Postsynthetic Strategy To Prepare ACN@Cu-BTCs with Enhanced

Subscriber access provided by MT ROYAL COLLEGE

Article

A Post-Synthetic Strategy to Prepare ACN@Cu-BTCs with Enhanced Water Vapor Stability and CO/CH Separation Selectivity 2

4

Zhedong Lin, Zhenqiang Lv, Xin Zhou, Huiyu Xiao, JUNLIANG WU, and Zhong Li Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b04468 • Publication Date (Web): 27 Feb 2018 Downloaded from http://pubs.acs.org on February 28, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 37 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

Industrial & Engineering Chemistry Research

A Post-Synthetic Strategy to Prepare ACN@Cu-BTCs with Enhanced Water Vapor Stability and CO2/CH4 Separation Selectivity Zhedong Lin1, Zhenqiang Lv1, Xin Zhou1*, Huiyu Xiao1, Junliang Wu3 Zhong Li1,2* 1 School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, PR China 2 State Key Lab of Subtropical Building Science of China, South China University of Technology, Guangzhou 510640, PR China 3 Guangdong Provincial Key Laboratory of Atmospheric Environment and Pollution Control, Guangzhou 510640, PR China * Corresponding authors: [email protected]; [email protected]

Abstract: Cu-BTC, a commercially available MOF with great potential in gas adsorption and separation, is vulnerable to moisture, hindering its practical application. Herein, we propose a post-synthetic strategy to prepare ACN@Cu-BTCs with enhanced water vapor stability and CO2/CH4 selectivity. Successful grafting of ACN was evidenced by FT-IR spectra, which completely inhibited the moisture-induced adsorptive capacity degeneration of ACN1/1@Cu-BTC at RH = 55% for CO2 capture. The water vapor-stability experiments showed that after being exposed to 55% RH for 20 days, Cu-BTC lost its crystallinity and CO2 adsorption capacity, while ACN1/3@Cu-BTC preserved 88% of its original CO2 capacity. In addition, ACN1/3@Cu-BTC showed a high CO2 capacity of 4.32 mmol/g at ambient conditions and inherited the decent CO2/CH4 adsorption selectivity from Cu-BTC. DFT calculation ascribed such an enhanced water vapor stability to the protection of Cu sites by ACN, which is worthy of further exploitation in enhancing the water vapor stability of other MOFs with unsaturated metal sites. 1

ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 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 2 of 37

Keywords: post-synthetic modification; ACN@Cu-BTC; water vapor stability; CO2 adsorption

Introduction The steeply increasing CO2 concentration in the atmosphere has caused destructive consequences such as polar glaciers melting and global warming, and thus has gathered extensive concern.1, 2 As an indispensable strategic measure, CO2 capture was proposed to restrain the ambient CO2 concentration.3, 4 Hence, the development of viable carbon capture and sequestration technology (CCS) becomes a scientific challenge of high priority. In recent decades, adsorption5, chemical absorption6 and membrane separation7,

8

have been developed for CCS. Among all alternatives,

physisorption-based processes are considered as one of the most energy-saving and cost-effective technologies.9, 10 Adsorbent is the core of the adsorption technology, and is a crucial part in achieving effective adsorption processes. Conventional adsorbents such as zeolite and activated carbon11,

12

have been

widely investigated for CCS. Yet, their adsorption properties require further development to meet the requirements in practical applications. In recent years, metal–organic frameworks (MOFs) have been widely studied as the promising adsorbents for CCS.13-15 MOFs are attracting vast interest because of their ultrahigh specific area, flexibility, tunable properties, and great potential in diverse applications.16, 17 Furukawa et al.18 synthesized MOF-210 with a CO2 capacity of 54.5 mmol/g at 50 bar and 298 K. The CO2 capacity of MIL-101 reported was up to 22.9 mmol/g at 298 K and 30 bar.19 In addition, some MOFs exhibited excellent 2


Page 3 of 37 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


adsorption capacity at ambient conditions. The CO2 capacity of MOF-5 was 2.1 mmol/g at 295 K and 1 atm20, while that of Cu-BTC21 and Mg2(DOBDC)22 were reported to be 6.49 mmol/g at 273 K and 8.9 mmol/g at 293 K, respectively. In spite of the superior CO2 capacity of these above-mentioned MOFs, most MOFs are vulnerable to moisture.23-25 Their poor water vapor stability is mainly attributed to the relatively weak metal-ligand coordination26-28, which could not survive H2O attack in moisture. For example, irreversible structural decomposition was reported for MIL-210, MOF-177, MOF-5, MOF-74(Mg) and Cu-BTC after being exposed to humid air, which seriously hinders their practical applications since water vapor is ubiquitous. Thus, it is imperative to improve the water vapor stability of MOFs for their practical applications. Surface modification is considered effective in improving water vapor stability of MOFs. Nan Ding et al.5 divided the open channel of MOF-5 into confined and hydrophobic compartments via in situ polymerization of 1,2-diethynylbenzene (DEB) at 443 K for 12 hours, and reported that the resulting material preserved its BET surface area after being placed in moisture with 40% relative humidity (RH) for 40 hours. Zhang et al.21 coated the surface of a series of vulnerable MOFs including MOF-5, HKUST-1, and ZnBT with a thin hydrophobic PDMS layer by a vapor deposition technique at 408 K, and reported the PDMS-modified MOFs were of significantly enhanced stability against moisture after being contacted with moisture for 1 day. Li et al.29 proposed a solvent-free mechanochemical method for the rapid synthesis of Cu-BTC and graphite oxide composites, and the resulting Cu-BTC@GO exhibited enhanced stability in water for 10 hours. Li et al.30 reported the ultrafast 3



