Effect of Cosolvent and Temperature on the Structures and Properties

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Effect of Co-solvent and Temperature on the Structures and Properties of Cu-MOF-74 in Low-temperature NH3-SCR Haoxi Jiang, Jiali Zhou, Caixia Wang, Yonghui Li, Yifei Chen, and Minhua Zhang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.6b03568 • Publication Date (Web): 13 Mar 2017 Downloaded from http://pubs.acs.org on March 17, 2017

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Industrial & Engineering Chemistry Research

Effect of Co-solvent and Temperature on the Structures and Properties of Cu-MOF-74 in Low-temperature NH3-SCR Haoxi Jianga,b, Jiali Zhoua,b, Caixia Wanga,b, Yonghui Li a,b*, Yifei Chen a,b, Minhua Zhang a,b a

Key Laboratory for Green Chemical Technology of Ministry of Education, R&D Center for Petrochemical Technology, Tianjin University, Tianjin 300072, China b Collaborative Innovation Center of Chemical Science and Engineering, Tianjin 300072, China *Corresponding author. Tel.: +86-22-27406119; fax: +86-22-27406119. E-mail address: [email protected]

Abstract: The novel Cu-MOF-74 materials were synthesized with various co-solvents at different temperatures by solvent-thermal method and then developed as the NO removing catalysts for low temperature selective catalytic reduction (SCR) with NH3. The physico-chemical properties of catalyst samples were characterized by multiple techniques, such as N2 adsorption−desorption, X-ray diffraction (XRD), scanning electron microscope (SEM), temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS). The effects of co-solvent on the catalysts performances were systematically investigated. It was found that Cu-MOF-74-iso-80 catalyst showed the highest NH3-SCR activity, giving 97.8% NO conversion and 100% N2 selectivity at 230 °C. BET test results suggested that Cu-MOF-74 showed larger specific surface area. The stronger NH3 adsorption ability was found, which could be beneficial for SCR at low-temperature. The catalyst also showed better water resistant performance. The adverse effect of H2O added intermittently could be quickly eliminated when the water environment was removed.

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Keyword: Cu-MOF-74; Solvothermal synthesis; Co-solvent and temperature effect; SCR; DeNOx 1. Introduction Nitrogen oxides (NO, NO2, and N2O) are well known as the major air pollutants which have a harmful effect on environment, such as photochemical smog, acid rain, ozone depletion and greenhouse effect[1, 2]. In recent years, the selective catalytic reduction (SCR) of nitrogen oxides by ammonia has become an efficient purification technique to eliminate NOx[3]. Some commercial catalysts based on V2O5/TiO2 have been widely used in the industrial processes[4], however, the disadvantage of rather high operating temperature (as high as 300-400 °C) cannot be ignored. Therefore, the searching for novel catalysts with high SCR activities at lower temperature below 250 °C is carried out actively. Over the past two decades, the metal–organic frameworks materials have attracted considerable attentions as they exhibit eminently promising properties: high specific surface areas, high porosity, well-defined structures and chemical tenability[5, 6]

. Hence, these materials are suitable for applications in gas storage[7], separation[8]

and particularly in catalysis[9]. M-MOF-74 (also known as CPO-27-M) series, which having formula M2(dobdc) (M = Cu, Mg, Mn, Co, Ni, Zn; dobdc4− is 2,5-dioxido-1,4 -benzenedicarboxylate) is an intensively studied structure type with versatile properties[10, 11]. The structure of M-MOF-74 features 12 Å wide hexagonal channels, lined with M2+ ions whose open coordination sites point directly into the channel[12]. The octahedral coordination of mental ions in M-MOF-74 materials is coordinate with six oxygen atoms. Three of them are from the carboxyl oxygen atoms in the ligand,


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two are from the oxygen atom of the hydroxyl group in the ligand, and the sixth one is from the oxygen atom in a solvent (such as DMF, methanol or H2O). The solvent molecules can be easily removed in vacuum or at high temperatures, providing the exposed unsaturated metal sites. The topology of MOF-74 has one of the highest known densities of open metal site. Recently, Sanz et al.[6] has reported the synthesis of Cu analogue of M-MOF-74, which is attracted extensive attentions. Due to the Jahn–Teller distortion of the Cu2+ octahedral, the coordination environment of the Cu2+ ions in MOF-74 or CPO-27 structure is distorted and one of the Cu2+−O bonds is elongated. As a result, the Cu2+ ions in Cu-MOF-74 exhibit a low partial positive charge[13]. Such a distortion could also cause the slightly lower enthalpy as the higher distances between the Cu2+ sites and the adsorbate molecules, compared to those in other transitional metal homologues. However, the residual solvent molecules can be desorbed easily and completely, leading to the MOF structure that can be full-desolvated to expose a greater number of open metal coordination sites[14]. In the synthesis of MOFs under hydrothermal or solvothermal conditions, the increase of temperature is favorable for the formation of single crystals. However, Cu2O and other by-products would be obtained at the high temperature. Therefore, the reaction temperature plays a crucial role in directing the formation of MOFs[15, 16]. Meanwhile, co-solvent plays the dominant role in affecting the coordination geometry of metal ions for formation of topological structure of MOF-type materials[17].



