English

• 0.   Introduction

  With the continuous development of industry, the unreasonable exploitation of natural resources, and the random discharge of wastewater, the problem of water pollution has become particularly prominent^[1-5]. The current water pollution problems mainly include organic pollution, heavy metal ion pollution, and biological pollution^[6]. The metallic chromium (Cr) is a common non - ferrous metal in life, and it has been widely used in material processing, paint making, and electroplating^[7]. Although Cr is an essential trace element for the human body, the heavy metal Cr(Ⅵ) ion is difficult to degrade, difficult to digest, easy to accumulate in the body, and has high biological toxicity. It is already an indicator of water quality testing^[8]. The removal methods of Cr(Ⅵ) ions include photocatalytic reduction, ion exchange, membrane separation, chemical precipitation, and adsorption separation^[9-12]. Among them, the adsorption removal method is to use the adsorbent to adsorb Cr(Ⅵ) ions through coordination bonds, electrostatic attraction, hydrogen bonds, and other forces to achieve the effect of removal. The adsorption method has the advantages of simple operation, low cost, fast and efficient, reproducible recycling, and has been widely studied and applied^[13-15]. The current adsorbents used for the removal of heavy metal ions such as Cr(Ⅵ) mainly include activated carbon, biomass activated carbon, zeolites, molecular sieves, gels, and carbon nanotubes^[16]. And research shows that adsorbents with high specific surface area, abundant adsorption sites, and well - developed pore size distribution often have good adsorption performance. However, the adsorption and removal of heavy metal ions by most adsorbents have the disadvantages of low adsorption capacity, poor selectivity, and difficulty in regeneration and reuse. Coordination polymers usually have a large specific surface area and the structure is easy to modify, and there are extensive studies in the fields of fluorescence, magnetic, adsorption separation, and photocatalytic degradation^[17-29]. They are showing the potential for application.

  In this paper, a copper - based coordination polymer: {[Cu(bipy)₄(1, 3-dab)][Cu(bipy)₂(ClO₄)₂](ClO₄)₂·(1, 3-dab)}_n (1) was successfully synthesized by using 4, 4' - bipyridine (bipy), 1, 3 -isophthalonitrile (1, 3- dab), Cu(ClO₄)₂·6H₂O as raw materials. The structure of 1 was characterized by IR, X - ray single - crystal diffraction, elemental analysis, and X -ray photoelectron spectroscopy (XPS). The influence of the dosage, temperature, pH, and coexisting ions on the adsorption of Cr(Ⅵ) by adsorbent 1 was explored.

  1.   Experimental

  1.1   Instruments and reagents

  The Nicolet 5DX FT-IR spectrometer was used to characterize and test the presence of hydroxyl functional groups in 1. The structure of 1 was tested and analyzed by using Rigaku's D/max 2500 X - ray powder diffractometer (XRD). The test conditions were as follows: Cu Kα (λ=0.156 04 nm), 40 kV (tube voltage), 150 mA (tube current), graphite monochromator, 5° - 65° (2θ). The morphology of 1 was observed by the Hitachi SU8010 scanning electron microscope (SEM), the acceleration voltage during the test was 1.0 kV. The structure of 1 was tested using APEX -Ⅱ CCD X - ray single crystal diffractometer produced by Bruker, Germany. The N₂ adsorption - desorption curve of 1 was gained at 77 K by AUTO CHEM II 2920 from American Micro Instrument Company, and the specific surface area was calculated by the Brunauer -Emmett- Teller method. The concentration of Cr(Ⅵ) was analyzed using UV-2601 UV-Vis spectrophotometer produced by Beijing Ruili Analytical Instrument Co., Ltd.

  The chemical reagents used in the experiment, such as bipy, Cu(ClO₄)₂·6H₂O, 1, 3 - dab, NaCl, KCl, MgCl₂, CaCl₂, CuCl₂, FeCl₃, NaNO₃, Na₂SO₄, NaHCO₃, Na₂CO₃, Na₃PO₄, and methanol were analytically pure reagents, produced by Energy Chemical Co., Ltd. (Shanghai, China). The pure water used in the experiment was prepared by reverse osmosis in the laboratory.