room temperature synthesis of the novel Imi@Cu-BTC, and the resulting Imi@Cu-BTC preserved 78% of its initial capacity after being exposed to humid air for 20 days. A flexible post-synthetic strategy that stabilizes Cu-BTC under humid conditions is highly desired as Cu-BTC has become commercially available. Al-Janabi et al.31 prepared glycine-grafted Cu-BTC via a facile post-synthetic modification (PSM) method. The as-synthesized composite exhibited improved hydrothermal stability, yet its CO2 adsorption capacity dropped to 2.2 mmol/g at 298 K and 1 bar. Hence, it is necessary to develop an effective strategy that improves water vapor stability of MOFs while preserves most of its adsorptive capacity. Herein, we proposed a post-synthetic strategy to functionalize the unsaturated metal site (UMS) of Cu-BTC with acetonitrile (ACN) to improve its water vapor stability. A series of ACN@Cu-BTCs with various ACN contents were prepared. Water vapor stability of ACN@Cu-BTCs was characterized by XRD, H2O (g) and CO2 isotherms before and after samples being exposed to 55% humidity. Regenerability of ACN1/3@Cu-BTC was investigated using five consecutive adsorption-desorption cycles of CO2 on ACN1/3@Cu-BTC. Thermogravimetric analysis of ACN@Cu-BTCs were carried out to evaluate the thermal stability of the modified materials. The mechanism of the enhanced water vapor stability was discussed based on DFT calculation.

4


Page 4 of 37

Page 5 of 37 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


2. Experimental 2.1. Materials All chemicals of reagent-grade quality were purchased from commercial resources and used as received without further purification. Cu-BTC was prepared according to a reported procedure.32 Synthesis of ACN@Cu-BTCs: The as-synthesized Cu-BTC was first activated for 6 hours at 423 K, then 0.35 g activated Cu-BTC transferred into a 20 mL screw-cap vial, followed by adding a certain volume (6, 10, 15, 30 µL) of acetonitrile (boiling point: 354-355 K, molecular weight: 41.05). The vial was sealed and heated in oven at 333 K for 1 hour. Then the sample was placed into the vacuum oven at 363 K for 1 hours to evacuate the physically adsorbed acetonitrile. The products were labeled as ACN1/5@Cu-BTC, ACN1/3@Cu-BTC, ACN1/2@Cu-BTC and ACN1/1@Cu-BTC, based on the mole ratio of ACN/Cu. 2.2. Characterization X-ray diffraction (XRD) data were collected on Advance X-ray Diffractometer (Bruker D8) with Cu-Kα emission at room temperature. The scan speed was 2 degree/min and the step size was 0.02º in 2 hours. The morphologies were observed through scanning electron microscope (SEM) on a Hitachi SU8010 instrument. The powder sample was previously dried and sputter-coated with a thin layer of gold before SEM analysis. Infrared (IR) spectra were carried out on Bruker Vector 33 spectrometer with KBr pellets in the wavenumber range of 4000-400 cm-1. N2 5



Page 6 of 37

isotherms were measured at 77 K to determine the pore textural properties using ASAP 2460 Micromeritics Accelerated Surface Area and Porosimetry Analyzer. BET surface area was calculated from N2 isotherms using the built-in software. Water vapor adsorption isotherms were measured with relative humidity ranging from 0 to 90% at 298 K. All samples were dried in vacuum at 363 K for 6 hours before use. Thermogravimetric analysis (TGA) of material was performed on NETZSCH TG 209F3 instrument at a rate of 5 K min-1 up to 873 K in nitrogen atmosphere. The water vapor stability of the samples was examined by exposing the samples to air with 55% RH, where the 55% RH was maintained with saturated magnesium nitrate aqueous solution at 293 K. 2.3. CO2 and CH4 adsorption measurements CO2 and CH4 isotherms of Cu-BTC and ACN1/3@Cu-BTC were measured with a Micromeritics 3-Flex at various temperatures (288, 298 and 308 K) in the pressure range of 0 to 100 kPa. The temperature was strictly controlled using a Dewar with a circulating jacket connected to a thermostatic bath with a precision of ±0.01 K. The free space of the system was determined by dosing He. Before each measurement, the samples were outgassed in vacuum at 363 K for 6 hours. He (99.999%), CO2 (99.99%), N2 (99.99%) were used for the measurements. 2.4. Computational method DFT calculations were performed with the Gaussian 09 software

33

at the B3LYP

level of theory. C, H, O, N were modeled by the 6-311+g(d,p) basis set 34, while Cu 6


Page 7 of 37

was modeled by the LANL2DZ with effective core potential

35

. All the selected

structures were geometrically optimized while the self-consistent field was set to quadratically convergent with an extra step if the first order SCF would not converge (XQC). Frequency calculations were subsequently applied to the optimized structure to yield the thermodynamic parameters of interest as well as the visualized lowest unoccupied molecular orbitals (LUMO) of all the optimized structures.

