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Three two-dimensional coordination polymers constructed from transition metals and 2,3-norbornanedicarboxylic acid: Hydrothermal synthesis, crystal structures and photocatalytic properties
Accepted Manuscript Three two-dimensional coordination polymers constructed from transition metals and 2,3-norbornanedicarboxylic acid: Hydrothermal synthesis, crystal structures and photocatalytic properties Jia Zhang, Chong-Chen Wang PII:
S0022-2860(16)31074-2
DOI:
10.1016/j.molstruc.2016.10.033
Reference:
MOLSTR 23034
To appear in:
Journal of Molecular Structure
Received Date: 16 August 2016 Revised Date:
6 October 2016
Accepted Date: 7 October 2016
Please cite this article as: J. Zhang, C.-C. Wang, Three two-dimensional coordination polymers constructed from transition metals and 2,3-norbornanedicarboxylic acid: Hydrothermal synthesis, crystal structures and photocatalytic properties, Journal of Molecular Structure (2016), doi: 10.1016/ j.molstruc.2016.10.033. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Three two-dimensional coordination polymers constructed from transition metals and 2,3-Norbornanedicarboxylic acid: hydrothermal synthesis, crystal structures and photocatalytic
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properties
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Three two-dimensional coordination polymers constructed from transition metals and 2,3-Norbornanedicarboxylic acid: hydrothermal synthesis, crystal structures and photocatalytic
Jia Zhang1,2, Chong-Chen Wang1,2∗ 1
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properties
Beijing Key Laboratory of Advanced Functional Materials for Building and Environment, Beijing
Key Laboratory of Urban Stormwater System and Water Environment (Ministry of Education),
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2
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University of Civil Engineering and Architecture, Beijing, 100044, China
Beijing University of Civil Engineering and Architecture, Beijing, 100044, China
Abstract:
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Three novel coordination polymers based on transition metals like Co(II), Cu(II) and Mn(II), namely [Co2(bpy)2(nbda)2(H2O)2]·2H2O (denoted as BUC-1), [Cu2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-2), [Mn2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-3), (where bpy = 4,4′-bipyridine, H2nbda =
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2,3-norbornanedicarboxylic acid, BUC = Beijing University of Civil Engineering and Architecture),
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were synthesized under hydrothermal conditions, and characterized by CNH elemental analyses (EA), Fourier Transform infrared spectroscopy (FTIR), and single crystal X-ray diffraction (SCXRD). BUC 1 - 3 were isostructural and crystallized in the monoclinic space group C2/c, in which the corresponding metal atoms were linked by typical bidentate bpy ligands into two adjacent 1D [M1(bpy)]n2n+ and [M2(bpy)]n2n+ (M = Co(II), Cu(II), Mn(II)), further joined by versatile nbda2- ligands
∗
Corresponding author. Tel.: +86 10 61209186; fax: +86 10 61209186.
E-mail address: [email protected]
ACCEPTED MANUSCRIPT into 2D [M2(bpy)2(nbda)2]n sheets. Finally, three-dimensional supramolecular frameworks were constructed with the aid of the intermolecular hydrogen bonding interactions. BUC 1 - 3 exhibited different photocatalytic degradation ability to decompose methylene blue (MB) and methyl orange
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(MO) under UV light irradiation. Additionally, a possible photocatalytic mechanism HOMO-LUMO was proposed and discussed, which was further confirmed by radicals trapping experiments using isopropanol as radical scavenger.
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Keywords: Coordination polymers, Photocatalysis, Degradation, Organic dyes
1. Introduction
Coordination polymers display versatile physical and chemical properties like high specific surface area, tunable pore size, great chemical variety, and relatively good thermal stability[1, 2], which have
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been widely applied in the field of gas separation[3, 4], gas storage[5, 6], catalysis[7, 8], chemical sensors[9], and so on[10, 11]. In addition, growing researches indeed demonstrated that some coordination polymers have been utilized as heterogeneous photocatalysts conduct organic pollutants
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degradation [7, 12, 13], CO2 reduction[14] and Cr(VI) reduction[15] under UV/visible/UV-visible light
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irradiation. For example, Garcia et al. firstly proposed MOF-5 as an active catalyst to photodegrade phenol[16]. Natarajan et al. used Co(II)/Ni(II)/Zn(II) coordination polymers as photocatalysts to degrade organic dyes[17]. Fu et al. employed a photoactive Ti-containing MOF, NH2-MIL-125(Ti), as photocatalysts to reduce CO2 into HCOO- [18]. Being compared with the traditional inorganic photocatalytic materials like TiO2, CdS, and ZnO, coordination polymers as efficient photocatalysts have many advantages: (i) their well-defined
crystalline structures are beneficial to investigate the corresponding structure-property relationship;
ACCEPTED MANUSCRIPT (ii) their modular natures of the synthesis methods allow the rational design and fine tuning of these catalysts at the molecular level; (iii) their structural features of tunable active sites like metal-oxoclusters and organic linkers result in solar harnessing more efficiently; (iv) their facile
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modification resulted from the introduction of linker substitutions such as amino group can arise their visible light photocatalytic activity; and (v) their intrinsic porosity and high surface area is
photocatalytic reaction efficiency [7, 14, 15].
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beneficial to transport guest molecules through the open channels rapidly and to increase the
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Meanwhile, a major challenge in crystal engineering and self-assembly of CPs is the predictability of the polymeric network structure which might depend on several factors like metal centers, organic ligands, metal-to-ligand radio, the presence of solvents and counter-ions[19-22]. There is still a very long way to develop the coordination polymers with the well-defined structures and useful functions.
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With this paper, 4,4′-bipyridine (bpy) and 2,3-norbornanedicarboxylic acid (H2nbda), as illustrated in Scheme 1, were utilized to construct three transition metal-based coordination polymers via hydrothermal method, namely, [M2(bpy)2(nbda)2(H2O)2]·2H2O (Co for BUC-1, Cu for BUC-2 and Mn
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for BUC-3). As far as we know, the organic ligand of 2,3-norbornanedicarboxylic acid (H2nbda) was
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for the first time used to construct coordination polymers, which can easily coordinate with metal atoms via M-O bond (M = metal atoms), and can be expected to construct more interesting architectures than the previously reported Co(bpy)2Cl2[23], Cu-X-bpy (X = Cl, Br)[24], Mn(bpy)2Cl2[25] from single bpy ligangd. The structures of BUC 1 - 3 were analyzed and discussed. In addition, their optical properties, photocatalytic activities towards methylene blue (MB) and methyl orange (MO) had also been studied.
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N COOH bpy
H2nbda
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Scheme 1 The structure of bpy and H2nbda
2. Experimental
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2.1 Materials and methods
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All chemicals were commercially available reagent grade, which were used without any further purification. C, H, N elemental analyses were conducted on an Elementar Vario EL-III instrument. The FTIR spectra were recorded in the region 400 - 4000 cm-1 on a Nicolet 6700 FTIR spectrophotometer with KBr pellets. UV-Vis absorption spectra of solid samples was measured from 200 to 800 nm with a
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Perkin Elmer Lamda 650S spectrophotometer, in which barium sulfate (BaSO4) was used as the standard with 100% reflectance.
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2.2 Synthesis of coordination polymers
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2.2.1 Synthesis of BUC-1
A mixture of CoCl2·6H2O (0.3 mmol, 0.0714 g), 2,3-norbornanedicarboxylic acid (H2nbda) (0.3 mmol, 0.0553 g) and 4,4′-bipyridine (bpy) (0.6 mmol, 0.0940 g) with a molar ratio of 1:1:2 was sealed in a 25 mL Teflon-lined stainless steel Parr bomb containing deionized water (20 mL), heated at 160 oC for 72 h, and then cooled down to room temperature. Dark red block-like crystals of [Co2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-1) were isolated and washed with deionized water and ethanol (yield 85% based on CoCl2·6H2O). Anal. Calc. for BUC-1, C38H44Co2N4O12: C, 52.6; N, 6.5; H, 5.1.
ACCEPTED MANUSCRIPT Found: C, 52.7; N, 6.5; H, 5.2. FTIR (KBr)/cm-1: 3378, 2993, 2969, 2870, 1606, 1557, 1488, 1438, 1409, 1322, 1278, 1248, 1220, 1113, 1064, 1046, 1006, 920, 859, 811, 772, 732, 693, 630, 519, 481,
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416 .
2.2.2 Synthesis of BUC-2
Synthesis of black block-like crystals of [Cu2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-2) followed the
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same procedure as for BUC-1, except that CoCl2·6H2O was replaced by CuCl2·2H2O (0.3 mmol,
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0.0511 g) (yield 74% based on CuCl2·2H2O). Anal. Calc. for BUC-2, C38H44Cu2N4O12: C, 52.1; N, 6.4; H, 5.0. Found: C, 52.2; N, 6.4; H, 5.2. FTIR (KBr)/cm-1: 3430, 3044, 1601, 1526, 1482, 1418, 1409, 1328, 1215, 1062, 978, 966, 853, 820, 799, 724, 633, 561, 475, 412.
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2.2.3 Synthesis of BUC-3
Synthesis of yellow block-like crystals of [Mn2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-3) followed the same procedure as for BUC-1, except that CoCl2·6H2O was replaced by MnCl2·4H2O (0.3 mmol,
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0.0594 g) (yield 77% based on MnCl2·4H2O). Anal. Calc. for BUC-3, C38H44Mn2N4O12: C, 53.1; N, 6.5;
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H, 5.1. Found: C, 53.2; N, 6.5; H, 5.1. FTIR (KBr)/cm-1: 3662, 3516, 3238, 2967, 2870, 1956, 1603, 1557, 1488, 1411, 1321, 1221, 1114, 1065, 1044, 1004, 951, 931, 919, 858, 732, 686, 626, 573, 510, 481, 407.
