English

• 1. INTRODUCTION

  Azo dyes are extensively used in industries such as printing, solar cells, traditional textiles, plastic, pharma-ceuticals, and so on. However, its dumping into water is harmful for human health because it is mutagenic, carcino-genic and toxic. Furthermore, owing to their relatively high chemical and photo stability, elimination of the azo dyes from waste water is a challenging task to the scientists. Since the discovery of photocatalytic splitting of water by TiO₂ electrodes, many traditional semiconductors have been used as photocatalysts to degrade organic contaminants^{[1, 2]}, but it has some shortcomings, such as loss of reactivity, low surface area, hardness to separation and so on. Therefore, it is a challenging task to sought new high efficient catalytic materials for environmental protection.

  Recently, the utilization of metal-organic frameworks (MOFs) has acquired enormous attention owing to their potential applications in magnetism^{[3, 4]}, chemosensor^{[5, 6]}, gas storage^[7-9], and catalysis^[10-12]. Particular interests are focused on the secondary building units (SBUs) with multinuclear metal clusters as catalysis, which are considered to be the primary reactive sites^[13]. There are abundant literatures demonstrating the correlation between the catalytic activity and a specific metal cluster^{[14, 15]}. Among the ligands to form MOFs based on SBUs, the semi-rigid dicarboxylate species (4, 4΄-oxydibenzoic acid, 4, 4΄-azanediylbenzoic acid, and so on) have attracted a great deal of interest due to the advantages: (1) semi-rigid dicarboxylate ligands have diverse coordination modes; (2) the rotation of C–O or C–N single bonds between benzene rings and ether group or amino group can adjust the coordination orientations. Herein, we report the synthesis and characterization of a novel complex, namely, {[Cu₃(oba)₂(μ³-OH)₂(H₂O)₂]⋅6H₂O}_n based on 4, 4΄-oxydi-benzoic acid. In addition, its catalytic oxidation activities towards safranin O (SO) and methylene blue (MB) in the presence of H₂O₂ were also studied. As far as we know, it is the first compound formed by infinite rod-shaped chains of Cu(II) to degradateazo dyes.

  2. EXPERIMENTAL

  2.1 Materials and instruments

  All chemicals except 4, 4΄-bis(imidazol-1-yl)diphenyl-thiother were commercially available and used without any treatment. 4, 4΄-bis(imidazol-1-yl)diphenylthiother was synthesized according to the literature method^[16]. Infrared spectrum of the complex was recorded in the range of 400~24000 cm^-1 by means of a nicolet (Impact 410) spectrometer with KBr pellets. Elemental analysis (C, H) was performed on a Perkin-Elmer model 240C elementalanalyzer. Thermogravimetric analysis (TGA) data were recorded on a Perkin-Elmer thermogravimetric analyzer. Powder X-ray diffraction (PXRD) data were collected on a Bruker D8 Advance X-ray diffractometer with CuKα radiation (λ = 0.15418 Å) under ambient conditions. UV-visible studies were performedusing a UV-T9 spectrophotometer ranging from 300 to 800 nm.

  2.2 Synthesis

  A mixture of CuCl₂⋅2H₂O (17.9 mg, 0.1 mmol), 4, 4΄-bis(imidazol-1-yl)diphenylthiother (34.0 mg, 0.1 mmol), H₂oba (25.8 mg, 0.1 mmol), DMF (1 mL), CH₃CN (1 mL) and H₂O (3 mL) was sealed in a 20 mL Teflon-lined autoclave and heated at 80 ℃ for 48h, then cooled to room temperature slowly. Needle-shaped blue crystals were formed and washed with methanol three times. The yield is ca. 54% based on H₂oba ligand. The crystal sample dried at ambient condition was used for photocatalytic studies and other characterizations. Anal. Calcd. for C₂₈H₃₆Cu₃O₂₀ (%): C, 38.08; H, 4.11. Found (%): C, 38.35; H, 3.95. IR (KBr pellet, cm^-1): 3417 (m), 1610 (s), 1452 (m), 1396 (s), 1250 (m), 1104 (w), 1009 (m), 911 (w), 771 (m), 734 (w), 726 (w), 701 (w), 506 (w).

