English

• 0.   Introduction

  With the rapid development of industrial and economic globalization, people are yearning for a high-quality living environment, so they are paying more and more attention to environmental pollutants^[1-4]. With a large number of toxic pollutants entering the environment, it seriously threatens the ecological environment of human survival and development. For example, the discharge of pollutants such as antibiotics, nitro explosives, metal ions, and raw chemicals will directly or indirectly threaten our lives^[5-8]. Therefore, it's critically important to rapidly develop efficient environmental surveillance techniques and diminish the release of pollutants^[9-12].

  At present, researchers have developed many classical analytical methods for controlling and reducing environmental pollution and removing environmental pollutants, which are used to detect various toxic and hazardous substances in gases or liquids, such as surface-enhanced Raman spectroscopy^[13-14], liquid/gas chromatography (LC/GC)^[15-16], gas chromatography- mas spectrometry (GC-MS)^[17-19], polymerase chain reaction (PCR)^[20-21], enzyme-linked immunosorbent assay (ELISA)^[22-23], fluorescence analysis^[24-25] and other techniques. However, traditional detection techniques like LC and GC-MS require complex pretreatment and expensive equipment. Techniques such as immunoassay and PCR require rigorous procedures and expensive reagents and are very time-consuming^[26-27]. Therefore, developing efficient and user-friendly techniques for overseeing environmental and food safety is essential. Fluorescence detection technology is widely regarded as an effective means to detect toxic and harmful substances because of its advantages of cost-effectiveness, easy operation, increased sensitivity, and specificity, swift response, intuitive visual recognition, and real-time tracking ability^[28-30].

  Coordination polymers (CPs) are a type of organic-inorganic hybrid materials, formed by merging metal ions with organic ligands through coordination bonds^[31-32], which has been widely used in catalysis^[33-34], drug delivery^[35-36], adsorption separation^[37-38], magnetism^[39-40], water treatment^[41-42], chemical sensor^[43-45], and biomedicine^[46-48], and has attracted the attention of many scientists. Thus the combination of CPs with fluorescence sensing can effectively improve the selectivity and sensitivity of the detected substances. Chen et al. designed and synthesized two Ln-CPs, capable of effectively and with high sensitivity identifying diverse pollutants present in water: aniline (ANI), nitrobenzene (NB), tetracycline (TC), pyrimethanil (Pth), and tryptophan (Trp). Investigations were also conducted into how fluorescence is suppressed^[49]. Cai et al. reported a Zn-CP ([Zn(H₂dpa)(bpy)_1.5]_n, H₄dpa=4-(2, 4-dicarboxyphenoxy) phthalic acid, bpy=2, 2'-bipyridine), which showed a strong fluorescent response to 2, 4, 6-trinitrophenol (TNP) and Pth, with the detection limits (LODs) of 5.49 and 74.1 nmol·L^-1 respectively^[50].

  In this work, a Cd-CP ({[Cd(H₂dpa)(bpy)]·3H₂O}_n) with excellent fluorescence properties was designed and hydrothermal synthesized by using H₄dpa (Scheme 1) and bpy ligands. Cd-CP could detect metal ions (Fe³⁺ and Zn²⁺), 2, 4, 6-trinitrophenylhydrazine (TRI), and pyrimethanil (Pth) effectively and sensitively. In particular, Cd-CP had a fluorescence quenching effect on Fe³⁺, but a fluorescence enhancement effect on Zn²⁺, so an "on-off-on" logic gate was designed to expand the application of logic gate switch devices in the field of chemistry.

  Scheme 1

  

  Scheme 1.  Structure of ligand H₄dpa

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  1.   Experimental

  The reagents and instrumentation can be found in the Supporting information.

  1.1   Synthesis of Cd-CP

  H₄dpa (17.3 mg, 0.05 mmol), bpy (7.8 mg, 0.05 mmol), and Cd(NO₃)₂·4H₂O (30.8 mg, 0.1 mmol) were placed into a 10 mL glass reaction flask to which was subsequently added HNO₃ (50 μL, 6 mol·L^-1), heated to 95 ℃ and maintained at this temperature for 120 h. The solution was slowly lowered to room temperature at a rate of 5℃·h^-1 to obtain a colorless crystal. The yield based on cadmium was 37%. Elemental analysis Calcd. for C₂₆H₂₂CdN₂O₁₂(%): C 46.76, H 3.31, N 4.19; Found(%): C 47.01, H 3.15, N 5.34. IR absorption peak (KBr, cm^-1): 3 750 (w), 3 000 (w), 2 378 (w), 1 637 (s), 1 560 (s), 1 476 (w), 1 421 (w), 1 342 (m), 1 222 (w), 1 068 (w), 743 (m), 623 (m).

  1.2   Luminescent sensing experiments

  1.2.1   Metal ions sensing experiment

  Based on the excellent luminescence performance of Cd-CP, the fluorescence sensing performance of Cd-CP was studied. Cd-CP (30 mg) into 100 mL of distilled water, after ultrasonic treatment for 30 min and aging for 3 d, a stable emulsion was formed and a fluorescence test was carried out. Fluorescence sensing experiments were carried out with 17 different metal ions (Zn²⁺, Pr³⁺, Cd²⁺, Tb³⁺, Mg²⁺, Eu³⁺, Er³⁺, Ag⁺, Ni²⁺, Ba²⁺, Co²⁺, Pb³⁺, K⁺, Y³⁺, Nd³⁺, Dy³⁺, Fe³⁺; 50 μL, 5 mmol·L^-1).

  1.2.2   Nitro explosives sensing experiment

  In the same way as the metal ions described above, several of the nitro explosives (NACs) were selected to test the fluorescence sensing ability of Cd-CP. The specific experimental method can be found in the Supporting information.

  1.2.3   Pesticides sensing experiment

  In the same way, as the metal ions described above, several pesticide sensing experiments were selected to detect the fluorescence sensing ability of Cd-CP. The specific experimental method can be found in the Supporting information.

  1.3   X-ray crystallography

  Data on intensity were gathered using a Bruker Smart APEX Ⅱ CCD diffractometer emitting graphite-monochromated Mo Kα radiation (λ=0.071 073 nm) at ambient temperature (25 ℃). The SADABS software was utilized to implement corrections based on empirical absorption. The direct technique of SHELXS-2018 was used to solve the structure and it was refined using the full matrix least squares method of SHELXL-2018 on F ². Every non-hydrogen atom underwent anisotropic refinement, while the hydrogen atoms in organic ligands were created using geometric methods. Table S2 lists the crystal data along with the structural refinement parameters for Cd-CP, and selected distances and angles of bonds can be found in detail in Table S3 and Table S4.