2.3 X-ray crystallography Single-crystal X-ray diffraction data collection for BUC 1 - 3 were performed with a Bruker Smart 1000 CCD area detector diffractometer with graphite-monochromatized MoKα radiation (λ = 0.71073
ACCEPTED MANUSCRIPT Å) using φ-ω mode at 298(2) K. The SMART software[26] was used for data collection and the SAINT software[27] for data extraction. Empirical absorption corrections were performed with the SADABS program[28]. The structures were solved by direct methods (SHELXS-97)[29] and refined by
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full-matrix-least squares techniques on F2 with anisotropic thermal parameters for all of the non-hydrogen atoms (SHELXL-97)[29]. All hydrogen atoms were located by Fourier difference synthesis and geometrical analysis. These hydrogen atoms were allowed to ride on their respective
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parent atoms. All structural calculations were carried out using the SHELX-97 program package[29].
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Crystallographic data and structural refinements for BUC 1 - 3 were summarized in Table 1. Selected bond lengths and angles were listed in Table 2.
Table 1 Details of X-ray data collection and refinement for BUC 1 - 3
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Table 2 Selected bond lengths (Å) and angles (o) for BUC 1 – 3
Table 3 Hydrogen bonds for BUC 1 - 3 [Å and o]
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2.4 Photocatalytic degradation experiments
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In order to evaluate the photocatalytic performance of BUC 1 - 3 as photocatalysts, methylene blue (MB) and methyl orange (MO) dyes were selected as target pollutants to be degraded in photocatalytic assessment system (Beijing Aulight Co. Ltd) in open air, under 500W Hg lamp irradiation and room temperature. The reactor employed in this study was 300 mL quartz reactor, and the distance between the light source and the reactor containing the reaction mixture was fixed at 5 cm. In order to keep the constant reaction temperature at 25 oC, cooling water was circulated through the annulus of the quartz tube.
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degradation experiment, the samples were collected at regular time intervals using a 0.45 µm syringe filter (Shanghai Troody) to remove the catalyst particles before analysis. A Laspec Alpha-1860
3. Results and discussion
3.1 FTIR analysis
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absorbance at 664 and 463 nm, respectively.
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spectrometer was used to monitor the concentration changes of MB and MO by the maximum
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BUC 1 - 3 were stable and insoluble in water and common organic solvents including but not limited to methanol, ethanol, ether and N,N’-dimethylformamide (DMF). In the FTIR spectra as listed in Fig. S1(ESI), a strong and broad absorptions at 3378, 3430 and 3516 cm-1 of BUC 1 - 3 were assigned to
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the O-H stretching vibration of lattice water molecules, respectively. The absence of an absorption peak
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around 1453 cm-1 from H2nbda indicated that the carboxyl groups were completely deprotonated. The positions of the stretching COO vibrations at 1606 (vas(COO)) and 1322 (vs(COO)) for BUC-1, 1601 (vas(COO)) and 1328 (vs(COO)) cm-1 for BUC-2 and 1603 (vas(COO)) and 1321 (vs(COO)) cm-1 for BUC-3, for which the corresponding △v values are 284 cm-1, 273 cm-1, and 284 cm-1, respectively, which being larger than 200 cm-1 suggests that the COO- groups were coordinated to corresponding metal centers via bis-monodentate mode[30]. The vibration of pyridine group was also observed in 630, 633, 626 cm-1 the region for the BUC 1 - 3. The presence of weak band at 519, 561, 407 cm-1 can be attributed to
ACCEPTED MANUSCRIPT the stretching vibration of the Co-N, Cu-N, and Mn-N bond[31, 32].
3.2 Structural description
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All three coordination polymers BUC 1 - 3 were isomorphous and isostructural, and crystallized in the monoclinic space group C2/c, except for the metal atoms (Co for BUC-1, Cu for BUC-2 and Mn for BUC-3). Hence, only the structure of BUC-1 was described in details. In BUC-1, both Co1(II) and
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Co2(II) adopted octahedral geometries. Co1 was six-coordinated by two nitrogen atoms at the axial
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positions from two different bpy ligands and four oxygen atoms occupying the four sites of equatorial plane from two different completely deprotonated nbda2- ligands. While the four sites of the octahedral Co2 were occupied by two oxygen atoms from two different completely deprotonated nbda2- ligands and two oxygen atoms from two coordinated water molecules, and the remaining two axial sites were
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taken up by two nitrogen atom from two different bpy, as shown in Fig. 1(a). The Co-O and Co-N bond distances were similar to the previously reported Cobalt-based coordination polymers [33-35]. In the equatorial plane, the bond angles of O(1)-Co(1)-O(3)#1, O(1)#1-Co(1)-O(3)#1, O(1)#1-Co(1)-O(3),
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O(1)-Co(1)-O(3) were 98.27(18), 81.73(18), 98.27(18), 81.73(18)° for Co1 and O(2)-Co(2)-O(5),
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O(2)#2-Co(2)-O(5), O(2)#2-Co(2)-O(5)#2, O(2)-Co(2)-O(5)#2 were 98.5(2), 81.5(2), 98.5(2), 81.5(2)° for Co2, respectively, and the bond angles of N(1)-Co(1)-N(2), N(3)-Co(2)-N(3)#2 were 180.000(4), 180.000(1)° showing that Co-centered coordinated octahedron was slightly distorted. The Co1 and Co2 atoms were linked by typical bidentate bpy ligands into two adjacent 1D infinite cationic [Co1(bpy)]n2n+ and [Co2(bpy)]n2n+ chains, respectively, which were further joined by tridentate nbda2ligands into 2D neutral [Co2(bpy)2(nbda)2]n sheets, as shown in Fig. 1(b). The completely deprotonated nbda2- acts as tridentate ligand to link Co1 via O1 and O3 from two different COO- group and to
ACCEPTED MANUSCRIPT coordinate Co2 via O2 from the COO-, as depicted in Fig. 1(c) and (d). The O6 atoms from the discrete lattice water molecules acted as nodes to join the adjacent [Co2(bpy)2(nbda)2(H2O)2] layers via hydrogen bonds like O5-H5E…O6 [d(D…A) = 2.821 Å], O6-H6E…O4 [d(D…A) = 2.699 Å] and
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O6-H6F…O4 (-x+1/2, -y+3/2, -z+1) [d(D…A) = 2.967 Å]. Finally, the two-dimensional [Co2(bpy)2(nbda)2(H2O)2] sheets were linked into three-dimensional supramolecular frameworks via the hydrogen-bonding interactions provided by both lattice water and coordination water molecules
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[Table 3 and Fig. 1(e)], which was further strengthened by the intramolecular hydrogen bonding
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interactions like O5-H5D…O3 [d(D…A) = 2.875 Å] and O5-H5D…O1 [d(D…A) = 2.842 Å].
Fig. 1 (a) Asymmetric unit of [Co2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-1) and coordination environments around the Co atoms. Water molecules and corresponding H atoms was omitted for clarify. (b) Packing view of 2D [Co2(bpy)2(nbda)2]n sheet for BUC-1. (c) and (d) The coordination environment of H2nbda. (e) Packing view of the three-dimensional framework along the
3.3 UV-Vis DRS
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b-axis for BUC-1.
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In order to investigate the optical properties and electronic structure of the synthesized BUC 1 - 3,
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the UV-Vis absorption spectra of powder samples were carried out at room temperature[36]. As shown in Fig. 2, three coordination polymers showed an adsorption peak in the range 250-400 nm, indicative their selective absorptions in the ultraviolet region for all the three coordination polymers.
Fig. 2 UV-Visible diffuse reflectance spectra of BUC 1 - 3.
3.4 Photocatalytic activities
ACCEPTED MANUSCRIPT It was well known that coordination polymers had already been used as new photocatalytic materials for the potential applications in the degradation treatment of the organic pollutants[7]. Herein, two typical organic dyes, methylene blue (MB) and methyl orange (MO), were selected as the pollutant
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targets to evaluate the photocatalytic performances of BUC 1 - 3. In addition, control experiments on degradation of MB and MO in the absence of any catalysts under UV light irradiation were carried out. By measuring the maximum absorbance intensity at λ = 664 and 463 nm of the MB and MO,
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respectively, the phtocatalytic performances of BUC 1 - 3 were monitored.
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As illustrated in Fig. 3(a), the photodegradation efficiency (C/C0) of organic dyes (MB and MO) versus the reaction time (t) of BUC 1 - 3 was plotted. It can be seen that the removal percentage of MB increased from 8.6% (control experiment without any catalysts) to 69.6%, 30.4% and 54.8% with BUC 1 - 3 as catalysts under UV light irradiation for 120 min, respectively, and the MO removal percentage
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increased from 3.6% (without any catalysts) to 97.4%, 34.5% and 40.6% in the presence of BUC 1 - 3, respectively, under the same conditions up to 120 min. Especially, the MO degradation in the presence of BUC-1 as photocatalyst was up to 97.4% after 60 min, demonstrating that it appeared to be active
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for the photocatalytic decomposition of MO organic dyes, which was similar to the reported CP
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[Co(4,4’-bpy)2(H2bptc)] [37]. Our previously reported CPs like [M(phen)3(H3bptc)2]·5H2O (M = Co, Ni, Zn, Cd and Mn) were isostructural, and possessed nearly identical Eg values, but only [Ni(phen)3(H3bptc)2]·5H2O
and
[Mn(phen)3(H3bptc)2]·5H2O
exhibited
efficient
photocatalytic
activities toward organic dye molecules [38]. The difference of their photocatalytic performance might be contributed to that most CPs can be considered as molecular photocatalysts rather than semiconductor ones, and HOMO-LUMO gap terminology was often used to clarify the discrete characteristic of the light-induced transitions in CPs materials. Series CPs reported by our research
ACCEPTED MANUSCRIPT group revealed that the metal atoms and their corresponding coordination environment along with the coordination mode of the organic ligands in the CPs played important role in their photocatalytic activities [12, 13, 37]
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For BUC 1 - 3, the degradation reactions of MB and MO dyes followed the pseudo-first-order kinetic model, as evidenced by the linear plot of ln(C/C0) versus reaction time t. The pseudo-first-order rate constants (k) and the corresponding square of the correlation coefficients (R2) for the photocatalytic
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degradation of the MB and MO with catalysts BUC 1 - 3 were listed in Table 4, indicating that with the
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increase of pseudo-first-order rate constants (k), the photocatalysis efficiencies increased obviously.
