English

• The discovery of antibiotics was a critical milestone in the history of human therapeutic medicine, but now years later, the potential risks of excessive use of antibiotics has been recognized [1]. Most antibiotics cannot degrade spontaneously in the natural environment, and their overuse has led to the evolution of drug-resistant bacteria [2]. Fortunately, more and more countries have begun to take measures to control the use of antibiotics [3]. Nevertheless, there is still an urgent need to develop effective technologies for detecting and removing antibiotics from the aqueous environment. To date, the detection of antibiotics is mostly dependent on various instrumental approaches, such as high-performance liquid chromatography, gas chromatography, capillary electrophoresis, Raman spectroscopy [4–7]. The relatively high cost and cumbersome operational processes may hinder the wider applicability of the aforementioned methods [8]. As for removing antibiotics from contaminated environments, the mainstream methods mainly include advanced oxidation, photocatalysis, adsorption, biodegradation, etc. [9–12]. Among the above removal methods, adsorption stands out due to its desirable advantages of simple operation, low energy consumption and comparatively high efficiency [13,14]. Generally, in most cases, adsorption and detection are two separate processes [15]. It is time-consuming and costly [16]. Therefore, desirably, if an antibiotic adsorbent can be exploited to detect the target substances efficiently, this can greatly improve the efficiency and provide new prospects for the design of related materials.

  In recent years, many studies have focused on the modification of materials in analytical chemistry [17–19]. For example, by combining various fluorescent substances (such as quantum dots, molecularly-imprinted substances and carbon dots) with porous solids, multifunctional composite materials can be obtained to realize the near-simultaneous removal and detection of antibiotics [20,21]. Besides, light-emitting metal-organic frameworks (LMOFs), which possess light-emitting properties and have porous structures, are a kind of promising candidate material for the removal and detection of contaminants [22–27]. Li et al. prepared a composite fluorescent sponge by integrating a porous fluorescent metal-organic framework and a melamine sponge to achieve effective removal and detection of mycotoxins, which has great potential in the fabrication of new sensors for practical applications [28]. Gai et al. synthesized ultra-stable porous three-dimensional zinc-based LMOFs, with excellent fluorescence performance, successfully used it for the simultaneous or near-simultaneous removal and detection of various antibiotics in water [29]. Although several LMOFs with excellent removal/detection performance have been developed, it is difficult to separate and recycle the LMOFs in real applications [4].

  Layered double hydroxides (LDHs), also known as hydrotalcite, are a class of ionic layered compounds composed of positively charged metal hydroxide layers and interlayer exchangeable anions. Layered double oxides (LDOs) are obtained by calcination of LDHs [30,31], which have strong ferromagnetism when possessing Ni and Fe as cations [32,33]. Thus, combined with LDO, the recycling process of LMOFs can be simplified. Meanwhile, with the large surface area of an LDO, ion exchange and "memory effect" may make it an ideal material for synergistic adsorption and detection of antibiotics with LMOFs [34,35]. In addition, MOFs with adjustable structures have fascinated many researchers. They have adopted different methods to design the topological structures of MOFs, such as the modification of organic ligands, the change and mixing of metal ions, acid etching, and to obtain many MOFs with excellent performance [36]. The topological design of MOFs has been applied in various fields, such as catalysis, gas adsorption, separation [37,38]. However, on the aspects of antibiotic adsorption and detection, the relationship between topological configuration and adsorption performance has been rarely reported hitherto. It is therefore of great interest and desirability for the topic to be studied further [39].

  In this work, LDO@MOFs with different functional groups were obtained by in-situ approach (Scheme 1). Due to synergism, the composites show excellent performance for removal and fluorescence detection antibiotics in wastewater. The doping of LDO not only enhance the adsorption capacity, but also provide great convenience for regeneration. In addition, the mechanisms were investigated, to provide a basis for the rational design of LDO@MOFs [40,41].

  Scheme 1

  

  Scheme 1.  Synthetic routes, topological analysis and application of LDO@Zn-MOFs.

