English

• 0.   Introduction

  Sulfasalazine (SSZ) has been used to treat rheumatoid arthritis for decades^[1]. It belongs to the aminosalicylic acid preparation, has anti-inflammatory and immune adjustment effects, is a common drug used to treat ulcerative colitis^[2], and has positive effects on skin diseases^[3]. At present, research on the new use of SSZ as an anti-tumor adjuvant drug in the treatment of various types of malignant tumors is ongoing^[4].Although SSZ has been widely used in clinical practice, it also has some adverse reactions, such as serious adverse reactions to the digestive system and bloodsystem^[5-7].

  Glutaraldehyde (GA) is widely used in the medical industry, and hospitals as a preservative and disinfectant because of its wide range, high efficiency, low toxicity, low corrosion to metals, good stability, and other advantages^[8]. However, GA has certain toxicity and strong irritation to the eyes and skin, and long-term exposure can even cause bronchitis and pulmonary edema^[9]. In recent years, people's attention to health and the requirements for a safe living environment have increased, which makes the detection of glutaraldehyde very necessary.

  Currently reported methods for the detection of GA mainly include capillary electrophoresis^[10], ultraviolet spectrophotometry^[11], gas chromatography^[12], high-performance liquid chromatography^[13], gas chromatog-raphy-mass spectrometry^[14] and liquid chromatography-mass spectrometry^[10]. The detection methods of SSZ include high-performance liquid chromatography^[15] and liquid chromatography-mass spectrometry^[16]. However, some of these methods are complex to operate and require expensive equipment, and some are difficult to achieve fast real-time detection. Therefore, it is of great significance to establish a simple, cheap, and rapid method for the detection of GA and SSZ. Fluorescence spectroscopy can quickly and accurately analyze samples without complicated pretreatment and consumables and has been widely used for the detection of drugs and organic molecules.

  Metal-organic frameworks (MOFs) are a kind of coordination polymers formed by metal ions and organic ligands through coordination bonds. Due to the different types, it can be synthesized by proportions and coordination modes of metal ions and organic ligands, coordination polymers with different shapes, sizes, and structures. In recent years, due to their adjustable porosity, controllable structure, good stability, and easy functional modification, MOF materials have been studied in many fields such as catalysis, gas separation, chemical sensing, gas adsorption, and drug delivery^[17-21]. Lanthanide metal-organic frameworks(Ln-MOFs), as an important branch of MOFs, have obvious luminescence, long emission lifetime, large Stokes shift, and high quantum yield, and have broad application prospects in the field of fluorescence sensing. At present, Ln-MOFs have been applied to the fluorescence sensing detection of metal cations^[22], anions^[23], nitro explosives^[24], antibiotics^[25], pesticides^[26], volatile organic compounds^[27], amino acids, and drugs^[28]. However, in the field of electromagnetism, transition metal materials have always occupied a dominant position^[29-30]. Therefore, we combine lanthanide metals and transition metals to form heteronuclear bimetallic organic frameworks, so that they not only have lanthanide fluorescence properties but also have the magnetic properties of transition metals, making MOF materials more multi-functional.

  In this work, two lanthanide-transition bimetallic organic frameworks [Eu-Co-MOF (1) and Sm-Co-MOF (2)] with similar molecular structures were designed and constructed by the solvothermal method based on 3, 5-di(2', 4'-dicarboxylphenyl) benzoic acid (H₅L) ligands. The crystal structure and properties of the complexes were characterized by single crystal X-ray diffraction, elemental analysis, thermogravimetric (TG) analysis, powder X-ray diffraction (PXRD), IR spectra, fluorescence spectra, and magnetic properties. Fluores- cence analysis showed that 1 has good luminescence properties and can be used for rapid and sensitive detection of SSZ in an aqueous solution and GA in an ethanol solution. This research lays a foundation for the development of special miniaturized bimetallic organic framework sensors.

  1.   Experimental

  1.1   Materials and methods

  Eu(NO₃)₃·6H₂O, SmCl₃·6H₂O, Co(NO₃)₂·6H₂O, H₅L, 4, 4'-bipyridine, N, N-dimethylformamide (DMF)and other reagents used were analytically pure, which will not be further purified. Among them, Co(NO₃)₂·6H₂O was from Xi'an Chemical Reagent Factory, DMF was from Shanghai Aladdin Biochemical Technology Co., Ltd., and others were from Jinan Henghua Sci. & Tec. Co., Ltd.

  The crystallographic data were collected on a single crystal diffractometer (Smart apex Ⅱ CCD, Bruker, Germany). The contents of C, H, and N elements were measured on an Element analyzer (Element UNICUBE, Germany); TG analyses were performed under nitrogen with a heating rate of 10 ℃·min^-1 using a thermogravimetric analyzer (STA 449F3, Netzsch, Germany). The PXRD patterns were obtained using D8 advance X-ray powder diffractometer (working voltage: 40 kV, working current: 40 mA, source of radiation: Cu Kα, wavelength: 0.154 06 nm, scan range: 5°-30°). The FTIR spectra were recorded on an infrared spectrometer (IRAFFINITY-1S, Shimadzu, Japan) using KBr pellets in a range of 4 000-400 cm^-1. Fluorescence spectra were collected by a fluorescence spectrophotometer(F-7000, Hitachi, Japan) equipped with 450 W xenon light. UV-Vis spectral data were collected on an ultraviolet spectrophotometer (UV-3600, Shimadzu, Japan).

  1.2   Synthesis of Ln-Co-MOF

  Eu(NO₃)₃·6H₂O or SmCl₃·6H₂O (0.03 mmol), Co(NO₃)₂·6H₂O (0.03 mmol), H₅L (0.06 mmol), 4, 4' -bipyridine (0.05 mmol), DMF (1 mL), H₂O (6 mL) and 10% HNO₃ (0.25 mL) were added into 10 mL glass bottles and mixed evenly. The bottles were put into a 25 mL hydrothermal reactor with polytetrafluoroethylene lined which would be heated to 160 ℃ under normal pressure. The temperature was maintained for 72 h and then reduced to 30 ℃ at a speed of 3 ℃ ·h^-1. The filtered crystals were washed with water and ethanol respectively and dried in air.