  2.3 X-ray crystallographic study

  A blue crystal of the complex was selected for crystal structure determination and glued to thin glass fiber, and data collection was performed on a Bruker SMART Apex II CCD diffractometer using Mo-Kα radiation (λ = 0.71073 Å) at 298K. The structures were solved by direct methods, and all non-hydrogen atoms were refined anisotropicallyon F² by full-matrix least-squares procedure using the SHELXL-97 (Sheldric, 2008)^[17]. Hydrogen atoms except those of water molecules were generated geometrically. The guest water molecules were removed using the SQUEEZE routine in PLANTON^[18]. The details of selected bond lengths and bond angles are summarized in Table 1.

  Table 1

  

  Table 1.  Selected Bond Distances (Å) and Bond Angles (º)

  DownLoad: CSV

  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Cu(1)–O(2W) Cu(1)–O(2W)#1 Cu(1)–O(2)	1.911(5) 1.911(5) 1.966(5)		Cu(1)–O(2)#1 Cu(2)–O(5)#2 Cu(2)–O(1W)	1.966(5) 1.907(4) 1.953(5)		Cu(2)–O(2W)#1 Cu(2)–O(2W)#3 Cu(2) –O(1)	1.981(5) 2.066(5) 2.111(4)
  Angle	(º)		Angle	(º)		Angle	(º)
  O(2W)–Cu(1)–O(2W)#1 O(2W)#1–Cu(1)–O(2)#1 O(2W)–Cu(1)–O(2)#1 O(2W)#1–Cu(1)–O(2) O(2W)–Cu(1)–O(2) O(2)#1–Cu(1)–O(2)	180.0(4) 88.4(2) 91.6(2) 91.6(2) 88.4(2) 180.0(3)		O(5)#2–Cu(2)–O(1W) O(5)#2–Cu(2)–O(2W)#1 O(1W)–Cu(2)–O(2W)#1 O(5)#2–Cu(2)–O(2W)#3 O(1W)–Cu(2)–O(2W)#3 O(2W)#1–Cu(2)–O(2W)#3	92.7(2) 91.3(2) 172.4(2) 143.0(2) 91.2(2) 81.72(18)		O(5)#2–Cu(2)–O(1) O(1W)–Cu(2)–O(1) O(2W)#1–Cu(2)–O(1) O(2W)#3–Cu(2)–O(1)	131.0(2) 89.88(17) 92.30(19) 85.8(2)
  Symmetry codes: #1: 1–x, –y, –z; #2: 1–x, –1/2+y, 1/2–z; #3:–1+ x, y, z

  3. RESULTS AND DISCUSSION

  3.1 IR analysis

  The FT-IR spectrum of the complex with the wide absorption peak at 3417 cm^-1 can be assigned to the OH^- group of H₂O. The strong absorption bands observed at 1610 and 1452 cm^-1 characterize the asymmetric and symmetric stretching vibration of the carboxylate groups^[19]. A splitting of 158 cm^-1 (separation between v_as(COO^-) and v_s(COO^-)) indicates the presence of bridging coordination mode for the carboxylate group^[20].

  3.2 Crystal structure description of {[Cu₃(oba)₂(μ³-OH)₂(H₂O)₂]⋅6H₂O}_n

  The asymmetric unit of the complex contains one and a half crystallographically independent Cu(II) ions, one oba^2- ligand, one coordinating water molecule, a bridging OH^- group (O2W) and three lattice water molecules. As shown in Fig. 1, the Cu(II) ions have different coordination geometries. Cu(1) is in a square planar geometry coordinated by two carboxyl oxygen atoms and two μ³-OH oxygen atoms. Herein, the Cu(1) center exhibits conspicuous Jahn Teller effect^[21]. The Cu(2) atom is penta-coordinatedby one coordinated water molecule, two μ³-OH oxygen atoms and two carboxyl oxygen atoms, and the coordination geometry of Cu(2) can be regarded as a distorted trigonal bipyramidal configuration. The Cu–O bond distances range from 1.907(4) to 2.111(4) Å, being comparable to those found for copper-oxygen donor compounds^{[22, 23]}. The oba^2- ligand connected to three Cu(II) metal centers with a (к¹-к¹)(к¹)-μ₃ coordination mode (Scheme 1). The torsional angle for the two phenyl rings of the oba^2- ligand is 60.109º.

