NaI

Article pubs.acs.org/crystal

Heterotrimetallic Organic Framework Assembled with FeIII/BaII/NaI and Schiff Base: Structure and Visible Photocatalytic Degradation of Chlorophenols Hui-Hui Wang,† Jin Yang,† Ying-Ying Liu,*,† Shuyan Song,*,‡ and Jian-Fang Ma*,† †

Key Lab of Polyoxometalate Science, Department of Chemistry, Northeast Normal University, Changchun 130024, P. R. China State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, P. R. China

‡

Downloaded by UNIV OF CAMBRIDGE on September 12, 2015 | http://pubs.acs.org Publication Date (Web): September 11, 2015 | doi: 10.1021/acs.cgd.5b00925

S Supporting Information *

ABSTRACT: A porous heterotrimetallic organic framework, [BaNa(FeL)2(μ2OH)(H2O)]·DMF·2H2O (1) [H4L = 1,2-cyclohexanediamino-N,N′-bis(3-methyl5-carboxysalicylidene)], has been synthesized and characterized. Each FeIII ion is embedded in the internal [N2O2] pocket of an L4− anion and further bridged by a μ2OH anion to give an (FeL)2(μ2-OH) dimer. The external carboxylate groups of L4− anions coordinate to BaII and NaI atoms to generate a three-dimensional periodic network. The sorption properties and UV−vis spectrum of 1 have been studied. The photodegradation of 2-chlorophenol (2-CP), 3-CP, and 4-CP by 1 at different pH values under visible light has also been systematically investigated.

■

other frameworks using this strategy. As far as we know, FeIIIcontaining ternary HMOFs based on Schiff base ligands have not been documented previously. Herein we report the synthesis of an unprecedented ternary HMOF based on FeIII/BaII/NaI metals and the H4L ligand, namely, [BaNa(FeL)2(μ2-OH)(H2O)]·DMF·2H2O (1). The compound was characterized by IR spectroscopy, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). Particularly, we also systematically investigated the photocatalytic degradation of 2-CP, 3-CP, and 4-CP by 1 under visible-light irradiation.

INTRODUCTION The sustained attention on heterometallic transition metal complexes arises from their diverse applications, such as magnetic materials, gas adsorption, and heterogeneous catalysis.1−13 In this context, functionalized Schiff base ligands are well-known and are good candidates for the generation of heterometallic complexes.14−20 Various heterobimetallic and heterotrimetallic compounds have been designed and investigated, such as V/Mn, V/Fe, Fe/Cu, Fe/Cu/Co, and Cu/Co/ Ni compositions.21−25 Among these, the limited ternary metallic complexes display discrete or multinuclear structures. Moreover, they have shown catalytic ability to oxidize alkanes.21 Photocatalysis is a topic of contemporary research interest that has been used widely in many fields such as elimination of gas/water pollutants, catalysis, and chemical separations.26−33 Work on enhancing the activity and reactive selectivity of photocatalysts is ongoing because they are required for applications. For quite some time, we have had an ongoing project involving the syntheses of FeIII-containing heterometallic organic frameworks (HMOFs) because of their photocatalytic ability toward organic pollutants.34 Our group recently reported two binary HMOFs constructed from Zn(Cd)/Fe metals and a dicarboxyl-functionalized Schiff base ligand, 1,2-cyclohexanediamino-N,N′-bis(3-methyl-5-carboxysalicylidene) (H4L), and we also carried out a pioneering study of their photocatalytic degradation of 2-chlorophenol (2-CP) under visible-light irradiation.34 Aiming to further explore possible ways of synthesizing HMOFs and further applications in photocatalytic decomposition, we have attempted to produce © XXXX American Chemical Society