  (C₂H₆NH₂)₅{[Eu₉Co(L)₆(H₂O)₅(OH)₄] ·5DMF}_n (1): pink block, 51% yield based on Eu. Anal. Calcd. for C₁₆₃H₁₄₃N₁₀O₇₄CoEu₉(%): C, 40.33; H, 2.95; N, 2.89.Found(%): C, 39.15; H, 2.97; N, 2.47.

  (C₂H₆NH₂)₂{[Sm₉Co(L)₆(H₂O)₃Cl]·5DMF}_n (2): pink block, 59% yield based on Sm. Anal. Calcd. for C₁₅₇H₁₁₁N₇O₆₈ClCoSm₉(%): C, 40.70 H, 2.40; N, 2.12.Found(%): C, 40.06; H, 2.49; N, 2.12.

  1.3   X-ray crystallography

  Crystals 1 or 2 with good crystallinity and suitable size were selected, and placed on a single-crystal diffractometer. The diffractometer was equipped with Oxford Cryostream 800 cryodevice and Mo Kα radiation (λ =0.071 073 nm) light source. X-ray diffraction data were collected at 293 K (1) and 296 K (2). All data were restored using the SAINT program, and a multi-scan absorption correction using SADABS was applied. The structures were solved by partial structure expansion using SHELXL and refined by full-matrix least-squares methods against F² by SHELXL. Nonhydrogen atoms are refined by anisotropic temperature coefficients. Hydrogen atoms are determined by theoretical hydrogenation. The disordered solvent molecules were removed by the PLATON/SQUEEZE program. The crystallographic data of 1 and 2 are listed in Table 1, and the main bond lengths and bond angles are listed in Table S1-S2 (Supporting information).

  Table 1

  

  Table 1.  Crystallographic data for Ln-Co-MOFs 1 and 2

  下载: 导出CSV

  Parameter	1	2
  Empirical formula	C163H143N10O74CoEu9	C157H111N7O68ClCoSm9
  Formula weight	4 849.54	4 628.59
  Temperature / K	293(2)	296(2)
  Crystal system	Trigonal	Trigonal
  Space group	R3	R3
  a / nm	3.881 50(17)	3.885 6(8)
  b / nm	3.881 50(17)	3.885 6(8)
  c / nm	1.112 78(9)	3.885 6(8)
  Volume / nm3	14.519 7(17)	14.591(7)
  Z	3	3
  Dc / (g·cm-3)	1.460	2.246
  Absorption coefficient / mm-1	3.027	2.898
  F(000)	6 126	9 924
  θrange for data collection / (°)	1.817-25.996	2.428-24.705
  Reflection collected	26 819	23 933
  Unique reflection	10 340 (Rint=0.023 1)	10 785 (Rint=0.018 3)
  Data, restraint, number of parameters	10 340, 2 024, 597	10 785, 941, 566
  Goodness-of-fit on F 2	1.317	1.088
  Final R indices [I > 2σ(I)]	R1=0.045 0, wR2=0.113 7	R1=0.041 5, wR2=0.089 3
  R indices (all data)	R1=0.045 4, wR2=0.114 0	R1=0.043 2, wR2=0.090 2

  1.4   Fluorescence properties and sensing experiment

  1.4.1   Fluorescent properties of Ln-Co-MOFs 1 and 2

  3 mg powder 1 (or 2) was dissolved in 3 mL aqueous solution at room temperature for 30 min of ultrasonication and then its fluorescence spectrum was determined at the optimal excitation wavelength.

  1.4.2   Fluorescence sensing experiment

  3 mg powder 1 was dispersed in 3 mL of different solutions, ultrasonic treatment was performed for 30 min to form a suspension, and then its fluorescence spectrum was determined (λ_ex=318 nm). Different solutions included different drugs (0.1 mmol·L^-1), different solvents, and different concentrations of SSZ (or GA) solutions.

  Different drugs included H₂O, cimetidine(CIM), ribavirin(RBV), piroxicam(PIX), amoxicillin (AMX), vitamin B1 (VB1), azithromycin (AZM), sulfasalazine(SSZ), ampicillin (AMP), acetaminophen (ACM), nitrofurantoin (NEC), trihexyphenidyl (TH), chlorpheniramine (CPM), phenolphthalein (PHPH), medroxyprogesterone acetate (MPA), metoclopramide (MCPM).

  Different organic solvents included ethyl alcohol(EA), formaldehyde (HCHO), ethyl acetate (EAC), glutaraldehyde (GA), cyclohexane (CYH), n-butyl alcohol(NBA), benzene (PhH), ethylene glycol (EG), n-hexane(Hex), DMF, N, N-dimethylacetamide (DMAC), isopropyl alcohol (IPA).

  The concentrations of SSZ were 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90 μmol·L^-1, and the concentrations of GA were 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 120, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700 μmol·L^-1, respectively.

  2.   Results and discussion

  2.1   Infrared spectra analysis

  The infrared spectra of H₅L and Ln-Co-MOFs 1 and 2 were measured in a range of 4 000-400 cm^-1(Fig. 1). For the ligand H₅L, the sharp C＝O stretching vibration characteristic peak of carboxylic acid was at 1 700 cm^-1. The wide and scattered peaks near 3 000 cm^-1 are inferred to be the O—H stretching vibration absorption peaks of the dimer produced by the hydrogen bond association reaction within carboxylic acid molecules. The peaks at 1 383 and 1 250 cm^-1 are the result of the coupling of the dimer O—H plane bending vibration and C—O stretching vibration. These all illustrated the presence of the carboxyl group in the ligand^[31]. However, both 1 and 2 showed no absorption peaks near 1 700 cm^-1. The asymmetric stretching vibration and symmetric stretching vibration of COO^- were observed at 1 617 and 1 387 cm^{-1 [32]}, which indicates successful coordination between the metal and the carboxyl oxygen atom on the ligand. Moreover, the infrared spectra of 1 and 2 had a high similarity, and the combined crystallographic data suggested that they had similar structures.

