Synthesis of the nanoparticles

We synthesized a metal–organic framework using the hydrothermal method and loaded it with the fungicide IPC. UiO-66 was synthesized with a yield ratio of ZrCl₄: H₂BDC: UiO-66 = 1:0.714:1.55. This method is characterized by high yield, simplicity, ease of operation, and excellent reproducibility. We examined the function of the outer surface of IPC@UiO-66, formed using metal ions complexed with TA. TA possesses multiple reactive functional groups that chelate with metal ions through ligand bonds, forming complexes of different sizes and morphologies. These complexes can create a range of metal polyphenol shields, referred to as nano-protective armor [14, 17].

This two-step self-assembly interaction between the nano-protective armor and the metal framework facilitated the efficient encapsulation of IPC by the nano-armor, addressing the critical issue of low LC. Given that TA is hydrophilic while IPC is hydrophobic, an emulsion method was used to disperse IPC@UiO-66 in a TA solution with a surfactant. The IPC@UiO-66-TA-metal ion nanoparticles with CuII, FeII, and ZnII ions as cross-linking agents showed dark green, black, and white colors, respectively. However, the LC results showed minimal variation among these nanoparticles. When ZnII was used, yield values significantly improved relative to those with CuII and FeII (4.05–5.21 times higher). This improvement may be attributed to the competitive coordination bonding between metal ions and TA in different media [16].

LC of IPC@UiO-66-TA-ZnII

In the optimization of the nano-formulation and drug-loading process, the LC is an important index for evaluating the drug delivery system. The central composite design of response surface methodology (CCD/RSM) was used to optimize the LC of IPC@UiO-66-TA-ZnII [23]. Two factors, namely surfactant concentration (A) and ultrasonic time (B), were considered. As the values of these factors increased, the effect on LC initially increased and then decreased (Fig. 2b and c). The residuals in the plot tended to cluster around the diagonal of the predicted results (Fig. 2d and e), which indicated that the assumption of normality was satisfactory and that these two factors significantly affected LC. The resulting multivariate quadratic regression equation of surfactant concentration (A) versus ultrasound time (B) is as follows: \(\text\hspace=\hspace12.89\hspace+\hspace0.8234\text\hspace+\hspace0.3659\text\hspace+\hspace0.0331\text- }^- }^\).

Fig. 2

Intermolecular interactions between UiO-66 clusters and TA were investigated through molecular modelling (a). Response surface map (b) and contour map (c) illustrate the effects of various factors (surfactant concentration: 0 to 5%; ultrasonic time: 0 to 120 min) on LC. Relationships between actual and predicted responses are shown (d), along with normality plots (e) for residuals from the LC analyses. The residuals clustered around the diagonal line of the predicted results, indicating that the assumption of normality was met (R2 for LC = 99%, p-value < 0.0001, n = 3)

IPC@UiO-66-TA-ZnII (10.55 ± 0.48%) prepared under these optimal conditions were used for characterization and performance studies. High productivity, high loading efficiency, and potential fungicidal activity led to the selection of ZnII as the crosslinking agent for fabricating IPC@UiO-66-TA-ZnII nanoparticles loaded with IPC.

Characterization of IPC@UiO-66-TA-ZnII

The morphological characteristics of UiO-66, IPC@UiO-66, and IPC@UiO-66-TA-ZnII samples were observed using SEM and TEM. Uniform octahedral UiO-66 nanoparticles with an average size of approximately 163 nm were observed (Figs. 3a-1 and a-2). The morphology of the nanoparticles imchanged upon the addition of IPC to the UiO-66 (Fig. 3a-3). TEM-Energy Dispersive Spectrometer (EDS) images confirmed the presence of Zr, O, C, Cl, and Zn elements, corresponding to Zr from UiO-66, Cl from IPC, and Zn from TA-ZnII. This was consistent with x-ray photoelectron spectroscopy (XPS) results (Figs. 3b, d–f and S1). The presence of IPC in the nanoparticles and the formation of a “nano-protective armor” shield by TA-ZnII on the surface of IPC@UiO-66 were confirmed. Compared to UiO-66 and IPC@UiO-66, the IPC@UiO-66-TA-ZnII particles (296 nm) were uniformly encapsulated in rounded spheres, demonstrating a successful transition from an octahedral to a spherical substrate structure (Figs. 3a-4–a-6). A proposed mechanism for the morphological changes is as follows: TA, possessing a rigid molecular chain, binds to the metal framework through van der Waals forces during the first self-assembly step (Fig. 2a). The crosslinking between TA and ZnII creates a more rigid and ordered structure, resulting in a shield with enhanced mechanical properties that prevents morphological collapse and completes the second self-assembly step. The assembled TA-ZnII shield is positioned on the outer surface of the metal framework, forming a compact structure that effectively encapsulates the fungicide.