■

EXPERIMENTAL SECTION

Synthesis of 1. BaCl2·2H2O (0.020 g, 0.12 mmol), H4L (0.013 g, 0.03 mmol), FeCl3·6H2O (0.009 g, 0.03 mmol), NaCl (0.004 g, 0.06 mmol), N,N-dimethylformamide (DMF) (1 mL), EtOH (4 mL), and water (2 mL) were mixed to obtain a brown suspension. The mixture was placed in a Teflon reactor, heated at 100 °C for 3 days, and then slowly cooled to room temperature. The brown crystals were filtered, washed with H2O, and dried in air (yield: 31%). Anal. Calcd for C51H51N5O17Fe2BaNa (Mr = 1277.34): C, 47.91; H, 3.99; N, 5.48. Found: C, 47.78; H, 3.86; N, 5.32. IR (cm−1): 3394 (m), 2932 (w), 2858 (w), 1607 (w), 1565 (w), 1388 (w), 1308 (w), 1286 (w), 1217 (w), 1122 (m), 1027 (s), 978 (s), 952 (s), 919 (s), 861 (s), 794 (m), 760 (m), 712 (m), 582 (m). Received: July 3, 2015 Revised: September 2, 2015

A

DOI: 10.1021/acs.cgd.5b00925 Cryst. Growth Des. XXXX, XXX, XXX−XXX

Crystal Growth & Design

Article

Crystal Data for 1. C51H51N5O17Fe2BaNa, M = 1278.00, orthorhombic, space group F222, T = 20 °C, a = 31.955(3) Å, b = 65.386(2) Å, c = 12.9570(16) Å, α = β = γ = 90°, V = 27072(4) Å3, Z = 16, Dcalc = 1.116 g·cm−3, a total of 9112 reflections were collected, Rint = 0.0437, final R1 = 0.0818 for I > 2σ(I), wR2 = 0.2554 for all data, GOF = 1.026.


■

RESULTS AND DISCUSSION

Crystal Structure of [BaNa(FeL)2(μ2-OH)(H2O)]·DMF· 2H2O (1). The single-crystal X-ray diffraction study revealed that 1 crystallizes in the orthorhombic space group F222. As shown in Figure 1a, the asymmetric unit consists of two kinds of FeL units, three kinds of unique BaII ions (in which Ba1 and Ba2 are quarter-occupied and Ba3 is half-occupied), two halves of NaI ions, two kinds of L4− anions, two halves of μ2-OH anions, two halves of coordinated water, one free DMF, and two free water molecules. Each FeIII ion lies at an inversion center and possesses a square-pyramidal [N2O3] sphere that is completed by the internal pocket of an L4− anion and one μ2OH anion. Two FeL units are further bridged by a μ2-OH anion to give an (FeL)2(μ2-OH) dimer (Figure 1b).35,36 Three unique BaII ions exhibit two types of coordination geometry. Each Ba1 and Ba2 ion is octacoordinated by oxygen atoms from eight distinct L4− anions. Ba3 is hexacoordinated by four L4− anions and two coordinated water molecules, exhibiting a distorted octahedral coordination sphere. Both NaI ions are tetracoordinated by oxygen atoms. Two forms of L4− anions coordinate to (three Ba/two Na) and (two Ba/two Na) atoms, respectively. In this way, a porous three-dimensional (3D) framework is engendered. The pores of the net have an effective window size of approximately 12.679 Å × 14.541 Å along the crystallographic b and a axes, respectively (Figure 1c). Sorption and PXRD Patterns. Compound 1 contains potential channels, so the crystals were evacuated at 130 °C under vacuum for 5 h to acquire the activated sample. The N2, CO2, and water vapor adsorption properties of 1 were studied under different conditions (Figure S2). Compound 1 assimilates a spot of N2 (17.19 cm3/g) with a Brunauer− Emmett−Teller (BET) surface area of 47.83 m2/g at −196 °C as well as a low CO2 uptake (11.89 cm3/g) at 20 °C.37,38 As expected, 1 also shows very low water vapor adsorption at 20 °C (1.64 cm3/g).39 These results suggest that the flexible framework of 1 tends to shrink upon the activation process. The activated crystals and the sample after gas adsorption both kept their structural stabilities according to the PXRD patterns (Figure S3). UV−Vis Spectra. The UV−vis spectra of solid-state ligand H4L and compound 1 were measured (Figure S4). Two absorption bands of H4L centered at 267 and 415 nm can be ascribed to π* → π or π* → n transitions. Compound 1 exhibits a broad band over almost the entire test region. Two obvious peaks in the UV region are mainly attributed to ligand absorption. The additional absorption above 450 nm in the visible region is dominated by d−d transitions of the coordinated metal ions.40,41 Photocatalytic Properties. Persistent organic pollutants (POPs) possess the characteristics of high toxicity, bioaccumulation, long-time persistentence, and long-distance migration. As a series of POPs, CPs have been enjoyed worldwide attention.42,43 In this study, the ability of catalyst 1 to degrade 2-CP, 3-CP, and 4-CP under visible-light irradiation was investigated. The irradiated samples were analyzed using gas chromatography (GC) during the process. Systematically, the

