the BUC-95/PDS system, a continuous flow reactor was developed to simulate the continuous flow of pollutants in water.

Continued long-term removal (Fig. 5a, c). Using PVB as a linker, BUC-95 was immobilized on a 2.0 cm × 2.0 cm × 1.0 cm polyurethane sponge to prepare a supported BS catalyst (Fig. 5b, d). Compared with the blank sponge (water contact angle 113.97°), the hydrophilicity of BS was significantly enhanced (54.85°), which is beneficial for continuous catalytic experiments (Fig. 5b). When 10.0 mg L⁻¹ of OFC wastewater was prepared with pure water and treated continuously for 110 h and 192.0 h, the system maintained an OFC removal efficiency of over 99.99% and 85.0%, respectively, demonstrating its good practical application potential (Fig. 5e). Experiments using T.E.S.T. toxicity simulation software, bean sprout growth, E. coli inhibition zones, and various bacterial chromogenic media confirmed that the system has a good detoxification effect on OFC (Fig. 5f-h). This study synthesized a novel homo-interpenetrating MOF (BUC-95) with a flexible and dynamically stretched structure and applied it to the catalytic activation of PDS for the efficient degradation of various organic pollutants. The flexible and dynamically stretched behavior of BUC-95 was confirmed by various characterization methods, including in-situ PXRD, Raman, FTIR, XAFS, and XPS. Experiments showed that Fe(IV)=O is the main reactive oxygen species in the degradation of OFC. Combining experiments and DFT calculations, its formation mechanism was proposed and verified: the dynamic double Fe-Fe' sites in BUC-95 regulate the electron density of Fe 3d orbitals by adsorbing -OH, significantly reducing the reaction energy barrier and thus promoting the formation of Fe(IV)=O. Compared to the hydrogen-bonded, hydrogen-bonded stretching of the BUC-96 framework, the flexible dynamic stretching of BUC-95 effectively overcomes the inherent bottleneck of electron transfer from Fe-Fe sites to PDS, resulting in a 184.0-fold increase in the OFC degradation rate constant. Furthermore, BUC-95 exhibits excellent OFC degradation stability (>99.99%, sustained for 110.0 h) and good detoxification performance in continuous flow reactions. These results were further validated through simulation calculations, plant (mung bean) growth, and bacterial testing, highlighting the application potential of the BUC-95/PDS system in practical water treatment. This work provides important theoretical basis and research foundation for using dynamically stretched structures as a key design principle to advance the development of environmental remediation materials and technologies.

Fei Wang, Yu-Hang Li, Fu-Xue Wang, Chong-Chen Wang*, Ya Gao, Xiao-Hong Yi, Weijian Yu, Peng Wang, Mingyi Liu, Haodong Ji*, Yifei Sun, Wen Liu*. Dynamic stretching beyond electron transfer in a homointerpenetrated metal‒organic framework for enhanced Fenton-like reactions, Nature Communications, 2026, 17, 2185.

https://www.nature.com/articles/s41467-026-68917-z