  DownLoad: Full-Size Img PowerPoint

  As shown in the XRD patterns (Fig. 1a and Fig. S1 in supporting information), the corresponding positions of the characteristic diffraction peaks of LDH, LDO and Zn-MOFs are consistent with the literature [17,42]. This indicates the successful synthesis of the above materials. The XRD patterns of LDO@Zn-MOF-COOH showed characteristic peaks similar to those of LDO and Zn-MOF-COOH, indicating that they were successfully combined. In addition, the characteristic peaks of LDH corresponding to the (003) and (006) crystal planes reappeared in LDO@Zn-MOF-COOH. This is probably due to the "memory effect" of LDH under hydrothermal conditions, whereby LDO was partially reduced to LDH again.

  Figure 1

  

  Figure 1.  (a) XRD pattern and (b) FT-IR spectra of Zn-MOF-COOH, LDO and LDO@Zn-MOF-COOH. (c) Changes of saturate magnetization with the calcination time of LDO. The TEM images of (d) LDO, (e) Zn-MOF-COOH and (f, g) LDO@Zn-MOF-COOH. The SEM images of (h) LDO and (i) LDO@Zn-MOF-COOH.

  DownLoad: Full-Size Img PowerPoint

  The FT-IR spectra of LDO, Zn-MOFs and LDO@Zn-MOFs are depicted in Fig. 1b and Fig. S2 (Supporting information). These spectra included pyridyl stretching vibration peaks at 1620 cm⁻¹, 1580 cm⁻¹, and 1475 cm⁻¹, as well as an out-of-plane bending vibration peak of a benzene ring at 763 cm⁻¹. The peaks near 1510 cm⁻¹ and 1610 cm⁻¹ in LDO@Zn-MOF-NO₂ were attributed to the asymmetric stretching vibration of the nitro group. The LDO@Zn-MOF-COOH exhibited a broad absorption band at 2500–3500 cm⁻¹, which was attributed to the symmetric stretching of the carboxyl group. The absorption bands at 2960 cm⁻¹ and 2870 cm⁻¹ were due to the stretching vibration of the methyl groups. The magnetic property of LDO@Zn-MOF-COOH is indicated in Fig. 1c. LDO@Zn-MOF-COOH showed strong ferromagnetism and the powder can be attracted by a magnet in 2 s. The magnetic properties of LDO@Zn-MOF-COOH increased with the calcination time of LDO.

  As shown in Figs. 1d–g, TEM images revealed that the Zn-MOF-COOH had a rod-like morphology with a length of 2 µm and LDO nanosheets with uniform size and hexagonal shapes. In the sample of LDO@MOF-COOH, LDO particles with a size of about 100 nm were observed to be uniformly supported on the surface of the rod-like MOF. The morphology of LDO@MOF-COOH was further confirmed by the SEM results (Figs. 1h and i).

  The specific surface area and pore distribution data were measured by the N₂ adsorption desorption isotherm at 77 K, as shown in Fig. S3 in Supporting information. The N₂ isotherm of LDO@Zn-MOFs conformed to the isotherm of the microporous structure. According to the BET model, the specific surface areas of LDO@Zn-MOFs were 223.57 m²/g, 259.38 m²/g, 333.25 m²/g, 395.56 m²/g, respectively. It is clear that large specific surface area and appropriate pore diameter make LDO@Zn-MOFs suitable to be used as adsorbents for analytes, including antibiotics in the present context.

  Four typical sulfonamides (sulfadiazine, SDZ and sulfamethazine, SMZ) and quinolones (enrofloxacin, ENR and ciprofloxacin, CIP) were selected to study their adsorption properties by different adsorbents. Antibiotic molecules present diverse ionic states in different acid-base environments, and pH is one of the most important factors in their adsorption process. As shown in Fig. 2a and Figs. S4a–c (Supporting information), pH values affected significantly the adsorption capacity of LDO@MOFs. (The adsorption capacity was calculated using the following Eq. S1 (Supporting information). Taking the adsorption of SDZ by LDO@Zn-MOF-COOH as an example, its capacity increased in the pH range of 4.0–6.0 and decreased in the range of 6.0–9.0, with the maximum capacity at pH 6.0. Analogously, the optimal pH values for antibiotic adsorption of LDO@Zn-MOF, LDO@Zn-MOF-CH₃ and LDO@Zn-MOF-NO₂ were 7.0, 8.0 and 8.0, respectively.