Figure 1. (a) Coordination environments of the metal atoms. (b) Structure of an (FeL)2(μ2-OH) dimer. (c) View of the 3D porous framework.

degradation effects of catalytic 1 on these CPs at pH 3, 4, and 6 as a function of irradiation time were measured (Figures 2−4). The blank experiments were conducted without any catalyst under similar conditions (Figure S5). As shown in Figure 2, the photocatalytic activity of 1 toward 2-CP increased from 24.2% (without catalyst) to 33.3% (pH 6), B




Article

Figure 2. Changes in the mass of 2-CP (a) without any catalyst and (b−d) with the addition of catalyst at (b) pH 3, (c) pH 4, and (d) pH 6. (e) Merged catalytic results for 2-CP at different pH values.

improve the electron density of the carbon atoms at the para and ortho positions. As a consequence, these two positions are readily attacked by electrophilic reagents. This may mainly lead to the result that the photocatalytic activity toward 4-CP is higher than those toward 2-CP and 3-CP. Other factors such as the number and the nature of the intermediates may also have an impact on the degradation rate of CPs.45 Unprecedentedly, this is the first systematic investigation of photocatalytic degradation of CPs using a trimetal-based HMOF as a catalyst under visible-light irradiation. In order to confirm the stability of the structure, fresh crystals and crystals used as catalysts were characterized by PXRD (Figure 6). The PXRD pattern after photocatalysis is nearly identical to that of the original sample. The results prove that

41.7% (pH 4), and 55.5% (pH 3) after irradiation for 80 min. The activity increased as the pH decreased, and obviously, the best degradation efficiency toward 2-CP was at pH 3. The photocatalytic activities of 1 toward 3-CP and 4-CP (Figures 3 and 4) show that the best degradation efficiencies after irradiation for 80 min were 40.3% (pH 4) and 71% (pH 3), respectively. On the basis of these findings, we postulate that the catalytic activity of 1 is favored under acidic conditions. The results also demonstrate that the photocatalytic activity ranked in the order meta < ortho < para with respect to substituent position (Figure 5). It is clear that the position discrimination of the chloro substituent leads to this photocatalytic degradation difference.44−46 As an electron-donating group, −OH can C




Article


tert-butyl alcohol (TBA) under the best degradation efficiency conditions, as it is well-known that photocatalytic degradation is supposed to depend on ·OH radicals. TBA is a typical hydroxyl radical remover that can capture ·OH radicals as fast as possible.44,47,48 Thus, TBA was utilized here as a probe molecule to test whether ·OH radicals are involved in the reaction process. As depicted in Figure 7, a lower rate of photocatalytic degradation was observed upon the addition of TBA. The catalytic efficiency of the system was found to decrease from 71% to 23% in the presence of TBA. That is, the photodegradation process with 1 as the catalyst predominantly depends on ·OH radicals to attack the aromatic ring of 4-CP.

the crystals can maintain crystallinity after experiments and that the stability of the structure in the process of photocatalysis is good. For the sake of testing the reproducible capability of compound 1, we conducted further photocatalytic tests with recycled catalyst and 4-CP at pH 3 under identical circumstances. The results suggested that the activity decreased, dropping from 71.0% to 65.7%, and 59.6% after recycling three times (Figure S6). The PXRD patterns confirmed that the stability of the structure is good (Figure S7). To elaborate the potential photocatalytic reaction pathway, the experiment with 4-CP was performed in the presence of D