  2.   Results and discussion

  2.1   Structure description of Cd-CP

  Cd-CP is a member of the monoclinic crystallographic system, P2₁/c space group. Every asymmetric unit has one Cd(Ⅱ) ion, one H₂dpa^2- ligand, one coordinated bpy ligand, and three lattice water molecules. Cd1 is surrounded by two nitrogen atoms (N1 and N2) from one chelating bpy ligand [Cd1—N1 0.226 8(4), Co1—N2 0.230 7(3) nm], four oxygen atoms (O3, O4, O5, and O5B) from three carboxylate groups of three H₂dpa^2- ligands (Fig.1a). The bond lengths for the Cd—O bond are in a range of 0.225 4(14)-0.251 7(18) nm. The coordination geometry at the center of Cd1 can be described as a distorted octahedral geometry.

  Figure 1

  

  Figure 1.  (a) Coordination environment of Cd-CP; (b) View of 1D double chain; (c) 3D supramolecular structure

  Ellipsoid probability level: 50%; Symmetry codes: A: 2-x, 2-y, 1-z; B: 1-x, 1-y, 1-z; C: x, 1+y, z; D: x, -1+y, z; E: 2-x, -y, 1-z; F: x, -2+y, z; G: 2-x, 3-y, 1-z.

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  The H₄dpa ligand partially deprotonates to form the H₂dpa^2- ion, employing a μ₃-η¹-η² chelating and bridging coordination mode. A carboxylate group binds with a Cd(Ⅱ) ion in a bidentate manner. A carboxylate group links a Cd²⁺ through a singular bridging coordination mode. A pair of Cd(Ⅱ) ions attach to a pair of carboxyl groups, each containing two H₂dpa^2- ions, creating dimeric structures with Cd1…Cd1 distances measuring 0.365 6 nm. The adjacent Cd dimer units are linked to two H₂dpa^2- ions to form a 1D double chain (Fig.1b). By identifying the neighboring 1D double chains, a 3D supramolecular network is formed (Fig.1c) through interactions of hydrogen bonds [O10…O1B 0.280 8(4) nm, O10…O12A 0.276 2(5) nm, O11…O6 0.284 7(3) nm, and O8…O12 0.256 8(3) nm] (Table S4).

  2.2   Powder X-ray diffraction measurement and thermal properties of Cd-CP

  Powder X-ray diffraction (PXRD) experiments were conducted to assess the phase purity of Cd-CP. Comparing the simulated XRD peaks of Cd-CP powder with those obtained by the experiment, it was found that the peaks are almost identical, which not only confirms the high purity of Cd-CP but also confirms the consistency of its structure, indicating that Cd-CP sample is pure phase (Fig.S1).

  To evaluate the thermal stability of Cd-CP, thermogravimetric analysis (TGA) was performed in an atmosphere of N₂ at a heating rate of 10 ℃·min^-1. As shown in Fig.S2, Cd-CP was relatively stable until 223 ℃, and then lost lattice water molecules below 223 ℃, with a weight loss of 7.63% (Calcd. 8.12%). Then the weight was further decreased in a range of 271-795 ℃, with a weight loss of 73.46% (Calcd. 75.04%), indicating the decomposition of H₂dpa^2- and bpy ligands. The remaining weight of 19.80% might be CdO (Calcd. 19.25%).

  2.3   Luminescent properties of Cd-CP

  Solid fluorescence characteristics of Cd-CP were analyzed at room temperature, and its emission and excitation spectra are shown in Fig.S3. When excited at 335 nm, the H₄dpa ligand shows a maximum emission peak at 404 nm. Under the same excitation wavelength, the maximum emission peak of Cd-CP appeared at 388 nm. Since the fluorescence emission peak position of Cd-CP was close to that of the H₄dpa ligand and the peak shape was similar, it is speculated that the fluorescence emission mechanism of Cd-CP may be ligand-centered luminescence.

  2.4   Metal ions sensing experiments

  The fluorescence intensity of Cd-CP aqueous solution (1 mL, 0.45 mmol·L^-1) was observed by adding different metal cations, and the corresponding detection results were obtained (Fig.2a). It is worth noting that when Fe³⁺ was added to the sample, the fluorescence intensity was quenched, while when Zn²⁺ was added, the fluorescence intensity was significantly increased. Under the same conditions, the reaction of other metal ions to Cd-CP is not significant. The anti-interference ability of Fe³⁺ to different metal ions was also studied. In different metal ion environments, there was still a good selectivity for Fe³⁺, and its quenching effect is still the strongest, thus confirming the high selectivity and anti-interference of Cd-CP to Fe³⁺ (Fig.2b).

  Figure 2

  

  Figure 2.  (a) Fluorescence intensities of Cd-CP in different metal cations; (b) Anti-interference of Cd-CP sensing Fe³⁺ after adding different cations; (c) Anti-interference of Cd-CP sensing Zn²⁺ after adding different cations; (d) Emission spectra of Cd-CP for different volumes of 5 mmol·L^-1 Fe³⁺ solution; (e) Emission spectra of Cd-CP for different volumes of 5 mmol·L^-1 Zn²⁺ solutions; (f) Stern-Volmer plot for Cd-CP sensing Fe³⁺; (g) Stern-Volmer plot for Cd-CP sensing Zn²⁺

  In f and g, c_M=5×10^-6, 1×10^-6, 1.5×10^-5, 2×10^-5, 2.5×10^-5, 3×10^-5, 3.5×10^-5 mol·L^-1.

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  Furthermore, the resilience against potential interferences from other metal ions was evaluated in the context of Zn²⁺ presence, offering insights into its selective performance amidst a complex metal matrix (Fig.2c). In the presence of other metal ions, the fluorescence properties of Zn²⁺ increased significantly. It is proved that Cd-CP also has high selectivity and anti- interference against Zn²⁺. In summary, since Cd-CP has opposite effects on the fluorescence behavior of Fe³⁺ and Zn²⁺, it can be used to design an "on-off-on" logic gate.