  Figure 1

  

  Figure 1.  Coordination environment of Cu(II) in the title complex. Hydrogen atoms and lattice water molecules are omitted for clarity (#1: 1–x, –y, –z; #2: 1–x, –1/2+y, 1/2–z; #3:–1+ x, y, z)

  DownLoad: Full-Size Img PowerPoint

  Scheme 1

  

  Scheme 1.  Coordination mode of oba^2- in the title complex

  DownLoad: Full-Size Img PowerPoint

  The μ³-OH groups play a critical role informing the infinite rod-shaped SBUs (Fig.2). Each μ³-OH group bridges one Cu(1) and two Cu(2) (Cu(2)···Cu(2) 3.062Å) atoms and the μ³-OH groups lengthen the Cu₃O sub-unit through COO^- into an infinite Cu–O–C chain. The Cu₃O sub-unit is considered to be a tetrahedral geometry with the Cu–(µ³-O)–Cu angles of 98.3(2)º, 112.9(3)º and 120.3(3)º. Interestingly, the Cu–O–C connectivity pattern is identical to structures [Zn₃(OH)₂-(bpdc)₂]·4DEF·2H₂O and [Zn₃(µ-OH)₂(sdba)₂]_n⋅2nH₂O, in which similar μ³-OH also exist^{[24, 25]}. The infinite rod-shaped SBUs are connected by the diphenyl ether from oba^2- to form a three-dimensional network (Fig.3). In addition, the 3D network is stabilized by co-effects of inter-layer C–H···π interactions between the benzene rings of two oba^2- ligands (edge-to-face orientation with the C(10)–H(10)···π and C(12)–H(12)···π separations of 3.018 and 3.045 Å, respecttively). The benzene rings of oba^2- ligands are connected into an infinite zigzag chain through C–H···π interactions (Fig.4). To the best of our knowledge, it's the first MOF based on 4, 4΄-oxydibenzoic acid featuring coterminous C–H···π interactions.

  Figure 2

  

  Figure 2.  Ball and stick representation of infinite rod-shaped SBU

  DownLoad: Full-Size Img PowerPoint

  Figure 3

  

  Figure 3.  3D supramolecular framework of the title complex (Hydrogen atoms are omitted for clarity)

  DownLoad: Full-Size Img PowerPoint

  Figure 4

  

  Figure 4.  C–H…π interactions of the title complex. Some hydrogen atoms are omitted for clarity (Insert shows detailed C–H…π interactions. Cg1, C(2)~C(7)

  DownLoad: Full-Size Img PowerPoint

  The complex has a solvent-accessible volume of 8.6% of the total cell volumes after removal of lattice water molecules, which is calculated by PLATON analysis. It is worth noting that 4, 4΄-bis(imidazol-1-yl) diphenylthiother was not found in the complex, but it plays a significant role because no crystals were formed without it in the reaction.

  3.3 Thermal analysis and PXRD results

  In order to inspect whether the crystal structure of the complex is truly representative of the bulk material, the powder X-ray diffraction patterns (PXRD) experiment was carried out at room temperature, which is shown in Fig.5. The pivotal peak positions of the experimental and simulated PXRD patterns were in good agreement with each other, demonstrating that the complex is a single phase.

  Figure 5

  

  Figure 5.  Powder X-ray diffraction patterns (PXRD) of the title complex

  DownLoad: Full-Size Img PowerPoint

  The thermal stability of the complex was determined from 25 to 800 ℃ under a nitrogen atmosphere at a heating rate of 5 ℃/min (Fig.6). The release of all lattice and coordinated water molecules is observed in the temperature range of 25~250 ℃ (calcd. 20.4%, found 21.0%). The remaining is 27.3%, which corresponds to CuO (calcd. 27.0%, found 28.1%).

  Figure 6

  