3. Results and discussion 3.1. Characterization (a) 500

(b)

300

Cu-BTC ACN1/5@Cu-BTC

200

ACN1/3@Cu-BTC ACN1/2@Cu-BTC

100

ACN1/1@Cu-BTC

Intensity + constant (a.u.)

400

3

Quantity Adsorbed (cm /g STP)

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


ACN1/1@Cu-BTC

ACN1/2@Cu-BTC ACN1/3@Cu-BTC ACN1/5@Cu-BTC

0

Cu-BTC 0.0

0.2

0.4 0.6 0.8 Relative Pressure (P/P0)

1.0

10

20

30 2θ (degree)

40

50

Figure 1. (a) N2 isotherms at 77 K and (b) XRD patterns of ACN@Cu-BTCs and Cu-BTC Table 1. Porosity parameters of the samples ACN@Cu-BTCs and Cu-BTC

BET surface area

BET surface area

Pore Volume

(m2/g)

(m2/mmol)

(cm3/g)

Cu-BTC

1713

1043

0.7272

ACN1/5@Cu-BTC

1596

1011

0.6575

Adsorbent

7



Page 8 of 37

ACN1/3@Cu-BTC

1504

977

0.6320

ACN1/2@Cu-BTC

1449

971

0.6193

ACN1/1@Cu-BTC

1406

1029

0.6131

Figure 1 (a) presents N2 isotherms of Cu-BTC and ACN@Cu-BTCs. All isotherms are of a typical type-I profile, which suggests their predominating microporous structures. Table 1 lists the porosity parameters of the samples. All ACN@Cu-BTCs were of slightly lower specific surface area (m2/g) than that of the as-synthesized

Cu-BTC,

which

followed

the

order:

ACN1/5@Cu-BTC

>

ACN1/3@Cu-BTC > ACN1/2@Cu-BTC > ACN1/1@Cu-BTC. However, it is interesting that the specific surface area of the Cu-BTC based on quantity (m2/mmol) was well inherited by the ACN@Cu-BTCs, indicating such a post-synthetic treatment won’t compromise the porosity of the materials. Figure 1 (b) presents XRD patterns of the Cu-BTC and ACN@Cu-BTCs. The characteristic peaks of ACN@Cu-BTCs were consistent with that of the Cu-BTC, except that their relative intensities were somewhat different. Figure S1 compares the SEM images of Cu-BTC and ACN1/3@Cu-BTC, which shows smaller crystals of the ACN1/3@Cu-BTC compared to Cu-BTC. Hence, it seems that the post-synthetic functionalization of Cu-BTC in heated acetonitrile vapor changed the texture of its crystals, and the different relative intensities of the XRD peaks could be ascribed to the changed preferred orientation of the crystals.

8


Page 9 of 37

(b) 100

ACN Cu-BTC

Mass (%)

(a)



80

ACN1/3@Cu-BTC

60

ACN1/2@Cu-BTC

40

ACN1/1@Cu-BTC

0

ACN1/2@Cu-BTC

390K DTG

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


ACN1/1@Cu-BTC

-1 -2

2500

2000 1500 -1 1000 Wavenumber (cm )

400

500

500

600 700 Temperature (K)

800

900

Figure 2. (a) IR spectra, (b) TGA (above) and DTG (below) curves of the samples.

Figure 2 (a) shows IR spectra of the Cu-BTC and ACN@Cu-BTCs. The IR spectra of ACN@Cu-BTCs exhibited profiles similar to that of Cu-BTC in the range of 500 – 2000 cm-1. Meanwhile, the peaks at around 2252 cm-1 were assigned to C-N stretching vibration from acetonitrile, indicating the presence of ACN in ACN@Cu-BTCs. Furthermore, the C-N stretching vibrations in ACN@Cu-BTCs blue shifted by about 8 cm-1, which can be attributed to the confined C-N stretching vibrations when ACN being coordinated to the unsaturated Cu site.36 Figure 2 (b) presents the TGA and DTG curves of Cu-BTC and ACN@Cu-BTCs. There were two major weight losses for Cu-BTC, which could be separately assigned to the removal of guest molecules (330-390 K) and the decomposition of organic ligands (580-640 K). In contrast, there was an additional weight loss for ACN@Cu-BTCs in 390-520 K, which was assigned to dissociation of ACN from Cu sites. Figure S2 replots the TGA curves from 390 K, which shows the weight loss follows Cu-BTC < ACN1/5@Cu-BTC < ACN1/3@Cu-BTC < ACN1/2@Cu-BTC < ACN1/1@Cu-BTC, being consistent with the grafting ACN quantity. Hence, ACN@Cu-BTCs were stable in the temperature range up to 390 K, which is sufficient to meet the requirement of conventional pressure swing adsorption processes. 9



(a)

(b)

Intensity (a.u.)