Table 4 Parameters of pseudo-first-order kinetics for photocatalytic reactions of MB and MO dyes in BUC 1 – 3
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As illustrated in the Fig. 3(b) and 3(c), taking the degradation of MB and MO in BUC-1 as examples, when the simulated wastewater samples containing MB/MO were irradiated under UV light, the maximum absorption peaks of the MB and MO decreased obviously with reaction time. Additionally,
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no other new peaks were observed during the process of degradation, implying that photocatalytic
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process did not produce the new pollutants. In order to understand the photocatalytic degradation of the organic dyes in BUC 1 – 3, a simple approach based upon highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) was employed. Accordingly, the charge transfer state of the HOMO and LUMO in the absence of the UV light was that the HOMO had two electrons, and the LUMO was vacant[17]. For the photocatalytic process of BUC 1 – 3, UV light induced charge transfer by promoting an electron from the HOMO to LUMO. But the excited state of electron in the LUMO was easily lost, while the HOMO
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In order to confirm the possible mechanism, radicals trapping experiments were carried out in degradation of organic dyes MB and MO with BUC-1 as a photocatalyst[12, 42]. The results affirmed that the addition of 1 mM isopropanol (IPA) as a radical scavenger considerably inhibited the
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degradation efficiencies of MB (giving a decrease from 69.6% without IPA to 54.3% with IPA as
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scavenger) and MO (giving a decrease from 97.4% in the absence of IPA to 58.1% in the presence of IPA) under UV light irradiation after 120 min, as illustrated in Fig. 3(e), 3(f) and (g), which suggested that hydroxyl radicals were the main active species in the photodegradation process.
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Fig. 3 (a) Plots of concentration vs. irradiation time for MB and MO under irradiation by Hg lamp light with BUC 1 - 3 as photocatalysts. (b) and (c) UV-Vis absorption spectra of MB (b) and MO (c) solution during the decomposition reaction under Hg lamplight irradiation with BUC-1.
(d) and (e) UV-Vis absorption spectra of MB (d) and MO (e) solution during the
decomposition reaction under Hg lamplight irradiation with BUC-1 and radical scavenger (IPA). (f). organic dyes removal
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percentage under UV light irradiation in different conditions with BUC-1.
To test photocatalysts practicability, BUC-1 was selected to test the recyclability and stability by circulating runs in the photocatalytic degradation of MO over the UV light system. Four catalyst cycles in repetitive degradation of MO (10 mg/L) in the presence of BUC-1 (50 mg) had been examined. As illustrated in Fig. 4(a), the results showed that the removal percentage of MO with BUC-1 stayed above 90% and showed only a small decrease after four runs of photocatalytic experiments, suggesting that BUC-1 was extremely stable during the photocatalysis of MO and can be used for the repeated
ACCEPTED MANUSCRIPT degradation of MO. Moreover, the PXRD diffraction patterns of the used BUC-1 also matched well with the simulated pattern generated from the result of single-crystal diffraction data and as-synthesized product as shown in the Fig. 4(b), indicating that there was no noticeable change in the
reusability and high stability for organic dyes decomposition.
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crystallographic and morphology of the catalyst during the experiments. Hence, BUC-1 was in a good
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Fig. 4 (a) The cycling of the degradation of MO (10 mg/L) over BUC-1 in the UV light system. (b). PXRD patterns of BUC-1
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before and after photocatalytic reaction and the simulated XRD pattern from the single crystal structure of BUC-1.
4. Conclusions
In summary, the synthesis of BUC 1 - 3 had been accomplished via hydrothermal methods. The crystal structure revealed that BUC 1 - 3 consisted of two-dimensional sheets, which were further
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linked into three-dimensional supramolecular framework via the hydrogen bonding interactions. The degradation percentage of MB was 69.6%, 30.4% and 54.8% and the MO degradation percentage was
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97.4%, 34.5% and 40.6% in the presence of BUC 1 – 3, respectively, under UV light irradiation, implying the metal atom was important for the photocatalytic performances. Radicals trapping
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experiments demonstrated that hydroxyl radicals were the main active species in the photodegradation process. Additionally, BUC-1 possessed excellent reproducibility and great stability. Further researches should be carried out to study the photocatalytic activities on other organic pollutants.
5. Supplementary materials CCDC 1434390, 1447557 and 1483357 contain the supplementary crystallographic data for BUC 1-3, respectively. These data can be obtained free of charge from the Cambridge Crystallographic Data
ACCEPTED MANUSCRIPT Centre via www.ccdc.cam.ac.uk/data_request/cif, or from the Cambridge Crystallographic Data Centre, 12
Union
Road,
Cambridge
CB2
1EZ,
UK;
fax:
(+44)
1223-336-033;
or
e-mail:
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[email protected].
Acknowledgements
We thank the financial support from National Natural Science Foundation of China (51578034), the
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Beijing Natural Science Foundation & Scientific Research Key Program of Beijing Municipal
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Commission of Education (KZ201410016018), the Training Program Foundation for the Beijing Municipal Excellent Talents(2013D005017000004), the Importation & Development of High-Caliber Talents Project of Beijing Municipal Institutions (CIT&CD201404076), and Hundred, Thousand and
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Ten Thousand Talent Project of Beijing (2016023).
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ACCEPTED MANUSCRIPT Table 1 Details of X-ray data collection and refinement for BUC 1 - 3 BUC-2
BUC-3
Formula
C38H44Co2N4O12
C38H44Cu2N4O12
C38H44Mn2N4O12
M
866.63
875.85
858.65
Crystal system
Monoclinic
Monoclinic
Monoclinic
space group
C2/c
C2/c
C2/c
a, ( Å )
18.1711 (16)
18.4079(17)
18.3569(16)
b, ( Å )
11.4010(9)
11.6910(11)
c, ( Å )
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BUC-1
11.6730(9)
20.1711(18)
90
90
o
β, ( )
112.979(2)
113.023(3)
γ, (o)
90
90
3818.6(6)
3995.2(6)
3976.9(6)
4
4
4
1.131
0.701
α, ( )
3
V, (Å ) Z
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20.0209(17)
o
20.1531(18) 90
112.940(3) 90
µ(Mo, Kα) (mm )
0.938
Total Reflections
9327
3454
3497
Unique
3345
3454
3497
1800
1816
1784
Goodness-of-fit on F
1.123
1.065
1.452
Rint
0.0746
0.0000
0.0000
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-1
F(000) 2
0.0836
0.1180
0.1215
0.2314
0.3081
0.3579
R1(all data)
0.1127
0.1711
0.1441
0.2416
0.3618
0.3815
1.839, -0.580
1.026, -0.971
1.398, -0.658
ωR2(all data)
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R0 ωR2
3
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Largest diff. Peak and hole(e/Å )
ACCEPTED MANUSCRIPT Table 2 Selected bond lengths (Å) and angles (o) for BUC 1 – 3