  Figure 6.  TGA curve of the title complex

  DownLoad: Full-Size Img PowerPoint

  3.4 Toxicazo dye adsorption and photocatalytic degradation studies

  The capability of the complex to degrade SO and MB in aqueous solution under UV light was investigated. And the adsorption experiment was operated as follows: 10 mg crystal of the complex was added to 20 mL of 15 ppm zao dyes aqueous solution in a quartz beaker under UV light irradiation. Then 2 mL was taken out from the reaction suspension at different time intervals and handled by centrifugation, then transferred to a glass cell to measure the UV-vis spectra from 300 to 800 nm. There is no remarkable change in absorption intensity or color change for the dye solution in 60 min, which demonstrates that the direct degradation of azo dyes by the complex is not energetically favorable (Fig.8a, Fig.9a). According to the literature reported, the addition of hydrogen peroxide would enhance the photocatalytic performance for producing highly reactive intermediate of ⋅OH^[26], which promotes us to study the photocataytic performance through H₂O₂-assisted solution. A control experiment on H₂O₂ itself was performed: 0.8 mL 30% H₂O₂ was added to 20 mL of 15 ppm azo dye solution in a quartz beaker under UV light for 60 min, and the decline for absorption peaks is less than 17% for SO and MB. However, the color of the azo dye solution bleached the bright color under UV light after the addition of 2 drops of 30% H₂O₂ and the title complex (Fig.7). For the present study, 2 drops of 30% H₂O₂ with 10 mg of crystals were added to 40 mL of 15 ppm azo dye solution of either SO or MB in a quartz beaker under a 400 W Hg lamp. The intensity of the characteristic peaks, 520 nm for SO and 665 nm for MB, decreased gradually with time. It was noticed that after 30 min, the photocatalytic efficiencies of SO and MB were found to be 84% and 89%, respectively. In addition, the appearance of isosbestic points at ~440 nm in the photo-degradation process of SO and at ~560 nm for MB confirms that new compounds are formed after the degradation of the azo dyes (Fig.8b, Fig.9b)^[27].

  Figure 7

  

  Figure 7.  Remarkable color disappearance of SO (a) and MB (b) dye solution with time by the title complex in the presence of H₂O₂

  DownLoad: Full-Size Img PowerPoint

  Figure 8

  

  Figure 8.  (a) Photocatalytic SO degradation using the title under different conditions (b)Time-dependent UV-vis absorption for the system of the complex/H₂O₂/SO/UV light (For all reactions: the complex, 10 mg; H₂O₂, 2 drops)

  DownLoad: Full-Size Img PowerPoint

  Figure 9

  

  Figure 9.  (a) Photocatalytic MB degradation using the title compound under different conditions, (b) Time-dependent UV-vis absorptionfor the system of the complex/H₂O₂/MB/UV light (For all reactions: the complex, 10 mg; H₂O₂, 2 drops)

  DownLoad: Full-Size Img PowerPoint

  The possible mechanism may be "free radical" and "complex" pathways, as reported by Gray and Lekchiri, respectively^{[28, 29]}.

  "Free radical" pathway pointed out that whether Cu(II) coordinated or uncoordinated to the ligand, it can react with H₂O₂ to produce HO₂˙ and Cu(I). The Cu(I) and H₂O₂ ultimately produce the radical of HO˙ in a "fenton-like" fashion:

  $\begin{aligned} & \mathbf{\mathrm{H}_2 \mathrm{O}_2 \longrightarrow \mathrm{HOO}^{-}+\mathrm{H}^{+}} \\ & \mathbf{\mathrm{HOO}+\mathrm{Cu}(\mathrm{II}) \longrightarrow \mathrm{HO}_2{}^{˙}+\mathrm{Cu}(\mathrm{I}) }\\ & \mathbf{\mathrm{Cu}(\mathrm{I})+\mathrm{H}_2 \mathrm{O}_2 \longrightarrow \mathrm{HO}^˙+\mathrm{Cu}(\mathrm{II})+\mathrm{OH}} \end{aligned} $

  However, in the "complex" pathway, the Cu(II) metal center, which coordinates to the ligands, reacts with H₂O₂ within the sphere of coordinate bonds and lead to the formation of radical of HO˙. The reaction steps are as follows:

  $\begin{aligned} & \mathbf{\mathrm{H}_2 \mathrm{O}_2 \longrightarrow \mathrm{HOO}^{-}+\mathrm{H}^{+} }\\ & \mathbf{\mathrm{HOO}+\mathrm{Cu}(\mathrm{II}) \mathrm{L} \longrightarrow[\mathrm{Cu}(\mathrm{II}) \mathrm{L}(\mathrm{OOH})]^{-} }\\ & \mathbf{{[\mathrm{Cu}(\mathrm{II}) \mathrm{L}(\mathrm{OOH})]^{-}+\mathrm{H}_2 \mathrm{O}_2 \longrightarrow\left[\left.\mathrm{Cu}(\mathrm{II}) \mathrm{L}(\mathrm{OOH})\left(\mathrm{H}_2 \mathrm{O}_2\right)\right|^{-}\right.}} \\ & \mathbf{{\left[\mathrm{Cu}(\mathrm{II}) \mathrm{L}(\mathrm{OOH})\left(\mathrm{H}_2 \mathrm{O}_2\right)\right]^{-} \longrightarrow \mathrm{HO}^{·}+\mathrm{H}_2 \mathrm{O}+\mathrm{O}_2+\mathrm{Cu}(\mathrm{II}) \mathrm{L}}} \end{aligned} $