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Therefore, a sensible choice of reaction co-solvent is of great importance in the synthesis of porous MOFs. In this paper, the influences of synthetic temperature and co-solvent on the physic-chemical properties (ie. morphology, crystal structure, thermal stability and adsorption capacity) of Cu-MOF-74 have been studied. Then the catalytic activities of Cu-MOF-74 as prepared for the low temperature NH3-SCR of NOx have been investigated. 2. Experiment 2.1 Catalysts preparation The Cu-MOF-74-iso sample was synthesized by the solvent-thermal method according to the procedure described by Sanz et al.[6]. In a typical experimental procedure, a mixture of 2,5-dihydroxyterephthalic acid (H2dhtp) and trihydrated copper nitrate(II) (2.2 g and 5.9 g respectively) was added to the 20:1 (v/v) mixed solution consisted of N,N-dimethylformamide (DMF) and isopropanol (250 ml). The suspension was stirred for about 15 min until homogeneous solution was obtained. This homogeneous solution was then transferred into five Teflon-lined stainless steel autoclaves with the capacity of 100 ml, separately. The autoclaves were sealed, and then the mixtures were hydrothermally treated at 80 °C for 18 h. After the autoclave was cooled down to room temperature naturally, the reddish crystals were collected by vacuum filtration and washed several times using DMF. Afterwards, the crystals were immersed in 100 mL of methanol for 3 days, renewed by fresh solvent every 12 h. Finally, the preliminary product was obtained after vacuum filtration and stored in


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desiccator. This catalyst sample was denoted as Cu-MOF-74-iso-80, where iso and 80 were meaned as the co-solvent (of isopropanol) and the preparation temperature of 80°C, respectively. The synthesis procedure of Cu-MOF-74-eth was slightly modified from the reported

preparation

method

of

Mn-MOF-74[18].

H2dhtp

(0.888

g)

and

Cu(NO3)2•3H2O (3.574 g) were dissolved in a 15:1:1 (volumetric ratios) mixture consisted of DMF, ethanol and water (400 ml). The solution was filled in five 100 ml autoclaves with Teflon liners, separately, and heated to 80 °C or 60 °C for 24 h. Other preparation steps followed the same procedure described above. The prepared samples were denoted as Cu-MOF-74-eth-X, where eth and X are the co-solvent ethanol and the numerical value of preparation temperatures (60 °C or 80 °C), respectively. 2.2 Characterization The crystal structures of Cu-MOF-74 samples were carried out by X-ray diffraction technique (XRD) on the instrument Rigaku D/Max 2500 X-ray diffractometer with Cu Kα radiation. The morphologies of all the samples were characterized by scanning electron microscope (SEM) on Hitachi S-4800 electronic microscope. The nitrogen adsorption-desorption isotherms were measured with the adsorption-desorption test instrument of Micromeritics Tristar 3000 using nitrogen at the low temperature of 77 K. The data on the specific surface area, micropore volume, and

mesoporous

pore

volume

were

calculated

by

the

formulas

of

Brunauer-Emmett-Teller (BET), Horvath-Kawazoe (HK) and Barrett-Joyner–Halenda (BJH), respectively. The thermal stability performance of the samples was measured



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using the thermo gravimetric analyzer (METTLER DSTA851), which was followed by the mass spectroscopic analyzer (Balzers PFEIFFER Thermo Star

TM

). The X-ray

photoelectron spectra (XPS) were acquired with the Perkin Elmer PHI-1600 X-ray spectrometer equipped with an Mg Kα radiation source by adjusting the binding energy (B.E.) of C 1s peak to 284.6 eV. The copper contents in the samples were determined by the inductively coupled plasma optic emission spectrometry (ICP-OES), on the instrument of Vista-MPX, USA. Using NH3 or NO as probe molecules, the temperature-programmed desorption (NH3-TPD or NO-TPD) experiments were performed on the AutoChemII 2920 adsorption testing instrument (Micromeritic, USA). First, about 30-50 mg of every catalyst sample was loaded in the sample tube, and pretreated in a He stream (flow rate of 50 ml/min) at 230 °C for 3 h, and then cooled to 100 °C in the same stream. The pretreated sample was then exposed to 1 % NH3 (or NO) in He mixed stream at a flow rate of 40 ml/min for 1 h. Before starting the TPD test experiment, the physically adsorbed NH3 (or NO) was removed by flushing the catalyst samples with He stream at the flow rate of 30 ml/min for 1 h. The NH3 (or NO)-TPD curves were recorded by linear- programmly heating the samples in He stream from 100 to 400 °C at the heating rate of 10 °C/min. 2.3 Catalyst activity evaluation The SCR activity measurements were carried out in a fixed-bed quartz reactor at atmospheric pressure with the following reactant gas composition: 1000 ppm NO, 1000 ppm NH3, 2% O2, and the balance gas Ar. All catalyst samples (0.2 g, 60–80 mesh) were uniformly mixed with quartz sand (0.4 g). The total flow rate was 100