BUC-1 Bond lengths (Å) 2.047(5)
Co(1)-O(1)
2.047(5)
Co(1)-O(3)#1
2.101(5)
Co(1)-O(3)
2.101(5)
Co(1)-N(1)
2.123(8)
Co(1)-N(2)
2.191(10)
Co(2)-O(2)
2.059(5)
Co(2)-O(2)#2
2.059(5)
Co(2)-O(5)
2.108(5)
Co(2)-O(5)#2
2.108(5)
Co(2)-N(3)
2.190(7)
Co(2)-N(3)#2
Bond angles (o)
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Co(1)-O(1)#1
179.5(3)
O(1)#1-Co(1)-O(3)#1
81.73(18)
O(1)-Co(1)-O(3)#1
98.27(18)
O(1)#1-Co(1)-O(3)
98.27(18)
O(1)-Co(1)-O(3)
81.73(18)
O(3)#1-Co(1)-O(3)
178.6(3)
O(1)#1-Co(1)-N(1)
90.25(15)
O(1)-Co(1)-N(1)
O(3)#1-Co(1)-N(1)
89.32(16)
O(3)-Co(1)-N(1)
O(1)#1-Co(1)-N(2)
89.75(15)
O(1)-Co(1)-N(2)
O(3)#1-Co(1)-N(2)
90.68(16)
O(3)-Co(1)-N(2)
N(1)-Co(1)-N(2)
180.000(4)
81.5(2)
O(5)-Co(2)-O(5)#2
180.000(1)
O(2)#2-Co(2)-N(3)
88.6(2)
O(5)#2-Co(2)-N(3)
89.5(2)
O(2)#2-Co(2)-N(3)#2
91.4(2)
O(5)#2-Co(2)-N(3)#2
90.5(2)
90.25(15) 89.32(16)
89.75(15)
90.68(16)
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98.5(2)
O(2)-Co(2)-O(5)#2
O(2)-Co(2)-O(2)#2
180.000(1)
O(2)#2-Co(2)-O(5)
81.5(2)
O(2)#2-Co(2)-O(5)#2
98.5(2)
O(2)-Co(2)-N(3)
91.4(2)
O(5)-Co(2)-N(3)
90.5(2)
O(2)-Co(2)-N(3)#2
88.6(2)
O(5)-Co(2)-N(3)#2
89.5(2)
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O(2)-Co(2)-O(5)
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O(1)#1-Co(1)-O(1)
2.190(7)
N(3)-Co(2)-N(3)#2
180.000(1)
Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+3/2 #2 -x+1, -y+1, -z+1 BUC-2 Bond lengths (Å) 2.125(6)
2.125(6)
Cu(1)-O(3)#1
2.179(7)
Cu(1)-O(3)
2.179(7)
Cu(1)-O(1)
Cu(1)-N(2)
2.288(11)
Cu(1)-N(1)
2.305(12)
Cu(2)-O(2)#2
2.144(7)
Cu(2)-O(2)
2.144(7)
Cu(2)-O(5)#2
2.220(8)
2.220(8)
Cu(2)-N(3)#2
2.324(9)
Cu(2)-N(3)
2.324(9)
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Cu(1)-O(1)#1
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Cu(2)-O(5) o
Bond angles ( )
O(1)#1-Cu(1)-O(1)
179.2(4)
O(1)#1-Cu(1)-O(3)#1
82.6(2)
O(1)-Cu(1)-O(3)#1
97.5(2)
O(1)#1-Cu(1)-O(3)
97.5(2)
O(1)-Cu(1)-O(3)
82.6(2)
O(3)#1-Cu(1)-O(3)
177.8(4)
O(1)#1-Cu(1)-N(2)
90.39(19)
O(1)-Cu(1)-N(2)
90.39(19)
O(3)#1-Cu(1)-N(2)
88.9(2)
O(3)-Cu(1)-N(2)
88.9(2)
O(1)#1-Cu(1)-N(1)
89.61(19)
O(1)-Cu(1)-N(1)
89.61(19)
O(3)#1-Cu(1)-N(1)
91.1(2)
O(3)-Cu(1)-N(1)
91.1(2)
N(2)-Cu(1)-N(1)
180.000(2)
O(2)#2-Cu(2)-O(2)
180.000(1)
O(2)#2-Cu(2)-O(5)#2
100.0(3)
O(2)-Cu(2)-O(5)#2
80.0(3)
O(2)#2-Cu(2)-O(5)
80.0(3)
O(2)-Cu(2)-O(5)
100.0(3)
O(5)#2-Cu(2)-O(5)
180.000(1)
O(2)#2-Cu(2)-N(3)#2
87.9(3)
O(2)-Cu(2)-N(3)#2
92.1(3)
O(5)#2-Cu(2)-N(3)#2
89.9(3)
ACCEPTED MANUSCRIPT O(5)-Cu(2)-N(3)#2
90.1(3)
O(2)#2-Cu(2)-N(3)
92.1(3)
O(2)-Cu(2)-N(3)
87.9(3)
O(5)#2-Cu(2)-N(3)
90.1(3)
O(5)-Cu(2)-N(3)
89.9(3)
N(3)#2-Cu(2)-N(3)
180.000(1)
Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+1/2
#2 -x+1, -y+1, -z+1
BUC-3 Bond lengths (Å) 2.119(6)
Mn(1)-O(1)#1
2.119(6)
Mn(1)-O(3)#1
2.165(6)
Mn(1)-O(3)
2.165(6)
Mn(1)-N(2)
2.256(10)
Mn(1)-N(1)
2.313(11)
Mn(2)-O(2)#2
2.124(6)
Mn(2)-O(2)
2.124(6)
Mn(2)-O(5)#2
Mn(2)-O(5)
2.197(8)
Mn(2)-N(3)
2.305(8)
Mn(2)-N(3)#2
o
Bond angles ( )
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Mn(1)-O(1)
178.9(3)
O(1)-Mn(1)-O(3)#1
82.6(2)
O(1)#1-Mn(1)-O(3)#1
97.5(2)
O(1)-Mn(1)-O(3)
97.5(2)
O(1)#1-Mn(1)-O(3)
82.6(2)
O(3)#1-Mn(1)-O(3)
O(1)-Mn(1)-N(2)
90.57(17)
O(1)#1-Mn(1)-N(2)
O(3)#1-Mn(1)-N(2)
89.05(17)
O(3)-Mn(1)-N(2)
O(1)-Mn(1)-N(1)
89.43(17)
O(1)#1-Mn(1)-N(1)
O(3)#1-Mn(1)-N(1)
90.95(17)
178.1(3)
90.57(17)
89.05(17)
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89.43(17)
O(3)-Mn(1)-N(1)
90.95(17)
180.000(2)
O(2)#2-Mn(2)-O(5)#2
100.3(3)
O(2)#2-Mn(2)-O(2)
180.000(1)
O(2)-Mn(2)-O(5)#2
79.7(3)
O(2)#2-Mn(2)-O(5)
79.7(3)
O(2)-Mn(2)-O(5)
100.3(3)
O(5)#2-Mn(2)-O(5)
180.000(1)
O(2)#2-Mn(2)-N(3)
88.3(2)
O(2)-Mn(2)-N(3)
91.7(2)
O(5)#2-Mn(2)-N(3)
89.8(3)
O(5)-Mn(2)-N(3)
90.2(3)
O(2)#2-Mn(2)-N(3)#2
91.7(2)
O(2)-Mn(2)-N(3)#2
88.3(2)
O(5)#2-Mn(2)-N(3)#2
90.2(3)
O(5)-Mn(2)-N(3)#2
89.8(3)
N(3)-Mn(2)-N(3)#2
180.000(1)
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N(2)-Mn(1)-N(1)
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Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+1/2
2.305(8)
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O(1)-Mn(1)-O(1)#1
2.197(8)
#2 -x+1, -y+1, -z+1
ACCEPTED MANUSCRIPT Table 3 Hydrogen bonds for BUC 1 - 3 [Å and o] D-H
d(D-H)
d(H..A)
d(D..A)
A
0.850
2.055
161.75
2.875
O3
O5-H5D
0.850
2.331
119.06
2.842
O1
O5-H5E
0.850
2.002
161.44
2.821
O6
O6-H6E
0.850
1.854
171.95
2.699
O4
O6-H6F
0.850
2.123
172.21
2.967
O4 [-x+1/2, -y+3/2, -z+1]
O5-H5D
0.850
2.017
161.53
2.836
O3
O5-H5D
0.850
2.441
116.65
2.923
O1
O5-H5E
0.850
2.047
162.81
2.870
O6
O6-H6E
0.850
1.904
171.79
2.748
O6-H6F
0.850
2.131
172.81
2.976
O5-H5C
0.850
2.057
O5-H5D
0.850
2.031
O5-H5D
0.850
2.433
O6-H6E
0.850
1.880
O6-H6F
0.850
2.126
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O5-H5D
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BUC-1
BUC-2
162.23
2.878
O6
161.78
2.851
O3 [-x+1, y, -z+1/2]
117.03
2.919
O1
171.08
2.724
O4 [-x+1, y, -z+1/2]
172.94
2.971
O4 [x+1/2, -y+1/2, z+1/2]
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O4 [-x+3/2, -y+1/2, -z+1]
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BUC-3
O4
ACCEPTED MANUSCRIPT Table 4 Parameters of pseudo-first-order kinetics for photocatalytic reactions of MB and MO dyes in BUC 1 – 3
BUC-1
BUC-2
BUC-3
R2
k(min-1)
R2
k(min-1)
R2
MB
0.0080
0.9859
0.0027
0.9733
0.0027
0.9330
MO
0.0513
0.8636
0.0018
0.9048
0.0053
0.9882
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k(min-1)
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Fig. 1 (a) Asymmetric unit of [Co2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-1) and coordination environments around the Co atoms. Water molecules and corresponding H atoms was omitted for clarify. (b) Packing view of 2D [Co2(bpy)2(nbda)2]n sheet for
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b-axis for BUC-1.
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BUC-1. (c) and (d) The coordination environment of H2nbda. (e) Packing view of the three-dimensional framework along the
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Fig. 2 UV-Visible diffuse reflectance spectra of BUC 1 - 3.
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Fig. 3 (a) Plots of concentration vs. irradiation time for MB and MO under irradiation by Hg lamp light with BUC 1 - 3 as photocatalysts. (b) and (c) UV-Vis absorption spectra of MB (b) and MO (c) solution during the decomposition reaction under (d) and (e) UV-Vis absorption spectra of MB (d) and MO (e) solution during the
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Hg lamplight irradiation with BUC-1.
decomposition reaction under Hg lamplight irradiation with BUC-1 and radical scavenger (IPA). (f). organic dyes removal
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percentage under UV light irradiation in different conditions with BUC-1.
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Fig. 4 (a) The cycling of the degradation of MO (10 mg/L) over BUC-1 in the UV light system. (b). PXRD patterns of BUC-1
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before and after photocatalytic reaction and the simulated XRD pattern from the single crystal structure of BUC-1.
ACCEPTED MANUSCRIPT
Highlights
Three 2D coordination polymers are constructed by typical 4,4′-bipyridine and stereo
The title coordination polymers exhibit different photocatalytic degradation ability to decompose methylene blue and methyl orange under UV light irradiation.
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experiments using isopropanol as radical scavenger.
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A possible photocatalytic mechanism was proposed, which was confirmed by radicals trapping
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2,3-norbornanedicarboxylic acid.