Article


O] and ·OH radicals are generated. The ·OH radicals more easily react with CPs, leading to the formation of small degradation products immediately.43−46,49 Further filtration experiments of 1 and inductively coupled plasma (ICP) measurements of FeIII ions were performed to rule out the possibility that the ·OH radicals originated from leaching of FeIII ions into the filtrate. Typically, the suspensions of 4-CP at pH 3 after 20 min were filtered to remove the catalyst, and the degradation effects of the filtrate versus

On the basis of above experimental findings and the literature, a possible route for the generation of ·OH radicals over catalyst 1 is proposed (Figure 8). It is generally accepted that the basic [L−FeIII] units of catalyst 1 easily form [L−FeIII− OH] species in aqueous solution.49 Then, the nucleophilic addition reagent H2O2 adds to the FeIII center, yielding [L− FeIII−OOH] species. Under visible-light irradiation, [L-FeIIIOOH] undergoes a transition to the [L−FeIII−OOH]* excited state. After that, through rupture of the O−O bond, [L−FeV E



Article

Figure 8. Possible route for the generation of ·OH radicals over catalyst 1 with H2O2 as the oxidant.


Figure 5. Comparison of the best degradation efficiencies toward the three CPs at different pH values.

(9%; Figure 4a). It turns out that the ·OH radicals involved in the reaction mainly originated from the Fe-based MOFs. The ICP measurements also indicated that there were no FeIII ions in the filtrate.

■

CONCLUSIONS We have successfully developed a new procedure to synthesize ternary HMOFs, and one heterotrimetallic 3D framework based on FeIII/BaII/NaI metals and a dicarboxyl-functionalized Schiff base has been synthesized. The photodegradation of 2CP, 3-CP, and 4-CP by catalyst 1 at different pH values under visible light was investigated systematically. The results indicate that 1 shows high and stable photocatalytic activity toward 4CP at pH 3. This photocatalyst offers a new potential possibility for degrading persistent organic pollutants in aquatic environments under visible-light irradiation.

■

ASSOCIATED CONTENT

S Supporting Information *

Figure 6. PXRD patterns for 1: simulated (black), experimental (red), and after degradation of 4-CP at pH 3 (blue).

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.cgd.5b00925. Characterization, TGA curves, sorption isotherms, PXRD patterns, UV−vis spectra, histograms of CPs, selected bond lengths and angles, and GC of CPs (PDF) Crystallographic data for 1 (CIF)

irradiation time were measured. As shown in Figure S8, the degradation of 4-CP in the filtrate of 1 (12%) is far less than that of the reaction system with catalyst (37%; Figure 4b) and is closer to that found in the blank experiment without catalyst

Figure 7. (a) Changes in the mass of 4-CP under visible-light irradiation with 1 as the catalyst in the presence of TBA at pH 3. (b) Comparison of photocatalytic degradation abilities at pH 3 with 1 as catalyst only (blue), with 1 in the presence of TBA (red), and without catalyst (green). F