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ml/min (under ambient conditions), corresponding to a GHSV of 50,000 h−1. The activity tests were performed at the reaction temperature range from 80 to 240 °C and the system was always maintained for 1 h at the each test temperature condition. The NO and NO2 inlet concentrations were continually monitored by a flue gas analyzer (KM9106 produced by Quintox Kane Ltd.). The effluent streams were analyzed by gas chromatography at 30 °C (Agilent GC-6820, instrument, equipped with a 5 Å molecular sieve column for N2 and a Porapak Q column for N2O analysis). In order to remove the solvent and open the void space for desired guest molecules, MOF materials need to be activated at elevated temperature at 230 °C under N2 atmosphere for 3 h and then cooled to 80 °C in a flow of N2 before the activity evaluation of Cu-MOF-74 materials. The activated temperature was determined according to the TG curves of Cu-MOF-74 under N2 atmosphere (as shown in Fig. 4a). Therefore, all solvent molecules can be removed. 3. Results and discussion 3.1 Structure characterization The powder X-ray diffraction patterns of Cu-MOF-74 are shown in Fig. 1. Peak broaden of Cu-MOF-74 can be observed carefully compared to simulation result[12], which was mainly due to the defect sites in the prepared MOF structure and the variations of degree of hydration[19, 20]. It can be clearly seen from Fig. 1 that the ratio of the two intensity of characteristic peaks: I300/I2-10 follows the degradation order of eth-65 > iso-80 > eth-80. Generally speaking, the crystal structures become more perfect and the relative intensity of characteristic diffraction peaks are getting closer



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to simulation values with increasing synthesis temperatures. Table 1 shows the lattice parameters obtained from the calculation of the characteristic diffraction peaks for (2 -1 0) and (3 0 0) lattice planes. The difference from lattice parameters may be related to the Jahn−Teller effect[6, 13, 14, 21]. Because Cu2+ ions in MOFs are in coordination environment with distortion, the strength and distance between the Cu2+ sites and the adsorbate molecules are different. Therefore, MOFs structure had a slight deformation after removal of solvent. The SEM images of Cu-MOF-74 samples are shown in Fig. 2. It can be seen that the Cu-MOF-74 synthesized by using isopropyl alcohol shows rod-like structure for scattered distribution, while that was synthesized by ethanol method, shows bouquet-like structure. Different morphologies may be related to the growing environment of the crystal surface of Cu-MOF-74. The aqueous solution of ethanol (volumetric ratio of 1:1) might result in the stronger hydration. The degree of deionization to ligand is smaller than those in isopropyl alcohol. As a result, crystal faces show preference for a certain direction, hence the prepared crystal can exhibit bouquet shape. It can be seen from the crystal end face observation of the samples, that all samples show hexagonal prism structure, which is mainly determined by the characteristic hexagonal crystal structure of Cu-MOF-74. The characteristics of pore structure of Cu-MOF-74 samples are obtained from nitrogen adsorption-desorption isotherms at 77 K and the test results are given in Fig. 3 and Table 2. From the comparison between test data, it can be concluded that 1) absorption isotherms for all samples follow Langmuir Ⅰtype model; 2) there exist


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hysteresis loops in the adsorption isotherms for eth-80 and eth-65, which indicate tentatively the existence of mesopores apart from that of micropores in these samples, while only micropores exists in iso-80. Compare the specific surface area of different samples, it can be found that higher specific surface area and pore volume, which were 1025 m2/g and 0.420 cm3/g respectively, could be obtained by the method using isopropyl alcohol. The specific surface areas of the samples prepared by ethanol method were relatively low (837.8 m2/g at 80 °C and 753.7 m2/g at 65 °C). This was mainly because the samples prepared by ethanol contained certain mesoporous structure, while only microporous structure exists in the samples synthesized by isopropyl alcohol. The specific surface area of eth-80 catalyst is larger than that of eth-65 catalyst, but its catalytic activity is lower than eth-65, which indicates that the BET specific surface area is not the predominant factor affecting the difference of eth-65 and eth-80 catalytic activity. 3.2 Thermal stability analysis The thermal stability of Cu-MOF-74 samples were studied under three different atmospheres (N2, 2%, air and the SCR reaction gases) in thermogravimetric analysis (TGA) experiments (Figure 4). The first weight loss of all the TGA curves up to around 100 °C can be attributed to the loss of methanol solvent. It can be seen from Fig. 4a that, after a plateau, a second step indicates the disintegration of the metal-organic structure from 310 °C (or so) on. The final collapse for Cu-MOF-74 occurred at 415 °C approximately with the weight loss of 52.5 %. In air (Fig. 4b), the frames of Cu-MOF-74 begin to decompose at about 223 to 247 °C, and completely