  Figure 2

  

  Figure 2.  Evaluation of (a) initial pH value, (b) temperature and (c) time for adsorption of SDZ on LDO@Zn-MOFs, (d) zero-charge point test of different LDO@Zn-MOFs.

  DownLoad: Full-Size Img PowerPoint

  The effect of temperature on the adsorption performance of different adsorbents for each antibiotic is shown in Fig. 2b and Figs. S4d–f (Supporting information). The experimental results showed that the most favorable adsorption temperature of LDO@Zn-MOF-COOH for antibiotics was 30 ℃. When the experimental temperature was lower than 45 ℃, the overall adsorption capacity increased with the increase in temperature, while it decreased when the temperature was higher than 45 ℃. The optimal adsorption temperatures of LDO@Zn-MOF, LDO@Zn-MOF-CH₃ and LDO@Zn-MOF-NO₂ were 35 ℃, 30 ℃ and 35 ℃, respectively.

  The effect of time on the adsorption capacity was studied and the results as shown in Fig. 2c and Figs. S4g–i. Taking the adsorption of SDZ as an example, at the beginning of the adsorption, with the increase of the adsorption time, the adsorption capacity of the various adsorbents increased sharply. The adsorption amounts of LDO@Zn-MOF-COOH and LDO@Zn-MOF-NO₂ reached equilibrium after 60 and 90 min, respectively, while LDO@Zn-MOF-CH₃ and LDO@Zn-MOF needed 120 min. These results indicated that LDO@Zn-MOF-COOH and LDO@Zn-MOF-NO₂ showed faster and more efficient adsorption for antibiotics, and the adsorption capacity was significantly improved after functional group modification. To better understand the adsorption kinetics, the Lagrangian pseudo-first-order and Lagrangian pseudo-second-order models (Eqs. S2 and S3 in Supporting information) were used to fit the experimental data (Figs. S5a–h and Tables S1–S4 in Supporting information). The results indicated that the Lagrangian pseudo-second-order kinetic model was more consistent with the adsorption behavior of antibiotics on LDO@Zn-MOFs.

  As shown in Figs. S5i–p (Supporting information), the adsorption capacities of LDO@Zn-MOFs for antibiotics with different concentrations were evaluated using Langmuir and Freundlich adsorption models, which were fitted and analyzed by Eqs. S4 and S5 (Supporting information). It can be seen that with the increase of the initial concentration of antibiotics, the adsorption capacity of each adsorbent showed a significant increase. The fitting results indicate that the Langmuir model could better describe the adsorption of antibiotic molecules on LDO@Zn-MOFs (Tables S5–S8 in Supporting information). This means that a uniform monolayer adsorption occurred between the antibiotic molecules and the adsorbent, and each adsorbent had a fixed adsorption site.