■

Article

(26) Gupta, K. C.; Sutar, A. K. Coord. Chem. Rev. 2008, 252, 1420− 1450. (27) Yoon, H.; Burrows, C. J. J. Am. Chem. Soc. 1988, 110, 4087− 4089. (28) Mirkhani, V.; Moghadam, M.; Tangestaninejad, S.; Mohammadpoor-Baltork, L.; Shams, E.; Rasouli, N. Appl. Catal., A 2008, 334, 106−111. (29) Huang, Y. B.; Liu, T. F.; Lin, J. X.; Lü, J.; Lin, Z. J.; Cao, R. Inorg. Chem. 2011, 50, 2191−2198. (30) Zhang, S. Q.; Han, L.; Li, L. N.; Cheng, J.; Yuan, D. Q.; Luo, J. H. Cryst. Growth Des. 2013, 13, 5466−5472. (31) Huang, M. L.; Yan, Y.; Feng, W. H.; Weng, S. X.; Zheng, Z. Y.; Fu, X. Z.; Liu, P. Cryst. Growth Des. 2014, 14, 2179−2186. (32) Ferreira, R.; García, H.; de Castro, B.; Freire, C. Eur. J. Inorg. Chem. 2005, 4272−4279. (33) Wen, L. L.; Wang, F.; Feng, J.; Lv, K. L.; Wang, C. G.; Li, D. F. Cryst. Growth Des. 2009, 9, 3581−3589. (34) Li, J.; Yang, J.; Liu, Y.-Y.; Ma, J.-F. Chem. - Eur. J. 2015, 21, 4413−4421. (35) Cho, Y. I.; Joseph, D. M.; Rose, M. J. Inorg. Chem. 2013, 52, 13298−13300. (36) Coggins, M. K.; Toledo, S.; Kovacs, J. A. Inorg. Chem. 2013, 52, 13325−13331. (37) Wang, S.; Wang, X. Small 2015, 11, 3097−3112. (38) Wang, S.; Lin, J.; Wang, X. Phys. Chem. Chem. Phys. 2014, 16, 14656−14660. (39) Liu, Y.; Liu, S.; Lai, X.; Miao, J.; He, D.; Li, N.; Luo, F.; Shi, Z.; Liu, S. Adv. Funct. Mater. 2015, 25, 4480−4485. (40) Wang, C.; Dekrafft, K. E.; Lin, W. J. Am. Chem. Soc. 2012, 134, 7211−7214. (41) Alvaro, M.; Carbonell, E.; Ferrer, B.; Llabrés i Xamena, F. X.; Garcia, H. Chem. - Eur. J. 2007, 13, 5106−5112. (42) Sharma, S.; Mukhopadhyay, M.; Murthy, Z. V. P. Ind. Eng. Chem. Res. 2010, 49, 3094−3098. (43) Lei, L. C.; Zhang, Y.; Zhang, X. W.; Du, Y. X.; Dai, Q. Z.; Han, S. Ind. Eng. Chem. Res. 2007, 46, 5469−5477. (44) Ding, X.; Zhao, K.; Zhang, L. Z. Environ. Sci. Technol. 2014, 48, 5823−5831. (45) Devi, L. G.; Krishnamurthy, G. J. Phys. Chem. A 2011, 115, 460−469. (46) Vallejo, M.; San Román, M. F.; Ortiz, I. Environ. Sci. Technol. 2013, 47, 12400−12408. (47) Wang, H.; Wang, J. L. Appl. Catal., B 2009, 89, 111−117. (48) Huang, C. P.; Chu, C.-s. J. Environ. Eng. 2012, 138, 375−385. (49) Huang, Y. P.; Li, J.; Ma, W. H.; Cheng, M. M.; Zhao, J. C.; Yu, J. C. J. Phys. Chem. B 2004, 108, 7263−7270.

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. *E-mail: [email protected]. *E-mail: [email protected]. Fax: +86-431-85098620. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We thank the National Natural Science Foundation of China (Grants 21471029, 21301026, 21277022, and 21371030) and the Open Funds for the Key Lab of Polyoxometalate Science of the Ministry of Education.