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collapse at about 260 °C with 61.3 % weight loss. Fig. 4c shows that Cu-MOF-74 decomposes at about 260 °C, and the significant final collapse is observed at about 370 °C. The order of thermal stability of Cu-MOF-74 in three different atmospheres is as follows: N2 > SCR reaction gases > air. It can be inferred that the stability of Cu-MOF-74 in a reducing atmosphere is higher than that under oxidizing atmosphere, mainly because the MOFs framework structure contains a number of carboxylic groups or hydroxyl groups, which can be easily oxidized to form H2O, resulting in the collapse of skeletal structure and decomposition. From the thermal stability data of the three Cu-MOF-74 samples under different atmospheres (as shown in Table 3), it can be observed that the stability order of the three samples is: iso-80 > eth-65 > eth-80, which is corresponded with the result of XRD. The smaller lattice parameters of Cu-MOF-74 lead to better integrity of crystal structure and higher degree of crystallinity, which would contribute to the frame with better thermal stability. 3.3 Surface chemical states and adsorption capacity XPS is performed to study the valence states of the as-prepared samples. Obvious signals from Cu, O and C elements are shown in the obtained XPS full spectra (Fig. 5(a),(c),(e)). The high-resolution of Cu 2p spectrum is shown in Figures 5 (b),(d),(f), which illuminates the coexistence of Cu2+ and Cu+ species on the surface of all samples. In order to determine the content of Cu in bulk phase of Cu-MOF-74 samples, the results of ICP analyses are shown in Table 4. It can be noted that the contents of Cu in bulk phase of different Cu-MOF-74 samples are not much different. It can be inferred that co-solvent and temperature have little influence on the content


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of Cu in bulk phase of Cu-MOF-74 materials. NH3-TPD and NO-TPD experiments are performed to study the distribution performances of acid sites on the surface of Cu-MOF-74 samples and their adsorption capacities for NH3 and NO. The results are shown in Fig. 6 and Fig. 7, respectively. As shown in Fig. 6 and Fig. 7, the solvents can apparently affect the adsorption capacity for NH3 and NO, respectively. Two desorption peaks (centered at 165.5 °C and 215.8 °C) of iso-80 are seen in the NH3-TPD results, while only one NH3-desorption peak (centered at 182.5 °C) is observed in eth-65 and eth-80. It can be inferred that there exist two kinds of weaker acid sites with different acidic strength in iso-80, and only one kind of weaker acid site both in eth-65 and eth-80. This phenomenon further indicates that the adsorption capacity for NH3 of iso-80 is much stronger than those of eth-65 and eth-80 catalysts. The total amount of NH3 desorption of Cu-MOF-74 sample are given in Table 5. We can notice that the total amount of NH3 desorption of these samples follows the degradation order of iso-80>eth-65>eth-80. That means the overall acidity of these samples follows the same order[22]. This fact indicates that, iso-80 sample catalyst shows more adsorption sites for the probe NH3. Hence, to some extent, iso-80 catalyst sample would be more beneficial for the NH3-SCR reaction, which differences correspond also to the results of catalytic activity test. The NO-TPD spectra of as-prepared Cu-MOF-74 samples are shown in Fig. 7, which are characterized by the well-resolved NO-desorption peaks. Two desorption peaks (centered at 138.0 °C and 213.9 °C for iso-80, and centered at 154.0 °C and



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191.6 °C for both eth-65 and eth-80) are detected for all prepared Cu-MOF-74 samples. Wherein, the peak temperatures of NO-desorption peaks are almost same, but the strength of high temperature NO-desorption peak for eth-65 is significantly weaker. Intriguingly, the strength of low NO-desorption peak for eth-X (X=65, 80) is higher than those of iso-X (X=80), while strength of the high temperature NO-desorption peak for eth-X (X=65, 80) is lower than those of iso-X(X=80). It can be concluded that there exist two kinds NO adsorption sites with different adsorption strengths, and the Cu-MOF-74 sample prepared using isopropanol as co-solvent shows stronger adsorption ability to probe molecule NO. According to the previous studies

[23,24]

, this result also reveals that the unstable or metastable nitrate species

would appear at low temperature. Besides, the stable nitrates would occupy the active sites on the surface of Cu-MOF-74 samples, and are not beneficial to catalyze the SCR reactions at low temperatures. Table 5 shows the differences in the areas of NO-desorption peaks per gram of Cu-MOF-74 samples. It is clearly observed that the area of NO-desorption peaks per gram of iso-80 sample is larger than those both of eth-65 and eth-80, which indicates that iso-80 has more adsorption sites for NH3. For the eth-X (X=60, 80) samples series, the peak area of NO-desorption per gram of eth-65 is larger than that of eth-80. That inflects eth-65 has a stronger adsorption capacity on NO than eth-80 does. This result is consistent with the SCR activity results. 3.4 Catalytic activity evaluation The DeNOx activities for Cu-MOF-74 samples are presented in Fig. 8. In general,