  LDO@Zn-MOFs possess high adsorption capacities for the four antibiotics and the values can reach at least 150 mg/g and up to 313 mg/g, as shown in Tables S5-S8. As is known, the porosity of an adsorbent is a critical factor that determines adsorption performance. The larger specific surface area and pores provide more adsorption sites. Of the four materials, LDO@Zn-MOF-COOH had the highest specific surface area and porosity. In our opinion, the structural features of LDO@Zn-MOF-COOH endowed relatively stronger enrichment capability on this composite. Compared with methyl and nitro groups, the carboxyl group in LDO@Zn-MOF-COOH has a slightly larger size. The presence of bigger substituent groups led to a large cage configuration, which provided more access and space for the antibiotic molecules. Also, oxygen-containing functional groups can serve as donors forming stronger hydrogen bonds. We hypothesize that the electrostatic effect was also a main factor in the adsorption of antibiotics. So, the zero-charge point of different materials was measured using a pH meter. As shown in Fig. 2d, the zero-charge point of LDO@Zn-MOF-COOH at 6.4, meant that when pH < 6.4, its surface charge was positive, while when pH > 6.4, the material was negatively charged. The dissociation constants pK_a1 and pK_a2 of SDZ are 1.57 and 6.5, respectively [43]. When pH < 1.57, most of the SDZ existed as cations. When 1.57 < pH < 6.5, it existed mainly as a zwitterion, and the number of anions gradually increased with the increase of pH value. When pH > 6.5, the main forms of SDZ were as anions. After testing, it was found that the adsorption effect was the best when the pH value was 6. This is because the surface charge of LDO@Zn-MOF-COOH was positive when the pH value was 6, and SDZ mainly existed as zwitterions (72%) and anions (28%). Thus, the adsorption can be most appropriately considered as being due to an electrostatic effect [44]. LDO has a strong adsorption capacity for anions due to its interlayer ion exchange [45]. Therefore, the synergistic electrostatic effect of Zn-MOFs and LDO in LDO@Zn-MOFs was an important factor determining adsorption capacity [46,47]. To verify the synergistic effect in composite materials, the adsorption performances of Zn-MOFs and LDO alone for different antibiotic molecules were investigated, and compared with those of the LDO@Zn-MOF composites [24]. As shown in Fig. S6 (Supporting information), compared with LDO and Zn-MOFs, the LDO@Zn-MOFs had a higher adsorption quantity, indicating that the doping of LDO indeed promoted the adsorption capacity of antibiotics to the composites.

  The four Zn-MOFs have the same central metal ions and similar organic ligands, but the supermolecule topological networks have some difference (Figs. S9 and S10 in Supporting information). Due to the introduction of oxygen-containing substituents, hydrogen bonding is the main force for construction of supermolecule frameworks in Zn-MOF-NO₂ and Zn-MOF-COOH. Different from the open networks of Zn-MOF and Zn-MOF-CH₃, the supermolecule frameworks of the other two Zn-MOFs have more cavities or cages. Undoubtedly, the confined spaces can effectively increase the specific surface areas of the corresponding materials to provide more adsorption active sites [48–50]. The experiment results mentioned above showed that the advantages of functionalized Zn-MOFs in supermolecule topological networks were preserved by the related composite materials.

  Considering the practical applicability of the materials considered, the adsorbents need good reusable performance. The cyclic adsorption effect of the different materials on the four antibiotics was tested, yielding the results given in Fig. S11 (Supporting information). After five cycles of adsorption and regeneration experiments, the adsorbed antibiotic amount achieved by LDO@Zn-MOFs reached 75% of that of the first-time use, indicating that LDO@Zn-MOFs have reasonable regenerative/recyclability and stability properties. Nevertheless, we believe this is an aspect of the present work that needs improvement.

  Before the detection of antibiotics was undertaken, the fluorescence characteristics of the composites were tested. As shown in Fig. S12 (Supporting information), all four materials showed strong fluorescence signals (excitation at 260 nm, producing strong emission at 364 nm, 382 nm, 404 nm, and 422 nm, respectively). The fluorescence intensity was measured, and the quenching efficiency was calculated by Eq. S6. The effect of different pH values and temperatures on detection were explored, as shown in Fig. S13 (Supporting information). Taking LDO@Zn-MOF-COOH for the detection of SDZ as an example, the most favorable pH for detecting antibiotics was 6, and the temperature 30 ℃, which were consistent with the most suitable adsorption conditions. The adsorption of antibiotics by LDO@Zn-MOFs obviously had a pre-concentration effect, as expected, thereby improving the detection performance [51].