Fig. 3

SEM images of UiO-66 (a-1 and a-2) and IPC@UiO-66 (a-3); SEM and TEM images of IPC@UiO-66-TA-ZnII (a-4–a-6) (scale bar: 500 nm–5 μm for SEM and 50 nm for TEM). EDS mapping characterization of IPC@UiO-66-TA-ZnII (b; b-1–b-4) (Scale bar: 200 nm). FTIR spectra within the range of 4000 to 400 cm.−1 (c), XPS results within the range of 1300 to 0 eV (d), high resolution chlorine spectrum (e), zinc spectra (f), nitrogen adsorption–desorption isotherms (g), and DTG/TG within the range of 35 to 550℃ (h and i) results for the samples. XRD patterns within the range of 5 to 80° (j), and the ζ-potentials (k)

Fourier-transform infrared spectroscopy (FTIR) spectrum of IPC@UiO-66-TA-ZnII showed characteristic peaks of UiO-66 at 1395.3 cm−1 (C–O–C), 678.8 cm−1 (Zr-O), and 1583.8 cm−1 (C = O). The characteristic peak of IPC was at 1508.6 cm−1 (C-N) was also present, confirming successful loading into the nanoparticles (Fig. 3c). The successful modification of IPC@UiO-66-TA-ZnII with TA-ZnII was further evidenced by the appearance of the characteristic peak (C = O–O) of TA at 1724.5 cm−1 in IPC@UiO-66-TA-ZnII [24]. The intensities of UiO-66’s characteristic peaks at 1586.7 cm−1 (C = O) and 1397.2 cm−1 (C–O–C) are weakened in IPC@UiO-66-TA-ZnII, possibly due to van der Waals forces between UiO-66 and the TA-ZnII shield [24]. Interestingly, the characteristic peak of the ester group of TA at 1714.4 cm−1 (C = O–O) in IPC@UiO-66-TA and IPC@UiO-66-TA-ZnII decreases, suggesting van der Waals forces cross-linking between UiO-66’s benzoic acid moiety and TA’s phenol moiety. The analysis reveals that initially, UiO-66 and TA form van der Waals forces, initiating the first stage of coordination self-assembly (Fig. 2a). Subsequently, UiO-66-TA reacts with ZnII, culminating in the completion of the final shield assembly. The two-step self-assembly process minimizes the likelihood of individual complexation of TA and ZnII, consistent with SEM and TEM results.

The porosity of the samples was then determined from N2 adsorption–desorption isotherms. The surface area of pristine UiO-66 composites was approximately 818.75 m2/g, as shown in Fig. 3g. The reason for the reduced surface area of IPC@UiO-66 (Brunauer–Emmett–Teller = 362.87 m2/g) was the presence of IPC molecules in their pores. More porosity reduction was observed after assembling the TA-ZnII shield, which was attributed to the sealing of the pores by the shield.