  To evaluate the stability of the complex as photocatalyst, it was filtered and washed after degradation experiments. The PXRD patterns match well with the original compound (Fig.5), which demonstrates that the complex may be recycled for the photocatalytic degradation of azo dyes.

  The photodegradation reaction kinetic accords with pseudo-first-order kinetic and described as follows,

  $ \ln \left(A_0 / A_{\mathrm{t}}\right)=\ln \left(C_0 / C_{\mathrm{t}}\right)=k_{\mathrm{A}} t $

  A₀ and C₀ are the absorbance and concentration of azo dye initially, A_t and C_t are the absorbance and concentration at different time, respectively. k_A is an apparent rate constant, which was calculated using the plot of ln(C₀/C_t) vs. time (min). The rate constants (k_A) are estimated to be 0.0495 min^-1 (8.25×10^-4 s^-1) and 0.0698 min^-1 (1.16×10^-3 s^-1) for SO and MB, respectively (Fig.10), which can be compared with other reported MOFs. For example, Wang et al. reported two copper MOFs, which can degrade rhodamine B and the k_A are 0.057 and 0.083 min^-1, respectively^[30]. Balaet al. reported a copper compound for efficient degradation organic dyes under UV irradiation, and the k_A is 0.0225 min^-1 for methylene blue and 0.0114 min^-1 for methyl orange^[31].

  Figure 10

  

  Figure 10.  Kinetic study of the title complex with SO and MB

  DownLoad: Full-Size Img PowerPoint

  4. CONCLUSION

  In summary, a new complex based on 4, 4΄-oxydibenzoic acid has been synthesized by hydrothermal method and characterized. The μ³-OH groups lengthen the Cu₃O sub-unit intoa rare infinite rod-shaped SBU, which is connected by the diphenylether from oba^2- to form a 3D network. The complex also shows excellent photocatalytic activity for SO and MB under UV light irradiation and it may be used a potential material to purify waste water.

  
  
• 1. [1]

     Jennifer, S. J.; Jana, A. K. Influence of pyrazine/piperazine based guest molecules in the crystal structures of uranyl thiophene dicarboxylate coordination polymers: structural diversities and photocatalytic activities for the degradation of organic dye. Cryst. Growth Des. 2017, 17, 5318−5329. doi: 10.1021/acs.cgd.7b00826

  2. [2]

     Han, L. J.; Kong, Y. J.; Yan, T. J.; Fan, L. T.; Zhang, Q.; Zhao, H. J.; Zheng, H. G. A new five-coordinated copper compound for efficient degradation of methyl orange andcongo red in the absence of UV-visible radiation. Dalton Trans. 2016, 45, 18566−18571. doi: 10.1039/C6DT03273G

  3. [3]

     Maspoch, D.; Domingo, N.; Ruiz, M. D.; Wurst, K.; Hernandez, J. M.; Vaughan, G.; Rovira, C.; Lloret, F.; Tejada, J.; Veciana, J. Coexistence of ferroand antiferromagnetic interactions in a metal-organic radical-based (6, 3)-helical network with large channels. Chem. Commun. 2005, 40, 5035−5037.

  4. [4]

     Li, H. H.; Shi, W.; Xu, N.; Zhang, Z. J.; Niu, Z.; Han, T.; Cheng, P. Structural diversity of four metal-organic frameworks based on linear homo/heterotrinuclear nodes with furan-2, 5-dicarboxylic acid: structures and luminescent and magnetic properties. Cryst. Growth Des. 2012, 12, 2602−2612. doi: 10.1021/cg300196w

  5. [5]

     Wang, J.; Gao, L. L.; Zhang, J.; Zhao, L.; Wang, X. Q.; Niu, X. Y.; Fan, L. M.; Hu, T. M. Syntheses, gas adsorption, and sensing properties of solvent controlled Zn(II) pseudo-supramolecular isomers and Pb(II) supramolecular isomers. Cryst. Growth Des. 2019, 19, 630−637. doi: 10.1021/acs.cgd.8b01077