S0022-2860(16)31074-2
DOI:
10.1016/j.molstruc.2016.10.033
Reference:
MOLSTR 23034
To appear in:
Journal of Molecular Structure
Received Date: 16 August 2016 Revised Date:
6 October 2016
Accepted Date: 7 October 2016
Please cite this article as: J. Zhang, C.-C. Wang, Three two-dimensional coordination polymers constructed from transition metals and 2,3-norbornanedicarboxylic acid: Hydrothermal synthesis, crystal structures and photocatalytic properties, Journal of Molecular Structure (2016), doi: 10.1016/ j.molstruc.2016.10.033. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Three two-dimensional coordination polymers constructed from transition metals and 2,3-Norbornanedicarboxylic acid: hydrothermal synthesis, crystal structures and photocatalytic
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properties
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Three two-dimensional coordination polymers constructed from transition metals and 2,3-Norbornanedicarboxylic acid: hydrothermal synthesis, crystal structures and photocatalytic
Jia Zhang1,2, Chong-Chen Wang1,2∗ 1
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properties
Beijing Key Laboratory of Advanced Functional Materials for Building and Environment, Beijing
Key Laboratory of Urban Stormwater System and Water Environment (Ministry of Education),
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2
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University of Civil Engineering and Architecture, Beijing, 100044, China
Beijing University of Civil Engineering and Architecture, Beijing, 100044, China
Abstract:
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Three novel coordination polymers based on transition metals like Co(II), Cu(II) and Mn(II), namely [Co2(bpy)2(nbda)2(H2O)2]·2H2O (denoted as BUC-1), [Cu2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-2), [Mn2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-3), (where bpy = 4,4′-bipyridine, H2nbda =
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2,3-norbornanedicarboxylic acid, BUC = Beijing University of Civil Engineering and Architecture),
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were synthesized under hydrothermal conditions, and characterized by CNH elemental analyses (EA), Fourier Transform infrared spectroscopy (FTIR), and single crystal X-ray diffraction (SCXRD). BUC 1 - 3 were isostructural and crystallized in the monoclinic space group C2/c, in which the corresponding metal atoms were linked by typical bidentate bpy ligands into two adjacent 1D [M1(bpy)]n2n+ and [M2(bpy)]n2n+ (M = Co(II), Cu(II), Mn(II)), further joined by versatile nbda2- ligands
∗
Corresponding author. Tel.: +86 10 61209186; fax: +86 10 61209186.
E-mail address: [email protected]
ACCEPTED MANUSCRIPT into 2D [M2(bpy)2(nbda)2]n sheets. Finally, three-dimensional supramolecular frameworks were constructed with the aid of the intermolecular hydrogen bonding interactions. BUC 1 - 3 exhibited different photocatalytic degradation ability to decompose methylene blue (MB) and methyl orange
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(MO) under UV light irradiation. Additionally, a possible photocatalytic mechanism HOMO-LUMO was proposed and discussed, which was further confirmed by radicals trapping experiments using isopropanol as radical scavenger.
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Keywords: Coordination polymers, Photocatalysis, Degradation, Organic dyes
1. Introduction
Coordination polymers display versatile physical and chemical properties like high specific surface area, tunable pore size, great chemical variety, and relatively good thermal stability[1, 2], which have
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been widely applied in the field of gas separation[3, 4], gas storage[5, 6], catalysis[7, 8], chemical sensors[9], and so on[10, 11]. In addition, growing researches indeed demonstrated that some coordination polymers have been utilized as heterogeneous photocatalysts conduct organic pollutants
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degradation [7, 12, 13], CO2 reduction[14] and Cr(VI) reduction[15] under UV/visible/UV-visible light
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irradiation. For example, Garcia et al. firstly proposed MOF-5 as an active catalyst to photodegrade phenol[16]. Natarajan et al. used Co(II)/Ni(II)/Zn(II) coordination polymers as photocatalysts to degrade organic dyes[17]. Fu et al. employed a photoactive Ti-containing MOF, NH2-MIL-125(Ti), as photocatalysts to reduce CO2 into HCOO- [18]. Being compared with the traditional inorganic photocatalytic materials like TiO2, CdS, and ZnO, coordination polymers as efficient photocatalysts have many advantages: (i) their well-defined
crystalline structures are beneficial to investigate the corresponding structure-property relationship;
ACCEPTED MANUSCRIPT (ii) their modular natures of the synthesis methods allow the rational design and fine tuning of these catalysts at the molecular level; (iii) their structural features of tunable active sites like metal-oxoclusters and organic linkers result in solar harnessing more efficiently; (iv) their facile
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modification resulted from the introduction of linker substitutions such as amino group can arise their visible light photocatalytic activity; and (v) their intrinsic porosity and high surface area is
photocatalytic reaction efficiency [7, 14, 15].
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beneficial to transport guest molecules through the open channels rapidly and to increase the
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Meanwhile, a major challenge in crystal engineering and self-assembly of CPs is the predictability of the polymeric network structure which might depend on several factors like metal centers, organic ligands, metal-to-ligand radio, the presence of solvents and counter-ions[19-22]. There is still a very long way to develop the coordination polymers with the well-defined structures and useful functions.
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With this paper, 4,4′-bipyridine (bpy) and 2,3-norbornanedicarboxylic acid (H2nbda), as illustrated in Scheme 1, were utilized to construct three transition metal-based coordination polymers via hydrothermal method, namely, [M2(bpy)2(nbda)2(H2O)2]·2H2O (Co for BUC-1, Cu for BUC-2 and Mn
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for BUC-3). As far as we know, the organic ligand of 2,3-norbornanedicarboxylic acid (H2nbda) was
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for the first time used to construct coordination polymers, which can easily coordinate with metal atoms via M-O bond (M = metal atoms), and can be expected to construct more interesting architectures than the previously reported Co(bpy)2Cl2[23], Cu-X-bpy (X = Cl, Br)[24], Mn(bpy)2Cl2[25] from single bpy ligangd. The structures of BUC 1 - 3 were analyzed and discussed. In addition, their optical properties, photocatalytic activities towards methylene blue (MB) and methyl orange (MO) had also been studied.
ACCEPTED MANUSCRIPT COOH N
N COOH bpy
H2nbda
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Scheme 1 The structure of bpy and H2nbda
2. Experimental
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2.1 Materials and methods
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All chemicals were commercially available reagent grade, which were used without any further purification. C, H, N elemental analyses were conducted on an Elementar Vario EL-III instrument. The FTIR spectra were recorded in the region 400 - 4000 cm-1 on a Nicolet 6700 FTIR spectrophotometer with KBr pellets. UV-Vis absorption spectra of solid samples was measured from 200 to 800 nm with a
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Perkin Elmer Lamda 650S spectrophotometer, in which barium sulfate (BaSO4) was used as the standard with 100% reflectance.
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2.2 Synthesis of coordination polymers
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2.2.1 Synthesis of BUC-1
A mixture of CoCl2·6H2O (0.3 mmol, 0.0714 g), 2,3-norbornanedicarboxylic acid (H2nbda) (0.3 mmol, 0.0553 g) and 4,4′-bipyridine (bpy) (0.6 mmol, 0.0940 g) with a molar ratio of 1:1:2 was sealed in a 25 mL Teflon-lined stainless steel Parr bomb containing deionized water (20 mL), heated at 160 oC for 72 h, and then cooled down to room temperature. Dark red block-like crystals of [Co2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-1) were isolated and washed with deionized water and ethanol (yield 85% based on CoCl2·6H2O). Anal. Calc. for BUC-1, C38H44Co2N4O12: C, 52.6; N, 6.5; H, 5.1.
ACCEPTED MANUSCRIPT Found: C, 52.7; N, 6.5; H, 5.2. FTIR (KBr)/cm-1: 3378, 2993, 2969, 2870, 1606, 1557, 1488, 1438, 1409, 1322, 1278, 1248, 1220, 1113, 1064, 1046, 1006, 920, 859, 811, 772, 732, 693, 630, 519, 481,
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416 .
2.2.2 Synthesis of BUC-2
Synthesis of black block-like crystals of [Cu2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-2) followed the
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same procedure as for BUC-1, except that CoCl2·6H2O was replaced by CuCl2·2H2O (0.3 mmol,
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0.0511 g) (yield 74% based on CuCl2·2H2O). Anal. Calc. for BUC-2, C38H44Cu2N4O12: C, 52.1; N, 6.4; H, 5.0. Found: C, 52.2; N, 6.4; H, 5.2. FTIR (KBr)/cm-1: 3430, 3044, 1601, 1526, 1482, 1418, 1409, 1328, 1215, 1062, 978, 966, 853, 820, 799, 724, 633, 561, 475, 412.
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2.2.3 Synthesis of BUC-3
Synthesis of yellow block-like crystals of [Mn2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-3) followed the same procedure as for BUC-1, except that CoCl2·6H2O was replaced by MnCl2·4H2O (0.3 mmol,
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0.0594 g) (yield 77% based on MnCl2·4H2O). Anal. Calc. for BUC-3, C38H44Mn2N4O12: C, 53.1; N, 6.5;
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H, 5.1. Found: C, 53.2; N, 6.5; H, 5.1. FTIR (KBr)/cm-1: 3662, 3516, 3238, 2967, 2870, 1956, 1603, 1557, 1488, 1411, 1321, 1221, 1114, 1065, 1044, 1004, 951, 931, 919, 858, 732, 686, 626, 573, 510, 481, 407.
2.3 X-ray crystallography Single-crystal X-ray diffraction data collection for BUC 1 - 3 were performed with a Bruker Smart 1000 CCD area detector diffractometer with graphite-monochromatized MoKα radiation (λ = 0.71073
ACCEPTED MANUSCRIPT Å) using φ-ω mode at 298(2) K. The SMART software[26] was used for data collection and the SAINT software[27] for data extraction. Empirical absorption corrections were performed with the SADABS program[28]. The structures were solved by direct methods (SHELXS-97)[29] and refined by
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full-matrix-least squares techniques on F2 with anisotropic thermal parameters for all of the non-hydrogen atoms (SHELXL-97)[29]. All hydrogen atoms were located by Fourier difference synthesis and geometrical analysis. These hydrogen atoms were allowed to ride on their respective
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parent atoms. All structural calculations were carried out using the SHELX-97 program package[29].