  Figure 1

  

  Figure 1.  Infrared spectra of H₅L and Ln-Co-MOFs 1 and 2

  下载: 全尺寸图片 幻灯片

  2.2   Crystal structure

  The X-ray single crystal analysis results show that Ln-Co-MOFs 1 and 2 belong to the trigonal R3 space group, and their structures are very similar. Their asymmetric units all include three crystallographically independent Ln³⁺ ions, one Co²⁺ ion, and two L^5- ligands.However, there are four coordinated H₂O molecules and one OH^- ion in 1, while there are one Cl^- anion and three coordinated H₂O molecules in 2 (Fig. 2a and 2b). Ligands are two high coordination modes: κ₁κ₁-κ₁κ₁- κ₁κ₁ -κ₁κ₁ -κ₁κ₁ -μ₇ to link seven Ln³⁺ ions (Fig. 2c and 2d) and κ₁κ₁-κ₂κ₁-κ₁κ₁-κ₁κ₁-κ₁κ₁-μ₆ to link seven Ln³⁺ ions (Fig. 2e and 2f).

  Figure 2

  

  Figure 2.  Structures of Ln-Co-MOFs 1 (left) and 2 (right)

  (a, b) Asymmetric unit; (c-f) Coordination patterns of the L^5- ligand; (g, h) Binary metal units; (i, j) Four-membered metal unit; (k, l) Six-membered ring; (m, n) 3D structure diagram; Symmetry codes: a: -y+1, x-y+1, z; b: -x+y, -x+1, z; c: -x+y+1/3, -x+2/3, z+2/3; d: -x+y+1/3, -x+2/3, z-1/3; f: x, y, z+1; h: -x+y, -x+1, z+1; i: -y+2/3, x-y+1/3, z-2/3; j: x, y, z-1; k: -x+y+2/3, -x+4/3, z+1/3; l: -y+1, x-y+1, z-1 for 1; a: -y+1, x-y, z; b: -x+y+1, -x+1, z; c: -x+y+1, -x+1, z-2; d: -x+y+2/3, -x+4/3, z-2/3; e: x, y, z-1; f: -y+2/3, x-y+1/3, z-2/3; g: -y+4/3, x-y+2/3, z+2/3; h: x, y, z+1; i: -x+y+1/3, -x+2/3, z+2/3; j: -y+1, x-y, z+2; k: -y-1, x-y, z-2; m: x, y, z-2; n: -x+y+2/3, -x+4/3, z+1/3 for 2.

  下载: 全尺寸图片 幻灯片

  There are two coordination models for Eu³⁺ in 1, Eu1 ion is nine-coordinated by nine O atoms (O1, O11, O12, O13, O14, O17, O18, O19, and O9c) from three ligands, among them, O11 and O12, O13 and O14, O17 and O18 are chelating coordination, O1, O19, and O9c are bridged coordination (Fig. 2g). The coordination pattern of Eu2 is identical to that of Eu1 (Fig. 2g).Meanwhile, Eu1 and Eu2 ions are bridging to form binary metal nucleus (Eu1-Eu2) by four pairs of oxygen atoms (O1 and O2, O11 and O12, O19 and O20, O9c and O10c). In which O1 and O12 are both chelating and bridging oxygen atoms (Fig. 2g). Eu3 ion forms a eight-coordinated pattern with four O atoms (O5, O6, O15, and O1b) from three L^5- ligands and four oxygen atoms (O21, O22, O23, O23b) from four water molecules, in which O5 and O6 are chelating coordination(Fig. 2i). Co ions form a seven-coordinated pattern with seven O atoms (O23, O23a, O23b, O24, O25, O25a, O25b) from seven water molecules (Fig. 2i). And the three O23 atoms coordinated with Co are bridged coordinated with three Eu3 ions, at the same time, three O atoms (O15, O15a, and O15b) are bridged coordinated with three Eu3 ions to form a four-metallic unit of Eu3-Eu3a-Eu3b-Co (Fig. 2i). Each four-metallic unit is connected with six pairs of Eu1-Eu2 binary metal unit by ligands to form six - membered ring (Fig. 2k). The six - membered ring are connected by the L^5- ligands to form 3D microporous structures (Fig. 2m).

  In MOF 2, Sm2 coordinates with nine oxygen atoms (O1, O2, O16f, O17f, O10d, O14e, O15e, O18e, O19e) from four ligands. In which O16f and O17f, O14e and O15e, O18e and O19e are chelating coordination, O1, O10d, and O2 are bridging coordination (O2 and O17f has both chelating and bridging modes.).Sm3 has the same coordination pattern as Sm2. Sm3 and Sm2 are connected by bridging oxygen atoms O10d and O11d, O16f and O17f, O1 and O4, O2 and O3 to form a binary metal unit (Sm2-Sm3, Fig. 2h). Sm1 coordinates with four oxygen atoms (O5, O6b, O20c, O21c) from three L^5- ligands, two O atoms (O9, O9b) from two water molecules, and one Cl^- anion, in which O20c and O21c are chelated coordination and other oxygen atoms are bridging oxygen atoms (O5 and O9 with Sm1a ion, O6b and O9b with Sm1b ion, and O9 and O9b with Co²⁺ ions). Furthermore, Sm1, Sm1a, and Sm1b coordinate with Cl^- ions to form Sm1-Sm1a-Sm1b-Co four-metallic units (Fig. 2j). A four-membered metal unit and six pairs of binary metal units (Sm2-Sm3) are linked by six L^5- ligands to form a six - membered ring(Fig. 2l). The six - membered ring are further linked by L^5- ligands to form 3D microporous structure (Fig. 2n).