  6. [6]

     Rao, P. C.; Mandal, S. Europium-based metal-organic framework as a dual luminescence sensor for the selective detection of phosphate anion and Fe³⁺ ion in aqueous media. Inorg. Chem. 2018, 57, 11855−11858. doi: 10.1021/acs.inorgchem.8b02017

  7. [7]

     Chen, C.; Zhang, M. X.; Zhang, W. W.; Bai, J. F. Stable amide-functionalized metal-organic framework with highly selective CO₂ adsorption. Inorg. Chem. 2019, 58, 2729−2735. doi: 10.1021/acs.inorgchem.8b03308

  8. [8]

     Wang, Q.; Bai, J. F.; Lu, Z. Y.; Pan, Y.; You, X. Z. Finely tuning MOFs towards high-performance post-combustion CO₂ capture materials. Chem. Commun. 2016, 52, 443−452. doi: 10.1039/C5CC07751F

  9. [9]

     Du, L. T.; Lu, Z. Y.; Zheng, K. Y.; Wang, J. Y.; Zheng, X.; Pan, Y.; You, X. Z.; Bai, J. F. Fine-tuning pore size by shifting coordination sites of ligands and surface polarization: a porous coordination polymer of metal-organic frameworks to sharply enhance the selectivity for CO₂. J. Am. Chem. Soc. 2013, 135, 562−565. doi: 10.1021/ja309992a

  10. [10]

      Ding, Y.; Chen, Y. P.; Zhang, X.; Chen, L.; Dong, Z.; Jiang, H. L.; Xu, H.; Zhou, H. C. Controlled intercalation and chemical exfoliation of layered metal-organic frameworks using a chemically labile intercalating agent. J. Am. Chem. Soc. 2017, 139, 9136−9149. doi: 10.1021/jacs.7b04829

  11. [11]

      He, P.; Yu, X. Y.; Lou, X. W. Carbon-incorporate nickel-cobalt mixed metal phosphide nanoboxes with enhanced electro-catalytic activity for oxygen evolution. Angew. Chem., Int. Ed. 2017, 56, 3897−3900. doi: 10.1002/anie.201612635

  12. [12]

      Huang, Y. B.; Liang, J.; Wang, X. S.; Cao, R. Multifunctional metal-organic framework catalyst: synergistic catalysis and tandem reations. Chem. Soc. Rev. 2017, 46, 126−157.

  13. [13]

      Roy, M.; Sengupta, S.; Bala, S.; Bhattcharya, S.; Mondal, R. Systematic study of mutually inclusive influences of temperature and substitution on the coordination geometry Co(II) in a series of coordination polymers and their properties. Cryst. Growth Des. 2016, 16, 3170−3179. doi: 10.1021/acs.cgd.5b01835

  14. [14]

      Qin, L.; Chen, H. Z.; Lei, J.; Wang, Y. Q.; Ye, T. Q.; Zheng, H. G. Photodegradation of some organic dyes over two metal-organic frameworks with especially high efficiency for safranine T. Cryst. Growth Des. 2017, 17, 1293−1298. doi: 10.1021/acs.cgd.6b01690

  15. [15]

      Chen, Y. Q.; Li, G. R.; Qu, Y. K.; Zhang, Y. H.; He, K. H.; Gao, Q.; Bu, X. H. Water-insoluble heterometal-oxide-based photocatalysts effective for the photo-decomposition of methyl organge. Cryst. Growth Des. 2013, 13, 901−907. doi: 10.1021/cg3016244

  16. [16]

      Wang, Z. J.; Han, L. J.; Gao, X. J.; Zheng, H. G. Three Cd(II) MOFs with different functional groups: selective CO₂ capture and metal ions detection. Inorg. Chem. 2018, 57, 5232−5239. doi: 10.1021/acs.inorgchem.8b00272

  17. [17]

      Sheldrick, G. M. SHELXL-97, Program for X-ray Crystal Structure Refinement. University of Göttingen, Germany 1997.