  1.2   Synthesis of complex 1

  A mixture of Cu(ClO₄)₂·6H₂O (0.074 0 g, 0.2 mmol), and bipy (0.061 0 g, 0.2 mmol) in 10 mL of water and 10 mL of anhydrous methanol was added 5 mg of 1, 3-dab, and a blue solution was obtained. After the reaction was over, the mixture was filtered and the filtrate was collected in a 50 mL beaker. The filtrate was naturally volatilized for 5 d to obtain blue - purple massive crystals. The yield was about 78% (based on Cu²⁺). Elemental Anal. Calcd. for C₈₀H₆₄Cl₄Cu₂N₁₆O₁₆ (%): C 54.10, N 12.62, H 3.61; Found(%): C 54.10, N 12.61, H 3.61. IR(KBr, cm^-1): 3 443(s), 2 978(m), 2 911 (w), 2 263(w), 1 626(s), 1 384(w), 1 095(w), 1 036(m), 878(m), 630(w).

  1.3   X-ray single crystal diffraction

  A single crystal with a size of approximately 0.13 mm × 0.12 mm × 0.11 mm for 1 was used for structural test analysis on a Bruker's APEX-Ⅱ CCD single crystal diffractometer. The test conditions were as follows: Mo Kα (λ =0.071 073 nm), T =150(2) K. A total of 9 218 reflections were collected during the test, of which 7 120 reflections were used. Olex2 software was used to analyze the structure of 1, add hydrogen atoms and refine the structure. The parameters of 1 are listed in Table 1, and selected bond lengths and bond angles are listed in Table 2.

  表 1

  

  表 1  Crystal data and refinement parameters of 1

  下载: 导出CSV

  Parameter	1		Parameter	1
  Empirical formula	C80H64Cl4Cu2N16O16		μ / mm-1	0.77
  Formula weight	1 774.37		Limiting indices	-14 ≤ h ≤ 10, -15≤ k ≤ 13, -22 ≤ l ≤ 41
  Crystal system	Orthorhombic		F(000)	1 823
  Space group	P2221		θ range / (°)	2.6-28.6
  a / nm	1.115 52(5)		Total reflection collected, unique	9 217, 7 586 (Rint=0.045)
  b / nm	1.116 66(4)		Data, restraint, parameter	9 217, 0, 537
  c / nm	3.11684(15)		S	1.05
  Volume / nm3	3.8825(3)		Final R indices [I > 2σ(I)]	R1=0.050, wR2=0.092
  Z	2		Largest diff. peak and hole / (e·nm-3)	1 100 and -520
  Dc / (Mg·m-3)	1.518

  表 2

  

  表 2  Selected bond length (nm) and bond angle (°) of 1

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  Cu1—O1A	0.248 2(2)	Cu1—N2	0.202 5(3)	Cu1—O1	0.248 2(2)
  Cu1—N3B	0.203 3(3)	Cu1—N1	0.204 1(2)	Cu1—N1A	0.204 1(2)
  Cu2—N4D	0.203 7(2)	Cu2—N5	0.203 9(3)	Cu2—N4	0.203 7(2)
  Cu2—N6E	0.201 9(3)
  O1A—Cu1—O1	178.71(10)	N2—Cu1—N1	89.15(6)	N1A—Cu1—O1A	91.59(9)
  N2—Cu1—N1A	89.15(6)	N1A—Cu1—O1	88.39(9)	N3B—Cu1—O1	90.65(5)
  N1—Cu1—O1A	88.39(9)	N3B—Cu1—O1A	90.65(5)	N1—Cu1—O1	91.59(9)
  N3B—Cu1—N1	90.85(6)	N1A—Cu1—N1	178.29(13)	N3B—Cu1—N1A	90.85(6)
  N2—Cu1—O1	89.35(5)	N3B—Cu1—N2	180.0	N2—Cu1—O1A	89.35(5)
  O2—Cl1—O1	108.39(14)	N4—Cu2—N4D	178.56(12)	N6E—Cu2—N4D	89.28(6)
  N5—Cu2—N4D	90.72(6)	N6D—Cu2—N4	89.28(6)	N5—Cu2—N4	90.72(6)
  N6D—Cu2—N5	180.0
  Symmetry codes: A: x, -y+1, -z; B: x-1, y, z; C: x, -y, -z; D: -x+1, y, -z+1/2; E: x, y-1, z.