3.2. Water vapor stability of ACN@Cu-BTCs

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

Page 10 of 37

Cu-BTC

ACN1/3@Cu-BTC ACN1/3@Cu-BTC-10d

Cu-BTC-10d ACN1/3@Cu-BTC-20d

Cu-BTC-20d 10

20

30 2 Theta (2θ)

40

50

10

20

30 2 Theta (2θ)

40

50

Figure 3. PXRD patterns of (a) Cu-BTC and (b) ACN1/3@Cu-BTC before and after being exposed to humid air.

The water vapor stability of these samples was examined by exposing the samples to the air with 55% RH at room temperature. Figure 3 compares PXRD patterns of the samples before and after being exposed to humid air. It was observed that the characteristic peaks of Cu-BTC drastically diminished after the exposure in moisture, and meanwhile, a new peak arose at 10 degree for the remains. In contrast, ACN1/3@Cu-BTC managed to preserve its major characteristic peaks even after 20 days’ exposure, indicating that its water vapor stability had been significantly improved. Although all samples eventually exhibited the small peak at 10 degree after a long exposure of 20 days in moisture, the intensity of this peak decreased with the grafting acetonitrile quantity as is shown in Figure S3. Hence, grafting ACN onto Cu-BTC helps to maintain its crystallinity in moisture.

10


Page 11 of 37

(b) 5

4

CO2 Adsorbed Amount (mmol/g)

Cu-BTC ACN1/5@Cu-BTC ACN1/3@Cu-BTC ACN1/2@Cu-BTC

3

ACN1/1@Cu-BTC

2 1 0

0

(c) 5 4

20

40 60 Pressure (kPa)

80


(d)

4


2 1

ACN1/2@Cu-BTC 3

20

ACN1/1@Cu-BTC

2 1

20


80

100

80 60 40 20 0

0

ACN1/3@Cu-BTC

100

ACN1/2@Cu-BTC 3


0 0

100

Preserved CO2 capacity (%)


(a) 5


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

C TC -BTC Cu-BTC Cu-BT -BTC @ Cu-B @Cu @Cu @ N N /2 /5 N N /1 AC 1 AC 1 AC 1/3 AC 1

Figure 4. CO2 isotherms of Cu-BTC and ACN@Cu-BTCs (a) before and after being exposed to 55% RH at 298K for (b) 10 and (c) 20 days, (d) a comparison of the CO2 capacity in (c).

Figure 4 (a)-(c) show CO2 isotherms of the samples before and after being exposed to humid air. For the as-synthesized samples, ACN@Cu-BTCs inherited the decent CO2 capacity of their parental Cu-BTC with deviations consistent to their BET surface area. Besides, ACN@Cu-BTCs managed to preserve most of their original capacity after being exposed to humid air for 20 days, while Cu-BTC almost lost all its capacity as is shown in Figure 4(d). For example, only 14% CO2 capacity was remained for Cu-BTC after 10 days exposure in humid air, while in contrast ACN1/3@Cu-BTC managed to preserve 96% of its original CO2 capacity. Moreover, for ACN1/1@Cu-BTC where all Cu unsaturated sites were protected by equimolar ACN, the degeneration of its structure under moisture was negligible even after 20 11



days in moisture. Hence, the post-synthetic ACN grafting strategy provides an effective approach to enhance water vapor stability of the commercially available Cu-BTC, which is significant in facilitating their practical application.

Figure 5. DFT optimized Cu-BTC derived conformations and their corresponding LUMO. (Red, white, gray, dark blue and orange spheres represent O, H, C, N, and Cu, respectively.)

Figure 5 illustrates the DFT optimized Cu-BTC derived conformations and their corresponding LUMO. The LUMO locating around unsaturated Cu sites (as shown in Figure 5a) makes it readily accept a lone pair to bond H2O (as shown in Figure 5b), which might lead to a structural destruction via the subsequent hydrolysis or ligand displacement. However, it has been reported that the presence of additional alkane groups from ligand could enhance the stability of MOFs with a steric effect that shields metal cluster of MOFs from H2O attack.37, 38 Besides, our previous work proposed an in-situ strategy that functionalizes unsaturated metal sites of Cu-BTC with imidazole (Imi) during synthesis to yield Imi@Cu-BTC with significantly improved water vapor stability.30 Based on the validated mechanism proposed in these works, herein we constructed a methyl-shielding microenvironment for the unsaturated Cu sites to shield H2O attack by directly grafting a methyl group to the unsaturated Cu sites through the Cu-N bond. When H2O molecule bonds to Cu, the 12


Page 12 of 37

Page 13 of 37 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


corresponding Cu-O bond length was calculated to be 2.33 Å. However, when ACN is grafted to the Cu (as shown in Figure 5c), the corresponding Cu-N bond length was calculated to be 2.30 Å. Although these bond lengths are close to each other, ACN and H2O construct distinct microenvironments around the Cu sites. Once H2O bonds to the unsaturated Cu site, it tends to bond more H2O to H2O@Cu-BTC through hydrogen bond, and eventually leads to the decomposition of Cu-BTC. In contrast, when ACN is functionalized to Cu-BTC to form ACN@Cu-BTC, it constructed a hydrophobic microenvironment around the Cu sites, which repels H2O and thus inhibits further hydrolysis. Hence, the hydrophobic microenvironment as well as the steric hindrance constructed by ACN well explains the origination of the enhanced water vapor stability of ACN@Cu-BTC. Furthermore, water vapor isotherms were experimentally recorded in Figure S4, showing the decreased water vapor uptake with

the

grafting

ACN

quantity,

which

proved

the

more

hydrophobic

microenvironment of the ACN@Cu-BTC compared to Cu-BTC.