  18. [18]

      Spek. A. L. PLATON SQUEEZE: a tool for the calculation of the disordered solvent contribution to the calculate structure factors. Actacrystallogr. Sect. C: Struct. Chem. 2015, 71, 9−18. doi: 10.1107/S2053229614024929

  19. [19]

      Wang, A. L.; Zhou, D.; Chen, Y. N.; Li, J. J.; Zhang, H. X.; Zhao, Y. L.; Chu, H. B. Crystal structure and photoluminescence of europium, terbium and samarium compounds with halogen-benzoate and 2, 4, 6-tri(2-pyridyl)-s-triazine. J. Lumin. 2016, 177, 22−30. doi: 10.1016/j.jlumin.2016.04.024

  20. [20]

      Xu, W. T.; Chen, L.; Jiang, F. L.; Hong, M. C. Synthesis, crystal structure and properties of a nanotubular metal-organic framework (MOFs) based on Cu(II) oxide chains and benzenedicarboxylates. Chin. J. Struct. Chem. 2012, 3, 321−326.

  21. [21]

      Li, X.; Chen, D. Y.; Lin, J. L.; Li, Z. F.; Zheng, Y. Q. Di-, tetra-, and hexanuclear hydroxy-bridged copper(II) cluster compounds: syntheses, structures, and properties. Cryst. Growth Des. 2008, 8, 2853−2861. doi: 10.1021/cg701150q

  22. [22]

      Veselska, O.; Cai, L. W.; Podbevšek, D.; Ledoux, G.; Guillou, N.; Pilet, G.; Fateeva, A.; Demessence, A. Structural diversity of coordination polymers based on a heterotopic ligand: Cu(II)-carboxylate vs Cu(I)-thiolate. Inorg. Chem. 2019, 58, 2736−2743. doi: 10.1021/acs.inorgchem.8b03310

  23. [23]

      Tomar, K.; Verma, A.; Bharadwaj, P. K. Exploiting dimensional variability in Cu paddle-wheel secondary building unit based mixed valence Cu(II)/Cu(I) frameworks from a bispyrazole ligand by solvent/pH variation. Cryst. Growth Des. 2018, 18, 2397−2404. doi: 10.1021/acs.cgd.8b00002

  24. [24]

      Rosi, N. L.; Kim, J.; Eddaoudi, M.; Chenm B. L.; O'Keeffe, M.; Yaghi, O. M. Rod packings and metal-organic frameworks constructed from rod-shaped secondary building units. J. Am. Chem. Soc. 2005, 127, 1504−1518 doi: 10.1021/ja045123o

  25. [25]

      Li, N.; Chen, L.; Lian, F. Y.; Jiang, F. L.; Hong, M. C. Syntheses and crystal structures of three novel Zn^Ⅱ-sulfonyldibenzoilatecoordination polymers. Chin. J. Struct. Chem. 2009, 28, 1417−1426.

  26. [26]

      Zhang, C. H.; Ai, L. H.; Jiang, J. Graphene hybridized photoactive iron terephthalate with enhanced photocatalytic activity for the degradation of rhodamine B under visible light. J. Ind. Eng. Chem. Res. 2015, 54, 153−163. doi: 10.1021/ie504111y

  27. [27]

      Akhtar, S.; Bala, S.; De, A.; Das, K. S.; Adhikary, A.; Jyotsna, S.; Poddar, P.; Mondal, R. Designing multifunctional MOFs using the inorganic motif [Cu₃(μ₃-OH)(μ-pyz)] as an SBU and their properties. Cryst. Growth Des. 2019, 19, 992−1004. doi: 10.1021/acs.cgd.8b01540

  28. [28]

      Pham, N.; Xing, G.; Miller, C.; Waite, T. D. Fenton-like copper redox chemistry revisited: hydrogen peroxide and superoxide mediation of copper-catalyzed oxidant production. J. Catal. 2013, 301, 54−64. doi: 10.1016/j.jcat.2013.01.025

  29. [29]

      Gray, R. D. Kinetic of oxidation of copper(I) by molecular oxygen in perchloric by the Cu²⁺-2, 2΄-bipyridyl complex. J. Am. Chem. Soc. 1969, 91, 56−62. doi: 10.1021/ja01029a012

  30. [30]

      Wang, C. K.; Xing, F. F.; Bai, Y. L.; Zhao, Y. M.; Li, M. X.; Zhu, S. R. Synthesis and structure of semirigid tetracarboxylate copper(II) porous coordination polymers and their versatile high-efficiency catalytic dye degradation in neutral aqueous solution. Cryst. Growth Des. 2016, 16, 2277−2288. doi: 10.1021/acs.cgd.6b00065