  CCDC: 2114736.

  1.4   Adsorption experiment

  During the experiment, a certain amount (0.001 0- 0.005 0 g) of 1 was put into a 250 mL beaker with a circulating water system, and then 50 mL of Cr₂O₇^2- (5 mg·L^-1, pH=3-7) was added into the beaker. After stirring and adsorbing for 30, 60, 90, and 120 min at a certain temperature (25, 30, 35, 40, 45 ℃), 5 mL of the mixed solution was drawn with a 10 mL syringe equipped with a 0.45 μm filter, and the collected filtrate was put into a cuvette. The absorbance was measured with an UV - Vis spectrophotometer at a wavelength of 420 nm. The corresponding concentration of Cr₂O₇^2- was calculated by the standard curve: A= 0.005 4c- 0.001 6 (R²=0.994 5), where A is the absorbance of the solution and c is the concentration of Cr₂O₇^2-. The adsorption performance was evaluated by the change of Cr₂O₇^2- concentration before and after the adsorption. The adsorption rate (R) was calculated as follows:

  $ R = \left( {1 - \frac{{{c_t}}}{{{c_0}}}} \right) \times 100\% $

  For the adsorption experiment, the c₀ and c_t are the initial concentration and the concentration at t, respectively (mg·L^-1).

  The regeneration of the adsorbent will affect its application. Therefore, a high - speed centrifuge was used to collect 1 after the adsorption of Cr(Ⅵ) by centrifugal separation. The HCl solution with pH=1 was added to the adsorbent, then the mixture was sonicated for 20 min, and centrifuged to collect the solid powder. The solid powder was washed with deionized water and dried in a blast drying oven at 100 ℃ for 12 h. Then, the desorbed 1 was used for the cycling experiment in Cr₂O₇^2- solution with T=30 ℃ and pH=5.

  2.   Results and discussion

  2.1   Structure of 1

  Herein, a copper-based coordination polymer: {[Cu(bipy)₄(1, 3-dab)] [Cu(bipy)₂(ClO₄)₂] (ClO ₄)₂· (1, 3 - dab)}_n (1) was successfully synthesized by the bipy, Cu(ClO₄) ₂·6H₂O, and 1, 3 - dab as raw materials. The XPS test result (Fig. 1a) showed that 1 was composed of Cu, C, N, and O elements. The XPS spectra of 1 showed that it had characteristic diffraction peaks related to copper ions at 933, 934, 943, 952, 954, and 963 eV (Fig. 1b). Among them, the diffraction peaks at 933 and 934 eV are the characteristic diffraction peaks of the Cu2p_3/2 orbital in Cu²⁺. The diffraction peaks at 943 eV are the shock peaks of the Cu2p_3/2 orbital in Cu²⁺. The two diffraction peaks at 952 and 954 eV belong to the Cu²⁺ spin-orbit splitting peak. The diffraction peak at 963 eV is the excitatory peak of the Cu2p_1/2 orbital in Cu²⁺. Therefore, the metal ions in 1 are all Cu²⁺, and its outermost nuclear electron arrangement should be 3d⁹.