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the results show that all synthesized Cu-MOF-74 samples showed good catalytic performance within the sufficient low temperature window range. For all three prepared catalyst samples, the NO conversions increased with the increasing temperature, and the highest NO conversion of 97.8 % is attained at 230 °C. Chromatographic detection cannot find any information of N2O, indicating about 100 % N2 selectivity for all catalyst samples. The high catalytic activity of Cu-MOF-74 could be attributed to its strong adsorption capability for NH3 as reported in the literacture[23]. Evidently, Cu-MOF-74 sample prepared by isopropanol is more beneficial for this low-temperature SCR process. In such MOFs, the coordinatively unsaturated metal sites should be the active centers in the catalytic reaction. During the SCR reaction, the Cu open-metal sites in the framework are reactive as Lewis acid sites, which are accessible for the NOx adsorption and catalytic conversions[25,26]. Therefore, the two kinds of acidic sites (as shown in Fig. 6 and Fig. 7) could present in iso-80 sample simultaneously, resulting higher possibility for NH3-adsorption than those in eth-65 and eth-80, and finally facilitates high NOx conversions. Apart from iso-80, the total amount of NH3 desorption of eth-65 is larger than that of eth-80, which means eth-65 shows stronger overall acidity. What’s more, the peak area of NO of eth-80 is smaller than that of eth-65, which inflects eth-80 presents a weaker adsorption capacity on NO than eth-65. As a result, for eth-65 sample, its stronger overall acidity and adsorption capacity leads to its higher NO conversion. 3.5 Influences of H2O and SO2 on SCR reaction It is well known that water vapor can lead to deactivation of the SCR catalyst.



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Hence, in order to explore the stability of Cu-MOF-74 in the SCR atmosphere containing H2O, the water stability of Cu-MOF-74-iso-80 sample with better catalytic activity of SCR is further investigated. in two different ways: a) adding 5 % H2O into the SCR atmosphere directly before it enters the reactor; b) operating the SCR reaction at the optimum activation temperature (230 °C) and allow it to stabilize for 3 h before the addition of 5% H2O, then removing the H2O after 1h. It is clearly observed that adding 5% H2O into the inlet flow before the reaction shows a negative influence on the deNOx activity (as shown in Fig. 9). However, the NO conversion is still increased with the increase of temperatures and the catalyst exhibits the highest catalytic activity, which is close to the value before adding H2O, which shows NO conversion of 94.8 % at 230 °C. It is believed that competing adsorption between water and ammonia on the acid sites takes place, which could result in that the partial active sites on the catalyst surface are occupied by H2O. The H2O absorbed on the catalysts decreases with the increase of the temperature, which contributes to the increment of effective active sites and results in the increase of NO conversion. When 5 % H2O is added into the reactants at the optimum temperature (230 °C), the NO conversion for Cu-MOF-74 is decreased rapidly to about 53.5 % within 1 h. Besides the effect of competitive adsorption between H2O and NH3/NO, the number of Brønsted acid sites increases because the Brønsted-acidic hydroxyl groups are supplied by H2O on the surface of catalysts[27]. It is interesting to note that the catalytic activity can recover quickly when the H2O supply is turned off, then the NO conversion is recovered to 97.2 % after 3 h, showing that the inhibiting effect of water


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is reversible. Because this work focuses the de-NOx SCR catalysis on stationary sources, thus sulfur poisoning becomes one of the challenges for the SCR reaction, especially at the lower temperature. Fig. 10 shows the resistance to SO2 and the stability test of SCR reaction of Cu-MOF-74-iso-80 catalyst sample, which manifested higher catalytic activity after SO2 poisoning. When introducing 100 ppm SO2 in the inlet flow, the NO conversion can be still maintained to higher than 85%, which demonstrates SO2 shows only little influence on the SCR catalytic activity. The possible reason for the decrease of NO conversion might be the formation of certain sulfates species, which include metal sulfates and ammonium sulfates, on the surface of the catalyst. Interestingly, the NO conversion over Cu-MOF-74-iso-80 sample is again increased to 93% within 4 h after adding SO2. It is possible that some new acidic sites might occur after the sulfuration. Therefore, stronger surface acidity facilitates the catalytic activity. This result is consistent with previous reports[28]. After terminating the SO2 supply, it is surprisingly observed that the SCR catalytic activity is rapidly restored, the NO conversion is increased to 98%. Therefore, Cu-MOF-74 catalyst is potential and promising practical one for low-temperature SCR of NO with NH3. 4. Conclusion In summary, nanocrystalline Cu-MOF-74 materials are successfully prepared by the solvent-thermal method, and their catalytic activities have been systematically tested for the SCR deNOx process. The solvothermal temperature and co-solvent are considered as the crucial factors for the physicochemical properties of Cu-MOF-74.



