Dry-Gel Conversion Synthesis of Zr-Based Metal–Organic Frameworks

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Dry-Gel Conversion Synthesis of Zr-Based Metal-Organic Frameworks Ningyue Lu, Fan Zhou, Huanhuan Jia, Hongyan Wang, Binbin Fan, and Ruifeng Li Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b04010 • Publication Date (Web): 13 Nov 2017 Downloaded from http://pubs.acs.org on November 16, 2017

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Industrial & Engineering Chemistry Research

Dry-Gel Conversion Synthesis of Zr-Based Metal-Organic Frameworks Ningyue Lu1, Fan Zhou1, Huanhuan Jia1, Hongyan Wang1, Binbin Fan1*, and Ruifeng Li1,2*

1

College of Chemistry and Chemical Engineering, Taiyuan University of Technology,

Taiyuan 030024, P.R. China 2

Key Laboratory of Coal Science and Technology MOE, Taiyuan University of

Technology, Taiyuan 030024, P.R. China

* Corresponding authors: Binbin Fan, Ruifeng Li E-mail address: [email protected](B.B. Fan); [email protected] (R.F. Li) Telephone: +86-351-6018384, Fax: +86-351-6010121

Abstract 1

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UiO-66 was successfully synthesized in the absence of any amide solvents and hydrochloric acid by using the dry-gel conversion (DGC) method for the first time. The prepared UiO-66 samples (denoted as UiO-66-DGC) were characterized by XRD, SEM, TGA, CO2 adsorption, NH3-TPD and N2 adsorption. The results showed that the UiO-66-DGC-E sample synthesized by using ethanol as solvent has similar crystallinity and morphology to the UiO-66 sample prepared by the conventional solvothermal method (denoted as UiO-66-S). However, it has more linker deficiencies, indicating the presence of more defects exposed in Zr clusters. As a result, the prepared UiO-66-DGC-E sample exhibited high catalytic activity and reusability in esterification. This preparation method provides a new alternative method for the efficient and eco-friendly synthesis of MOFs and modification of their properties.

Keywords: UiO-66, MOFs, dry-gel conversion synthesis, defect, acid catalyst

1. Introduction

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Metal-organic frameworks (MOFs) are a class of interesting crystalline porous materials. They are built through the self-assembly of metal ions or clusters and multidentate organic ligands.1,2 Due to their high porosity, large surface area and chemical tenability, they have shown potential application prospect in gas storage,3 separation,4 chemical sensing,5 drug delivery,6 and catalysis.7,8 However, their relatively low stability and high cost still remain the serious problems for the large industrial application.9 Among a variety of MOFs, a series of MOFs based on carboxylate linkers and 12-coordinate cationic Zr6O4(OH)412+ clusters, exemplified by terephthalate-based UiO-66 and its derivatives, have attracted considerable attention due to their high thermal, chemical and mechanical stability as well as the ease introduction of a wide range of functionalities. UiO-66 and its derivates can be synthesized by multitude procedures, but these procedures generally involve using amidic solvents and acid modulators.10 The amidic solvents are toxic, while the acid modulators not only limit the yield but also produce large amounts of toxic Therefore, for the Zr-based MOFs, the development of safe, economic and environment-friendly synthetic methods is desirable. Recently, Užarević et al. the mechanochemical and solvent-free routes for Zr-based MOFs.14 UiO-66 and UiO-66-NH2 can be synthesized on the gram scale without strong acid, high temperatures or excess reactants, but it needs high Zr/BDC ratios and Zr6O4(OH)4(C2H3CO2)12 as precursor. Ploskonka et al. reported synthesis of UiO-66 and UiO-66-NH2 in acetone.15 The MOFs prepared in this synthesis system can be activated just by heating under vacuum without needing for solvent exchange owing