  2.3   Phase purity and thermal stability

  The PXRD patterns of Ln-Co-MOFs 1 and 2 (Fig.S1) showed that the diffraction peak positions were consistent with the simulated values, indicating that they had good phase purity. TG curves (Fig.S2) showed that both 1 and 2 had two weight-loss processes. Their weight loss for the first time was at a temperature of below 100 ℃. The weight loss rates were approximately 12.30% (1) and 10.40% (2) respectively, which are attributed to the loss of C₂H₆NH₂⁺ and DMF (Calcd.12.27% and 9.79%, respectively). The weight loss for the second time was in the ranges of 250-400 ℃ (1) and 300-400 ℃ (2), and the weight loss rate was approximately 52.00% (1) and 50.00% (2) respectively, which should be the gradual collapse process of the complex skeleton. Finally, stable oxides were formed with experimental values of 34.5% (1) and 35.5% (2) (Calcd. 34.20% for 1 and 35.22% for 2) respectively.

  2.4   Fluorescence properties

  The fluorescence spectra of the MOFs and H₅L in the solid state and aqueous solutions are shown in Fig.S3. It could be seen that both H₅L and MOF 2 had a sharp emission peak at about 350 nm when the excitation wavelength was 320 nm, which indicates that the emission peak of 2 is the emission peak of ligand H₅L.However, MOF 1 had two sharp emission peaks at 592 and 614 nm when the excitation wavelength was 318 nm, which corresponded to the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ energy level transitions of Eu(Ⅲ) ions^[33-34]. Compared with 1, 2 had weaker fluorescence. Therefore, the strongest characteristic emission peak of 1 at 614 nm was selected as the detection peak of fluorescence sensing.

  2.5   Fluorescence sensing of drug molecules by MOF 1

  The fluorescence intensities of MOF 1 in different drug solutions are shown in Fig. S4. It could be seen that different drugs had different effects on the fluorescence intensity of 1. In particular, SSZ had obvious quenching effect on the fluorescence of 1, and the luminescence intensity of 1 decreased gradually with the increase of SSZ solution concentration(Fig. 3a), which showed a good first-order exponential relationship: y=2 279.9e^-x/716.42+1 954.9e^-x/16.564-1 758.3 (R²=0.996 80) (Fig. 3b). There was a good linear relationship between the concentration of SSZ and the luminescence intensity of 1 when the concentration of SSZ solution was in a range of 2-20 μmol·L^-1: y=-68.346x+2 303.8 (R²=0.990 57) (Fig. 3b). The limit of detection (LOD) was 0.95 μmol·L^-1 calculated by equation: LOD=3σ/k, where k was the slope of the linear relationship and σ was the standard deviation of 11 sets of blank solutions. Compared with the literature^[35], 1 showed superior fluorescence sensing performance. At the same time, the interference results of common drugs on 1 sensing SSZ are shown in Fig.S5. It can be seen that the presence of other drug molecules did not affect the fluorescence detection of SSZ, indicating that the complex has good selectivity and anti-interference ability.

  Figure 3

  

  Figure 3.  (a) Fluorescence spectra of MOF 1 in SSZ solutions with different concentrations; (b) Linear and nonlinear relationship between luminescence intensity of 1 and SSZ concentration

  下载: 全尺寸图片 幻灯片

  2.6   Fluorescence sensing of organic small molecules by MOF 1

  The fluorescence intensities of MOF 1 in different organic solvents are shown in Fig.S6. It showed that the fluorescence intensity of 1 in ethanol solution was strongest, which might be due to the enhanced fluorescence of Eu³⁺ caused by the vibration of the hydroxyl group in ethanol^[36-37]. GA had an obvious quenching effect on the luminescence intensity of 1, so we chose ethanol as a solvent for fluorescence detection of GA to increase the sensitivity. When 1 was dispersed in an ethanol solution of different concentrations of GA (0-700 mmol·L^-1) (Fig. 4a), the luminescence intensity of 1 was decreased with the increase of GA concentration, and showed a good nonlinear relationship: y=4 596.9e^-x/230.38+208.21 (R²=0.998 66) (Fig. 4b). In the low concentration range (0-50 mmol·L^-1), the fluorescence intensity of 1 showed a good linear relationship with concentration of GA: y=-24.422x+5 014.0 (R²=0.997 85) (Fig. 4b). The LOD calculated by the formula 3σ/k was 2.1 μmol·L^-1.

  Figure 4

  

  Figure 4.  (a) Fluorescence spectra of MOF 1 in ethanol solution with different concentrations of GA; (b) Linear and nonlinear relationship between luminescence intensity of 1 and GA concentration

  下载: 全尺寸图片 幻灯片

  At the same time, the interference results of common organic solvents on MOF 1 sensing GA are shown in Fig. S7. It could be seen that the presence of other organic solvents did not affect the fluorescence detection of GA, indicating that 1 had good selectivity and anti-interference ability.

  2.7   Cyclic stability test

  The reuse of sensors could help reduce costs and expand practical applications. We investigated the reversibility of MOF 1 sensing SSZ/GA, and the results are shown in Fig. 5. The results showed that the sensor has good stability and repeatability. It is an excellent luminescent sensor for detecting SSZ/GA.

  Figure 5

  

  Figure 5.  Reversibility of MOF 1 sensing SSZ (a) and GA (b)

  下载: 全尺寸图片 幻灯片

  2.8   Preliminary exploration of fluorescence quenching mechanism

  The mechanism of fluorescence quenching generally has the following three kinds: (1) the emission of the fluorescent substance is decreased due to energy transfer, and the fluorescence lifetime will change significantly. At the same time, the emission peak of the fluorescent substance overlaps with the UV-Vis absorption of the measured substance. (2) Competitive absorption leads to fluorescence quenching, in which the excitation or emission peaks of the fluorescent substance may overlap with the UV-Vis absorption of the tested substance, and the fluorescence lifetime will not change significantly. (3) The tested substance forms a non-luminous substance with a fluorescent substance, and the emission peak changes^[38-39].