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The Cu-MOF-74 samples synthesized at 80 °C with isopropanol as co-solvent show rod-like morphology, while those synthesized at 65 °C and 80 °C with ethanol as co-solvent show unidirectional and bidirectional bouquet-like structure, respectively. The sectional view of the crystal of all the Cu-MOF-74 samples is regular hexagons. Cu-MOF-74-iso-80 sample shows the largest specific surface area, of 1025.0 m2/g. Meanwhile, its adsorption ability for NO is stronger than other samples. The total amount of NH3 desorption of iso-80 sample is larger than eth-X (X=60, 80) samples series. Additionally, the Cu-MOF-74 materials exhibit high catalytic activity for the low temperature deNOx reactions. Cu-MOF-74-iso-80 shows better catalytic performances with the highest NO conversion of 97.8 % attained at 230 °C. Besides, Cu-MOF-74-iso-80 sample shows also good water resistance and higher resistance to SO2 poisoning, although H2O in the feed gas could exert an adverse effect on the NOx conversion to some extent. However, the effect of H2O added intermittently could be quickly eliminated after its removal in inlet flow. This preliminary work indicates that Cu-MOF-74 could be a potential useful catalyst material used for the low-temperature SCR deNOx process. Acknowledgements

This work is supported by the National Natural Science Foundation of China (Contract No.21506150). The Project is also sponsored by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry.

References


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[1] Smirniotis, P.G.; Pena, D.A.; Uphade, B.S. Low-Temperature Selective Catalytic Reduction (SCR) of NO with NH3 by Using Mn, Cr, and Cu Oxides Supported on Hombikat TiO2. Angew. Chem. Int. Ed. 2001, 40(13), 2479-2482. [2] Thirupathi, B.; Smirniotis, P.G. Nickel-doped Mn/TiO2 as an efficient catalyst for the low-temperature SCR of NO with NH3: Catalytic evaluation and characterizations. J. Catal. 2012, 288, 74-83. [3] Chen, H.Y.; Wei, Z.; Kollar, M.; Gao, F.; Wang, Y.; Szanyi, J.; Peden, C.H. A comparative study of N2O formation during the selective catalytic reduction of NOx with NH3 on zeolite supported Cu catalysts. J. Catal. 2015, 329, 490-498. [4] Liu, F.; He, H.; Zhang, C. Novel iron titanate catalyst for the selective catalytic reduction of NO with NH3 in the medium temperature range. Chem. Commun. 2008, 17, 2043-2045. [5] Dietzel, P.D.; Morita, Y.; Blom, R.; Fjellvåg, H. An In Situ High‐Temperature Single‐Crystal Investigation of a Dehydrated Metal-Organic Framework Compound and Field ‐ Induced Magnetization of One-Dimensional Metal-Oxygen Chains. Angew. Chem., 2005, 117(39), 6512-6516. [6] Sanz, R.; Martínez, F.; Orcajo, G.; Wojtas, L.; Briones, D. Synthesis of a honeycomb-like Cu-based metal-organic framework and its carbon dioxide adsorption behaviour. Dalton Trans. 2013,42(7), 2392-2398. [7] Kesanli, B.; Cui, Y.; Smith, M.R.; Bittner, E.W.; Bockrath, B.C.; Lin, W. Highly interpenetrated metal-organic frameworks for hydrogen storage. Angew. Chem. Int. Ed. 2005, 44(1), 72-75.



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[8] Bradshaw, D.; Prior, T.J.; Cussen, E.J.; Claridge, J.B.; Rosseinsky, M.J. Permanent microporosity and enantioselective sorption in a chiral open framework. J. Am. Chem. Soc. 2004, 126(19), 6106-6114. [9] Zhang, S.Y.; Liu, H.; Sun, C.C.; Liu, P.F.; Li, L.C.; Yang, Z.H.; Feng, X.; Huo, F.W.; Lu, X.H. CuO/Cu2O porous composites: shape and composition controllable fabrication inherited from metal organic frameworks and further application in CO oxidation, J. Mater. Chem. A., 2015,3,5294-5298. [10] Bloch, E.D.; Murray, L.J.; Queen, W.L.; Chavan, S.; Maximoff, S.N.; Bigi, J.P.; Krishna, R.; Peterson, V.K.; Grandjean, F.; Long, G.J. Selective binding of O2 over N2 in a redox-active metal-organic framework with open iron (II) coordination sites. JACS. 2011, 133 (37), 14814-14822. [11] Lee, K.; Isley, III W.C.; Dzubak, A.L.; Verma, P.; Stoneburner, S.J.; Lin, L.C.; Howe, J.D.; Bloch, E.D.; Reed, D.A.; Hudson, M.R. Design of a metal-organic framework with enhanced back bonding for separation of N2 and CH4. J. Am. Chem. Soc. 2013, 136 (2), 698-704. [12] Haldoupis, E.; Borycz, J.; Shi, H.; Vogiatzis, K.D.; Bai, P.; Queen, W.L.; Gagliardi, L.; Siepmann, J.I. Ab Initio Derived Force Fields for Predicting CO2 Adsorption and Accessibility of Metal Sites in the Metal-Organic Frameworks M-MOF-74 (M= Mn, Co, Ni, Cu). J. Phys. Chem. C. 2015, 119 (28), 16058-16071. [13] Pham, T.; Forrest, K.A.; Eckert, J.; Space, B. Dramatic Effect of the Electrostatic Parameters on H2 Sorption in an M-MOF-74 Analogue. Cryst. Growth Des. 2015, 16 (2) 867-874.