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to the lower boiling point of acetone. The dry-gel conversion (DGC), involving treating amorphous gel powder to form a crystalline zeolite upon contact with the vapors of water or volatile amines, is an environmental benign route for synthesis of porous materials and has been applied in the preparation of zeolites and zeolite membranes.16-19 Compared with the conventional hydrothermal synthesis, DGC has potential advantages, including minimum waste disposal, reduced consumption of templates, and the possibility of continuous production.17,20-22 ZIF-8,23 MIL-100 (Fe)24 and MIL-101 (Cr)25 have been successfully synthesized by this method. However, the synthesis of UiO family by using the DGC method has not been reported. In this work, the synthesis of UiO-66 via environmental friendly DGC method with ethanol or acetone as solvent without addition of acid and salt was reported. The synthesized UiO-66 samples were characterized by XRD, SEM, CO2 adsorption, N2 adsorption, NH3-TPD, TGA analysis as well as catalytic reaction and compared with the UiO-66 synthesized by the conventional solvothermal method. 2. Experimental 2.1. Sample preparation 2.1.1. Solvothermal synthesis of UiO-66 The solvothermal synthesis of UiO-66 (denoted as UiO-66-S) was based on the literature with some changes.26 In a typical synthesis, a mixture of zirconium tetrachloride

(ZrCl4,

0.53

g),

terephthalic acid

(H2BDC,

0.37

g),

and

N,N-dimethylformamide (DMF, 30 mL) was heated in a 100 mL of Teflon-lined

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autoclave for 24 h in an oven set at 120 oC. After the Teflon-lined autoclave was cooled to room temperature, the white precipitate was filtered off, washed with DMF to remove the excess of the un-reacted substrates. The DMF residue in the pores of UiO-66-S was removed by immersing the product in methanol solution for solvent exchange. After filtration, the product was dried overnight at 80 oC and denoted as UiO-66-S.

Scheme 1 The synthesis route for the preparation of the UiO-66-DGC samples. 2.1.2. DGC synthesis of UiO-66 The synthesis of UiO-66 by DGC was carried out in the apparatus shown in Scheme 1. Firstly, 2.12 g zirconium tetrachloride (ZrCl4, 9.08 mmol) and 1.51 g terephthalic acid (H2BDC, 9.08 mmol) were well grinded. Then, the mixture was transported into a small Teflon cup supported by a Teflon holder. Subsequently, the cup and holder were placed in a bigger Teflon-lined stainless steel autoclave loaded with the solvent (10 mL). At last, the crystallization was carried out at 100 oC for 24 h. The obtained solid products were washed according to the method described for UiO-66-S and the samples synthesized by DGC using ethanol, water and acetone as the solvent were denoted as UiO-66-DGC-E, UiO-66-DGC-W and UiO-66-DGC-A, 5



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respectively. 2.2. Sample characterization The XRD patterns were recorded on a Shimadzu XRD-6000 Diffractometer with Cu Kα radiation. Nitrogen adsorption isotherms were measured at -196 oC on a Quantachrone Autosorb analyzer. Before the measurement, the sample was evacuated at 300 oC for 3 h. The BET surface area was calculated from desorption branch, while the pore volume was estimated at a relative pressure of 0.99. The Nova 1200e analyzer was used to measure the CO2 adsorption isotherms of the UiO-66 samples at 0 oC. Before the measurement, the sample was also evacuated at 300 oC for 3 h. Morphologies of crystals were observed by an S-4800 Hitachi scanning electron microscope. Thermogravimetric analysis (TGA) measurement was carried out in a flowing air atmosphere (50 mL/min) using a NETZSCH STA 449 F3 instrument. Acid properties of the synthesized UiO-66 samples were determined by NH3-TPD. The measurement was performed using AutoChem 2720 instrument with He as carrier gas (30 mL/min). Before the measurement, the sample was activated at 300 oC for 3 h in He atmosphere. The C contents were determined by a vario EL cube elemental analyzer and the Zr contents were measured by inductively coupled plasma (ICP) analysis. 2.3 Catalytic measurement 2.3.1 Esterification reaction of acetic acid with ethanol 0.1 g catalyst (activated at 300 oC for 1 h under vacuum), 0.11 mL acetic acid (2 mmol) and 10 mL ethanol were added to a 50 mL Teflon-lined stainless steel