  图 1

  

  图 1.  XPS spectra of 1: (a) survey; (b) Cu2p

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  The X-ray single-crystal diffraction analysis

  results show that 1 belongs to the orthorhombic crystal system P222₁ space group. The asymmetric structural unit of 1 (Fig. 2a) shows that it is composed of two Cu²⁺ ions, six bipy molecules, four ClO₄^- anions, and two 1, 3-dab molecules. In 1, the Cu²⁺ has two different coordination modes: [Cu(bipy)₄(1, 3-dab)]²⁺ and [Cu(bipy)₂ (ClO₄)₂]. In the structural unit of [Cu(bipy)₄(1, 3-dab)]²⁺, the central Cu²⁺ is coordinated with six N atoms, among which four N atoms are from four bipy molecules, and two N atoms are from 1, 3 - dab molecules (Fig. 2b). While in the structural unit of [Cu(bipy)₂(ClO₄)₂], the central Cu²⁺ is coordinated with four N atoms from two bipy molecules and two O atoms from ClO₄^- anions (Fig. 2c).

  图 2

  

  图 2.  (a) Asymmetric structural unit of 1; (b) Structural unit of [Cu(bipy)₄(1, 3-dab)]²⁺;(c) Structural unit of [Cu(bipy)₂(ClO₄)₂]; (d) 2D structure of 1

  Symmetry codes: A: x, -y+1, -z; B: x-1, y, z; D: -x+1, y, -z+1/2; E: x, y-1, z

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  Due to the influence of the Ginger - Taylor effect, in the structural unit of [Cu(bipy)₂(ClO₄)₂], the four N atoms in the ab plane approach the Cu²⁺ ion. The bond length of the Cu—N bond ranges from 0.202 5(3) to 0.204 1(2) nm. The O atom in the z - axis direction departs from Cu²⁺, causing the bond length to be elongated (Cu—O 0.248 2(2) nm). In complex 1, since there are two N atoms in the bipy molecule, it can coordinate with two Cu²⁺. Therefore, the bipy molecule in 1 bridges two similar Cu²⁺ ions by the form of μ₂. Thus, a 2D material is formed (Fig. 2d). Usually, during the synthesis of the complex, the organic molecule bipy is introduced into the material in the form of a second ligand. Its coordination with metal ions can often form 1D^[30], 2D^[31], and 3D complexes^[32]. These complexes are constructed from more than two kinds of ligands. Complex 1 is similar to their coordination mode. The N₂ adsorption -desorption curve of 1 (Fig. 3) showed that it belongs to a typical s-type adsorption isotherm, and its specific surface area was 145 cm²·g^-1.

  图 3

  

  图 3.  N₂ adsorption-desorption curve of 1

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  2.2   Adsorption of Cr(Ⅵ)

  2.2.1   Effect of adsorbent dosage on the adsorption

  At 30 ℃, a certain amount (0.001 0-0.005 0 g) of 1 adsorbent was added to the Cr₂O₇^2- solution with pH=7 to study the effect of adsorbent dosage on the adsorption of Cr. The experimental results (Fig. 4a) showed that adsorption of Cr₂O₇^2- by 1 reached equilibrium after 120 min of adsorption. At this time, the adsorption capacities (q_e) were 230, 250, 220, 211, and 198 mg·g^-1, respectively. It can be seen that the q_e of the adsorbent does not increase with the increase of the adsorbent dosage, but there is an optimal q_e. The optimal dosage of 1 adsorbent was 0.002 0 g (Fig. 4b). That is when the adsorbent mass concentration (ρ₁) was 0.04 g·L^-1, the adsorption performance of 1 was the best. Therefore, the subsequent experiments of pH and temperature effects on 1 adsorption of Cr(Ⅵ) were carried out when the adsorbent dosage was 0.002 0 g. Although the maximum q_e of 1 can be as high as 250 mg·g^-1, which is better than most adsorbents^[33], which may be due to the structure of 1. Because 1 has a cationic structural framework, in addition to being able to adsorb Cr(Ⅵ) through hydrogen bonding, it can also adsorb Cr(Ⅵ) through strong electrostatic attraction. However, it is inferior to the maximum q_e of 372.6 mg· g^-1 reported in the literature^[34].