Page 18 of 33

Page 19 of 33

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[14] Dincă, M.; Han, W.S.; Liu, Y.; Dailly, A.; Brown, C.M.; Long, J.R. Observation of Cu2+-H2 Interactions in a Fully Desolvated Sodalite-Type Metal-Organic Framework. Angew. Chem. Int. Ed. 2007, 46 (9), 1419-1422. [15] Sun, Y.X.; Sun, W.Y. Influence of temperature on metal-organic frameworks, Chin. Chem. Lett. 2014, 25 (6), 823-828. [16] Yang, G.P.; Hou, L.; Ma, L.F.; Wang, Y.Y. Investigation on the prime factors influencing the formation of entangled metal-organic frameworks. CrystEngComm. 2013, 15 (14), 2561-2578. [17] Li, J.; Yang, G.; Hou, L.; Cui, L.; Li, Y.; Wang, Y.Y.; Shi, Q.Z. Three new solvent-directed 3D lead (ii)-MOFs displaying the unique properties of luminescence and selective CO2 sorption. Dalton Trans. 2013, 42 (37), 13590-13598. [18] Zhou, W.; Wu, H.; Yildirim T. Enhanced H2 Adsorption in Isostructural MetalOrganic Frameworks with Open Metal Sites: Strong Dependence of the Binding Strength on Metal Ions, JACS. 2008, 130 (46), 15268-15269. [19] Schlichte, K.; Kratzke, T.; Kaskel, S. Improved synthesis, thermal stability and catalytic properties of the metal-organic framework compound Cu3(BTC)2. Microporous Mesoporous Mater. 2004, 73 (1), 81-88. [20] Chowdhury, P.; Bikkina, C.; Meister, D.; Dreisbach, F.; Gumma, S. Comparison of adsorption isotherms on Cu-BTC metal organic frameworks synthesized from different routes. Microporous Mesoporous Mater. 2009, 117 (1), 406-413. [21] Orcajo, G.; Villajos, J.A.; Martos, C.; Botas, J.Á.; Calleja, G. Influence of chemical composition of the open bimetallic sites of MOF-74 on H2 adsorption.



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Adsorption. 2015, 21 (8), 589-595. [22] Sullivan, J. A; Keane, O. A combination of NOx trapping materials and urea-SCR catalysts for use in the removal of NOx from mobile diesel engine. Appl. Catal. B 2007, 70(1): 205-214. [23] Jiang, H.X; Wang, Q.Y.; Wang, H.Q.; Chen, Y.F.; Zhang, M.H. MOF-74 as an Efficient Catalyst for the Low-Temperature Selective Catalytic Reduction of NOx with NH3. ACS Appl Mater Interfaces. 2016, 8(40), 26817-26826. [24] Zhao, W.; Zhong, Q.; Zhang, T.J.; Pan Y.X. Characterization study on the promoting effect of F-doping V2O5/TiO2 SCR catalysts. RSC Adv. 2012, 2(20), 7906-7914. [25] Jian, L.J; Chen, C.; Lan, F.; Deng, S.J.; Xiao, W.M.; Zhang, N. Catalytic activity of unsaturated coordinated Cu-MOF to the hydroxylation of phenol. Solid-State Sci. 2011, 13(5), 1127-1131. [26] Schlichte, K.; Kratzke, T.; Kaskel, S. Improved synthesis, thermal stability and catalytic properties of the metal-organic framework compound Cu3(BTC)2. Microporous Mesoporous Mater. 2004, 73(1), 81-88. [27] Lietti, L.; Alemany, J.L.; Forzatti, P.; Busca, G.; Ramis. G.; Giamello, E.; Bregani, F. Reactivity of V2O5-WO3/TiO2 catalysts in the selective catalytic reduction of nitric oxide by ammonia. Catal. Today. 1996, 29(1-4), 143-148. [28] Yu, J.; Guo, F.; Wang, Y.L.; Zhu, J.H.; Liu, Y.Y.; Su, F.B.; Gao, S.Q. Sulfur poisoning resistant mesoporous Mn-base catalyst for low-temperature SCR of NO with NH3. Appl. Catal. B 2010, 95(1), 160-168.


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Fig. 1 XRD patterns of Cu-MOF-74.

eth-65

Intensity(a.u.)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


eth-80

iso-80 (2-10)

Simulate

(300)

10

20

30

40

50

2θ(°)

Fig. 2 SEM images of Cu-MOF-74 samples: (a, d) eth-65, (b, e) eth-80, (c, f) iso-80.



Fig. 3 The N2 adsorption and desorption isotherms of Cu-MOF-74 samples.