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autoclave. The resulting mixture was stirred at 75 oC for a period of time. At the end of the reaction, the catalyst was separated by centrifugation, and the liquid product was analyzed by a GC-2014C gas chromatograph (Stabilwax column, 30m×0.25mm, df = 0.25µm). The catalyst was washed with ethanol for three times for the next run. 2.3.2 Esterification reaction of benzyl alcohol with n-hexylic acid 0.1 g catalyst (activated at 300 oC for 1 h under vacuum), 0.52 mL benzyl alcohol (5 mmol) and 0.62 mL n-hexylic acid (5 mmol) were dissolved to methylbenzene (2 mL). Then, the reaction mixture was placed in a preheated oil bath with refluxing and stirred magnetically at 130 oC. After reaction, the catalyst was separated by centrifugation, and the analyses of liquid products were based on the above method. 3. Results and discussion 3.1 Solvent effects on synthesis of UiO-66 by DGC At present, the most reliable synthesis of UiO-66 and its analogues involves using aggressive hydrochloric acid and toxic amidic solvent.27 Thus, in this work, our main purpose is to use the relative environmental friendly solvents to substitute the toxic amidic solvent in the absence of hydrochloric acid by an operationally simple technique. Based on this consideration, we first investigated the solvents effects on the synthesis of UiO-66 materials by DGC method, and the most used ethanol, acetone and water were selected as the solvents. Figure 1(a) is the XRD patterns of the samples synthesized by DGC with different solvents before washing. As shown in Figure 1(a), under the identical

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synthesis temperature and time, the unwashed samples synthesized with the different solvents showed different XRD patterns. Typical characteristic diffraction peaks of UiO-66 were observed in the XRD patterns of UiO-66-DGC-E and UiO-66-DGC-A, but the peaks at 2θ=17.5, 25.4 and 28o, ascribed to the terephthalic acid ligand, appeared in the XRD pattern of the unwashed UiO-66-DGC-A. No whole typical diffraction peaks of UiO-66 were observed except the diffraction peaks of terephthalic acid ligand in the XRD pattern of the unwashed UiO-66-DGC-W. These results indicated that the properties of the selected solvent have great influences on UiO-66 crystallization. After washing, the obtained UiO-66-DGC-W (Figure 1(b)) still did not show the whole characteristic diffraction peaks of UiO-66, while the products obtained with other two organic solvents exhibited the nearly same well-defined reflections, with positions consistent with UiO-66 structure. Moreover, the crystallinity of UiO-66-DGC-E was comparable to that of UiO-66-S synthesized by the conventional solvothermal method, even if it was synthesized at a lower temperature (100 oC). Unlike UiO-66-S and UiO-66-DGC-A, a broad weak peak at 2θ = 7.4o (asterisk) appeared in the XRD pattern of UiO-66-DGC-E. This peak can be assigned to the missing cluster defects existed in correlated nanoregions of the reo topology, which was thought of as UiO-66 with one quarter of its clusters missing.28 In the reo phase, the missing clusters result in reduction of linker connectivity for ideal UiO-66. 3.2 Effects of the ratios of solid amount to liquid (solvent) amount For DGC synthesis method, the ratios of the solid (ZrCl4 and H2BDC) amount to