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Crystallographic data and structural refinements for BUC 1 - 3 were summarized in Table 1. Selected bond lengths and angles were listed in Table 2.
Table 1 Details of X-ray data collection and refinement for BUC 1 - 3
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Table 2 Selected bond lengths (Å) and angles (o) for BUC 1 – 3
Table 3 Hydrogen bonds for BUC 1 - 3 [Å and o]
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2.4 Photocatalytic degradation experiments
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In order to evaluate the photocatalytic performance of BUC 1 - 3 as photocatalysts, methylene blue (MB) and methyl orange (MO) dyes were selected as target pollutants to be degraded in photocatalytic assessment system (Beijing Aulight Co. Ltd) in open air, under 500W Hg lamp irradiation and room temperature. The reactor employed in this study was 300 mL quartz reactor, and the distance between the light source and the reactor containing the reaction mixture was fixed at 5 cm. In order to keep the constant reaction temperature at 25 oC, cooling water was circulated through the annulus of the quartz tube.
ACCEPTED MANUSCRIPT Fifty microgram of photocatalyst was added to 200 mL of MB or MO (10 mg/L) aqueous solution in a 300 mL breaker. Prior to the UV light irradiation, the suspension was magnetically stirred in the dark for 120 min to ensure the adsorption/desorption equilibrium. In the process of photocatalytic
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degradation experiment, the samples were collected at regular time intervals using a 0.45 µm syringe filter (Shanghai Troody) to remove the catalyst particles before analysis. A Laspec Alpha-1860
3. Results and discussion
3.1 FTIR analysis
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absorbance at 664 and 463 nm, respectively.
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spectrometer was used to monitor the concentration changes of MB and MO by the maximum
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BUC 1 - 3 were stable and insoluble in water and common organic solvents including but not limited to methanol, ethanol, ether and N,N’-dimethylformamide (DMF). In the FTIR spectra as listed in Fig. S1(ESI), a strong and broad absorptions at 3378, 3430 and 3516 cm-1 of BUC 1 - 3 were assigned to
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the O-H stretching vibration of lattice water molecules, respectively. The absence of an absorption peak
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around 1453 cm-1 from H2nbda indicated that the carboxyl groups were completely deprotonated. The positions of the stretching COO vibrations at 1606 (vas(COO)) and 1322 (vs(COO)) for BUC-1, 1601 (vas(COO)) and 1328 (vs(COO)) cm-1 for BUC-2 and 1603 (vas(COO)) and 1321 (vs(COO)) cm-1 for BUC-3, for which the corresponding △v values are 284 cm-1, 273 cm-1, and 284 cm-1, respectively, which being larger than 200 cm-1 suggests that the COO- groups were coordinated to corresponding metal centers via bis-monodentate mode[30]. The vibration of pyridine group was also observed in 630, 633, 626 cm-1 the region for the BUC 1 - 3. The presence of weak band at 519, 561, 407 cm-1 can be attributed to
ACCEPTED MANUSCRIPT the stretching vibration of the Co-N, Cu-N, and Mn-N bond[31, 32].
3.2 Structural description
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All three coordination polymers BUC 1 - 3 were isomorphous and isostructural, and crystallized in the monoclinic space group C2/c, except for the metal atoms (Co for BUC-1, Cu for BUC-2 and Mn for BUC-3). Hence, only the structure of BUC-1 was described in details. In BUC-1, both Co1(II) and
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Co2(II) adopted octahedral geometries. Co1 was six-coordinated by two nitrogen atoms at the axial
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positions from two different bpy ligands and four oxygen atoms occupying the four sites of equatorial plane from two different completely deprotonated nbda2- ligands. While the four sites of the octahedral Co2 were occupied by two oxygen atoms from two different completely deprotonated nbda2- ligands and two oxygen atoms from two coordinated water molecules, and the remaining two axial sites were
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taken up by two nitrogen atom from two different bpy, as shown in Fig. 1(a). The Co-O and Co-N bond distances were similar to the previously reported Cobalt-based coordination polymers [33-35]. In the equatorial plane, the bond angles of O(1)-Co(1)-O(3)#1, O(1)#1-Co(1)-O(3)#1, O(1)#1-Co(1)-O(3),
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O(1)-Co(1)-O(3) were 98.27(18), 81.73(18), 98.27(18), 81.73(18)° for Co1 and O(2)-Co(2)-O(5),
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O(2)#2-Co(2)-O(5), O(2)#2-Co(2)-O(5)#2, O(2)-Co(2)-O(5)#2 were 98.5(2), 81.5(2), 98.5(2), 81.5(2)° for Co2, respectively, and the bond angles of N(1)-Co(1)-N(2), N(3)-Co(2)-N(3)#2 were 180.000(4), 180.000(1)° showing that Co-centered coordinated octahedron was slightly distorted. The Co1 and Co2 atoms were linked by typical bidentate bpy ligands into two adjacent 1D infinite cationic [Co1(bpy)]n2n+ and [Co2(bpy)]n2n+ chains, respectively, which were further joined by tridentate nbda2ligands into 2D neutral [Co2(bpy)2(nbda)2]n sheets, as shown in Fig. 1(b). The completely deprotonated nbda2- acts as tridentate ligand to link Co1 via O1 and O3 from two different COO- group and to
ACCEPTED MANUSCRIPT coordinate Co2 via O2 from the COO-, as depicted in Fig. 1(c) and (d). The O6 atoms from the discrete lattice water molecules acted as nodes to join the adjacent [Co2(bpy)2(nbda)2(H2O)2] layers via hydrogen bonds like O5-H5E…O6 [d(D…A) = 2.821 Å], O6-H6E…O4 [d(D…A) = 2.699 Å] and
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O6-H6F…O4 (-x+1/2, -y+3/2, -z+1) [d(D…A) = 2.967 Å]. Finally, the two-dimensional [Co2(bpy)2(nbda)2(H2O)2] sheets were linked into three-dimensional supramolecular frameworks via the hydrogen-bonding interactions provided by both lattice water and coordination water molecules
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[Table 3 and Fig. 1(e)], which was further strengthened by the intramolecular hydrogen bonding
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interactions like O5-H5D…O3 [d(D…A) = 2.875 Å] and O5-H5D…O1 [d(D…A) = 2.842 Å].
Fig. 1 (a) Asymmetric unit of [Co2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-1) and coordination environments around the Co atoms. Water molecules and corresponding H atoms was omitted for clarify. (b) Packing view of 2D [Co2(bpy)2(nbda)2]n sheet for BUC-1. (c) and (d) The coordination environment of H2nbda. (e) Packing view of the three-dimensional framework along the
3.3 UV-Vis DRS
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b-axis for BUC-1.
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In order to investigate the optical properties and electronic structure of the synthesized BUC 1 - 3,
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the UV-Vis absorption spectra of powder samples were carried out at room temperature[36]. As shown in Fig. 2, three coordination polymers showed an adsorption peak in the range 250-400 nm, indicative their selective absorptions in the ultraviolet region for all the three coordination polymers.
Fig. 2 UV-Visible diffuse reflectance spectra of BUC 1 - 3.
3.4 Photocatalytic activities
ACCEPTED MANUSCRIPT It was well known that coordination polymers had already been used as new photocatalytic materials for the potential applications in the degradation treatment of the organic pollutants[7]. Herein, two typical organic dyes, methylene blue (MB) and methyl orange (MO), were selected as the pollutant
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targets to evaluate the photocatalytic performances of BUC 1 - 3. In addition, control experiments on degradation of MB and MO in the absence of any catalysts under UV light irradiation were carried out. By measuring the maximum absorbance intensity at λ = 664 and 463 nm of the MB and MO,
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respectively, the phtocatalytic performances of BUC 1 - 3 were monitored.
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As illustrated in Fig. 3(a), the photodegradation efficiency (C/C0) of organic dyes (MB and MO) versus the reaction time (t) of BUC 1 - 3 was plotted. It can be seen that the removal percentage of MB increased from 8.6% (control experiment without any catalysts) to 69.6%, 30.4% and 54.8% with BUC 1 - 3 as catalysts under UV light irradiation for 120 min, respectively, and the MO removal percentage
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increased from 3.6% (without any catalysts) to 97.4%, 34.5% and 40.6% in the presence of BUC 1 - 3, respectively, under the same conditions up to 120 min. Especially, the MO degradation in the presence of BUC-1 as photocatalyst was up to 97.4% after 60 min, demonstrating that it appeared to be active
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for the photocatalytic decomposition of MO organic dyes, which was similar to the reported CP
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[Co(4,4’-bpy)2(H2bptc)] [37]. Our previously reported CPs like [M(phen)3(H3bptc)2]·5H2O (M = Co, Ni, Zn, Cd and Mn) were isostructural, and possessed nearly identical Eg values, but only [Ni(phen)3(H3bptc)2]·5H2O
and
[Mn(phen)3(H3bptc)2]·5H2O
exhibited
efficient
photocatalytic
activities toward organic dye molecules [38]. The difference of their photocatalytic performance might be contributed to that most CPs can be considered as molecular photocatalysts rather than semiconductor ones, and HOMO-LUMO gap terminology was often used to clarify the discrete characteristic of the light-induced transitions in CPs materials. Series CPs reported by our research
ACCEPTED MANUSCRIPT group revealed that the metal atoms and their corresponding coordination environment along with the coordination mode of the organic ligands in the CPs played important role in their photocatalytic activities [12, 13, 37]
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For BUC 1 - 3, the degradation reactions of MB and MO dyes followed the pseudo-first-order kinetic model, as evidenced by the linear plot of ln(C/C0) versus reaction time t. The pseudo-first-order rate constants (k) and the corresponding square of the correlation coefficients (R2) for the photocatalytic
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degradation of the MB and MO with catalysts BUC 1 - 3 were listed in Table 4, indicating that with the
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increase of pseudo-first-order rate constants (k), the photocatalysis efficiencies increased obviously.