  To expand our understanding of how Fe³⁺ and Zn²⁺ concentrations modulate the fluorescence output of Cd-CP, we conducted a systematic concentration titration study. With the gradual increase of Fe³⁺ concentration, the luminescence performance of Cd-CP gradually decreased, and finally, it was almost completely quenched (Fig.2d). The luminescence of Cd-CP was significantly enhanced with the increase of Zn²⁺ concentration (Fig.2e). At the same time, to achieve a clearer and more precise understanding of the relationship between metal ion concentrations and fluorescence intensity, the Stern-Volmer (SV) equation (I₀/I-1= K_SVc_M) was applied as an analytical framework to decipher the patterns of variation in fluorescence intensity as a function of changes in Fe³⁺ and Zn²⁺ concentrations. Fig.2f shows a K_SV of 1.89×10⁴ L·mol^-1 for Fe³⁺, showing the expected linear trend over the low concentration range (R²=0.990 6). The LOD of Fe³⁺ was calculated to be 33.3 nmol·L^-1. The LOD of Cd-CP for Fe³⁺ was lower than that reported in other literature (Table 1). As shown in Fig.2g, the SV plot for Cd-CP sensing Zn²⁺ was approximately linear in a range of 5×10^-6-3.5×10^-5 mol·L^-1, and the R² value was 0.998 4. The linear relationship of Cd-CP and Zn²⁺ was discussed, consistent with the linear equation Y=-28 487.96X+0.104 with a slope of -28 487.96 and the LOD was 52.6 nmol·L^-1. The results show that Cd-CP has a high sensitivity to the detection of Fe³⁺ and Zn²⁺, which provides a reliable basis for the subsequent experimental research. Meanwhile, after Fe³⁺ ion (30 μL, 5 mmol·L^-1) was added to quench it, then Zn²⁺ ion was added to see whether it could be enhanced, and the experimental results proved the concentration titration experiments of Zn²⁺ in the presence of Fe³⁺ (Fig.S4a). As shown in Fig.S4b, in the presence of Fe³⁺, the SV plot was approximately linear in a low concentration range of 5×10^-6-2.5×10^-5 mol·L^-1 for Cd-CP sensing Zn²⁺, the linear equation was Y=-20 765.24X+0.25 with a slope of -20 765.24, and the R² value was 0.999 5.

  Table 1

  

  Table 1.  Response times and LOD values of some MOFs sensing Fe³⁺

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  Material	LOD / (mol·L-1)	Response time	Reference
  {[Cd(H2dpa)(bpy)]·3H2O}n	3.33×10-8	25 s	This work
  Zr-MOF	3.78×10-8		[51]
  [(CH3)2NH2]2[Eu6(μ3-OH)8(EDDC)6]·8DMA·3MeOH·6H2O	5.99×10-6		[52]
  [Ni2(BDC)2(DABCO)]	2.5×10-6	< 1 min	[53]

  Furthermore, the luminescence response time of Cd-CP to Fe³⁺ (10 μL, 1 mmol·L^-1) and Zn²⁺ (7 μL, 1 mmol·L^-1) in water was measured (Fig.S5a and S6a). Upon the introduction of Fe³⁺ and Zn²⁺, the luminous intensity associated with Cd-CP underwent an immediate alteration, subsequently attaining a stable level within 25 s and sustaining this intensity for an extended duration. Additionally, the solution-phase recyclability of Cd-CP was rigorously evaluated to assess its potential for reuse. The recovery process involves centrifugal filtration drying, enabling the rejuvenation of Cd-CP. After its utilization in detecting Fe³⁺ and Zn²⁺, Cd-CP demonstrated remarkable recyclability, with the ability to undergo four consecutive cycles of detection (Fig.S5b and S6b). This underscores the potential of Cd-CP as a reliable and reusable sensing material for the detection of both Fe³⁺ and Zn²⁺.

  2.5   NACs sensing experiments

  NACs are highly explosive substances, especially nitrocellulose aromatics, whose extensive use has brought irreversible consequences to the environment and human life safety. Therefore, it is essential to achieve rapid detection of nitroaromatics to protect and maintain environmental sustainability. The fluorescence quenching of Cd-CP was most obvious by TRI (Fig 3a). The fluorescence properties of TRI in the presence of other NACs are shown in Fig 3b. Even in the presence of other NACs, TRI still had a strong fluorescence quenching effect on Cd-CP, indicating that Cd-CP has a strong selectivity and anti-interference effect on TRI. Subsequently, a concentration titration experiment was performed, and it was found that the luminescence intensities of Cd-CP gradually decreased with the increase of TRI concentration (Fig.3c). At the same time, the relationship between TRI (1 mmol·L^-1) and the fluorescence intensities of Cd-CP was further investigated by using SV equation. As shown in Fig.3d, the SV plot had a good linear relationship in a low concentration range of 3×10^-5-7×10^-5 mol·L^-1 (R²=0.998 6), the K_SV was calculated to be 1.1×10⁵ L·mol^-1. Utilizing the gradient of the regression line and considering the variability represented by the standard deviation of the sample′s blank baseline, the sensitivity threshold for TRI detection has been determined to be 0.255 μmol·L^-1, demonstrating a high degree of analytical precision and sensitivity.

  Figure 3

  

  Figure 3.  (a) Fluorescence response of Cd-CP to different NACs; (b) Fluorescence response of Cd-CP after the addition of TRI to different NACs; (c) Emission spectra of Cd-CP upon the addition of TRI solution (1 mmol·L^-1); (d) SV plot for Cd-CP sensing TRI

  4-NPH=p-nitrophenylhydrazine, PNBA=p-nitrobenzoic acid, NB=nitrobenzene, 4-NP=p-nitrophenol, O-NT=o-nitroaniline, TNP=2, 4, 6-trinitrophenol, 2-NP=o-nitrophenol, 3-NT=m-nitroaniline; In d, c_TRI=3×10^-5, 4×10^-5, 5×10^-5, 6×10^-5, 7×10^-5 mol·L^-1.

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  The stability experiment of Cd-CP sensing TRI (10 μL, 1 mmol·L^-1) was further explored. Upon the introduction of TRI into the Cd-CP solution, a swift decline in fluorescence intensity was observed within 25 s, followed by a sustained level, signifying the material′s exceptional responsiveness and stability towards TRI, as evidenced in Fig.S7a. Investigations into the recyclability of Cd-CP revealed that after multiple detections of TRI, the material could be effectively recovered through centrifugal filtration and drying processes. Notably, the regenerated crystals retained their initial luminescence intensity for at least four cycles, underscoring their potential for reuse (Fig S7b).