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the liquid (solvent) amount (S/L, mmol/mL) also have great influences on the crystallization of UiO-66. In industrial operation, high S/L is beneficial to increasing production efficiency. In this work, we investigated the effects of S/L ratios on the synthesized samples. In all the synthesis system, ZrCl4/H2BDC (molar ratio) was 1.0, the synthesis temperature was 100 oC, time was 24 h and solvent was 10 mL. Figure 2 is the XRD patterns of the unwashed samples synthesized with different solvents at the different S/L ratios. From Figure 2, it can be seen that the effects of S/L ratios on the products greatly related with the properties of the solvents. In the case of water solvent, all the samples synthesized at different S/L ratios showed the nearly the same XRD patterns. No typical diffraction peaks of UiO-66 were observed, and only the diffraction peaks, ascribed to H2BDC ligand, became stronger with the increase of S/L ratios. In the case of acetone solvent, the strong characteristic diffraction peaks of UiO-66 and H2BDC simultaneously existed in the XRD patterns of the synthesized samples as the S/L ratios were below 0.9. However, as the S/L ratio reached 1.8, the intensity of the diffraction peaks attributed to UiO-66 phase gradually became very weak, while the intensity of the diffraction peaks contributed by H2BDC became very strong and at the same time some unidentified phase appeared. In the case of ethanol solvent, the pure UiO-66 phase was obtained and the crystallinities of the synthesized samples increased as the S/L ratios were below 0.9, but the H2BDC phase was observed as the S/L ratios were above 1.8. The different results are closely related with the interaction of the solvent with ZrCl4/H2BDC. It is generally considered that the formation mechanism of UiO-66 involves the following two steps: the first step is

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the formation of the Zr4+/hydroxo clusters; in the second step, the clusters react with the deprotonated BDC2- organic ligand to generate the UiO-66 particles.13 Water can promote the hydrolysis of ZrCl4, but the solubility of H2BDC in water is slight, resulting in the formation of deprotonated BDC2- organic ligand is difficult. As a consequence, no UiO-66 crystal phase appeared in the products synthesized by DGC method as water was used as the solvent. In contrast, the presence of acetone and ethanol can dissociate ZrCl4 and deprotonate H2BDC, thus UiO-66 crystal phase was observed in the products synthesized by DGC as acetone and ethanol were used as solvents. However, different from ethanol, acetone likely formed other products via aldol condensation in the presence of HCl from the dissociation of ZrCl4,15 and these reactions will affect the UiO-66 crystallization, thereby resulting in many ligand residue. For ethanol solvent, the appearance of the ligand residue at high S/L ratios, maybe related to the mass limitation. In addition, the obtained solid amounts of UiO-66-DGC-E and UiO-66-DGC-A samples were also listed in Table 1. Before washing, the solid amounts in the two DGC synthesis systems basically reached above 90% of the amount calculated in theory. This result indicated that less ZrCl4/H2BDC were removed from the synthesis system by dissolution. 3.3 Effects of synthesis time and temperature The effects of the synthesis parameters on the DGC synthesis of UiO-66 were investigated with ethanol as the solvent. Figure 3 is the XRD patterns of the synthesized UiO-66-DGC-E samples (unwashed) at different temperatures. No UiO-66 phase was detected as the synthesis temperature was below 80 oC (not shown

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in Figure 3). The UiO-66 phase started to emerge at 80 oC. With the increasing synthesis temperature, the reflections ascribed to ligand gradually became weak, while the reflections ascribed to UiO-66 phase became strong. As the synthesis temperature was above 100 oC, the reflection intensity of UiO-66 phase no longer enhanced. This phenomenon can be explained by the physical property of ethanol. When the synthesis temperature was above the boiling point of ethanol, the autoclave was full with ethanol steam. The ethanol molecules would interact with some of the substrate, resulting in the formation of UiO-66 composites. Upon the synthesis temperature above 100 oC, a gas-liquid equilibrium state in the Teflon lined autoclaves maybe gotten.23 To understand the crystallization process in DGC synthesis of UiO-66, the XRD patterns of the unwashed products obtained after different synthesis times at 100 oC are shown Figure 4. When the reaction time was extended beyond 1 h, weak diffraction peaks characteristic of UiO-66 began to appear in the XRD pattern, implying reorganization between the organic ligand and ZrCl4 had occurred under the ethanol steam. When the steam treatment was increased from 1 h to 24 h, the diffraction peaks of UiO-66 gradually became sharper accompanied by the complete disappearance of ligand XRD reflections, indicating that UiO-66 crystallization was basically finished after 24 h at 100 oC. 3.4 Characterization The N2 adsorption isotherms (Figure 5) of the UiO-66-S and UiO-66-DGC samples showed a mixture of type I and IV curves. The steep increase in the adsorbed