Thermogravimetric analysis and derivative thermogravimetry (TG-DTG) analysis revealed that the weight loss above 350℃ corresponded to the gradual oxidation of UiO-66 to zirconium oxide (Fig. 3h). The weight of IPC TC started to decrease rapidly from 230 °C to 310 °C. Additionally, IPC@UiO-66-TA-ZnII exhibited a gradual weight loss starting at 300 °C and 390 °C, attributed to the successful loading of IPC. The temperature at which IPC decomposes is noticeably elevated in IPC@UiO-66-TA-ZnII compared to IPC TC. This phenomenon is attributed to the protective nature of the TA-ZnII shield (Fig. 3i). X-ray diffraction (XRD) analysis indicated that the characteristic diffraction peaks of both UiO-66 and IPC were retained in IPC@UiO-66-TA-ZnII, thereby indicating the successful loading of IPC without destroying the UiO-66 metal framework or crystal structure of IPC during the loading modification (Fig. 3j).

Finally, the change in ζ-potential was measured to study the interactions among the materials. The surfaces of UiO-66 had more pronounced positive ζ-potentials (27.01 mV), as shown in Fig. 3k. The decrease in the potential of IPC@UiO-66 (18.75 mV), demonstrates the successful adsorption of IPC by UiO-66. The final IPC@UiO-66-TA-ZnII nanoparticles (– 22.78 mV) were negatively charged.

The stimulus-responsive controlled release mechanism of nanopesticides in response to pathogen spread

To evaluate the effect of the TA-ZnII shield on release performance, IPC@UiO-66 and IPC@UiO-66-TA-ZnII were examined under varying temperatures and pH values. IPC@UiO-66-TA-ZnII showed significant resistance to premature release. The cumulative release efficiency of IPC@UiO-66-TA-ZnII over 90 h was notably lower at 10 °C, 20 °C, and 30 °C, with values of 6.7%, 24.8%, and 51.6%, respectively. In contrast, IPC@UiO-66 (without TA-ZnII shields) exhibited rapid and substantial release under the same conditions, with cumulative efficiencies as high as 8.3%, 34.8%, and 73.9% (Fig. 4a and b). At pH levels of 5, 7, and 9, IPC@UiO-66 released IPC with cumulative efficiencies of 27.6%, 39.9%, and 59.6% after 90 h, while IPC@UiO-66-TA-ZnII achieved lower release efficiencies of 24.7%, 32.1%, and 39.3% due to partial disintegration of the TA-ZnII shield (Fig. 4d and e). This nano-protective armor not only protects the active ingredient on the metal framework but also significantly extends the active ingredient’s effective periods.

Fig. 4

Effects of temperature (10℃, 20℃, 30℃) (a, b, c) and pH values (5, 7, 9) (d, e, f) on the release of IPC@UiO-66 and IPC@UiO-66-TA-ZnII in ethanol: deionized water = 3:7 (v/v). Plots of the Ritger-Peppas model for the release of pesticide (c, f). Schematic diagram of IPC@UiO-66-TA-ZnII release at various temperature and pH values (g)

After being subjected to the nano-armor protection strategy, IPC release was tested under different pH and temperature conditions to explore the response characteristics of IPC@UiO-66-TA-ZnII. After 120 h, the release at 30 °C increased by 25.9% and 43.5% compared to 20 °C and 10 °C, respectively. The final cumulative release rate at pH 5 was 59.0%, whereas release efficiencies at pH 7 and 9 were lower only 45.9% and 37.9%, respectively. The release profiles at various temperatures and pH values best fit the Peppas equation (Fig. 4c and f; Table S2–5). IPC release may be driven by thermal effects and attenuated TA-ZnII coordination interactions. Under acidic conditions, the release of active ingredients from nanomaterials can be promoted by reducing the coordination between TA and metal ions [14, 25]. Moreover, cross-linking of ZnII may be disrupted in acidic environments, leading to fewer phenolate binding sites for metal ion complexation, while protonation of TA’s phenolic groups diminishes intermolecular interaction strength. Conversely, at high pH, the deprotonation of TA’s pyrogallol/catechol moiety increases its complexation strength, resulting in slow IPC release from IPC@UiO-66-TA-ZnII (Fig. 4g).