  To understand the fluorescence quenching mechanism of 1 by SSZ (or GA), the PXRD of 1 before and after sensing SSZ (or GA) was performed. It was found that the position of the characteristic peak of 1 did not change (Fig. S1), indicating that the structure of 1 did not collapse. From the fluorescence spectra of each system, the emission wavelength of 1 did not shift after sensing SSZ (or GA). It showed that SSZ (or GA) did not form new nonluminescent substances with 1. The fluorescence lifetimes of 1, 1+SSZ, and 1+GA systems were determined (Table 2). The fluorescence lifetime decay curves are shown in Fig.S8. It was found that the fluorescence lifetime of 1 changed significantly before and after adding SSZ (or GA), indicating that this quenching was not caused by competitive absorption.Further comparison of the UV-Vis absorption spectra of SSZ (or GA) with the excitation and emission spectra of 1 and 1 in SSZ aqueous solution(or 1 in GA ethanol solution) (Fig.S9 and S10) could show that the SSZ (or GA) had strong UV-Vis absorption peaks in a range of 300-360 nm, which completely overlapped with the excitation spectra of 1 while there was no overlap with the emission spectrum. Above all, the fluorescence quenching of 1 by SSZ (or GA) might be caused by energy transfer.

  Table 2

  

  Table 2.  Fluorescence lifetime of MOF 1, 1-SSZ, and 1-GA*

  下载: 导出CSV

  Sample	τ1/ns(ω/%)	τ2/ns(ω/%)	τ3/ns(ω/%)	τ/ns	χ2
  1	0.57 (100)			0.57	1.297
  1+SSZ	0.10 (78.94)	0.84 (21.06)		0.26	1.296
  1+GA	0.40 (37.43)	2.07 (35.00)	8.87 (27.57)	3.32	1.063
  * τ is the fluorescence lifetime, ω is the proportion, and χ2 is the chi-square test.

  2.9   Magnetism

  The DC electromagnetic susceptibilities of MOFs 1 and 2 are shown in Fig. 6. For 1, the _χMT value at 300 K was 34.77 cm³·mol^-1·K, and when it cooled to 3 K, the _χMT value gradually decreased to 2.22 cm³·mol^-1·K. For 2, the _χMT value at 300 K was 30.84 cm³·mol^-1·K, and when cooled to 3 K, the _χMT value gradually decreased to 2.02 cm³·mol^-1·K. The _χMT values of 1 and 2 were slightly lower than the experimental value of 2.921 4 cm³·mol^-1·K for a cobalt ion (S=3/2), which might be due to the paramagnetic interaction of europium ion or samarium ion. It indicates that 1 and 2 exhibit global antiferromagnetic interactions. The magnetic susceptibility data of 1 were in accordance with CurieWeiss law, ${\chi _{\rm{M}}} = \frac{C}{{T-\theta }}$^[40], in which χ_M is molar magnetic susceptibility, C is the Curie constant, θ is called the Weiss constant, T is the temperature. When the θ is positive, it is called ferromagnetic interaction. When the θ is negative, it is called an antiferromagnetic interaction. The fitting result was C=66.225 cm³·mol^-1 and θ=-264.9 K. The Weiss constant of -264.9 K indicates a strong antiferromagnetic interaction between europium or samarium and cobalt ions in 1 and 2.

  Figure 6

  

  Figure 6.  DC electromagnetic susceptibility of MOFs 1 and 2 in a range of 2-300 K

  下载: 全尺寸图片 幻灯片

  3.   Conclusions

  We designed, synthesized, and characterized two structurally similar lanthanide-cobalt bimetallic organic frameworks (Ln-Co-MOFs) using the solvothermal method. MOFs 1 and 2 belong to the R3 space group of the trigonal crystal system, and both have novel 3D structures and good thermal stability. Among them, Eu-Co-MOF(1) had good luminescence performance and unique sensing and recognition ability for the sulfasalazine and glutaraldehyde. And it was easy and fast to operate, and was a promising luminescence sensor.Magnetic tests showed that both 1 and 2 were antiferromagnetic. In general, this work provides a reference for the detection of drug molecules and organic molecules by metal-organic frameworks, and some ideas for the multi-functional design of metal-organic frameworks.

  
  Acknowledgements: This work was supported by the National Natural Science Foundation of China (Grant No. 22063010) and the Graduate Innovation program of Yan'an University (Grant No.YCX2024062) Conflicts of interest: The authors declare no competing financial interest.
  Supporting information is available at http://www.wjhxxb.cn
  
• 1. [1]

     Nozaki Y, Inoue A, Kinoshita K, Funauchi M, Matsumura I. Efficacy of iguratimod vs.salazosulfapyridine as the first line csDMARD for rheumatoid arthritis.[J]. Mod. Rheumatol., 2020, 30(2):  249-258. doi: 10.1080/14397595.2019.1572267

  2. [2]

     Claytor J, Kumar P, Ananthakrishnan N A, Colombel J, Agrawal M, Ungaro C R. Mild Crohn's disease: Definition and management[J]. Curr. Gastroenterol. Rep., 2023, 25(3):  45-51. doi: 10.1007/s11894-023-00863-y

  3. [3]

     Mushtaq S, Sarkar R. Sulfasalazine in dermatology: A lesser explored drug with broad therapeutic potential[J]. Int. J. Dermatol., 2020, 6(3):  191-198.

  4. [4]

     Yu H, Hu K, Zhang T, Ren H. Identification of target genes related to sulfasalazine in triple-negative breast cancer through network pharmacology[J]. Med. Sci. Monit., 2020, 26:  e926550.