3.3. Isosteric heats of CO2 and CH4 adsorption on ACN1/3@Cu-BTC Isosteric heat of adsorption is usually applied to evaluate the interaction between adsorbate and adsorbent 39. The isosteric heat of adsorption can be estimated from the isotherms at different temperatures by using Clausius-Clapeyron equation: ∆ுೞ

ோ் మ

= −ቀ

డ௟௡௣ డ்

ቁ

௤

(1)

where the ∆‫ܪ‬௦ (kJ mol-1) is the isosteric heat of adsorption at a given specific surface loading, R (J mol-1 K-1) is the universal gas constant, T (K) is the temperature,

p (bar) is the pressure, and q (mmol/g) is the amount of the adsorbed adsorbate, by 13



integrating the equation gives:

݈݊‫ = ݌‬−

∆ுೞ ோ்

+ ‫( ܥ‬2)

where C is an integral constant.

4 3

(b) 32

Cu-BTC-CO2 Cu-BTC-CH4

28

ACN1/3@Cu-BTC-CO2

24

Isosteric Heat (KJ/mol)

(a) 5

Adsorbed Amount (mmol/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

Page 14 of 37

ACN1/3@Cu-BTC-CH4

2 1

20 16

Cu-BTC-CO2

12

ACN1/3@Cu-BTC-CO2 Cu-BTC-CH4

8

ACN1/3@Cu-BTC-CH4

4 0 0

20


80

100

0

0.0

0.5

1.0 1.5 2.0 2.5 3.0 Adsorption quantity (mmol/g)

3.5

4.0

Figure 6. (a)The adsorption isotherms and (b) isosteric heats of CO2 and CH4 on Cu-BTC and ACN1/3@Cu-BTC.

Figure S5 shows the CO2/CH4 isotherms at different temperatures. The isosteric heats of CO2 and CH4 adsorption were calculated from these isotherms. Figure 6 plots the CO2 and CH4 adsorption isotherms and isosteric heats to the adsorbate loading on the samples. It can be seen that the isosteric heats of CO2 adsorption on ACN1/3@Cu-BTC were close to that on Cu-BTC, indicating this post-synthetic grafting of ACN might not compromise to the selective removal of CO2 from CO2/CH4 mixtures. Besides, the isosteric heats of CO2 adsorption were higher than that of CH4 adsorption on both samples, while the isosteric heats of CH4 adsorption on the two samples were almost the same.

14


Page 15 of 37

Selectivity of CO2 vs CH4

10 8

Cu-BTC

6 ACN1/3@Cu-BTC 4 2 0

0

20


80

100

Figure 7. IAST-predicted selectivity for equimolar CO2/CH4 mixtures at 298 K on Cu-BTC and ACN1/3@Cu-BTC.

Ideal adsorbed solution theory (IAST) has been widely applied in predicting the adsorption selectivity of binary gas mixtures based on their pure component isotherms40,

41

. In this work, IAST model was applied to predict the CO2/CH4

adsorption selectivity. Figure 7 presents the IAST-predicted CO2/CH4 selectivity of ACN1/3@Cu-BTC and Cu-BTC, indicating that CO2/CH4 adsorption selectivity of ACN1/3@Cu-BTC was close to that of Cu-BTC. 100% Regeneration Efficiency (%)

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


1

97.3%

2

98.4%

98.2%

3 4 Regeneration Cycle

97.7%

5

Figure 8. Five consecutive CO2 adsorption-desorption cycles on ACN1/3@Cu-BTC at 298K.

To estimate the stability and reproducibility after regeneration of ACN@Cu-BTC in consecutive applications, five CO2 adsorption-desorption cycles were performed 15



Page 16 of 37

on ACN1/3@Cu-BTC. The regeneration cycles were performed at 1 bar for adsorption, and 0.05 mbar for desorption at 298 K. Figure 8 shows that the regeneration efficiency of the ACN1/3@Cu-BTC was in the range of 97.3-98.4%, suggesting its excellent stability and reproducibility after regeneration. Table 2 compares its CO2 capacities with other MOFs at 298 K and 1 bar for an intuitional comparison. It is noticed that ACN1/3@Cu-BTC is among the most promising MOFs for CO2 adsorption. Table 2. A comparison of CO2 capacity with other MOFs at 298 K and 1 bar.