  图 4

  

  图 4.  Effect of dosage of 1 on (a) the adsorption of Cr(Ⅵ), and (b) the maximum q_e

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  2.2.2   Effect of pH on the adsorption

  At 30 ℃, 0.002 0 g of adsorbent was added to the solutions with different pH values to study the effect of pH on the adsorption of Cr(Ⅵ). The experimental results (Fig. 5) showed that when pH=1 the adsorption rate (R) could reach 91.7% after 120 min; when pH=3 and 7, R =100% after 120 min; when pH=5, R=100% after 90 min; pH=9, R=81.8% after 120 min. It can be seen that the performance of 1 adsorbing Cr(Ⅵ) under acidic conditions is better than that under alkaline conditions. When pH=5, 1 has the best adsorption performance, and the average removal rate could reach 0.002 8 mg·min^-1.

  图 5

  

  图 5.  Effect of pH on the adsorption of Cr(Ⅵ) by 1

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  2.2.3   Effect of temperature on the adsorption

  To explore the effect of temperature (25-45 ℃) on the adsorption of Cr(Ⅵ), 0.002 0 g of 1 was added to the Cr₂O₇^2- solution with pH=5. The experimental results (Fig. 6) showed that when T=25℃, R=94.9% after 90 min; when T=30 ℃, R=100.0% after 90 min; when T=35 ℃, R=85.4% after 90 min; when T=40 ℃, R=73. 5% after 90 min; when T=45 ℃, R=63.5% after 90 min. Therefore, when the pH of the Cr(Ⅵ) solution was 5, the optimal adsorption temperature of 1 was 30 ℃.

  图 6

  

  图 6.  Effect of temperature on the adsorption of Cr(Ⅵ) by 1

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  2.3   Effect of ions on the adsorption

  Whether it is rivers, seas, domestic wastewater, or industrial wastewater, there are various ions in the water. These ions sometimes have a significant effect on adsorption. Therefore, the influence of ions on adsorption cannot be ignored. 1 L of inorganic salt solution with pH=5 was prepared (NaCl, KCl, MgCl₂, CaCl₂, CuCl₂, FeCl₃, NaNO₃, Na₂SO₄, NaHCO₃, Na₂CO₃, Na₃PO₄; c=0.1, 0.01, 0.001, and 0.000 1 mol·L^-1). At 30 ℃, 0.002 0 g of 1 was added to explore the influence of ions on the adsorption of Cr(Ⅵ).

  In the influence experiment for Na⁺ (Fig. 7a) and K⁺ (Fig. 7b), the study found that when the ion concentration was 0.000 1 mol·L^-1, the amount of Cr(Ⅵ) adsorbed by 1 was similar to that of the blank; but when the ion concentration was greater than 0.01 mol· L^-1, the Na⁺, and K⁺ had a certain effect on the removal of Cr(Ⅵ) by 1, and the adsorption rate remained above 80% after 120 min. In the experiment of the influence for Mg²⁺ (Fig. 7c), Ca²⁺ (Fig. 7d), and Cu²⁺ (Fig. 7e), the study found that the adsorption of Cr(Ⅵ) by 1 was similar to that of Na⁺ and K⁺. However, the inhibitory effect of Mg²⁺, Ca²⁺, and Cu²⁺ was higher than that of Na⁺ and K⁺; when the ion concentration was 0.000 1 mol·L^-1, 1 could adsorb about 98.3% of Cr(Ⅵ) after 120 min. The Fe³⁺ (Fig. 7f) inhibited 1 adsorbing Cr(Ⅵ) more obviously. When the ion concentration was 0.000 1 mol·L^-1, 1 could adsorb about 79.8% of Cr(Ⅵ) after 120 min. The effect of metal ions on the adsorption shows that the higher the ion concentration and valence, the greater the impact on the adsorption of Cr(Ⅵ) by 1.