Fig. 4 TG curves of Cu-MOF-74 under different atmospheres: (a) N2, (b) Air, (c) The SCR reaction gases.

100

eth-65 eth-80 iso-80

a

90

318°C

80

W eight (% )

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

70

307°C

60

415°C

50

40

30 100

200

300

400

T (°C)


500

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100

b


90

240°C

Weight (%)

80

247°C

223°C

70

60

50

263°C

249°C

40

257°C 30 100

200

300

400

500

T (°C)

c

100


90

80

Weight (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


259°C 250°C

70

262°C 60

367°C

50

40

372°C 348°C

30 100

200

300

400

T (°C)


500


Fig. 5 XPS spectra of Cu-MOF-74: (a,c,e) Full spectrum, (b,d,f) Cu 2p XPS spectra. eth-65 Cu2p1

a

c/s

Cu2p3

O1s C1s

1000

800

600

400

200

0

B.E.(eV)

eth-65

b

Cu2p 3/2

Cu2p 1/2

c/s

Statellite

960

955

950

945

940

935

930

925

920

B.E.(eV)

eth-80

c

Cu2p1 Cu2p3

c/s

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

O1s C1s

1000

800

600

400

200

B.E.(eV)


0

Page 24 of 33

eth-80

d Cu2p1/2 Cu2p3/2

c/s

Statellite

960

955

950

945

940

935

930

925

920

B.E.(eV)

iso-80 Cu2p1

e

Cu2p3

O1s c/s

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


C1s

1000

800

600

400

200

0

B.E.(eV)

iso-80

f

Cu2p3/2 Cu2p1/2

Statellite

c/s

Page 25 of 33

960

955

950

945

940

935

930

925

B.E.(eV)


920


Fig. 6 NH3-TPD-MS curves of Cu-MOF-74 samples:

MS Signal (a.u.)/(m/e=17)

iso-80

eth-65

eth-80

100

150

200

250

300

350

400

Temperature(°C)

Fig. 7 NO-TPD-MS curves of Cu-MOF-74 samples:

iso-80

MS Signal (a.u.)(m/e=30)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

eth-65

eth-80

100

150

200

250 300 Temperature(°C)

350


400

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Fig. 8 The low-temperature SCR activities of Cu-MOF-74 samples.

100

iso-80 eth-65 eth-80

90

NO Conversion(%)

80 70 60 50 40 30 20 10 0 80

100

120

140

160

180

200

220

240

Temperature(°C)

Fig. 9 The effects of H2O on the low-temperature SCR activities of Cu-MOF-74.

iso-80-SCR-5%H2O iso-80-SCR

100 90

NO conversion(%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


80 70

add 5%H2O

60

remove 5%H2O

50 40

230°C 30 80

120

160

Temperature( °C)

200

0

2

4

Time(h)


6


Fig. 10 The effects of SO 2 and stability test on the low-temperature SCR activities of Cu-MOF-74.

100 90

Stability test 100 ppm SO2

80

NO Conversion (%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

remove 100 ppm SO2 add 100 ppm SO2

70 60 50 40

230°C 30 0

2

4

6

8

10

12

14

16

18

20

Time (h)


22

24

Page 28 of 33

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 1 Lattice parameters of Cu-MOF-74. Samples

I300/I2-10

Lattice parameters a=b(Å)

Simulated

0.28

26.1532

eth-65

0.76

26.2112

eth-80

0.48

26.2139

iso-80

0.75

26.0976

Table 2 Textural properties of Cu-MOF-74 samples. BET surface area

Pore volume

Mean pore size

(m2/g)

(cm3/g)

(nm)

iso-80

1025.0

0.420

16.4

eth-80

837.8

0.358

17.1

eth-65

753.7

0.421

22.3

Samples



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Table 3 The thermogravimetric analysis of Cu-MOF-74 samples under different atmospheres. Under N2 Samples

Under air

Under SCR reaction gases

Started

Ended

Started

Ended

Started

Ended

(°C)

(°C)

(°C)

(°C)

(°C)

(°C)

iso-80

318

415

247

263

262

348

eth-80

307

415

223

249

250

367

eth-65

307

415

240

257

259

372


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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Table 4 Cu content in bulk phase of Cu-MOF-74 samples Samples

Cu content in bulk phase(wt/%)

iso-80

29.4

eth-80

31.5

eth-65

31.2



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 33

Table 5 The total amount of NH3 desorption and Peak Areas of NO of Cu-MOF-74 samples Sample

Peak Areas of NO (a.u./g) (Temperature (°C))

Total amount of NH3 desorption (µmol/g)

iso-80 Peak 1 Peak 2

eth-80 Peak 1 Peak 2

eth-65 Peak 1 Peak 2

8.5 (138.0)

2.6 (147.5)

11.1 (161.5)

7.7 (213.9) 42.1

4.7 (174.3) 33.2


-

39.9

Page 33 of 33

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Effect of Cosolvent and Temperature on the Structures and Properties

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