  2.6   Pesticides sensing experiments

  The irrational use of pesticides and pesticide residues is one of the main causes of environmental pollution. Exploring the detection of pesticides not only helps to improve the problem of environmental pollution but also indirectly protects human life. In this experiment, nine kinds of pesticides (10 μL, 5 mmol·L^-1) were selected for fluorescence sensing experiments. When different kinds of pesticides were added to the Cd-CP solution, they all affected the fluorescence intensity of Cd-CP to some extent (Fig.4a). It was found that the quenching of fluorescence burst caused by the addition of Pth was the most obvious. In the presence of the same amount of other pesticides, the addition of Pth still has a significant fluorescence quenching phenomenon. The anti-interference experiment further confirmed that Cd-CP has a strong selectivity and high sensitivity for the detection of Pth (Fig.4b). As depicted in Fig.4c, a meticulous investigation was conducted into the influence of varying Pth concentrations on the luminescence intensity of Cd-CP. The outcomes revealed a consistent pattern, wherein an augmentation in Pth concentration led to a progressive diminution in the luminescence intensity of Cd-CP. Notably, this decline became pronounced at a Pth concentration threshold of 12 μL, culminating in a near- total suppression of the Cd-CP luminescence. This observation carries profound significance for enhancing our comprehension and predictive capabilities regarding the environmental impacts of pesticides on organic substances. To explore the relationship between Pth concentration and fluorescence intensity one step further, the SV equation was used to further analyze the fluorescence quenching. The SV plot was approximately linear in a low concentration range of 3.0×10^-5-7.0×10^-5 mol·L^-1 (Fig.4d), and the R² value was 0.995 8. The K_SV obtained by the linear regression equation is 8.6×10⁴ L·mol^-1, and the LOD was 0.336 μmol·L^-1.

  Figure 4

  

  Figure 4.  (a) Fluorescence response of Cd-CP to different pesticides; (b) Fluorescence response of Cd-CP after the addition of Pth to different pesticides; (c) Emission spectra of Cd-CP upon the addition of Pth solution (5 mmol·L^-1); (d) SV plot for Cd-CP sensing Pth

  EmB=eemamectin benzoate, Tdi=triadimefon, Pro=prochloraz, 24-Epi=24-epibrassinolide, Pst=pyraclostronbin, Flu=fluazinam, Myc=Zhongshengmycin, Ima=imazalil; In d, c_Pth=3×10^-5, 4×10^-5, 5×10^-5, 6×10^-5, 7×10^-5 mol·L^-1.

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  The luminescence response speed of Cd-CP to Pth in water was also tested (Fig.S8a). Upon the addition of Pth (10 μL, 5 mmol·L^-1), a notable decrease in fluorescence intensity was immediately discernible, reaching its minimum level within just 25 s. This swift response, coupled with the subsequent stability of the fluorescence intensity, underscores the potential of this system for rapid and efficient detection of Pth in practical applications. Additionally, the remarkable recyclability of Cd-CP was demonstrated through centrifugal washing, enabling it to regain its original luminous intensity at least four consecutive times (Fig.S8b). This characteristic, along with its efficacy as a sensing material for Pth detection, highlights the excellent reliability and reusability of Cd-CP. Consequently, our findings indicate that Cd-CP represents a promising candidate for the development of reliable and efficient sensors for Pth detection, with potential applications spanning various fields.

  2.7   Fluorescence detection mechanism

  To delve into the underlying mechanisms governing the remarkable selectivity and sensitivity of Cd-CP in analyte detection, this research embarked on an initial investigation of the interplay between Cd-CP and Zn²⁺ through X-ray photoelectron spectroscopy (XPS). This analysis was meticulously conducted on Cd-CP samples, both before and after their immersion in a Zn²⁺ solution for 24 h. As evident from Fig.5a and 5b, a subtle yet discernible shift in the binding energies of O1s and N1s was observed, with values incrementing from 532.14 to 532.37 eV and 405.06 to 405.29 eV, respectively. This marginal alteration in binding energies underscores a feeble yet significant interaction between Cd-CP and Zn²⁺, which fundamentally contributes to the enhancement of fluorescence properties, thereby elucidating the primary mechanism behind its enhanced sensitivity and selectivity^[54].

  Figure 5

  

  Figure 5.  XPS binding energy changes for (a) O1s and (b) N1s of Cd-CP before and after the addition of Zn²⁺; (c) Excitation spectrum of Cd-CP and UV-Vis absorption spectra of Fe³⁺ and other metal ions in water; (d) Emission spectrum of Cd-CP and UV-Vis absorption spectra of some NACs in water; (e) Excitation spectrum of Cd-CP and UV-Vis absorption spectra of some pesticides in water

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  Then the emission spectra of Cd-CP and the UV-Vis absorption spectra of other analytes were compared. As shown in Fig.5c, only the UV absorption peak of Fe³⁺ was found to be close in position to the excited state peak of Cd-CP, and there was a relatively significant spectral overlap between them. In contrast, the spectral overlap between the UV absorption peaks of aqueous solutions of other metal ions and the excited state peak positions of Cd-CP was relatively small, which suggests that the more significant energy transfer between Fe³⁺ and Cd-CP is the main mechanism leading to the luminescence quenching of Cd-CP via an energy-competitive absorption process. The UV-Vis absorption peak of TRI overlapped greatly with the fluorescence emission spectra of Cd-CP (Fig.5d), and the fluorescence quenching may be due to the energy resonance transfer between the emission peak of Cd-CP and the absorption peak of TRI. The UV-Vis absorption peak of Pth overlapped with the fluorescence excitation spectrum of Cd-CP (Fig.5e), and its quenching effect may be caused by competitive energy absorption^[55].

  2.8   Application of "on-off-on" logic gates

  During the experimentation for metal ion detection, it is significant to observe that the concurrent presence of Fe³⁺ and Zn²⁺ elicited notable fluorescence surges in Cd-CP, as depicted in Fig.6a. Consequently, a sophisticated "on-off-on" logic gate was devised, leveraging Cd-CP as the logical element and Fe³⁺ and Zn²⁺ as dual inputs (Fig.6b). The fluorescence intensity measured at 250 nm served as the output signal, with the presence of Fe³⁺ (designated as input 1) and Zn²⁺ (input 2) encoded as "1" and their absence denoted as "0". Notably, a threshold fluorescence intensity level was established at 327 nm, which delineated four distinct scenarios (Fig.6c). In these scenarios, the output signal yielded "0" solely when Fe³⁺ was present, whereas it assumed "1" for all other input combinations. This underscores the capability of logic gates to not merely simplify chemical signals into binary 0/1 representations but also to broaden the horizons of logical operations within the realm of chemistry.