  5. [5]

     Sah N, Ramaiah B, Koneri R. Sulfasalazine-induced drug rash with eosinophilia and systemic symptoms syndrome in a seronegative spondyloarthritis patient: A case report[J]. Indian J. Pharmacol., 2021, 53(5):  391-393. doi: 10.4103/ijp.IJP_129_18

  6. [6]

     Sil A, Bhattacharjee S M, Chandra A, Pramanik D J. Sulfasalazine induced drug reaction with eosinophilia and systemic symptoms (DRESS) with concomitant acute chikungunya virus infection: possible role of new viral trigger[J]. BMJ Case Rep., 2021, 14(10):  e244063. doi: 10.1136/bcr-2021-244063

  7. [7]

     Winward J, Lyckholm L, Brown M S, Mokadem M. Republished: Case of relapsing sulfasalazine-induced hypersensitivity syndrome upon reexposure[J]. Drug and Therapeutics Bulletin, 2021, 59(11):  174-175. doi: 10.1136/dtb.2021.235803rep

  8. [8]

     Jolibois B, Guerbet M, Vassal S. Glutaraldehyde in hospital wastewater[J]. Arch. Environ. Contam. Toxicol., 2002, 42(2):  137-144. doi: 10.1007/s00244-001-0011-8

  9. [9]

     Ballantyne B, Jordan L S. Toxicological, medical and industrial hygiene aspects of glutaraldehyde with particular reference to its biocidal use in cold sterilization procedures[J]. J. Appl. Toxicol., 2001, 21(2):  131-151. doi: 10.1002/jat.741

  10. [10]

      Migneault I, Dartiguenave C, Vinh J, Bertrand M J, Waldron K C. Two glutaraldehyde immobilized trypsin preparations for peptide mapping by capillary zone electrophoresis, liquid chromatography, and mass spectrometry[J]. J. Liq. Chromatogr. Relat. Technol., 2008, 31(6):  789-806. doi: 10.1080/10826070801890413

  11. [11]

      Yu L Y, Wu M R, Dong W, Wen Y Q, Zhao C S, Liu S R, Jin J, Lin W. Rapid determination of glutaraldehyde in leather by UV spectroscopy reverse flow injection system[J]. J. Soc. Leather Technol. Chem., 2014, 98(5):  211-215.

  12. [12]

      Pieraccini G, Bartolucci G, Pacenti M, Dugheri S, Boccalon P, Focardi L. Gas chromatographic determination of glutaraldehyde in the workplace atmosphere after derivatization with O-(2, 3, 4, 5, 6-pentafluorobenzyl) hydroxylamine on a solidphase microextraction fibre[J]. J. Chromatogr. A, 2002, 955(1):  117-124. doi: 10.1016/S0021-9673(02)00199-1

  13. [13]

      Maggadani P B, Harmita , Isfadhila M. High-performance liquid chromatography analytical method validation glutaraldehyde and benzalkonium chloride in disinfeatants[J]. Int. J. Pharmaceut., 2018, 10(1):  248-251.

  14. [14]

      Kang H I, Shin H S. Sensitive determination of glutaraldehyde in environmental water by derivatization and gas chromatography-mass spectrometry[J]. Anal. Methods, 2016, 8(15):  3216-3223. doi: 10.1039/C5AY02798E

  15. [15]

      Tsamis V, Tsanaktsidou E, Karavasili C, Zacharis K C, Bouropoulos N, Fatouros G D, Markopoulou K C. Development and validation of HPLC-DAD and LC-(ESI)/MS methods for the determination of sulfasalazine, mesalazine and hydrocortisone 21-acetate in tablets and rectal suppositories: In vitro and ex vivo permeability studies[J]. J. Chromatogr. B, 2022, 1198:  123246. doi: 10.1016/j.jchromb.2022.123246

  16. [16]

      Louw V, Brownfoot F, Cluver C, Decloedt E, Kellermann T. An LCMS/MS method for the simultaneous quantitation of sulfasalazine and sulfapyridine in human placenta[J]. J. Pharmaceut. Biomed., 2023, 235:  115633. doi: 10.1016/j.jpba.2023.115633

  17. [17]

      张婕, 刘欣, 李梓欣, 裴玉婷, 杨宇琦, 李慧敏, 刘志强. 基于合成后修饰策略构建高灵敏度和选择性金属有机骨架基荧光静默系统用于抗坏血酸的检测[J]. 无机化学学报, 2024,40,(4): 823-833. doi: 10.11862/CJIC.20230310ZHANG J, LIU X, LI Z X, PEI Y T, YANG Y Q, LI H M, LIU Z Q. Assembling a luminescence silencing system based on post-synthetic modification strategy: A highly sensitive and selective turn-on metalorganic framework probe for ascorbic acid detection[J]. Chinese J. Inorg. Chem., 2024, 40(4):  823-833. doi: 10.11862/CJIC.20230310

  18. [18]

      Sakamoto R, Fukui N, Maeda H, Toyoda R, Takaishi S, Tanabe T, Komeda J, Amo-Ochoa P, Zamora F, Nishihara H. Layered metalorganic frameworks and metal-organic nanosheets as functional materials[J]. Coord. Chem. Rev., 2022, 472:  214787. doi: 10.1016/j.ccr.2022.214787

  19. [19]

      Zha X Q, Zhao X H, Webb E, Khan S U, Wang Y. Beyond pristine metal organic frameworks: Preparation of hollow MOFs and their composites for catalysis, sensing, and adsorption removal applications[J]. Molecules, 2023, 28(1):  144-164.

  20. [20]

      韩晓, 王林玉, 耿付江, 席改卿. 苯并咪唑基金属有机骨架/氧化石墨烯复合材料对罗丹明B的吸附[J]. 无机化学学报, 2023,39,(6): 1159-1168. doi: 10.11862/CJIC.2023.061HAN X, WANG L Y, GENG F J, XI G Q. Adsorption of rhodamine B by benzimidazole based metalorganic framework/graphene oxide composites[J]. Chinese J. Inorg. Chem., 2023, 39(6):  1159-1168. doi: 10.11862/CJIC.2023.061

  21. [21]

      Amooghin E A, Sanaeepur H, Ghomi M, Luque R, Garcia H, Banglin Chen. Flexible-robust MOFs/HOFs for challenging gas separations[J]. Coord. Chem. Rev., 2024, 505:  215660. doi: 10.1016/j.ccr.2024.215660

  22. [22]

      安燕燕, 卢丽萍, 朱苗力. 一种Cd^Ⅱ-MOF作为传感Fe (Ⅲ)和Cr (Ⅵ)的多响应荧光探针[J]. 无机化学学报, 2023,39,(5): 939-946. AN Y Y, LU L P, ZHU M L. One Cd^Ⅱ-MOF as a multi-responsive fluorescent probe for sensing Fe (Ⅲ) and Cr (Ⅵ)[J]. Chinese J. Inorg. Chem., 2023, 39(5):  939-946.