  To better understand the fluorescence detection performance of LDO@Zn-MOFs for different antibiotics, fluorescence titration experiments were conducted. Different materials were added into the antibiotic solutions with various concentrations. The fluorescence intensity and fluorescence quenching efficiency were measured. As can be seen from Fig. 3 and Figs. S14 and S15 (Supporting information), different materials showed different fluorescence quenching efficiencies for the various antibiotics. In the low concentration range (0.1–50 mg/L), the I₀/I ‒ 1 of LDO@Zn-MOFs showed a linear relationship with the antibiotic concentration, but as the concentration continued to increase, a linear shift phenomenon appeared, which may be the result of the competitive absorption between antibiotics and LDO@Zn-MOFs, charge transfer and the self-absorption of LDO@Zn-MOFs. The quenching constants of various antibiotics were obtained through fitting calculation, as shown in Tables S9–S12 (Supporting information). Among them, LDO@Zn-MOF-COOH showed the best quenching efficiency, likely due to the combination of electron transfer and competitive absorption. Besides, their high adsorption capacities led to their good enrichment effect for antibiotics, which may also be one of the factors affecting the detection effect.

  Figure 3

  

  Figure 3.  Effect on the emission spectra and the corresponding SV curves of LDO@Zn-MOF-COOH dispersed in different concentrations of (a) SDZ, (b) SMZ, (c) CIP and (d) ENR.

  DownLoad: Full-Size Img PowerPoint

  The detection mechanism with respect to the antibiotic molecules using LDO@Zn-MOFs as adsorbents was dominated by electron transfer and resonance energy transfer. From the electron transfer point of view, MOFs can be regarded as large "molecules", with valence band (VB) and conduction band (CB) energy levels resembling molecular orbitals (MOs). The CB level was higher than the lowest unoccupied molecular orbital (LUMO) energy level of the antibiotic, which led to the transfer of electrons, contributing to the occurrence of fluorescence quenching. Therefore, the highest occupied molecular orbital and LUMO energy levels of the four antibiotic molecules were obtained by density functional theory calculations (Table S13 in Supporting information). However, the trend of quenching efficiency did not completely correspond to the electron transfer theory, indicating that the electron transfer mechanism was not the only factor affecting fluorescence quenching, and that others may be involved in the detection process.

  Competitive absorption may be another reason for fluorescence quenching. The nonlinear relationship of the S-V curve of the antibiotic indicated that competitive absorption existed in the fluorescence quenching process. When the fluorescence excitation spectra of LDO@Zn-MOFs overlapped with the UV absorption spectra of the antibiotics, part of the energy of the excitation wave was partially absorbed by the antibiotics, representing a competitive effect, resulting in fluorescence quenching. The excitation spectra of LDO@Zn-MOFs and the UV absorption spectra of the four antibiotic molecules were normalized. As shown in Fig. S16 (Supporting information), the fluorescence excitation peak (260 nm) of LDO@Zn-MOFs overlapped with the UV absorption spectra of SDZ, SMZ, CIP and ENR, among which the overlap of SDZ (266 nm), ENR (261 nm) and CIP (263 nm) was significantly higher than that of SMZ (277 nm). Therefore, SDZ, ENR and CIP showed stronger fluorescence quenching efficiency. The spectrum of CIP had an absorption peak at 277 nm, far away from the excitation peak of LDO@Zn-MOFs. Its quenching was dominated by the electron transfer effect, and the fluorescence quenching ability was weaker than those of SDZ and ENR. In addition, the concentration effect caused by the adsorption of antibiotics on the adsorbents led to the enrichment of antibiotics in its pores, enhancing the contact between the pore surface and the analytes and further improved the detection performance. The synergistic effects of electron transfer, competitive absorption, and enrichment effect enabled LDO@Zn-MOFs to produce multiple quenching effects on various antibiotic molecules.

  To evaluate the applicability of the materials in a genuine environment (wastewater), antibiotics at different concentrations were added to such samples representing matrix-matched solutions for detection. The RSD and relative recovery values with different concentrations were calculated according to Eqs. S7 and S8 (Supporting information), and the results were shown in Table S14 (Supporting information). Antibiotic residues were detected in the genuine (unspiked) wastewater samples. Since the antibiotics in the wastewater could not be selectively removed (due to our viewpoint that the adsorbent had universal, rather than selective, adsorption capability), the total amount of antibiotics in the unspiked genuine sample solution was considered. The relative recoveries of the antibiotics from different solutions by LDO@Zn-MOF-COOH ranged from 95% to 115%, with the RSDs of < 6%. Thus, the data indicated that our strategy had high precision and accuracy. In addition, the method was demonstrably applicable to genuine complex wastewater samples.