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volume at a relative low pressure relates to the existence of micropores, while the slight secondary uptake points to the existence of mesopores. The textural parameters (Table 1) showed that the UiO-66-DGC-E and UiO-66-DGC-A had similar BET surface areas and pore volumes to that of UiO-66-S. Figure 6 is the CO2 adsorption results of UiO-66-DGC samples and UiO-66-S. It also gave the similar results to N2 adsorption. The results indicated that the UiO-66-DGC samples held comparable textural properties and adsorption behavior to UiO-66-S. Figure 7 shows the SEM images of the different UiO-66 samples. It is clear that UiO-66-DGC-E and UiO-66-S samples showed the octahedral-like morphology with different crystal sizes and dispersity. The particles of the UiO-66-DGC-E were smaller (ca. 100 nm) and more uniform in comparison with UiO-66-S (150-250 nm). However, the particles of the UiO-66-DGC-A were aggregated with block morphology, and much larger than the other two samples in sizes. The phenomena indicated that synthesis method and solvent have great effects on the crystal growth. This can be explained by the different coordination interactions between the solvent and the substrates/MOFs.29 The thermal stability and defect concentration of the synthesized different UiO-66 samples were probed by thermogravimetric analysis (TGA). The TGA curves of the different UiO-66 samples are presented in Figure 8. All the UiO-66 samples showed two steps of weight loss prior to the formation of final ZrO2 product. The first step from (50~350 oC) is ascribed to the evaporation of adsorbed water or solvent molecules, and the second step of weight loss (350~600 oC) is assigned to the

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framework decomposition.30 Based on the loss amount in this step, the ligand amount can be determined. Assuming that the ligands were burned out at such a high temperature, the final residue should be ZrO2, thus the moles of Zr can be calculated. The composition of the perfect dehydroxylated UiO-66 (defect free) is Zr6O6 (C8H4O4)6, and the ligand to Zr molar ratio should be equal to 1 theoretically.31 If the Zr/ligand molar ratio is not 1, it means that the as-synthesized sample is defective. The weight losses of UiO-66-S, UiO-66-DGC-E, and UiO-66-DGC-A in 350-600 oC are 37.4%, 29.4%, and 40.3%, respectively. The final ZrO2 amounts in the three samples are 39.9%, 38.6% and 46.2%. Based on the above calculating method and TGA results, the Zr/ligand molar ratios for UiO-66-S, UiO-66-DGC-E, and UiO-66-DGC-A were 1.28, 1.58 and 1.38, respectively, which can be further confirmed by ICP and elemental analysis results (Table 1). These results indicated that all the samples were linker deficient and the defect amounts in the DGC samples were a little larger than in UiO-66-S. Figure 9 shows the NH3-TPD curves of the different UiO-66 samples. For Zr-based MOFs, their Lewis acid character would arise from the occurrence of a (thermal) dehydroxylation of the [Zr6O4(OH)4]12+clusters to [Zr6O6]12+ exposing vacancies, together with the systematic formation of crystalline defects associated to linker deficiencies32. As missing linkers create open Zr sites which are accessible for catalytic transformations, many procedures, including varying the modulator concentration, synthesis time and synthesis temperature, were developed to increase the structural defects within the UiO-66 type materials.31,32 As shown in Figure 9,

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UiO-66-DGC-E and UiO-66-DGC-A have similar acid strength to UiO-66-S, but UiO-66-DGC-E has more acid sites. The more acid sites can be ascribed to the more missing linkers and as revealed by TGA results. 3.5 Catalytic performances of the different UiO-66 samples in esterification reaction Esterification is an important reaction for fine chemicals. In addition, esterification of organic acid in the presence of alcohol molecules can deoxygenate oxygen and reduce the acidity of the bio-oil derived from bio-mass, thereby improving the bio-oil stability. Therefore, recently esterification has gained much attention in biofuel field and is also a popular process for upgrading bio-oil.33-35 In industry, esterification is most commonly catalyzed by mineral acids, such as H2SO4. However, these mineral acids are highly corrosive and environmentally un-friendly, various solid acid catalysts, have been applied, including zeolites,36-39 metal oxides34, 40, 41