  Figure 6

  

  Figure 6.  (a) Fluorescence intensities of different input results; (b) Logic gate scheme; (c) Truth table of the logic gate

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  3.   Conclusions

  A novel Cd-CP was synthesized by using metal cadmium salt and H₄dpa and bpy ligands under hydrothermal conditions. Fluorescence analysis showed that Cd-CP had good fluorescence sensing properties for Fe³⁺, Zn²⁺, TRI, and Pth with high selectivity, high sensitivity, and fast response. The LOD values of Cd-CP for Fe³⁺, Zn²⁺, TRI, and Pth were 33.3 nmol·L^-1, 52.6 nmol·L^-1, 0.255 μmol·L^-1 and 0.336 μmol·L^-1, respectively. Especially in the detection of metal ion aqueous solution, based on the fluorescence quenching (off) and fluorescence enhancement (on) effect of Cd-CP on bimetals, so an "on-off-on" logic gate was designed to expand the application of logic gate switch devices in the field of chemistry. In summary, Cd-CP has excellent fluorescence sensing performance, so it has high value for rapid and sensitive detection of environmental pollutants.

  Supporting information is available at http://www.wjhxxb.cn

  
  
• 1. [1]

     WU G, MA J, LI S, LI J, WANG X Y, ZHANG Z Y, CHEN L X. Functional metal-organic frameworks as adsorbents used for water decontamination: Design strategies and applications[J]. J. Mater. Chem. A, 2023, 11(13): 6747-6771 doi: 10.1039/D3TA00279A

  2. [2]

     GAO Q, XU J, BU X H. Recent advances about metal-organic frameworks in the removal of pollutants from wastewater[J]. Coord. Chem. Rev., 2019, 378: 17-31 doi: 10.1016/j.ccr.2018.03.015

  3. [3]

     ZHANG S, WANG J Q, ZHANG Y, MA J Z, HUANG L T Y, YU S J, CHEN L, SONG G, QIU M Q, WANG X X. Applications of water- stable metal-organic frameworks in the removal of water pollutants: A review[J]. Environ. Pollut., 2021, 291: 118076 doi: 10.1016/j.envpol.2021.118076

  4. [4]

     ROJAS S, HORCAJADA P. Metal-organic frameworks for the removal of emerging organic contaminants in water[J]. Chem. Rev., 2020, 120(16): 8378-8415 doi: 10.1021/acs.chemrev.9b00797

  5. [5]

     SARAVANAN A, KUMAR P S, RANGASAMY G. Removal of toxic pollutants from industrial effluent: Sustainable approach and recent advances in metal organic framework[J]. Ind. Eng. Chem. Res., 2022, 61(43): 15754-15765 doi: 10.1021/acs.iecr.2c02945

  6. [6]

     HELAL A, CORDOVA K E, ARAFAT M E, USMAN M, YAMANI Z H. Defect-engineering a metal-organic framework for CO₂ fixation in the synthesis of bioactive oxazolidinones[J]. Inorg. Chem. Front., 2020, 7(19): 3571-3577 doi: 10.1039/D0QI00496K

  7. [7]

     LUSTIG W P, TEAT S J, LI J. Improving LMOF luminescence quantum yield through guest-mediated rigidification[J]. J. Mater. Chem. C, 2019, 7(46): 14739-14744 doi: 10.1039/C9TC05216J

  8. [8]

     PATRA S, MAITY N. Recent advances in (hetero) dimetallic systems towards tandem catalysis[J]. Coord. Chem. Rev., 2021, 434: 213803 doi: 10.1016/j.ccr.2021.213803

  9. [9]

     LIU L, CHEN X L, CAI M, YAN R K, CUI H L, YANG H, WANG J J. Dye@MOF composites (RhB@1): Highly sensitive dual emission sensor for the detection of pesticides, Fe³⁺ and ascorbic acid[J]. Chin. Chem. Lett., 2023, 34(10): 108411 doi: 10.1016/j.cclet.2023.108411

  10. [10]

      BAI W B, QIN G X, WANG J, LI L, NI Y H. 2-Aminoterephthalic acid co-coordinated Co MOF fluorescent probe for highly selective detection of the organophosphorus pesticides with p-nitrophenyl group in water systems[J]. Dyes Pigment., 2021, 193: 109473 doi: 10.1016/j.dyepig.2021.109473

  11. [11]

      LIU Q Q, YUE K F, WENG X J, WANG Y. Luminescence sensing and supercapacitor performances of a new (3, 3)-connected Cd-MOF[J]. CrystEngComm, 2019, 21(41): 6186-6195 doi: 10.1039/C9CE01087D

  12. [12]

      CHEN W T, LI L Y, LI X X, LIN L D, WANG G Q, ZHANG Z, LI L Y, YU Y. Layered rare earth organic framework as highly efficient luminescent matrix: The crystal structure, optical spectroscopy, electronic transition, and luminescent sensing properties[J]. Cryst. Growth Des., 2019, 19(8): 4754-4764 doi: 10.1021/acs.cgd.9b00635

  13. [13]

      XU W H, DAI Z Q, HUANG X X, JIANG G Z, CHANG M, WANG C Y, LAI T T, LIU H M, SUN R K, LI C Y. High sensitivity in quantitative analysis of mixed-size polystyrene micro/nanoplastics in one step[J]. Sci. Total Environ., 2024, 934: 173314 doi: 10.1016/j.scitotenv.2024.173314

  14. [14]

      OGULU D, BORA P P, BIHANI M, SHARMA S, ANSARI T N, WILSON A J, JASINSKI J B, GALLOU F, HANDA S. Phosphine ligand-free bimetallic Ni(0) Pd(0) nanoparticles as a catalyst for facile, general, sustainable, and highly selective 1, 4-reductions in aqueous micelles[J]. ACS Appl. Mater. Interfaces, 2022, 14(5): 6754-6761 doi: 10.1021/acsami.1c22282

  15. [15]

      罗云, 耿柠波, 陈双双, 程琳, 张海军, 陈吉平. 短链氯化石蜡对人体正常肝细胞的代谢干扰[J]. 色谱, 2024, 42(2): 176-184LUO Y, GENG N B, CHEN S S, CHENG L, ZHANG H J, CHEN J P. Metabolomic interference induced by short-chain chlorinated paraffins in human normal hepatic cells[J]. Chin. J. Chromatogr., 2024, 42(2): 176-184