Adsorbent

BET surface area

CO2 capacity

Temperature

(m2/g)

(mmol/g)

(K)

ACN1/3@Cu-BTC

1504

4.32

298

This work

UiO-66

1525

1.79

298

42

UIO-67

2505

1.02

298

43

BUT-11

1310

2.39

298

43

MIL-101(Cr,Mg)

3274

3.28

298

5

MIL-100(Fe)

2558

2.24

298

44

Ni-MOF-74

1418

6.08

298

45

Mg-MOF-74

816-1174

4.9-6.25

298

46

MOF-177

4508

0.8-1.05

298

46

ZIF-8

1475

0.83

298

11

MOF-5

2304

1.95

296

20

UTSA-40

1630

3.26

298

47

16


Reference

Page 17 of 37 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


Bi-MOF-11

1040

4.1

298

48

4. Conclusion In summary, we have proposed a post-synthetic strategy to functionalize Cu-BTC with ACN. The resulting ACN@Cu-BTCs were of promising water vapor stability against moisture. The 1:1 molar ratio ACN to Cu grafting completely inhibits the water-vapor-induced adsorptive capacity degeneration of ACN1/1@Cu-BTC in 55% RH moisture for CO2 capture. The enhanced stream stability of ACN@Cu-BTCs could be ascribed to the protection of unsaturated metal sites by ACN, which constructed a hydrophobic microenvironment around Cu sites to inhibit hydrolysis or replacement of ligands. Besides, the 1:3 functionalized ACN1/3@Cu-BTC showed an optimized CO2 capacity of 4.32 mmol/g at 1 bar and ambient temperature, which is among the most promising CCS adsorbents. Moreover, the CO2/CH4 selectivity of Cu-BTC was barely compromised by this post-synthetic strategy. Hence, this post-synthetic strategy could provide a simple technique to improve the water vapor stability of the commercially available MOFs with unsaturated metal sites.

Acknowledgements This work was supported by Key Program of National Natural Science Foundation of China (21436005), National Natural Science Foundation of China (U1662136), the Post-Doctoral Innovative Talents Project (BX201600053) from China Postdoctoral Science Foundation (176394), the Research Foundation of State Key Lab of Subtropical Building Science of China (C715023z), and the Guangdong 17



Province Science and Technology Project (2016A020221006).

Supporting Information Supplementary data associated with this article including SEM, XRD, water vapor isotherms, CO2 and CH4 isotherms and their fits.

References 1.

Obama, B., The irreversible momentum of clean energy. Science 2017, 355, (6321), 126-129.

2.

Hausfather, Z.; Cowtan, K.; Clarke, D. C.; Jacobs, P.; Richardson, M.; Rohde, R., Assessing recent warming using

instrumentally homogeneous sea surface temperature records. Science Advances 2017, 3, (1). 3.

Sanz-Perez, E. S.; Murdock, C. R.; Didas, S. A.; Jones, C. W., Direct Capture of CO2 from Ambient Air. Chemical

Reviews 2016, 116, (19), 11840-11876. 4.

Sumida, K.; Rogow, D. L.; Mason, J. A.; McDonald, T. M.; Bloch, E. D.; Herm, Z. R.; Bae, T. H.; Long, J. R., Carbon

dioxide capture in metal-organic frameworks. Chemical Reviews 2012, 112, (2), 724-81. 5.

Ding, N.; Li, H.; Feng, X.; Wang, Q.; Wang, S.; Ma, L.; Zhou, J.; Wang, B., Partitioning MOF-5 into Confined and

Hydrophobic Compartments for Carbon Capture under Humid Conditions. Journal of the American Chemical Society 2016, 138, (32), 10100-3. 6.

Lv, B.; Jing, G.; Qian, Y.; Zhou, Z., An efficient absorbent of amine-based amino acid-functionalized ionic liquids for

CO2 capture: High capacity and regeneration ability. Chemical Engineering Journal 2016, 289, 212-218. 7.

He, W.; Zhang, F.; Wang, Z.; Sun, W.; Zhou, Z.; Ren, Z., Facilitated Separation of CO2 by Liquid Membranes and

Composite Membranes with Task-Specific Ionic Liquids. Industrial & Engineering Chemistry Research 2016, 55, (49), 12616-12631. 8.

Huang, Y.; Liu, D.; Liu, Z.; Zhong, C., Synthesis of Zeolitic Imidazolate Framework Membrane Using

Temperature-Switching Synthesis Strategy for Gas Separation. Industrial & Engineering Chemistry Research 2016, 55, (26), 7164-7170. 9.

Konduru, N.; Lindner, P.; Assaf-Anid, N. M., Curbing the greenhouse effect by carbon dioxide adsorption with