  图 7

  

  图 7.  Effect of metal ions on the adsorption of Cr(Ⅵ) by 1

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  In the study of the effect of inorganic anions on the adsorption of Cr(Ⅵ) by 1, it is found (Fig. 8) that inorganic anions can significantly inhibit the adsorption of Cr(Ⅵ), and the higher the ion concentration and the valence, the more obvious the inhibitory effect. Since sodium salt was used in the experiment, the effect of Cl^- (Fig. 8a) on the adsorption was the same as that of Na⁺ (Fig. 7a). The inorganic anions NO₃^- and HCO₃^- are both negative monovalent anions, and their influence (Fig. 8b and 8c) on the adsorption was similar to that of Cl^-. The SO₄^2-, CO₃^2-, and Cr₂O₇^2- are all negative divalent anions, and the ionic radius of SO₄^2- or CO₃^2- is smaller than that of Cr₂O₇^2-, which significantly inhibited the adsorption. When the concentration of CO₃^2- and SO₄^2- was 0.000 1 mol·L^-1 (Fig. 8d and 8e), 1 could adsorb about 78.1% and 79.9% of Cr(Ⅵ) after 120 min, respectively. The PO₄^3- is a negative trivalent anion, which has a higher valence state than Cr₂O₇^2-, and had a greater inhibitory effect on the adsorption. When the concentration of PO₄^3- was 0.000 1 mol·L^-1 (Fig. 8f), 1 could only adsorb about 68.3% of Cr(Ⅵ) after 120 min. The inhibitory effect of anions on 1 adsorption of Cr(Ⅵ) is more obvious than that of metal cations, mainly because anions are more likely to be adsorbed on the surface of 1. They thus compete with Cr(Ⅵ) for adsorption. Although these ions can inhibit the adsorption of Cr(Ⅵ) by 1, they will not seriously affect the performance of 1 for adsorption and removal of Cr(Ⅵ).

  图 8

  

  图 8.  Effect of anions on the adsorption of Cr(Ⅵ) by 1

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  2.4   Regeneration and cycling experiment of the adsorbent

  For the regeneration of 1, the XRD results of 1 after desorption showed that its diffraction peaks were consistent with the theoretical simulation peaks (Fig. 9). This indicates that the structure of 1 remains unchanged after adsorption - desorption. The results of the cycle experiment (Fig. 10) showed that when the desorbed 1 was subjected to an adsorption cycle experiment, the q_e was still 250 mg·g^-1; when 1 was subjected to five adsorption cycles, the q_e was 248 mg·g^-1. The above results show that 1 has the advantages of easy regeneration and good Cr(Ⅵ) adsorption cycle performance.

  图 9

  

  图 9.  XRD patterns of 1 after desorption

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  图 10

  

  图 10.  Cycle experiment of the Cr(Ⅵ) adsorption by 1

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  3.   Conclusions

  In summary, a 2D copper-based coordination polymer: {[Cu(bipy) ₄ (1, 3-dab)][Cu(bipy)₂(ClO₄) ₂](ClO₄)₂·(1, 3- dab)}_n (1), was successfully synthesized by hydrothermal synthesis. The effects of adsorbent dosage, temperature, and pH on the adsorption of Cr(Ⅵ) by 1 were studied. The results show that the optimal adsorption conditions are: ρ₁=0.04 g·L^-1, pH=5, T= 30 ℃. The ion coexistence experiments show that the greater the ion concentration and the higher the valence state, the more obvious their influence on the adsorption of Cr(Ⅵ) by 1, and the inhibition of anion follows the order: PO₄^3- > SO₄^{2 -} > CO₃^2- > Cl^- > HCO₃^- > NO₃^-. The regeneration and cycling experiments of 1 show that it has the advantages of easy regeneration and good Cr(Ⅵ) adsorption cycle performance. Therefore, it has the potential for application.