  16. [16]

      KALWEIT C, BERGER S, KAMPFE A, RAPP T. Quantification and stability assessment of 7, 9-di-tert-butyl-1-oxaspiro(4, 5)deca-6, 9- diene-2, 8-dione leaching from cross-linked polyethylene pipes using gas and liquid chromatography[J]. Water Res., 2023, 243: 120306 doi: 10.1016/j.watres.2023.120306

  17. [17]

      TORRES M N, ALMIRALL J R. Evaluation of capillary microextraction of volatiles (CMV) coupled to a person-portable gas chromatograph mass spectrometer (GC-MS) for the analysis of gasoline residues[J]. Forensic Chem., 2022, 27: 100397 doi: 10.1016/j.forc.2021.100397

  18. [18]

      YUAN Y L, LIN X T, LI T H, PANG T Y, DONG Y R, ZHUO R J, WANG Q Q, CAO Y T, GAN N. A solid phase microextraction arrow with zirconium metal-organic framework/molybdenum disulfide coating coupled with gas chromatography-mass spectrometer for the determination of polycyclic aromatic hydrocarbons in fish samples[J], J. Chromatogr. A, 2019, 1592: 9-18 doi: 10.1016/j.chroma.2019.01.066

  19. [19]

      NOORPOOR Z. The needle trap extraction capability of a zinc-based metal organic framework with a nitrogen rich ligand[J]. J. Coord. Chem., 2021, 74(13): 2213-2226 doi: 10.1080/00958972.2021.1962524

  20. [20]

      CHAVES-SIERRA C, RODRIGUEZ-CRUZ M C, MEJIA- ALVARADO F S, RAMÍREZ-HIGUERA C, MEJÍA-ESLAVA A, ROMERO H M. Identification of 'Candidatus Liberibacter asiaticus', the huanglongbing bacterium, in citrus from Colombia[J]. Plant Dis., 2024, 108(5): 1169-1173 doi: 10.1094/PDIS-10-23-2003-SC

  21. [21]

      SUN C, CHENG Y, PAN Y, YANG J, WANG X, XIA F. Efficient polymerase chain reaction assisted by metal-organic frameworks[J]. Chem. Sci., 2020, 11(3): 797-802 doi: 10.1039/C9SC03202A

  22. [22]

      LI Y, ETTAH U, JACQUES S, GAIKWAD H, MONTE A, DYLLA L, GUNTUPALLI S, MOGHIMI S M, SIMBERG D. Optimized enzyme-linked immunosorbent assay for anti-PEG antibody detection in healthy donors and patients treated with PEGylated liposomal doxorubicin[J]. Mol. Pharm., 2024, 21(6): 3053-3060 doi: 10.1021/acs.molpharmaceut.4c00278

  23. [23]

      ZHAND S, RAZMJOU A, AZADI S, BAZAZ S R, SHRESTHA J, JAHROMI M A F, WARKIANIM M E. Metal-organic framework- enhanced ELISA platform for ultrasensitive detection of PD-L1[J]. ACS Appl. Bio Mater., 2020, 3(7): 4148-4158 doi: 10.1021/acsabm.0c00227

  24. [24]

      LI C, ZONG C, LIU Y, LIU Z, WANG K N, YU X. Probing mitochondrial damage using a fluorescent probe with mitochondria-to-nucleolus translocation[J]. Chin. Chem. Lett., 2024, 35(1): 378-382 doi: 10.1016/j.cclet.2023.108323

  25. [25]

      YANG X, CHENG L, ZHAO Y, MA H, SONG H, YANG X, ZHANG Y. Aggregation-induced emission-active iridium(Ⅲ)-based mitochondria-targeting nanoparticle for two-photon imaging-guided photodynamic therapy[J]. J. Colloid Interface Sci., 2024, 659: 320-329 doi: 10.1016/j.jcis.2023.12.172

  26. [26]

      WANG C, ZHANG N, HOU C Y, HAN X X, LIU C H, XING Y H, BAI F Y, SUN L X. Transition metal complexes constructed by pyridine-amino acid: Fluorescence sensing and catalytic properties[J]. Transition Met. Chem., 2020, 45: 423-433 doi: 10.1007/s11243-020-00394-9

  27. [27]

      ZHANG J F, ZHANG J W, LIU R R, XIA H Y, LIU Z Q. Ni(Ⅱ)-metal-organic framework based on 3, 3′-di(1H-imidazol-1-yl)-1, 1′-biphenyl: Synthesis, structure and luminescence detection[J]. Inorg. Chim. Acta, 2024: 121974

  28. [28]

      KAN C, WANG X, SHAO X, WU L, QIU S, ZHU J. A novel fluorescent probe of aluminum ions based on rhodamine derivatives and its application in biological imaging[J]. New J. Chem., 2021, 45(20): 8918-8924 doi: 10.1039/D1NJ01184G

  29. [29]

      LEI Y, GAO Y, XIAO Y, HUANG P, WU F Y. Zirconium-based metal-organic framework loaded agarose hydrogels for fluorescence turn-on detection of nerve agent simulant vapor[J]. Anal. Methods, 2023, 15(42): 5674-5682 doi: 10.1039/D3AY01539D

  30. [30]

      WANG Z, GUO L, TIAN J, HAN Y, ZHAI D, CUI L, ZHANG P S, ZHANG X W, YANG S Y, ZHANG L. A versatile MOF as an electrochemical/ fluorescence/colorimetric signal probe for the tri-modal detection of MMP-9 secretion in the extracellular matrix to identify the efficacy of chemotherapeutic drugs[J]. Anal. Chim. Acta, 2024, 1315: 342798 doi: 10.1016/j.aca.2024.342798

  31. [31]

      GUO J, FAN X Y, REN X F, WU S, ZHANG Y K, ZHANG W, HE Y C. Crystal structures, Hirshfeld surface analyses and optical properties of four new Cu(Ⅱ)-based coordination polymers[J]. Polyhedron, 2024, 261: 117143 doi: 10.1016/j.poly.2024.117143

  32. [32]

      FAN F X, FU L, CUI H G. Three robust luminescent Cd(Ⅱ) coordination polymers as multi-responsive fluorescent sensors for Cu²⁺, Hg²⁺, levofloxacin, and acetylacetone in water[J]. J. Mol. Struct., 2024, 1316: 139099 doi: 10.1016/j.molstruc.2024.139099