  In summary, we obtained four LDO@Zn-MOFs with ideal adsorption and detection performance for antibiotics in wastewater. The difference in adsorption properties was thought to came from the doping of different functional groups. Hydrogen bonds and electrostatic interaction were the key factors affecting the adsorption capacity. Moreover, the doping of magnetic LDO not only gave them practical recyclability, but also improved the adsorption capacities. Tripyridine ligands endowed Zn-MOFs with excellent fluorescence properties. The experiment results showed that the limits of detection of the antibiotics were at the parts per billion levels and the composite materials had enough high accuracy and precision for evaluation in real wastewater. This work provided not only an effective strategy for the synthesis of stable magnetic MOF composites, but also a new idea for the design of recyclable MOF composites that can be applied to the near-simultaneous removal (by adsorption), and detection of pollutants in water samples.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  Acknowledgments

  The authors are grateful for the financial support from the National Natural Science Foundation of China (Nos. 22276080, 21605105), the Foreign Expert Project, China (No. G2022014096L), the Natural Science Foundation of Jiangsu Province, China (No. BK20211340), and Graduate Research and Practice Innovation Program of Jiangsu Province, China (No. KYCX22_3835).

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2023.109338.

  
  
• 1. [1]

     P.H. Chang, C.Y. Chen, R. Mukhopadhyay, et al., J. Colloid Interface Sci. 623 (2022) 627–636. doi: 10.1016/j.jcis.2022.05.050

  2. [2]

     W. Wang, H. Yan, U. Anand, et al., J. Am. Chem. Soc. 143 (2021) 1854–1862. doi: 10.1021/jacs.0c10285

  3. [3]

     K. Yuan, K. Huang, Y.Q. Yang, et al., Nano Today 58 (2022) 47–57.

  4. [4]

     S. Bajkacz, E. Felis, E. Kycia-Slocka, et al., Sci. Total Environ. 726 (2020) 138071. doi: 10.1016/j.scitotenv.2020.138071

  5. [5]

     G. Barzan, A. Sacco, L. Mandrile, et al., Sens. Actuator. B: Chem. 118 (2020) 309–339.

  6. [6]

     M.A.F. Perez, D. Daniel, M. Padula, et al., Food Chem. 362 (2021) 129902. doi: 10.1016/j.foodchem.2021.129902

  7. [7]

     Y. Yao, T. Hu, Y.Q. Chai, et al., Sens. Actuator. B: Chem. 366 (2022) 131993. doi: 10.1016/j.snb.2022.131993

  8. [8]

     R. Abazari, A.R. Mahjoub, J. Shariati, J. Hazard. Mater. 366 (2019) 439–451. doi: 10.1016/j.jhazmat.2018.12.030

  9. [9]

     B. Lin, S. Li, Y. Peng, et al., J. Hazard. Mater. 406 (2021) 124675. doi: 10.1016/j.jhazmat.2020.124675

  10. [10]

      Z. Khazaee, A.R. Mahjoub, A.H. Cheshme Khavar, App. Catal. B: Environ. 183 (2021) 297–309.

  11. [11]

      H. Peng, W. Xiong, Z. Yang, et al., Chem. Eng. J. 376 (2021) 426–440.

  12. [12]

      C. Zhou, H. Zhou, Y. Yuan, et al., Chem. Eng. J. 389 (2021) 420–430.

  13. [13]

      W. Tian, J. Lin, H. Zhang, et al., J. Hazard. Mater. 423 (2022) 127083. doi: 10.1016/j.jhazmat.2021.127083

  14. [14]

      X. Weng, W. Cai, G. Owens, Z. Chen, J. Clean. Prod. 319 (2021) 128734. doi: 10.1016/j.jclepro.2021.128734

  15. [15]