zeolite 13X. Aiche Journal 2007, 53, (12), 3137-3143. 10. Cui, X.; Chen, K.; Xing, H.; Yang, Q.; Krishna, R.; Bao, Z.; Wu, H.; Zhou, W.; Dong, X.; Han, Y.; Li, B.; Ren, Q.; Zaworotko, M. J.; Chen, B., Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene. Science 2016, 353, (6295), 141-144. 11. McEwen, J.; Hayman, J.-D.; Ozgur Yazaydin, A., A comparative study of CO2, CH4 and N2 adsorption in ZIF-8, Zeolite-13X and BPL activated carbon. Chemical Physics 2013, 412, 72-76. 12. Bezerra, D. P.; Oliveira, R. S.; Vieira, R. S.; Cavalcante, C. L.; Azevedo, D. C. S., Adsorption of CO2 on nitrogen-enriched activated carbon and zeolite 13X. Adsorption 2011, 17, (1), 235-246. 13. Lee, J. Y.; Olson, D. H.; Pan, L.; Emge, T. J.; Li, J., Microporous metal-organic frameworks with high gas sorption and separation capacity. Advanced Functional Materials 2007, 17, (8), 1255-1262. 14. Hu, Z.; Kang, Z.; Qian, Y.; Peng, Y.; Wang, X.; Chi, C.; Zhao, D., Mixed Matrix Membranes Containing UiO-66(Hf)-(OH)2 Metal-Organic Framework Nanoparticles for Efficient H2/CO2 Separation. Industrial & Engineering Chemistry Research 2016, 55, (29), 7933-7940. 18


Page 18 of 37

Page 19 of 37 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


15. Pimentel, B. R.; Fultz, A. W.; Presnell, K. V.; Lively, R. P., Synthesis of Water-Sensitive Metal–Organic Frameworks within Fiber Sorbent Modules. Industrial & Engineering Chemistry Research 2017, 56, (17), 5070-5077. 16. Furukawa, H.; Cordova, K. E.; O'Keeffe, M.; Yaghi, O. M., The chemistry and applications of metal-organic frameworks. Science 2013, 341, (6149), 1230444. 17. Hu, P.; Liang, X.; Yaseen, M.; Sun, X.; Tong, Z.; Zhao, Z.; Zhao, Z., Preparationofhighly-hydrophobic novel N-coordinated UiO-66(Zr) with dopamine via fast mechano-chemical method for (CHO-/Cl-)-VOCs competitive adsorption in humid environment. Chemical Engineering Journal 2017. 18. Furukawa, H.; Ko, N.; Go, Y. B.; Aratani, N.; Choi, S. B.; Choi, E.; Yazaydin, A. Ö.; Snurr, R. Q.; O’Keeffe, M.; Kim, J., Ultrahigh porosity in metal-organic frameworks. Science 2010, 329, (5990), 424-428. 19. Zhang, Z.; Huang, S.; Xian, S.; Xi, H.; Li, Z., Adsorption Equilibrium and Kinetics of CO2 on Chromium Terephthalate MIL-101. Energy & Fuels 2011, 25, (2), 835-842. 20. Zhao, Z.; Li, Z.; Lin, Y. S., Adsorption and Diffusion of Carbon Dioxide on Metal−Organic Framework (MOF-5). Industrial & Engineering Chemistry Research 2009, 48, (22), 10015-10020. 21. Yan, X.; Komarneni, S.; Zhang, Z.; Yan, Z., Extremely enhanced CO2 uptake by HKUST-1 metal–organic framework via a simple chemical treatment. Microporous and Mesoporous Materials 2014, 183, 69-73. 22. Mason, J. A.; Sumida, K.; Herm, Z. R.; Krishna, R.; Long, J. R., Evaluating metal-organic frameworks for post-combustion carbon dioxide capture via temperature swing adsorption. Energy & Environmental Science 2011, 4, (8), 3030-3040. 23. Zhang, W.; Hu, Y.; Ge, J.; Jiang, H. L.; Yu, S. H., A facile and general coating approach to moisture/water-resistant metal-organic frameworks with intact porosity. Journal of the American Chemical Society 2014, 136, (49), 16978-81. 24. Burtch, N. C.; Jasuja, H.; Walton, K. S., Water stability and adsorption in metal-organic frameworks. Chemical Reviews 2014, 114, (20), 10575-612. 25. DeCoste, J. B.; Peterson, G. W.; Schindler, B. J.; Killops, K. L.; Browe, M. A.; Mahle, J. J., The effect of water adsorption on the structure of the carboxylate containing metal–organic frameworks Cu-BTC, Mg-MOF-74, and UiO-66. Journal of Materials Chemistry A 2013, 1, (38), 11922. 26. Mondloch, J. E.; Katz, M. J.; Planas, N.; Semrouni, D.; Gagliardi, L.; Hupp, J. T.; Farha, O. K., Are Zr6-based MOFs water stable? Linker hydrolysis vs. capillary-force-driven channel collapse. Chemical Communications 2014, 50, (64), 8944-8946. 27. DeCoste, J. B.; Peterson, G. W.; Jasuja, H.; Glover, T. G.; Huang, Y.-g.; Walton, K. S., Stability and degradation mechanisms of metal-organic frameworks containing the Zr6O4(OH)4 secondary building unit. Journal of Materials Chemistry A 2013, 1, (18), 5642-5650. 28. Lawrence, M. C.; Schneider, C.; Katz, M. J., Determining the structural stability of UiO-67 with respect to time: a solid-state NMR investigation. Chemical Communications 2016, 52, (28), 4971-4974. 29. Li, Y.; Miao, J.; Sun, X.; Xiao, J.; Li, Y.; Wang, H.; Xia, Q.; Li, Z., Mechanochemical synthesis of Cu-BTC@GO with enhanced water stability and toluene adsorption capacity. Chemical Engineering Journal 2016, 298, 191-197. 30. Li, H.; Lin, Z.; Zhou, X.; Wang, X.; Li, Y.; Wang, H.; Li, Z., Ultrafast Room Temperature Synthesis of Novel Composites Imi@Cu-BTC with Improved Stability against Moisture. Chemical Engineering Journal 2017, 307, 537-543. 31. Al-Janabi, N.; Deng, H.; Borges, J.; Liu, X.; Garforth, A.; Siperstein, F. R.; Fan, X., A Facile Post-Synthetic Modification Method To Improve Hydrothermal Stability and CO2 Selectivity of CuBTC Metal–Organic Framework. Industrial & Engineering Chemistry Research 2016, 55, (29), 7941-7949. 32. Zhao, J.; Nunn, W. T.; Lemaire, P. C.; Lin, Y.; Dickey, M. D.; Oldham, C. J.; Walls, H. J.; Peterson, G. W.; Losego, M. D.; Parsons, G. N., Facile Conversion of Hydroxy Double Salts to Metal-Organic Frameworks Using Metal Oxide Particles and Atomic Layer Deposition Thin-Film Templates. Journal of the American Chemical Society 2015, 137, (43), 13756-9. 33. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A.; Nakatsuji, H.; Caricato, M.; Li, X.; Hratchian, H. P.; Izmaylov, A. F.; Bloino, J.; Zheng, G.; 19