  33. [33]

      LIU L L, ZHANG R J, LI S Q, HU L, LIANG S, WANG L L, ZHOU N N, LIANG X, YANG X L, HAN Y S. Integrating selenium confinement in two-dimensional carbon matrix with Co catalysis for high-performance sodium-ion batteries[J]. Electrochim. Acta, 2024, 79: 143907 doi: 10.1016/j.electacta.2024.143907

  34. [34]

      WANG T T, CHEN F F, AN H, CHEN K, GAO J K. Metal-organic-framework-derived boron and nitrogen dual-doped hollow mesoporous carbon for photo-thermal catalytic conversion of CO₂[J]. J. Solid State Chem., 2024, 332: 124570 doi: 10.1016/j.jssc.2024.124570

  35. [35]

      ALAVIJEH R K, AKHBARI K. Cancer therapy by nano MIL-n series of metal-organic frameworks[J]. Coord. Chem. Rev., 2024, 503: 215643 doi: 10.1016/j.ccr.2023.215643

  36. [36]

      MA D W, WANG G, LU J S, ZENG X X, CHENG Y W, ZHANG Z W, CHEN Q. Multifunctional nano MOF drug delivery platform in combination therapy[J]. Eur. J. Med. Chem., 2023, 261: 115884 doi: 10.1016/j.ejmech.2023.115884

  37. [37]

      HUANG Z H, CHAI K G, KANG C J, KRISHNA R, ZHANG Z Q. Commensurate stacking within confined ultramicropores boosting acetylene storage capacity and separation efficiency[J]. Nano Res., 2023, 16(5): 7742-7748 doi: 10.1007/s12274-022-5346-7

  38. [38]

      ZHANG C, MA L, XI X, NIE Z. Adsorption and separation performance of tungsten and molybdenum on modified zirconium based metal organic frameworks UiO-66-CTAB[J]. J. Environ. Chem. Eng., 2024, 12(5): 113401 doi: 10.1016/j.jece.2024.113401

  39. [39]

      KILMOVSKIKH I I, EREMEEV S V, ESTYUNIN D A, FILNOV S O, SHIMADA K, GOLYASHOV V A, CHULKOV E V. Interfacing two-dimensional and magnetic topological insulators: Bi bilayer on MnBi₂Te₄-family materials[J]. Mater. Today Adv., 2024, 23: 100511 doi: 10.1016/j.mtadv.2024.100511

  40. [40]

      KHUNOU P B, NOMNGONGO N P, NYABA L. Application of MoS₄^2- intercalated magnetic layered double hydroxide for preconcentration of cadmium and lead from water samples[J]. J. Hazard. Mater. Adv., 2024, 15: 100446

  41. [41]

      ZHANG Z, HAN W, QING J, MENG T, ZHOU W, DING L. Functionalized magnetic metal organic framework nanocomposites for high throughput automation extraction and sensitive detection of antipsychotic drugs in serum samples[J]. J. Hazard. Mater., 2024, 465: 133189 doi: 10.1016/j.jhazmat.2023.133189

  42. [42]

      DE OLIVEIRA A, GRIGOLETTO S, VIEIRA L F M A, AMORIM S J F, DE ABREU H A. Unveiling the adsorption mechanism of arsenic species in the MOF-74 through an in-silico approach targeting the development of adsorbents for polluted water treatment[J]. Chem. Phys. Lett., 2023, 831: 116884 doi: 10.1016/j.cplett.2023.140841

  43. [43]

      LI W, ZHU Z, CHEN Q, LI J, TU M. Device fabrication and sensing mechanism in metal-organic framework-based chemical sensors[J]. Cell Rep. Phys. Sci., 2023, 4(12): 101679 doi: 10.1016/j.xcrp.2023.101679

  44. [44]

      ZHU X D, ZHANG K, WANG Y, LONG W W, SA R J, LIU T F, LÜ J. Fluorescent metal-organic framework (MOF) as a highly sensitive and quickly responsive chemical sensor for the detection of antibiotics in simulated wastewater[J]. Inorg. Chem., 2018, 57(3): 1060-1065 doi: 10.1021/acs.inorgchem.7b02471

  45. [45]

      CHAISURIYA W, CHAINOK K, WANNARIT N. Crystal structure and Hirshfeld surface analysis of a new mononuclear copper(Ⅱ) complex: [Bis-(pyridin-2-yl-κN)amine](formato-κO)(m-hydroxy-benzoato-κ²O, O′) copper(Ⅱ)[J]. Acta Crystallogr. Sect. E, 2023, E79(12): 1115-1120

  46. [46]

      XIA N, CHANG Y, ZHOU Q, DING S, GAO F. An overview of the design of metal-organic frameworks-based fluorescent chemosensors and biosensors[J]. Biosensors, 2022, 12(11): 928-935

  47. [47]

      LAZARO I A, FORGAN R S. Application of zirconium MOFs in drug delivery and biomedicine[J]. Coord. Chem. Rev., 2019, 380: 230-259 http://www.onacademic.com/detail/journal_1000040897098310_927e.html

  48. [48]

      RUBIO-MARTINEZ M, AVCI-CAMUR C, THORNTON A W, IMAZ I, MASPOCH D, HILL M R. New synthetic routes towards MOF production at scale[J]. Chem. Soc. Rev., 2017, 46(11): 3453-3480 http://www.onacademic.com/detail/journal_1000039912491610_c98e.html

  49. [49]

      闫睿魁, 陈小莉, 蔡苗, 任静, 崔华莉, 杨华, 王记江. 高灵敏、多响应的镧系金属有机骨架的设计、合成和荧光传感性能[J]. 无机化学学报, 2024, 40(4): 834-848 doi: 10.11862/CJIC.20230301YAN R K, CHEN X L, CAI M, REN J, CUI H L, YANG H, WANG J J. Design, synthesis and fluorescence sensing properties of highly sensitive and multiresponsive lanthanide metal-organic skeletons[J]. Chinese J. Inorg. Chem., 2024, 40(4): 834-848 doi: 10.11862/CJIC.20230301

  50. [50]

      蔡苗, 王竹云, 陈小莉, 闫睿魁, 崔华莉, 杨华, 王记江. 基于4-(2, 4-二羧基苯氧基)邻苯二甲酸配体的锌配位聚合物的合成、结构及其荧光传感性能[J]. 无机化学学报, 2023, 39(7): 1379-1388CAI M, WANG Z Y, CHEN X L, YAN R K, CUI H L, YANG H, WANG J J. Synthesis, structure and fluorescence sensing properties of zinc coordination polymer based on 4-(2, 4-dicarboxylic phenoxy) phthalic acid ligand[J]. Chinese J. Inorg. Chem., 2023, 39(7): 1379-1388