      L. Lu, Q. Yang, Q. Xu, et al., Crit. Rev. Environ. Sci. Technol. 52 (2021) 3493–3524. doi: 10.1109/tap.2020.3037713

  16. [16]

      Y. Tang, H. Huang, W. Xue, et al., Chem. Eng. J. 413 (2020) 384–416. doi: 10.1007/s10157-020-01853-4

  17. [17]

      D. Wu, P.F. Zhang, G.P. Yang, et al., Coord. Chem. Rev. 135 (2021) 434–476. doi: 10.1093/geroni/igab046.1687

  18. [18]

      C.Y. Wang, C.C. Wang, X.W. Zhang, et al., Chin. Chem. Lett. 33 (2022) 1353–1357. doi: 10.1016/j.cclet.2021.08.095

  19. [19]

      Y. Wang, X. Ma, Y. Peng, et al., J. Hazard. Mater. 416 (2021) 126098. doi: 10.1016/j.jhazmat.2021.126098

  20. [20]

      F. Ahmadijokani, H. Molavi, M. Rezakazemi, et al., Coord. Chem. Rev. 115 (2021) 445–466.

  21. [21]

      X.Z. Zhao, F.X. Zhan, G.Z. Liao, et al., J. Colloid Interface Sci. 620 (2022) 465–477. doi: 10.1016/j.jcis.2022.04.045

  22. [22]

      Q.Y. Xu, Z. Tan, X.W. Liao, C. Wang, Chin. Chem. Lett. 33 (2022) 22–32. doi: 10.1016/j.cclet.2021.06.015

  23. [23]

      W. Zhang, H. Ma, T. Li, C. He, Chin. Chem. Lett. 33 (2022) 3726–3732. doi: 10.1016/j.cclet.2021.11.002

  24. [24]

      J.L. Ni, Y. Liang, G.J. Li, et al., J. Mol. Struct. 98 (2022) 1257–1269.

  25. [25]

      C.S. Ji, R.Q. Fan, J. Zhang, et al., Sens. Actuator. B: Chem. 368 (2022) 131399.

  26. [26]

      K. Zhu, R.Q. Fan, J. Zhang, et al., Dalton Trans. 50 (2021) 15679–15687. doi: 10.1039/d1dt02733f

  27. [27]

      Y.Y. Yin, J. Zhang, R.Q. Fan, et al., J. Hazard. Mater. 446 (2023) 130753. doi: 10.1016/j.jhazmat.2023.130753

  28. [28]

      Z.S. Li, X.H. Xu, H.R. Quan, et al., Chem. Eng. J. 410 (2020) 128268.

  29. [29]

      S. Gai, J. Zhang, R. Fan, et al., ACS Appl. Mater. Interfaces 12 (2020) 8650–8662. doi: 10.1021/acsami.9b19583

  30. [30]

      S. Tang, G.H. Chia, H.K. Lee, J. Colloid Interface Sci. 437 (2015) 316–323. doi: 10.1016/j.jcis.2014.09.038

  31. [31]

      S. Tang, Y. Chang, G.H. Chia, H.K. Lee, Anal. Chim. Acta 885 (2015) 106–113. doi: 10.1016/j.aca.2015.05.029

  32. [32]

      S. Tang, G.H. Chia, Y. Chang, H.K. Lee, Anal. Chem. 86 (2014) 11070–11076. doi: 10.1021/ac503323e

  33. [33]

      S. Tang, H.K. Lee, Anal. Chem. 85 (2013) 7426–7433. doi: 10.1021/ac4013573

  34. [34]

      Y. Yao, T.Y. Chen, W. Mao, Sens. Actuator. B: Chem. 193 (2021) 343–354.

  35. [35]

      Y. Yao, M.L. Xue, W. Mao, et al., Analyst 146 (2021) 6470–6473. doi: 10.1039/d1an01405f

  36. [36]

      Z. Wu, H. Niu, J. Chen, J. Chen, Chemosphere 280 (2021) 130801. doi: 10.1016/j.chemosphere.2021.130801

  37. [37]