  31. [31]

      Bala, S.; Bhattacharya, S.; Goswami, A.; Adhikary, A.; Konar, S. Designing functional metal-organic frameworks by imparting a hexanuclear copper-based secondary building unit specific properties: structural correlation with magnetic and photocatalytic activity. Cryst. Growth Des. 2014, 14, 6391−6398. doi: 10.1021/cg501226v

• 

  Figure 1  Coordination environment of Cu(II) in the title complex. Hydrogen atoms and lattice water molecules are omitted for clarity (#1: 1–x, –y, –z; #2: 1–x, –1/2+y, 1/2–z; #3:–1+ x, y, z)

  下载: 全尺寸图片 幻灯片
  

  Scheme 1  Coordination mode of oba^2- in the title complex

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Ball and stick representation of infinite rod-shaped SBU

  下载: 全尺寸图片 幻灯片
  

  Figure 3  3D supramolecular framework of the title complex (Hydrogen atoms are omitted for clarity)

  下载: 全尺寸图片 幻灯片
  

  Figure 4  C–H…π interactions of the title complex. Some hydrogen atoms are omitted for clarity (Insert shows detailed C–H…π interactions. Cg1, C(2)~C(7)

  下载: 全尺寸图片 幻灯片
  

  Figure 5  Powder X-ray diffraction patterns (PXRD) of the title complex

  下载: 全尺寸图片 幻灯片
  

  Figure 6  TGA curve of the title complex

  下载: 全尺寸图片 幻灯片
  

  Figure 7  Remarkable color disappearance of SO (a) and MB (b) dye solution with time by the title complex in the presence of H₂O₂

  下载: 全尺寸图片 幻灯片
  

  Figure 8  (a) Photocatalytic SO degradation using the title under different conditions (b)Time-dependent UV-vis absorption for the system of the complex/H₂O₂/SO/UV light (For all reactions: the complex, 10 mg; H₂O₂, 2 drops)

  下载: 全尺寸图片 幻灯片
  

  Figure 9  (a) Photocatalytic MB degradation using the title compound under different conditions, (b) Time-dependent UV-vis absorptionfor the system of the complex/H₂O₂/MB/UV light (For all reactions: the complex, 10 mg; H₂O₂, 2 drops)

  下载: 全尺寸图片 幻灯片
  

  Figure 10  Kinetic study of the title complex with SO and MB

  下载: 全尺寸图片 幻灯片

  Table 1.  Selected Bond Distances (Å) and Bond Angles (º)

  Bond	Dist.		Bond	Dist.		Bond	Dist.
  Cu(1)–O(2W) Cu(1)–O(2W)#1 Cu(1)–O(2)	1.911(5) 1.911(5) 1.966(5)		Cu(1)–O(2)#1 Cu(2)–O(5)#2 Cu(2)–O(1W)	1.966(5) 1.907(4) 1.953(5)		Cu(2)–O(2W)#1 Cu(2)–O(2W)#3 Cu(2) –O(1)	1.981(5) 2.066(5) 2.111(4)
  Angle	(º)		Angle	(º)		Angle	(º)
  O(2W)–Cu(1)–O(2W)#1 O(2W)#1–Cu(1)–O(2)#1 O(2W)–Cu(1)–O(2)#1 O(2W)#1–Cu(1)–O(2) O(2W)–Cu(1)–O(2) O(2)#1–Cu(1)–O(2)	180.0(4) 88.4(2) 91.6(2) 91.6(2) 88.4(2) 180.0(3)		O(5)#2–Cu(2)–O(1W) O(5)#2–Cu(2)–O(2W)#1 O(1W)–Cu(2)–O(2W)#1 O(5)#2–Cu(2)–O(2W)#3 O(1W)–Cu(2)–O(2W)#3 O(2W)#1–Cu(2)–O(2W)#3	92.7(2) 91.3(2) 172.4(2) 143.0(2) 91.2(2) 81.72(18)		O(5)#2–Cu(2)–O(1) O(1W)–Cu(2)–O(1) O(2W)#1–Cu(2)–O(1) O(2W)#3–Cu(2)–O(1)	131.0(2) 89.88(17) 92.30(19) 85.8(2)
  Symmetry codes: #1: 1–x, –y, –z; #2: 1–x, –1/2+y, 1/2–z; #3:–1+ x, y, z

  下载: 导出CSV
•