  
  
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  图 1  XPS spectra of 1: (a) survey; (b) Cu2p

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  图 2  (a) Asymmetric structural unit of 1; (b) Structural unit of [Cu(bipy)₄(1, 3-dab)]²⁺;(c) Structural unit of [Cu(bipy)₂(ClO₄)₂]; (d) 2D structure of 1

  Symmetry codes: A: x, -y+1, -z; B: x-1, y, z; D: -x+1, y, -z+1/2; E: x, y-1, z

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  图 3  N₂ adsorption-desorption curve of 1

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  图 4  Effect of dosage of 1 on (a) the adsorption of Cr(Ⅵ), and (b) the maximum q_e

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  图 5  Effect of pH on the adsorption of Cr(Ⅵ) by 1

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  图 6  Effect of temperature on the adsorption of Cr(Ⅵ) by 1

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  图 7  Effect of metal ions on the adsorption of Cr(Ⅵ) by 1

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  图 8  Effect of anions on the adsorption of Cr(Ⅵ) by 1

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  图 9  XRD patterns of 1 after desorption

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  图 10  Cycle experiment of the Cr(Ⅵ) adsorption by 1

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  表 1  Crystal data and refinement parameters of 1

  Parameter	1		Parameter	1
  Empirical formula	C80H64Cl4Cu2N16O16		μ / mm-1	0.77
  Formula weight	1 774.37		Limiting indices	-14 ≤ h ≤ 10, -15≤ k ≤ 13, -22 ≤ l ≤ 41
  Crystal system	Orthorhombic		F(000)	1 823
  Space group	P2221		θ range / (°)	2.6-28.6
  a / nm	1.115 52(5)		Total reflection collected, unique	9 217, 7 586 (Rint=0.045)
  b / nm	1.116 66(4)		Data, restraint, parameter	9 217, 0, 537
  c / nm	3.11684(15)		S	1.05
  Volume / nm3	3.8825(3)		Final R indices [I > 2σ(I)]	R1=0.050, wR2=0.092
  Z	2		Largest diff. peak and hole / (e·nm-3)	1 100 and -520
  Dc / (Mg·m-3)	1.518

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  表 2  Selected bond length (nm) and bond angle (°) of 1

  Cu1—O1A	0.248 2(2)	Cu1—N2	0.202 5(3)	Cu1—O1	0.248 2(2)
  Cu1—N3B	0.203 3(3)	Cu1—N1	0.204 1(2)	Cu1—N1A	0.204 1(2)
  Cu2—N4D	0.203 7(2)	Cu2—N5	0.203 9(3)	Cu2—N4	0.203 7(2)
  Cu2—N6E	0.201 9(3)
  O1A—Cu1—O1	178.71(10)	N2—Cu1—N1	89.15(6)	N1A—Cu1—O1A	91.59(9)
  N2—Cu1—N1A	89.15(6)	N1A—Cu1—O1	88.39(9)	N3B—Cu1—O1	90.65(5)
  N1—Cu1—O1A	88.39(9)	N3B—Cu1—O1A	90.65(5)	N1—Cu1—O1	91.59(9)
  N3B—Cu1—N1	90.85(6)	N1A—Cu1—N1	178.29(13)	N3B—Cu1—N1A	90.85(6)
  N2—Cu1—O1	89.35(5)	N3B—Cu1—N2	180.0	N2—Cu1—O1A	89.35(5)
  O2—Cl1—O1	108.39(14)	N4—Cu2—N4D	178.56(12)	N6E—Cu2—N4D	89.28(6)
  N5—Cu2—N4D	90.72(6)	N6D—Cu2—N4	89.28(6)	N5—Cu2—N4	90.72(6)
  N6D—Cu2—N5	180.0
  Symmetry codes: A: x, -y+1, -z; B: x-1, y, z; C: x, -y, -z; D: -x+1, y, -z+1/2; E: x, y-1, z.

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