and ion-exchange resins.42-44 UiO-66, due to the unsaturated coordination of Zr in

its structure, usually display well Lewis acid character and have exhibited excellent catalytic performances in various acid-catalyzed reactions.45-48 Here, we choose esterification as a probe reaction to investigate the acid-catalyzed performance of UiO-66 samples synthesized in different synthesis system. The catalytic performances of the different UiO-66 samples were investigated in esterification of acetic acid/n-hexylic acid and ethanol/benzyl alcohol, and the results are presented in Figure 10. From Figure 10, it can be seen that the prepared UiO-66-DGC-E exhibited higher catalytic activity than UiO-66-S, which is related with its more acid sites as revealed by TGA and NH3-TPD. The selectivity of ethyl

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acetate and n-hexylic acid benzyl ester both reach 99.9%, and no other side products were detected. However, UiO-66-DGC-A gave lower catalytic activity than UiO-66-S, even if two samples have the similar acid strength and amount. This is maybe due to its larger particle size which greatly limited the diffusion of reactants and decreased the accessibility of the acid sites. The structural stability and recycling possibility of the prepared UiO-66 samples in the esterification reaction were further investigated. After reaction runs, the catalyst was recovered by the centrifugation and then reused for the next run under the same reaction conditions. Figure 11 shows the XRD patterns of the different UiO-66 samples after 1 cycle. The crystalline structures of the catalysts were mostly unchanged after catalytic reaction. Figure 12 shows the catalytic results of three successive recycles. It can be seen that the reused catalyst still retain its original activity. These results indicated that the UiO-66-DGC samples have the same stability and reusability as UiO-66-S. 4. Conclusions In conclusion, we have demonstrated an efficient, inexpensive and eco-friendly route to synthesis porous UiO-66 by using dry-gel conversion method. This synthesis method not only prohibits the usage of toxic organic solvent, but also decreases the cost of preparation of MOFs materials. The UiO-66-DGC-E sample has similar crystallinity and morphology to the UiO-66-S.

Meanwhile, the prepared

UiO-66-DGC-E sample exhibited high catalytic activity, stability and reusability in the esterification reaction. This preparation method provides a new alternative method

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for the efficient and green synthesis of MOFs and modification of their properties.

Acknowledgments The authors thank the Natural Science Foundation of China (No. 21576177 and 20971095).

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Table Table 1 The textural parameters of the UiO-66 samples. Zra

Ca

Zr/ligand

SBETb

VPoreb

(wt%)

(wt%)

molar ratio

(m2·g-1)

(cm3·g-1)

Samples

Yields (%) Before

After

washing washing UiO-66-S

39.1

30.6

1.35

922

0.52

91.2

87.2

UiO-66-DGC-E

43.2

27.0

1.69

830

0.41

93.6

89.6

UiO-66-DGC-A

40.8

29.1

1.48

896

0.51

97.1

84.7

a

Determined by elemental analysis; b Determined by N2 adsorption.

23



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

Figure captions Figure 1 XRD patterns of the samples synthesized by DGC with different solvents ((a) unwashed, (b) washed). Figure 2 XRD patterns of the unwashed samples synthesized with different solvents at the different S/L ratios. Figure 3 XRD patterns of the synthesized UiO-66-DGC-E samples (unwashed) at different temperatures. Figure 4 XRD patterns of UiO-66-DGC-E samples (unwashed) synthesized at 100 oC at different synthesis time. Figure 5 N2 adsorption isotherms of the different UiO-66 samples. Figure 6 CO2 adsorption isotherms of the different UiO-66 samples. Figure 7 SEM images of the different UiO-66 samples. ((a) UiO-66-DGC-E, (b) UiO-66-DGC-A, (c) UiO-66-S) Figure 8 TGA curves of the different UiO-66 samples. Figure 9 NH3-TPD curves of the different UiO-66 samples. Figure 10 Catalytic performances of the different UiO-66 samples. (Reaction conditions: (a) 0.1 g catalyst, 2 mmol acetic acid, 10 mL ethanol, 75 oC; (b) 0.1 g catalyst, 5 mmol n-hexylic acid, 5 mmol benzyl alcohol, 130 oC, 2 mL methylbenzene as solvent). Figure 11 XRD patterns of the different UiO-66 samples after cycles. Figure 12 Recycling of the different samples for esterification reaction. (Reaction conditions: 0.1 g catalyst, 2 mmol acetic acid, 10 mL ethanol, 75 oC, 6h).