Table 4 Parameters of pseudo-first-order kinetics for photocatalytic reactions of MB and MO dyes in BUC 1 – 3
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As illustrated in the Fig. 3(b) and 3(c), taking the degradation of MB and MO in BUC-1 as examples, when the simulated wastewater samples containing MB/MO were irradiated under UV light, the maximum absorption peaks of the MB and MO decreased obviously with reaction time. Additionally,
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no other new peaks were observed during the process of degradation, implying that photocatalytic
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process did not produce the new pollutants. In order to understand the photocatalytic degradation of the organic dyes in BUC 1 – 3, a simple approach based upon highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) was employed. Accordingly, the charge transfer state of the HOMO and LUMO in the absence of the UV light was that the HOMO had two electrons, and the LUMO was vacant[17]. For the photocatalytic process of BUC 1 – 3, UV light induced charge transfer by promoting an electron from the HOMO to LUMO. But the excited state of electron in the LUMO was easily lost, while the HOMO
ACCEPTED MANUSCRIPT strongly needed one electron to return to its stable state[7, 39]. Therefore, water molecules were oxygenated into the ·OH active species, which could decompose MB/MO efficiently to complete the photocatalytic process[40, 41].
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In order to confirm the possible mechanism, radicals trapping experiments were carried out in degradation of organic dyes MB and MO with BUC-1 as a photocatalyst[12, 42]. The results affirmed that the addition of 1 mM isopropanol (IPA) as a radical scavenger considerably inhibited the
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degradation efficiencies of MB (giving a decrease from 69.6% without IPA to 54.3% with IPA as
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scavenger) and MO (giving a decrease from 97.4% in the absence of IPA to 58.1% in the presence of IPA) under UV light irradiation after 120 min, as illustrated in Fig. 3(e), 3(f) and (g), which suggested that hydroxyl radicals were the main active species in the photodegradation process.
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Fig. 3 (a) Plots of concentration vs. irradiation time for MB and MO under irradiation by Hg lamp light with BUC 1 - 3 as photocatalysts. (b) and (c) UV-Vis absorption spectra of MB (b) and MO (c) solution during the decomposition reaction under Hg lamplight irradiation with BUC-1.
(d) and (e) UV-Vis absorption spectra of MB (d) and MO (e) solution during the
decomposition reaction under Hg lamplight irradiation with BUC-1 and radical scavenger (IPA). (f). organic dyes removal
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percentage under UV light irradiation in different conditions with BUC-1.
To test photocatalysts practicability, BUC-1 was selected to test the recyclability and stability by circulating runs in the photocatalytic degradation of MO over the UV light system. Four catalyst cycles in repetitive degradation of MO (10 mg/L) in the presence of BUC-1 (50 mg) had been examined. As illustrated in Fig. 4(a), the results showed that the removal percentage of MO with BUC-1 stayed above 90% and showed only a small decrease after four runs of photocatalytic experiments, suggesting that BUC-1 was extremely stable during the photocatalysis of MO and can be used for the repeated
ACCEPTED MANUSCRIPT degradation of MO. Moreover, the PXRD diffraction patterns of the used BUC-1 also matched well with the simulated pattern generated from the result of single-crystal diffraction data and as-synthesized product as shown in the Fig. 4(b), indicating that there was no noticeable change in the
reusability and high stability for organic dyes decomposition.
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crystallographic and morphology of the catalyst during the experiments. Hence, BUC-1 was in a good
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Fig. 4 (a) The cycling of the degradation of MO (10 mg/L) over BUC-1 in the UV light system. (b). PXRD patterns of BUC-1
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before and after photocatalytic reaction and the simulated XRD pattern from the single crystal structure of BUC-1.
4. Conclusions
In summary, the synthesis of BUC 1 - 3 had been accomplished via hydrothermal methods. The crystal structure revealed that BUC 1 - 3 consisted of two-dimensional sheets, which were further
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linked into three-dimensional supramolecular framework via the hydrogen bonding interactions. The degradation percentage of MB was 69.6%, 30.4% and 54.8% and the MO degradation percentage was
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97.4%, 34.5% and 40.6% in the presence of BUC 1 – 3, respectively, under UV light irradiation, implying the metal atom was important for the photocatalytic performances. Radicals trapping
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experiments demonstrated that hydroxyl radicals were the main active species in the photodegradation process. Additionally, BUC-1 possessed excellent reproducibility and great stability. Further researches should be carried out to study the photocatalytic activities on other organic pollutants.
5. Supplementary materials CCDC 1434390, 1447557 and 1483357 contain the supplementary crystallographic data for BUC 1-3, respectively. These data can be obtained free of charge from the Cambridge Crystallographic Data
ACCEPTED MANUSCRIPT Centre via www.ccdc.cam.ac.uk/data_request/cif, or from the Cambridge Crystallographic Data Centre, 12
Union
Road,
Cambridge
CB2
1EZ,
UK;
fax:
(+44)
1223-336-033;
or
e-mail:
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[email protected].
Acknowledgements
We thank the financial support from National Natural Science Foundation of China (51578034), the
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Beijing Natural Science Foundation & Scientific Research Key Program of Beijing Municipal
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Commission of Education (KZ201410016018), the Training Program Foundation for the Beijing Municipal Excellent Talents(2013D005017000004), the Importation & Development of High-Caliber Talents Project of Beijing Municipal Institutions (CIT&CD201404076), and Hundred, Thousand and
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Ten Thousand Talent Project of Beijing (2016023).
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ACCEPTED MANUSCRIPT Table 1 Details of X-ray data collection and refinement for BUC 1 - 3 BUC-2
BUC-3
Formula
C38H44Co2N4O12
C38H44Cu2N4O12
C38H44Mn2N4O12
M
866.63
875.85
858.65
Crystal system
Monoclinic
Monoclinic
Monoclinic
space group
C2/c
C2/c
C2/c
a, ( Å )
18.1711 (16)
18.4079(17)
18.3569(16)
b, ( Å )
11.4010(9)
11.6910(11)
c, ( Å )
RI PT
BUC-1
11.6730(9)
20.1711(18)
90
90
o
β, ( )
112.979(2)
113.023(3)
γ, (o)
90
90
3818.6(6)
3995.2(6)