  23. [23]

      Wang H M, Feng X N, Xia Y, Yin X B. Dual-ligand terbium metalorganic framework for visual ratiometric fluorescence sensing of nitrites in pickles[J]. ACS Food Sci. Technol., 2022, 2:  1911-1920. doi: 10.1021/acsfoodscitech.2c00278

  24. [24]

      徐涵, 潘兆瑞, 亓昭鹏, 孙洁. 基于V型配体的三个荧光Zn-MOF对水溶液中2, 4, 6-三硝基苯酚和Fe³⁺的荧光传感[J]. 无机化学学报, 2022,38,(12): 2479-2490. doi: 10.11862/CJIC.2022.238XU H, PAN Z R, QI Z P, SUN J. Three luminescent Zn-MOFs based on V-shaped ligands for fluorescence sensing of 2, 4, 6-trinitrophenol and Fe³⁺ in aqueous solution[J]. Chinese J. Inorg.Chem., 2022, 38(12):  2479-2490. doi: 10.11862/CJIC.2022.238

  25. [25]

      Liu X F, Ma Q Q, Feng X, Li R F, Zhang X Y. A recycled Tb-MOF fluorescent sensing material for highly sensitive and selective detection of tetracycline in milk[J]. Microchem. J., 2021, 170:  106714. doi: 10.1016/j.microc.2021.106714

  26. [26]

      Zhao Z Q, Yang S, Zhu M C, Zhang Y, Sun Y G, Wu S Y. A multicenter lanthanide coordination polymer for ratiometric pesticide monitoring[J]. Sens Actuator B-Chem., 2023, 383:  133593. doi: 10.1016/j.snb.2023.133593

  27. [27]

      朱子馨, 王萃娟, 刘成, 肖玉美, 罗丹, 刘冬宁, 王尧宇. 一种用于选择性检测苯乙烯的Zn-MOFs发光传感器[J]. 无机化学学报, 2020,36,(10): 1941-1947. doi: 10.11862/CJIC.2020.224ZHU Z X, WANG C J, LIU C, XIAO Y M, LUO D, LIU D N, WANG Y Y. A Zn-MOF luminescent sensor for selective detection of styrene[J]. Chinese J. Inorg. Chem., 2020, 36(10):  1941-1947. doi: 10.11862/CJIC.2020.224

  28. [28]

      Zhang G Q, Gao L J, Chai H M, Ren Y X. Novel multifunctional samarium-organic framework for fluorescence sensing of Ag⁺, MnO₄^-, and cimetidine and electrochemical sensing of o-nitrophenol in aqueous solutions[J]. ACS Omega, 2021, 6(10):  6810-6816. doi: 10.1021/acsomega.0c05867

  29. [29]

      Jimenez V O, Pham H T Y, Zhou D, Liu M, Nugera A F, Kalappattil V, Eggers T, Hoang K, Duong L D, Terrones M, Gutiérrez R H, Phan H M. Transition metal dichalcogenides: Making atomic-level magnetism tunable with light at room temperature[J]. Adv. Sci., 2024, 11(7):  2304792. doi: 10.1002/advs.202304792

  30. [30]

      Obeidat A, Aladerah B, Gharaibeh M, Aledealat K. Magnetism and magnetic properties of 3D transition metal monolayer on Pd (100)[J]. J. Magn. Magn. Mater., 2023, 585:  171116. doi: 10.1016/j.jmmm.2023.171116

  31. [31]

      丁龙龙, 张彦华, 顾继友, 谭海彦, 朱丽滨. 傅里叶变换红外测定氧化淀粉的羧基含量初探[J]. 光谱学与光谱分析, 2014,34,(2): 401-404. DING L L, ZHANG Y H, GU J Y, TAN H Y, ZHU L B. Determination of the carboxyl content of oxidized starch by Fourier transform infrared (FTIR) spectroscopy[J]. Spectrosc. Spectr. Anal., 2014, 34(2):  401-404.

  32. [32]

      Ramya A R, Reddy M L P, Cowley A H, Vasudevan K V. Synthesis, crystal structure, and photoluminescence of homodinuclear lanthanide 4(dibenzylamino) benzoate complexes[J]. Inorg. Chem., 2010, 49(5):  2407-2415.

  33. [33]

      Fan L H, Zhang J Y, Zhao Y, Sun C Y, Li W J, Chang Z D. A robust Eu-MOF as a multi-functional fluorescence sensor for detection of benzaldehyde, Hg²⁺, and Cr₂O₇^2-/CrO₄^2-[J]. Microchem. J, 2024, 196:  109712.

  34. [34]

      Song Q, Wang L, Zhang J, Liu Y, Zhang X, Kong X. Fabrication of Eu-MOFs rod-shaped nanospheres with dual emissions for ratiometric fluorescence detecting Hg²⁺ in water[J]. Spectroc. Acta Pt. A-Molec. Biomolec. Spectr., 2024, 312:  124013.

  35. [35]

      Dong X Y, Li D Q C, Li Y Y, Sakiyama H, Muddassir M, Pan Y, Srivastava D, Kumar A. A 3, 8-connected Cd (Ⅱ)-based metal-organic framework as an appropriate luminescent sensor for the antibiotic sulfasalazine[J]. CrystEngComm, 2022, 24:  7157-7165.