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b UiO-66-DGC-W

UiO-66-DGC-W

UiO-66-DGC-A

UiO-66-DGC-A

Intensity (a.u.)

Intensity (a.u.)

a

UiO-66-DGC-E

∗

UiO-66-DGC-E

UiO-66-S

UiO-66-S

5

10

15

20

25

30

35

40

45

5

10

15

2 Theta (degree)

20

25

30

35

40

45

2 Theta (degree)

Figure 1

∗

∗

UiO-66-DGC-W

∗

∗

H2BDC

∗

UiO-66-DGC-A

∗

UiO-66-DGC-E

∗

S/L=1.8

∗

S/L=1.8 ∗

S/L=1.8

S/L=0.9

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


S/L=0.9

S/L=0.9 S/L=0.5

S/L=0.5

S/L=0.5

S/L=0.2

S/L=0.2

S/L=0.2 10

20

30

2 Theta (degree)

40

50

10

20

30

40

50

2 Theta (degree)

Figure 2

25


10

20

30

2 Theta (degree)

40

50


111

200

o

120 C

o

Intensity (a.u.)

110 C

o

100 C

o

90 C

o

80 C

5

10

15

20

25

30

35

40

45

2 Theta (degree)

Figure 3

30 h 24 h 20 h 18 h 16 h

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

12 h 8h 6h 4h 3h 2h 1h 5

10

15

20

25

30

35

40

45

2 Theta (degree)

Figure 4

26


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0.03

400

a

UiO-66-S UiO-66-DGC-A UiO-66-DGC-E

350

b


3 -1

Pore Volume (cm g )

3 -1

Volume adsorbed (cm g )

300 250 200 150

0.02

0.01

100 50 0

0.00 0.0

0.2

0.4

0.6

0.8

0

1.0

5

10

Figure 5


50

40 3 -1

30

20

10

0 0

20

40

60

15

20

25

Pore Size (nm)

P/P0

Volume adsorbed (cm g )

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

100

P (kPa)

Figure 6

27


30

35

40


Figure 7

100

90 40.3%

80

Weight loss (%)

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

37.4% 70

60

29.4%

50 UiO-66-S UiO-66-DGC-A UiO-66-DGC-E

40

30 100

200

300

400

500

600

o

Temperature ( C)

Figure 8

28


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TCD response (a.u.)

UiO-66-DGC-E

UiO-66-DGC-A

UiO-66-S

50

100

150

200

250

300

350

400

o

Temperature ( C)

Figure 9 100

b

a

80

n-Hexylic acid Conversion (％)

80

Acetic acid 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


60

40 UiO-66-S UiO-66-DGC-A UiO-66-DGC-E 20

0

60

40


20

0

0

2

4

6

8

10

0

1

2

3

4

Reaction time (h)

Reaction time (h)

Figure 10

29


5

6

7


Intensity (a.u.)

UiO-66-DGC-A-R

UiO-66-DGC-E-R

UiO-66-S-R

5

10

15

20

25

30

35

40

45

2 Theta (degree)

Figure 11

100

UiO-66-S UiO-66-DGC-E

90

UiO-66-DGC-A 80 70

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

60 50 40 30 20 10 0

1

2

3

Reaction run

Figure 12

30


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Table of Contents and Abstract Graphics

Substrates Organic solvent

100 ℃, 24 h

UiO-66

31


Dry-Gel Conversion Synthesis of Zr-Based Metal–Organic Frameworks

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