■

REFERENCES

(1) Manna, K.; Zhang, T.; Lin, W. J. Am. Chem. Soc. 2014, 136, 6566−6569. (2) Sun, D.; Ye, L.; Li, Z. Appl. Catal., B 2015, 164, 428−432. (3) Wang, D.; Li, Z. Catal. Sci. Technol. 2015, 5, 1623−1628. (4) Wang, S.; Yao, W.; Lin, J.; Ding, Z.; Wang, X. Angew. Chem., Int. Ed. 2014, 53, 1034−1038. (5) Fu, Y.; Sun, D.; Chen, Y.; Huang, R.; Ding, Z.; Fu, X.; Li, Z. Angew. Chem., Int. Ed. 2012, 51, 3364−3367. (6) Sun, D.; Fu, Y.; Liu, W.; Ye, L.; Wang, D.; Yang, L.; Fu, X.; Li, Z. Chem. - Eur. J. 2013, 19, 14279−14285. (7) Wang, C.; Xie, Z.; Dekrafft, K. E.; Lin, W. J. Am. Chem. Soc. 2011, 133, 13445−13454. (8) Wang, D.; Huang, R.; Liu, W.; Sun, D.; Li, Z. ACS Catal. 2014, 4, 4254−4260. (9) Silva, C. G.; Luz, I.; Llabrés i Xamena, F. X.; Corma, A.; García, H. Chem. - Eur. J. 2010, 16, 11133−11138. (10) Li, H.; Han, Y.-F.; Lin, Y.-J.; Guo, Z.-W.; Jin, G.-X. J. Am. Chem. Soc. 2014, 136, 2982−2985. (11) Huang, S.-L.; Lin, Y.-J.; Hor, T. S. A.; Jin, G.-X. J. Am. Chem. Soc. 2013, 135, 8125−8128. (12) Buchwalter, P.; Rosè, J.; Braunstein, P. Chem. Rev. 2015, 115, 28−126. (13) Qian, J. J.; Jiang, F. L.; Su, K. Z.; Pan, J.; Liang, L. F.; Mao, L. F.; Hong, M. C. Cryst. Growth Des. 2015, 15, 1440−1445. (14) Song, F. J.; Wang, C.; Falkowski, J. M.; Ma, L. Q.; Lin, W. B. J. Am. Chem. Soc. 2010, 132, 15390−15398. (15) Liao, S.; Yang, X. P.; Jones, R. Cryst. Growth Des. 2012, 12, 970− 974. (16) Bogaerts, T.; Van Yperen-DeDeyne, A.; Liu, Y- Y.; Lynen, F.; Van Speybroeck, V.; Van Der Voort, P. Chem. Commun. 2013, 49, 8021−8023. (17) Yang, Z. W.; Zhu, C. F.; Li, Z. J.; Liu, Y.; Liu, G. H.; Cui, Y. Chem. Commun. 2014, 50, 8775−8778. (18) Zhang, H. D.; Xiang, S.; Li, C. Chem. Commun. 2005, 1209− 1211. (19) Chidara, V. K.; Du, G. D. Organometallics 2013, 32, 5034−5037. (20) Haak, R. M.; Decortes, A.; Escudero-Adán, E. C. E.; Belmonte, M. M.; Martin, E.; Benet-Buchholz, J.; Kleij, A. W. Inorg. Chem. 2011, 50, 7934−7936. (21) Nesterov, D. S.; Chygorin, E. N.; Kokozay, V. N.; Bon, V. V.; Boča, R.; Kozlov, V. N.; Shul’pina, L. S.; Jezierska, J.; Ozarowski, A.; Pombeiro, A. J. L.; Shul’pin, J. B. Inorg. Chem. 2012, 51, 9110−9122. (22) Bhattacharya, K.; Abtab, S. M. T.; Majee, M. C.; Endo, A.; Chaudhury, M. Inorg. Chem. 2014, 53, 8287−8297. (23) Nesterov, D. S.; Kokozay, V. N.; Dyakonenko, V. V.; Shishkin, O. V.; Jezierska, J.; Ozarowski, A.; Kirillov, A. M.; Kopylovich, M. N.; Pombeiro, A. L. Chem. Commun. 2006, 4605−4607. (24) Du, S. W.; Zhu, N. Y.; Chen, P. C.; Wu, S. T.; Lu, J. X. J. Chem. Soc., Dalton Trans. 1992, 339−344. (25) Nesterov, D. S.; Kokozay, V. N.; Jezierska, J.; Pavlyuk, O. V.; Boča, R.; Pombeiro, A. J. L. Inorg. Chem. 2011, 50, 4401−4411. G


NaI

Recommend Documents