pH influences fungal growth and plant seed germination. Fungal respiration and fermentation result in the formation of a weakly acidic microenvironment, while the long processing time of rice seed germination can increase the acidity [26]. Additionally, seeds immersed in water may lead to anaerobic respiration, producing alcohol and resulting in an acidic condition that negatively affects seed germination [27]. Thus, constructing a pH-responsive delivery system based on IPC@UiO-66-TA-ZnII to explore site-specific release behavior is worthwhile. F. fujikuroi exhibited optimal spore production at pH 5, generating up to (3.7 ± 0.29) × 106 spores/mL. The production was progressively reduced as pH increased to pH 7 [produced (2.4 ± 0.22) × 106 spores/mL] and 9 [produced (1.8 ± 0.63) × 106 spores/mL), aligning with findings by Yadav et al. and Zhang et al. [20, 21]. The TA-ZnII shields, positioned on the outer surface of a metal framework, “lock” the fungicide, while the protective mechanism of nano-armor essentially requires a trigger. The TA-ZnII shield exhibited sensitivity to acid under spore spread conditions, with low pH condition acting as a “key” to unlock the nano-armor and facilitate timely IPC release.

Bioactivities of the IPC@UiO-66-TA-ZnII nanoparticles

The fungicidal activity of IPC@UiO-66-TA-ZnII against F. fujikuroi was assessed under different pH conditions by measuring mycelial growth (Fig. 5a). Given that fungicide release from nanoparticles is a prolonged process, the concentration of free IPC in the IPC@UiO-66-TA-ZnII suspension was lower than in IPC TC. Consequently, the fungicidal efficacy of the IPC@UiO-66-TA-ZnII and IPC FS was slightly reduced compared to IPC TC at the same concentrations; however, IPC@UiO-66-TA-ZnII demonstrated superior activity compared to IPC FS. Control carriers, UiO-66-TA-ZnII, also showed some fungicidal activity against F. fujikuroi (Fig. S3), due to the biocidal activity of ZrIV/ZnII ions and tannic acid within the metal framework and coating shield [28, 29]. The concentration of zinc ions in the solution was determined by ICP/MS, revealing that the carrier system gradually released zinc ions into the solution (Fig. S2). It was observed that the TA-ZnII shell releases significantly more zinc ions at pH 5 compared to pH 7 and pH 9. Yadav et al. demonstrated that zinc ions released from zinc oxide nanoparticles effectively inhibit fungal growth [30]. Zinc is known for its antifungal properties against various fungi [31, 32]. Higazy et al. further reported that the inhibitory effect of metallic zinc is significantly enhanced when complexed with tannic acid [29]. Thus, the incorporation of zinc ions and TA on the surface of nanostructures can synergistically improve the bactericidal efficiency of IPC.

Fig. 5

Fungicidal activities of IPC TC, IPC@UiO-66-TA-ZnII, and IPC FS against F. fujikuroi and IPC@UiO-66-TA-ZnII against F. fujikuroi under different pH conditions (5, 7, 9) for 6 days at 25 °C (a). Control efficacy of IPC FS and IPC@UiO-66-TA-ZnII NFS against rice bakanae on potted rice seed plants (0.15–0.25 g/kg seed) (b, c). Seeds were soaked in a spore suspension (10⁶ units/mL) for 24 h, followed by treatment with seed coating. Rice seeds were treated with non-treated CK (A), spore suspension-treated CK (B), IPC FS (C), and IPC@UiO-66-TA-ZnII NFS (D), at 0.15 g/kg seed (b-1), 0.2 g/kg seed (b-2); 0.25 g/kg seed (b-3). Three-dimensional morphological maps of the surface roughness of rice seeds treated with water (d), IPC FS (e) and IPC@UiO-66-TA-ZnII NFS (f). An asterisk (∗) indicates a statistically significant difference at the 0.05 level, n = 5