  36. [36]

      Jia Y H, Wang J M, Zhao L M, Yan B. Eu³⁺-β-diketone functionalized covalent organic framework hybrid material as a sensitive and rapid response fluorescent sensor for glutaraldehyde[J]. Talanta, 2022, 236:  122877.

  37. [37]

      Xu X, Meng R, Lu C, Mei L, Chen L, Zhao J. Acetate-decorated triLn (Ⅲ)-containing antimonotungstates with a tetrahedral{WO₄}group as a structure-directing template and their luminescence properties[J]. Inorg. Chem., 2020, 59(6):  3954-3963.

  38. [38]

      Song X M, Hou X F, Zhao Q X, Ma Z H, Ren Y X. Fluorescence quenching mechanisms of novel isomorphic Zn/Cd coordination polymers for selective nitrobenzene detection[J]. Spectroc. Acta Pt. A-Molec. Biomolec. Spectr., 2024, 308:  123729.

  39. [39]

      Dong X P, Qi H X, Zhai Z H, Li W Q, Zhang P D. Probing the fluorescence quenching mechanism of N-doped carbon quantum dots by inorganic ions[J]. Microchem. J., 2024, 197:  109854.

  40. [40]

      崔术新, 张文文, 沈金铭, 茹莉莹, 赵宇, 徐宝, 左明辉. 铁镍双金属配合物[Fe (2, 2'-bpy)₂Ni (CN)₄]_n的合成、晶体结构及磁性[J]. 硅酸盐学报, 2020,48,(6): 919-924. CUI S X, ZHANG W W, SHEN J M, RU L Y, ZHAO Y, XU B, ZUO M H. Syntheses, crystal structures, and magnetic properties of bimetallic complex[Fe (2, 2'-bpy)₂Ni (CN)₄]_n[J]. J. Chin. Ceram. Soc., 2020, 48(6):  919-924.

• 

  Figure 1  Infrared spectra of H₅L and Ln-Co-MOFs 1 and 2

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Structures of Ln-Co-MOFs 1 (left) and 2 (right)

  (a, b) Asymmetric unit; (c-f) Coordination patterns of the L^5- ligand; (g, h) Binary metal units; (i, j) Four-membered metal unit; (k, l) Six-membered ring; (m, n) 3D structure diagram; Symmetry codes: a: -y+1, x-y+1, z; b: -x+y, -x+1, z; c: -x+y+1/3, -x+2/3, z+2/3; d: -x+y+1/3, -x+2/3, z-1/3; f: x, y, z+1; h: -x+y, -x+1, z+1; i: -y+2/3, x-y+1/3, z-2/3; j: x, y, z-1; k: -x+y+2/3, -x+4/3, z+1/3; l: -y+1, x-y+1, z-1 for 1; a: -y+1, x-y, z; b: -x+y+1, -x+1, z; c: -x+y+1, -x+1, z-2; d: -x+y+2/3, -x+4/3, z-2/3; e: x, y, z-1; f: -y+2/3, x-y+1/3, z-2/3; g: -y+4/3, x-y+2/3, z+2/3; h: x, y, z+1; i: -x+y+1/3, -x+2/3, z+2/3; j: -y+1, x-y, z+2; k: -y-1, x-y, z-2; m: x, y, z-2; n: -x+y+2/3, -x+4/3, z+1/3 for 2.

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) Fluorescence spectra of MOF 1 in SSZ solutions with different concentrations; (b) Linear and nonlinear relationship between luminescence intensity of 1 and SSZ concentration

  下载: 全尺寸图片 幻灯片
  

  Figure 4  (a) Fluorescence spectra of MOF 1 in ethanol solution with different concentrations of GA; (b) Linear and nonlinear relationship between luminescence intensity of 1 and GA concentration

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Reversibility of MOF 1 sensing SSZ (a) and GA (b)

  下载: 全尺寸图片 幻灯片
  

  Figure 6  DC electromagnetic susceptibility of MOFs 1 and 2 in a range of 2-300 K

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystallographic data for Ln-Co-MOFs 1 and 2

  Parameter	1	2
  Empirical formula	C163H143N10O74CoEu9	C157H111N7O68ClCoSm9
  Formula weight	4 849.54	4 628.59
  Temperature / K	293(2)	296(2)
  Crystal system	Trigonal	Trigonal
  Space group	R3	R3
  a / nm	3.881 50(17)	3.885 6(8)
  b / nm	3.881 50(17)	3.885 6(8)
  c / nm	1.112 78(9)	3.885 6(8)
  Volume / nm3	14.519 7(17)	14.591(7)
  Z	3	3
  Dc / (g·cm-3)	1.460	2.246
  Absorption coefficient / mm-1	3.027	2.898
  F(000)	6 126	9 924
  θrange for data collection / (°)	1.817-25.996	2.428-24.705
  Reflection collected	26 819	23 933
  Unique reflection	10 340 (Rint=0.023 1)	10 785 (Rint=0.018 3)
  Data, restraint, number of parameters	10 340, 2 024, 597	10 785, 941, 566
  Goodness-of-fit on F 2	1.317	1.088
  Final R indices [I > 2σ(I)]	R1=0.045 0, wR2=0.113 7	R1=0.041 5, wR2=0.089 3
  R indices (all data)	R1=0.045 4, wR2=0.114 0	R1=0.043 2, wR2=0.090 2

  下载: 导出CSV

  Table 2.  Fluorescence lifetime of MOF 1, 1-SSZ, and 1-GA*

  Sample	τ1/ns(ω/%)	τ2/ns(ω/%)	τ3/ns(ω/%)	τ/ns	χ2
  1	0.57 (100)			0.57	1.297
  1+SSZ	0.10 (78.94)	0.84 (21.06)		0.26	1.296
  1+GA	0.40 (37.43)	2.07 (35.00)	8.87 (27.57)	3.32	1.063
  * τ is the fluorescence lifetime, ω is the proportion, and χ2 is the chi-square test.

  下载: 导出CSV
•