      F.M. Amombo Noa, M. Abrahamsson, E. Ahlberg, et al., Chem 7 (2021) 2491–2512. doi: 10.1016/j.chempr.2021.07.006

  38. [38]

      L.T. Yang, P.Y. Cai, L.L. Zhang, et al., J. Am. Chem. Soc. 143 (2021) 12129–12137. doi: 10.1021/jacs.1c03960

  39. [39]

      W. Gong, H.M. Xie, K.B. Idrees, et al., J. Am. Chem. Soc. 144 (2022) 1826–1834. doi: 10.1021/jacs.1c11836

  40. [40]

      K. Yu, T. Wei, Z. Li, et al., J. Am. Chem. Soc. 142 (2020) 21267–21271. doi: 10.1021/jacs.0c10442

  41. [41]

      G. Chen, X. Kou, S. Huang, et al., Angew. Chem. Int. Ed. 59 (2020) 2867–2874. doi: 10.1002/anie.201913231

  42. [42]

      X.F. Zhang, Z.Y. Wang, L.L. Xu, et al., J. Colloid Interface Sci. 606 (2022) 1852–1865. doi: 10.1016/j.jcis.2021.08.143

  43. [43]

      Y. Zhang, S.Q. Hu, H.C. Zhang, et al., Sci. Total Environ. 228 (2018) 239–248.

  44. [44]

      J. Fan, Adsorption Behavior and Mechanism of Typical Endocrine-Disrupting Compounds and Antibiotics Onto Different Resin, Nanjing University, 2016 Ph. D. thesis.

  45. [45]

      S. Tokalioglu, E. Yavuz, S. Demir, S. Patat, Food Chem. 237 (2017) 707–715. doi: 10.1016/j.foodchem.2017.06.005

  46. [46]

      X. Zhang, W. Fan, M. Fu, et al., Chem. Commun. 56 (2020) 10513–10516. doi: 10.1039/d0cc04007j

  47. [47]

      R.R. Panicker, A. Sivaramakrishna, Coord. Chem. Rev. 459 (2022) 214426. doi: 10.1016/j.ccr.2022.214426

  48. [48]

      Z. Lu, Y. Jiang, P. Wang, et al., Anal. Bioanal. Chem. 412 (2020) 5273–5281. doi: 10.1007/s00216-020-02737-y

  49. [49]

      Y. Liang, X.X. Yang, X.Y. Wang, et al., Nat. Commun. 14 (2023) 1–14. doi: 10.1504/ejie.2023.10053627

  50. [50]

      X.P. Deng, M.J. Deng, Y.L. Li, et al., Chem. Eng. J. 474 (2023) 145694. doi: 10.1016/j.cej.2023.145694

  51. [51]

      L.Z. Han, X.J. Liu, X.W. Zhang, et al., J. Hazard. Mater. 302 (2022) 424–432.

• 

  Scheme 1  Synthetic routes, topological analysis and application of LDO@Zn-MOFs.

  下载: 全尺寸图片 幻灯片
  

  Figure 1  (a) XRD pattern and (b) FT-IR spectra of Zn-MOF-COOH, LDO and LDO@Zn-MOF-COOH. (c) Changes of saturate magnetization with the calcination time of LDO. The TEM images of (d) LDO, (e) Zn-MOF-COOH and (f, g) LDO@Zn-MOF-COOH. The SEM images of (h) LDO and (i) LDO@Zn-MOF-COOH.

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Evaluation of (a) initial pH value, (b) temperature and (c) time for adsorption of SDZ on LDO@Zn-MOFs, (d) zero-charge point test of different LDO@Zn-MOFs.

  下载: 全尺寸图片 幻灯片
  

  Figure 3  Effect on the emission spectra and the corresponding SV curves of LDO@Zn-MOF-COOH dispersed in different concentrations of (a) SDZ, (b) SMZ, (c) CIP and (d) ENR.

  下载: 全尺寸图片 幻灯片
•