Furthermore, the effectiveness of IPC@UiO-66-TA-ZnII was evaluated using a bioactivity assay against rice bakanae in pot experiments. Three-dimensional topography analysis revealed that the surface roughness of rice seeds increased after IPC@UiO-66-TA-ZnII NFS and IPC FS coating compared to the control (Fig. 5d–f). The surface of IPC@UiO-66-TA-ZnII NFS appeared smoother than that of IPC FS, indicating a more uniform coating layer. The nano-pesticide-loaded IPC@UiO-66-TA-ZnII NFS showed improved control of rice bakanae (Fusarium fujikuroi), with efficacy rates ranging from 84.09% to 93.10%, compared to IPC FS, which ranged from 81.82% to 84.48% (Fig. 5b and c). These findings suggest that IPC@UiO-66-TA-ZnII has promising applications in sustainable agriculture. Furthermore, the EC50 of IPC@UiO-66-TA-ZnII was 0.038 μg/mL at pH 5, and 0.042 and 0.057 μg/mL at pH 7 and 9, respectively, indicating that IPC release from IPC@UiO-66-TA-ZnII was enhanced under acidic conditions. Metal complexes are known to dissociate readily under acidic conditions [14, 25, 33]. Thus, the TA-ZnII shield dissociated and released IPC under the acidic conditions, resulting in an effective fungicidal effect. These findings underscore the significance of utilizing pH as a trigger to facilitate the timely release of fungicides, an innovative strategy to enhance the efficacy of IPC in the control of rice bakanae (F. fujikuroi).

Nanoparticle uptake by fungi and plants

A high degree of control over nanoparticle morphology and surface functionalization allows certain nanoparticles to penetrate plant and mycelial tissues [34]. Despite achievements in nano-mediated delivery within plants and mycelia using various sizes of nanoparticles and surface modifications [35], the entry of MOFs framework like UiO-66-TA-ZnII into plants and mycelia remains poorly understood. As shown in Fig. 6a and d, the control sample displayed no fluorescent signals. However, mycelia exposed to UiO-66-TA-ZnII-FITC showed clear fluorescence at a 488 nm laser excitation wavelength (Fig. 6b and c). SEM and TEM analyses exhibited structural deformations and ruptured cell surfaces of treated mycelia with UiO-66-TA-ZnII, including crumpling, cellular deformations, tangles, and discontinuities (Fig. 6h), indicating the potential of UiO-66-TA-ZnII as an effective carrier that can enter the mycelia. These results are consistent with Sharma et al. [19].

Fig. 6

F. fujikuroi mycelia treated with water (a), and with UiO-66-TA-ZnII-FITC (b, c) for 5 days; Rice root cells treated with water (d), and with UiO-66-TA-ZnII-FITC (e, f) for 7 days, which were observed under a CLSM at an excitation wavelength of 488 nm. Rice cells treated with UiO-66 (g-1) and UiO-66-TA-ZnII (g-2–g-4) observed under TEM. F. fujikuroi mycelia treated with UiO-66-TA-ZnII, observed under TEM (h-1 and h-2) and SEM (h-3 and h-4). The images show progressive magnifications from left to right, with the red boxes indicating nanoparticles associated with individual cell walls and the blue boxes indicating twisted F. fujikuroi mycelia. The filled arrows indicate the cell wall being broken or fractured. Scale bars from 500 nm to 20 µm. CW annotates cell wall