3976.9(6)
4
4
4
1.131
0.701
α, ( )
3
V, (Å ) Z
SC
20.0209(17)
o
20.1531(18) 90
112.940(3) 90
µ(Mo, Kα) (mm )
0.938
Total Reflections
9327
3454
3497
Unique
3345
3454
3497
1800
1816
1784
Goodness-of-fit on F
1.123
1.065
1.452
Rint
0.0746
0.0000
0.0000
M AN U
-1
F(000) 2
0.0836
0.1180
0.1215
0.2314
0.3081
0.3579
R1(all data)
0.1127
0.1711
0.1441
0.2416
0.3618
0.3815
1.839, -0.580
1.026, -0.971
1.398, -0.658
ωR2(all data)
TE D
R0 ωR2
3
AC C
EP
Largest diff. Peak and hole(e/Å )
ACCEPTED MANUSCRIPT Table 2 Selected bond lengths (Å) and angles (o) for BUC 1 – 3
BUC-1 Bond lengths (Å) 2.047(5)
Co(1)-O(1)
2.047(5)
Co(1)-O(3)#1
2.101(5)
Co(1)-O(3)
2.101(5)
Co(1)-N(1)
2.123(8)
Co(1)-N(2)
2.191(10)
Co(2)-O(2)
2.059(5)
Co(2)-O(2)#2
2.059(5)
Co(2)-O(5)
2.108(5)
Co(2)-O(5)#2
2.108(5)
Co(2)-N(3)
2.190(7)
Co(2)-N(3)#2
Bond angles (o)
RI PT
Co(1)-O(1)#1
179.5(3)
O(1)#1-Co(1)-O(3)#1
81.73(18)
O(1)-Co(1)-O(3)#1
98.27(18)
O(1)#1-Co(1)-O(3)
98.27(18)
O(1)-Co(1)-O(3)
81.73(18)
O(3)#1-Co(1)-O(3)
178.6(3)
O(1)#1-Co(1)-N(1)
90.25(15)
O(1)-Co(1)-N(1)
O(3)#1-Co(1)-N(1)
89.32(16)
O(3)-Co(1)-N(1)
O(1)#1-Co(1)-N(2)
89.75(15)
O(1)-Co(1)-N(2)
O(3)#1-Co(1)-N(2)
90.68(16)
O(3)-Co(1)-N(2)
N(1)-Co(1)-N(2)
180.000(4)
81.5(2)
O(5)-Co(2)-O(5)#2
180.000(1)
O(2)#2-Co(2)-N(3)
88.6(2)
O(5)#2-Co(2)-N(3)
89.5(2)
O(2)#2-Co(2)-N(3)#2
91.4(2)
O(5)#2-Co(2)-N(3)#2
90.5(2)
90.25(15) 89.32(16)
89.75(15)
90.68(16)
M AN U
98.5(2)
O(2)-Co(2)-O(5)#2
O(2)-Co(2)-O(2)#2
180.000(1)
O(2)#2-Co(2)-O(5)
81.5(2)
O(2)#2-Co(2)-O(5)#2
98.5(2)
O(2)-Co(2)-N(3)
91.4(2)
O(5)-Co(2)-N(3)
90.5(2)
O(2)-Co(2)-N(3)#2
88.6(2)
O(5)-Co(2)-N(3)#2
89.5(2)
TE D
O(2)-Co(2)-O(5)
SC
O(1)#1-Co(1)-O(1)
2.190(7)
N(3)-Co(2)-N(3)#2
180.000(1)
Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+3/2 #2 -x+1, -y+1, -z+1 BUC-2 Bond lengths (Å) 2.125(6)
2.125(6)
Cu(1)-O(3)#1
2.179(7)
Cu(1)-O(3)
2.179(7)
Cu(1)-O(1)
Cu(1)-N(2)
2.288(11)
Cu(1)-N(1)
2.305(12)
Cu(2)-O(2)#2
2.144(7)
Cu(2)-O(2)
2.144(7)
Cu(2)-O(5)#2
2.220(8)
2.220(8)
Cu(2)-N(3)#2
2.324(9)
Cu(2)-N(3)
2.324(9)
EP
Cu(1)-O(1)#1
AC C
Cu(2)-O(5) o
Bond angles ( )
O(1)#1-Cu(1)-O(1)
179.2(4)
O(1)#1-Cu(1)-O(3)#1
82.6(2)
O(1)-Cu(1)-O(3)#1
97.5(2)
O(1)#1-Cu(1)-O(3)
97.5(2)
O(1)-Cu(1)-O(3)
82.6(2)
O(3)#1-Cu(1)-O(3)
177.8(4)
O(1)#1-Cu(1)-N(2)
90.39(19)
O(1)-Cu(1)-N(2)
90.39(19)
O(3)#1-Cu(1)-N(2)
88.9(2)
O(3)-Cu(1)-N(2)
88.9(2)
O(1)#1-Cu(1)-N(1)
89.61(19)
O(1)-Cu(1)-N(1)
89.61(19)
O(3)#1-Cu(1)-N(1)
91.1(2)
O(3)-Cu(1)-N(1)
91.1(2)
N(2)-Cu(1)-N(1)
180.000(2)
O(2)#2-Cu(2)-O(2)
180.000(1)
O(2)#2-Cu(2)-O(5)#2
100.0(3)
O(2)-Cu(2)-O(5)#2
80.0(3)
O(2)#2-Cu(2)-O(5)
80.0(3)
O(2)-Cu(2)-O(5)
100.0(3)
O(5)#2-Cu(2)-O(5)
180.000(1)
O(2)#2-Cu(2)-N(3)#2
87.9(3)
O(2)-Cu(2)-N(3)#2
92.1(3)
O(5)#2-Cu(2)-N(3)#2
89.9(3)
ACCEPTED MANUSCRIPT O(5)-Cu(2)-N(3)#2
90.1(3)
O(2)#2-Cu(2)-N(3)
92.1(3)
O(2)-Cu(2)-N(3)
87.9(3)
O(5)#2-Cu(2)-N(3)
90.1(3)
O(5)-Cu(2)-N(3)
89.9(3)
N(3)#2-Cu(2)-N(3)
180.000(1)
Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+1/2
#2 -x+1, -y+1, -z+1
BUC-3 Bond lengths (Å) 2.119(6)
Mn(1)-O(1)#1
2.119(6)
Mn(1)-O(3)#1
2.165(6)
Mn(1)-O(3)
2.165(6)
Mn(1)-N(2)
2.256(10)
Mn(1)-N(1)
2.313(11)
Mn(2)-O(2)#2
2.124(6)
Mn(2)-O(2)
2.124(6)
Mn(2)-O(5)#2
Mn(2)-O(5)
2.197(8)
Mn(2)-N(3)
2.305(8)
Mn(2)-N(3)#2
o
Bond angles ( )
RI PT
Mn(1)-O(1)
178.9(3)
O(1)-Mn(1)-O(3)#1
82.6(2)
O(1)#1-Mn(1)-O(3)#1
97.5(2)
O(1)-Mn(1)-O(3)
97.5(2)
O(1)#1-Mn(1)-O(3)
82.6(2)
O(3)#1-Mn(1)-O(3)
O(1)-Mn(1)-N(2)
90.57(17)
O(1)#1-Mn(1)-N(2)
O(3)#1-Mn(1)-N(2)
89.05(17)
O(3)-Mn(1)-N(2)
O(1)-Mn(1)-N(1)
89.43(17)
O(1)#1-Mn(1)-N(1)
O(3)#1-Mn(1)-N(1)
90.95(17)
178.1(3)
90.57(17)
89.05(17)
M AN U
89.43(17)
O(3)-Mn(1)-N(1)
90.95(17)
180.000(2)
O(2)#2-Mn(2)-O(5)#2
100.3(3)
O(2)#2-Mn(2)-O(2)
180.000(1)
O(2)-Mn(2)-O(5)#2
79.7(3)
O(2)#2-Mn(2)-O(5)
79.7(3)
O(2)-Mn(2)-O(5)
100.3(3)
O(5)#2-Mn(2)-O(5)
180.000(1)
O(2)#2-Mn(2)-N(3)
88.3(2)
O(2)-Mn(2)-N(3)
91.7(2)
O(5)#2-Mn(2)-N(3)
89.8(3)
O(5)-Mn(2)-N(3)
90.2(3)
O(2)#2-Mn(2)-N(3)#2
91.7(2)
O(2)-Mn(2)-N(3)#2
88.3(2)
O(5)#2-Mn(2)-N(3)#2
90.2(3)
O(5)-Mn(2)-N(3)#2
89.8(3)
N(3)-Mn(2)-N(3)#2
180.000(1)
TE D
N(2)-Mn(1)-N(1)
AC C
EP
Symmetry transformations used to generate equivalent atoms: #1 -x+1, y, -z+1/2
2.305(8)
SC
O(1)-Mn(1)-O(1)#1
2.197(8)
#2 -x+1, -y+1, -z+1
ACCEPTED MANUSCRIPT Table 3 Hydrogen bonds for BUC 1 - 3 [Å and o] D-H
d(D-H)
d(H..A)
d(D..A)
A
0.850
2.055
161.75
2.875
O3
O5-H5D
0.850
2.331
119.06
2.842
O1
O5-H5E
0.850
2.002
161.44
2.821
O6
O6-H6E
0.850
1.854
171.95
2.699
O4
O6-H6F
0.850
2.123
172.21
2.967
O4 [-x+1/2, -y+3/2, -z+1]
O5-H5D
0.850
2.017
161.53
2.836
O3
O5-H5D
0.850
2.441
116.65
2.923
O1
O5-H5E
0.850
2.047
162.81
2.870
O6
O6-H6E
0.850
1.904
171.79
2.748
O6-H6F
0.850
2.131
172.81
2.976
O5-H5C
0.850
2.057
O5-H5D
0.850
2.031
O5-H5D
0.850
2.433
O6-H6E
0.850
1.880
O6-H6F
0.850
2.126
RI PT
O5-H5D
SC
BUC-1
BUC-2
162.23
2.878
O6
161.78
2.851
O3 [-x+1, y, -z+1/2]
117.03
2.919
O1
171.08
2.724
O4 [-x+1, y, -z+1/2]
172.94
2.971
O4 [x+1/2, -y+1/2, z+1/2]
TE D EP AC C
O4 [-x+3/2, -y+1/2, -z+1]
M AN U
BUC-3
O4
ACCEPTED MANUSCRIPT Table 4 Parameters of pseudo-first-order kinetics for photocatalytic reactions of MB and MO dyes in BUC 1 – 3
BUC-1
BUC-2
BUC-3
R2
k(min-1)
R2
k(min-1)
R2
MB
0.0080
0.9859
0.0027
0.9733
0.0027
0.9330
MO
0.0513
0.8636
0.0018
0.9048
0.0053
0.9882
AC C
EP
TE D
M AN U
SC
RI PT
k(min-1)
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Fig. 1 (a) Asymmetric unit of [Co2(bpy)2(nbda)2(H2O)2]·2H2O (BUC-1) and coordination environments around the Co atoms. Water molecules and corresponding H atoms was omitted for clarify. (b) Packing view of 2D [Co2(bpy)2(nbda)2]n sheet for
AC C
EP
b-axis for BUC-1.
TE D
BUC-1. (c) and (d) The coordination environment of H2nbda. (e) Packing view of the three-dimensional framework along the
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 2 UV-Visible diffuse reflectance spectra of BUC 1 - 3.
TE D
M AN U
SC
RI PT
ACCEPTED MANUSCRIPT
Fig. 3 (a) Plots of concentration vs. irradiation time for MB and MO under irradiation by Hg lamp light with BUC 1 - 3 as photocatalysts. (b) and (c) UV-Vis absorption spectra of MB (b) and MO (c) solution during the decomposition reaction under (d) and (e) UV-Vis absorption spectra of MB (d) and MO (e) solution during the
EP
Hg lamplight irradiation with BUC-1.
decomposition reaction under Hg lamplight irradiation with BUC-1 and radical scavenger (IPA). (f). organic dyes removal
AC C
percentage under UV light irradiation in different conditions with BUC-1.
SC
RI PT
ACCEPTED MANUSCRIPT
Fig. 4 (a) The cycling of the degradation of MO (10 mg/L) over BUC-1 in the UV light system. (b). PXRD patterns of BUC-1
AC C
EP
TE D
M AN U
before and after photocatalytic reaction and the simulated XRD pattern from the single crystal structure of BUC-1.
ACCEPTED MANUSCRIPT
Highlights
Three 2D coordination polymers are constructed by typical 4,4′-bipyridine and stereo
The title coordination polymers exhibit different photocatalytic degradation ability to decompose methylene blue and methyl orange under UV light irradiation.
EP
TE D
M AN U
experiments using isopropanol as radical scavenger.
SC
A possible photocatalytic mechanism was proposed, which was confirmed by radicals trapping
AC C
RI PT
2,3-norbornanedicarboxylic acid.