  51. [51]

      马学林, 韩利民, 张骁勇, 郝占忠, 杨威, 张玉恒, 王丽. 多响应锆基金属有机框架荧光传感器对Fe³⁺, Cr₂O₇^2-离子和有机小分子的识别[J]. 有机化学, 2020, 40(9): 2938-2948MA X L, HAN L M, ZHANG X Y, HAO Z H, YANG W, ZHANG Y H, WANG L. The multi-response zirconium fund is the identification of Fe³⁺, Cr₂O₇^2- ions and small organic molecules[J]. Chin. J. Org. Chem., 2020, 40(9): 2938-2948

  52. [52]

      冀超, 李文, 张丽荣, 华佳, 刘云凌. 一例Eu-MOF材料的构筑及对Fe³⁺与硝基芳香族爆炸物的荧光检测性能[J]. 高等学校化学学报, 2024, 45(2): 135-143JI C, LI WEN, ZHANG L R, HUA J, LIU Y L. Construction of Eu-MOF material and fluorescence detection of Fe³⁺ and nitroaromatic explosives[J]. Chem. J. Chinese Universities, 2024, 45(2): 135-143

  53. [53]

      BESHELI M E, RAHIMI R, FARAHANI Y D, SAFARIFARD V. A porous Ni-based metal-organic framework as a selective luminescent probe to Fe³⁺ metal ion and MeOH[J]. Inorg. Chim. Acta, 2019, 495: 118956 http://www.zhangqiaokeyan.com/journal-foreign-detail/0704019763060.html

  54. [54]

      YAN R K, CHEN X L, REN J, CUI H L, YANG H, WANG J J. Synthesis of highly sensitive and multi-response Eu-MOF, fluorescence sensing properties and anti-counterfeiting applications[J]. Spectroc. Acta Pt. A-Molec. Biomolec. Spectr., 2024, 322: 124855 http://www.nstl.gov.cn/paper_detail.html?id=850bd3a9ab87ee17556cdcfdba223d92

  55. [55]

      HE J, XU J, YIN J, LI N, BU X H. Recent advances in luminescent metal-organic frameworks for chemical sensors[J]. Sci. China Mater., 2019, 62(11): 1655-1678

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  Scheme 1  Structure of ligand H₄dpa

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  Figure 1  (a) Coordination environment of Cd-CP; (b) View of 1D double chain; (c) 3D supramolecular structure

  Ellipsoid probability level: 50%; Symmetry codes: A: 2-x, 2-y, 1-z; B: 1-x, 1-y, 1-z; C: x, 1+y, z; D: x, -1+y, z; E: 2-x, -y, 1-z; F: x, -2+y, z; G: 2-x, 3-y, 1-z.

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  Figure 2  (a) Fluorescence intensities of Cd-CP in different metal cations; (b) Anti-interference of Cd-CP sensing Fe³⁺ after adding different cations; (c) Anti-interference of Cd-CP sensing Zn²⁺ after adding different cations; (d) Emission spectra of Cd-CP for different volumes of 5 mmol·L^-1 Fe³⁺ solution; (e) Emission spectra of Cd-CP for different volumes of 5 mmol·L^-1 Zn²⁺ solutions; (f) Stern-Volmer plot for Cd-CP sensing Fe³⁺; (g) Stern-Volmer plot for Cd-CP sensing Zn²⁺

  In f and g, c_M=5×10^-6, 1×10^-6, 1.5×10^-5, 2×10^-5, 2.5×10^-5, 3×10^-5, 3.5×10^-5 mol·L^-1.

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  Figure 3  (a) Fluorescence response of Cd-CP to different NACs; (b) Fluorescence response of Cd-CP after the addition of TRI to different NACs; (c) Emission spectra of Cd-CP upon the addition of TRI solution (1 mmol·L^-1); (d) SV plot for Cd-CP sensing TRI

  4-NPH=p-nitrophenylhydrazine, PNBA=p-nitrobenzoic acid, NB=nitrobenzene, 4-NP=p-nitrophenol, O-NT=o-nitroaniline, TNP=2, 4, 6-trinitrophenol, 2-NP=o-nitrophenol, 3-NT=m-nitroaniline; In d, c_TRI=3×10^-5, 4×10^-5, 5×10^-5, 6×10^-5, 7×10^-5 mol·L^-1.

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  Figure 4  (a) Fluorescence response of Cd-CP to different pesticides; (b) Fluorescence response of Cd-CP after the addition of Pth to different pesticides; (c) Emission spectra of Cd-CP upon the addition of Pth solution (5 mmol·L^-1); (d) SV plot for Cd-CP sensing Pth

  EmB=eemamectin benzoate, Tdi=triadimefon, Pro=prochloraz, 24-Epi=24-epibrassinolide, Pst=pyraclostronbin, Flu=fluazinam, Myc=Zhongshengmycin, Ima=imazalil; In d, c_Pth=3×10^-5, 4×10^-5, 5×10^-5, 6×10^-5, 7×10^-5 mol·L^-1.

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  Figure 5  XPS binding energy changes for (a) O1s and (b) N1s of Cd-CP before and after the addition of Zn²⁺; (c) Excitation spectrum of Cd-CP and UV-Vis absorption spectra of Fe³⁺ and other metal ions in water; (d) Emission spectrum of Cd-CP and UV-Vis absorption spectra of some NACs in water; (e) Excitation spectrum of Cd-CP and UV-Vis absorption spectra of some pesticides in water

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  Figure 6  (a) Fluorescence intensities of different input results; (b) Logic gate scheme; (c) Truth table of the logic gate

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  Table 1.  Response times and LOD values of some MOFs sensing Fe³⁺

  Material	LOD / (mol·L-1)	Response time	Reference
  {[Cd(H2dpa)(bpy)]·3H2O}n	3.33×10-8	25 s	This work
  Zr-MOF	3.78×10-8		[51]
  [(CH3)2NH2]2[Eu6(μ3-OH)8(EDDC)6]·8DMA·3MeOH·6H2O	5.99×10-6		[52]
  [Ni2(BDC)2(DABCO)]	2.5×10-6	< 1 min	[53]

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