To confirm the fate of nanoparticles on the subcellular scale, TEM analysis of UiO-66-TA-ZnII and UiO-66 bound to rice root cells was conducted. Characteristic cellular structures, such as the cell wall, were used as indicators to determine whether nanoparticles were localized in the extracellular or intracellular space. We compared UiO-66-TA-ZnII and UiO-66 as well as nanoparticles of different sizes (163 and 296 nm) and shapes (ortho-octahedral and spherical) to investigate the factors affecting the entry of nanoparticles into plant root cells. Notably, TEM images showed UiO-66-TA-ZnII was embedded in the cell walls in the intracellular space (Fig. 6g-2–g-4), whereas the smaller-scaled UiO-66 was found outside the cell walls (Fig. 6g-1). This finding was confirmed by the CLSM results obtained (Fig. 6e and f). Interestingly, we found that UiO-66-TA-ZnII entered plant cells, albeit in the form of spheres with increased sizes. Mechanistic studies have suggested that the addition of nano-protective armored TA-ZnII shields could be a major factor responsible for the successful entry of UiO-66-TA-ZnII into the cell wall. Meng et al. discovered that acidic conditions facilitate the disintegration of the outer shield of the TA-CuII nano-framework, resulting in the release of the copper ion and drug [36]. This degradation releases chelated metal elements which may function as pro-oxidants, contributing to cellular destruction. Furthermore, zinc ions are known to compromise bacterial cell membranes and enter cells [37]. TA has high antioxidant capacity and inhibits biofilm formation by reducing the expression of oxidative stress genes. Additionally, TA can also induce cellular damage by chelating metal ions, leading to cellular rupture and thereby impeding biofilm formation. Jailani et al. demonstrated that TA inhibits biofilm formation on plant roots by SEM [38]. Alternatively, it is also possible that the spherical structures of the nanoparticles improve their freedom of movement in convection within the tissues, thereby facilitating their transport to individual cell walls. Accordingly, interactions between the TA-ZnII shields and plant cell walls have increased their residence time in the vicinity of cells, providing more opportunities for the UiO-66-TA-ZnII to contact (potentially damage) and be utilized by plant cells. Our results highlight important features of nanoparticle transport in plants, emphasizing their importance in transport within plant root tissues.

Impact of nanoparticles on the physicochemical properties of soil

In direct seeding of rice, germinating seeds encounter various stressors due to changes in soil physicochemical properties, such as a decrease in redox potential, leading to poor or delayed emergence [39]. Results showed that the IPC@UiO-66-TA-ZnII NFS treatment significantly increased soil pH, EC, and Eh throughout the experimental phase (Fig. 7a–c). In addition, OM levels increased by 0.44% to 0.67% over 35 days compared to the IPC FS and control treatments (Fig. 7d). These results are consistent with previous studies [40]. A-N in the soil treated with the IPC@UiO-66-TA-ZnII NFS decreased later in the experiment compared to the control and IPC FS treatments (Fig. 7e). However, P and K contents increased to some extent and differed significantly throughout the study (P excluded at 7 day) (Fig. 7f and g).

Fig. 7

Effects on physicochemical properties of soil sown with rice seeds under various treatments with the addition of IPC@UiO-66-TA-ZnII nanoparticles (NFS) and IPC fungicide suspension (IPC FS). The parameters measured include: pH (a), EC (b), Eh (c), OM (d), A-N (e), P (f), K (g), S-SC (h), S-UE (i), and S-PRO (j). Rice seeds were sown in soil treated with different coatings: no pesticide coating (CK), IPC FS coating with a dose of 0.2 g/kg seed, and IPC@UiO-66-TA-ZnII NFS with the same dose. Differences between treatments were analyzed using the Tukey’s test, with comparisons made against the control group. Bars labeled by different letters are significantly different (P < 0.05, n = 3)

From days 14 to 35, S-SC activity was significantly higher in the IPC@UiO-66-TA-ZnII NFS-treated group, increasing by 0.14% to 7.41% and 10.24% to 16.69% higher, respectively (Fig. 7h). S-UE activity was also elevated in this treatment compared to the control (Fig. 7i). Additionally, S-PRO activity in the IPC@UiO-66-TA-ZnII NFS-treated soil increased by 12.54% to 16.47% and 5.21% to 17.52% compared to the control and IPC FS groups (Fig. 7j). Previous studies have reported that plant rhizosphere nutrients are positively correlated with soil enzyme activities and soil microorganisms [41]. In conclusion, the addition of the IPC@UiO-66-TA-ZnII as a seed dressing positively influenced the soil microenvironment through improving key soil-related property indices.

Effects of IPC@UiO-66-TA-ZnII NFS on soil microbial communities

Changes in soil microbial communities significantly impact soil functions [42]. Previous studies have shown that conventional fungicides in FS significantly alter seed endophytic bacterial and fungal communities, leading to a reduction in both bacterial and fungal biomass [4]. Comparable reductions in bacterial and fungal populations are noted in soils treated with the fungicide myclobutanil and the herbicide mesosulfuron-methyl [42, 43]. In this study, the differences among IPC@UiO-66-TA-ZnII NFS, IPC FS, and control groups, with PC1 and PC2 accounting for 41.1% and 18% of the variance, respectively (Fig. 8a). PC1 is the primary factor distinguishing the three sample groups. Compared to the control, IPC FS showed a greater negative bias on PC1, while IPC@UiO-66-TA-ZnII NFS had a positive impact. Genera such as Sphingomonas, Lysobacter, Massilia, Pedobacter, SC-I-84, and Flavisolibacter were positively correlated with PC1, contributing significantly to the variance (Fig. 8b). These genera are known for their capability to degrade and remove challenging organic pollutants from the soil and are vital in remediating polluted environments (Bacteroidetes vadinHA17, Arenimonas, Lysobacter, Massilia, and Sphingomonas) as well as other beneficial bacteria, including Luteitalea, and SC-I-84 [44,45,46].

Fig. 8

Soil bacterial community after sowing rice seeds treated with IPC FS and IPC@UiO-66-TA-ZnII NFS, along with the non-treated control (CK) for 7 days. OPLS-DA scores plot (a). OPLS-DA loadings plot at the genus level (blue circles represent some of the beneficial bacteria) (b). Heatmap at the genus level for the top 40 species (c), with the legend on the right displaying color intervals for different R values (n = 3). Histograms showing species composition and relative abundance of the top 20 bacterial genera (d), and family level (e). Intergroup differences classification unit presentation chart (f). Pearson’s correlation analysis of environmental factors, Mantel test, and Spearman’s correlation analysis between bacterial community and environmental factors (g, upper right panel; g lower left panel; h). Red lines represent P < 0.01, green lines represent 0.01 < P < 0.05, grey lines represent P ≥ 0.05. The number of asterisks indicate the degree of correlation: * P ≤ 0.05; ** P ≤ 0.01

The presence of beneficial bacteria is key to the differences observed among IPC@UiO-66-TA-ZnII NFS, IPC FS, and control groups, as supported by the heatmap and Manhattan results (Figs. 8c and S4), which show that IPC@UiO-66-TA-ZnII NFS significantly increased their abundance. The IPC@UiO-66-TA-ZnII NFS treatment enhanced the bacterial communities at the familyand genus levels compared to CK and IPC FS-treated soil (Fig. 8d–f). Naked IPC in IPC FS had negative effects on soil flora, while the IPC@UiO-66-TA-ZnII effectively dispersed IPC at the nanoscale and encapsulated it, which reduced the adverse effects on soil flora.

Linking different bacterial communities to environmental variables has elucidated key factors affecting the variability of bacterial community composition in soil. The Mantel test and Pearson correlation plots showed the correlation and significance between the bacterial communities and each environmental factor. Soil bacterial communities were significantly affected by the EC, P, and S-PRO (P < 0.01) as well as by K content (P < 0.05) (Fig. 8g). Furthermore, the correlation heatmaps analyses utilize Spearman correlation to reveal the relationship between the abundance of the phyla and environmental factors (Fig. 8h). This analysis highlighted that the driving directions of pH and EC are clearly opposite, which aligns with the results reported by Gan et al. [47]. This indicates that these factors are interdependent within the soil ecosystem.

Safety evaluation of IPC@UiO-66-TA-ZnII in zebrafish

As shown in Table S6, at 96 h, the LC50 values were 1.983 and 2.588 mg/L for IPC FS and IPC TC, respectively, while it was 6.283 mg/L for IPC@UiO-66-TA-ZnII. The toxicity of IPC FS and IPC TC to zebrafish was significantly higher than that of the IPC@UiO-66-TA-ZnII nanoparticles. This lower toxicity may be attributed to the slow release of IPC encapsulated in the IPC@UiO-66-TA-ZnII nanoparticle system, thus reducing both the concentration of IPC in the solution and its acute toxicity to zebrafish, unlike IPC FS. Additionally, the surfactants present in IPC FS may contribute to toxicity [