Sonnenberg, J. L.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Vreven, T.; Montgomery Jr., J. A.; Peralta, J. E.; Ogliaro, F.; Bearpark, M. J.; Heyd, J.; Brothers, E. N.; Kudin, K. N.; Staroverov, V. N.; Kobayashi, R.; Normand, J.; Raghavachari, K.; Rendell, A. P.; Burant, J. C.; Iyengar, S. S.; Tomasi, J.; Cossi, M.; Rega, N.; Millam, N. J.; Klene, M.; Knox, J. E.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski, J. W.; Martin, R. L.; Morokuma, K.; Zakrzewski, V. G.; Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, Ö.; Foresman, J. B.; Ortiz, J. V.; Cioslowski, J.; Fox, D. J. Gaussian 09, Gaussian, Inc.: Wallingford, CT, USA, 2009. 34. Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A., Self-consistent molecular orbital methods. XX. A basis set for correlated wave functions. Journal of Chemical Physics 1980, 72, (1), 650-654. 35. Hay, P. J.; Wadt, W. R., Ab initio effective core potentials for molecular calculations-potentials for K to Au including the outermost core orbitals. Journal of Chemical Physics 1985, 82, 299-310. 36. Matsuura, H.; Yoshida, H.; Hieda, M.; Yamanaka, S.-y.; Harada, T.; Shin-ya, K.; Ohno, K., Experimental Evidence for Intramolecular Blue-Shifting C−H···O Hydrogen Bonding by Matrix-Isolation Infrared Spectroscopy. Journal of the American Chemical Society 2003, 125, (46), 13910-13911. 37. Jasuja, H.; Walton, K. S., Effect of catenation and basicity of pillared ligands on the water stability of MOFs. Dalton transactions 2013, 42, (43), 15421-6. 38. Jasuja, H.; Jiao, Y.; Burtch, N. C.; Huang, Y. G.; Walton, K. S., Synthesis of cobalt-, nickel-, copper-, and zinc-based, water-stable, pillared metal-organic frameworks. Langmuir : the ACS journal of surfaces and colloids 2014, 30, (47), 14300-7. 39. Wang, X.; Wu, Y.; Zhou, X.; Xiao, J.; Xia, Q.; Wang, H.; Li, Z., Novel C-PDA adsorbents with high uptake and preferential adsorption of ethane over ethylene. Chemical Engineering Science 2016, 155, 338-347. 40. Walton, K. S.; Sholl, D. S., Predicting multicomponent adsorption: 50 years of the ideal adsorbed solution theory. AIChE Journal 2015, 61, (9), 2757-2762. 41. Liang, W.; Zhang, Y.; Wang, X.; Wu, Y.; Zhou, X.; Xiao, J.; Li, Y.; Wang, H.; Li, Z., Asphalt-derived high surface area activated porous carbons for the effective adsorption separation of ethane and ethylene. Chemical Engineering Science 2017, 162, 192-202. 42. Hu, Z.; Faucher, S.; Zhuo, Y.; Sun, Y.; Wang, S.; Zhao, D., Combination of Optimization and Metalated-Ligand Exchange: An Effective Approach to Functionalize UiO-66(Zr) MOFs for CO2 Separation. Chemistry - A European Journal 2015, 21, (48), 17246-17255. 43. Wang, B.; Huang, H.; Lv, X.-L.; Xie, Y.; Li, M.; Li, J.-R., Tuning CO2 Selective Adsorption over N2 and CH4 in UiO-67 Analogues through Ligand Functionalization. Inorganic Chemistry 2014, 53, (17), 9254-9259. 44. Mei, L.; Jiang, T.; Zhou, X.; Li, Y.; Wang, H.; Li, Z., A novel DOBDC-functionalized MIL-100(Fe) and its enhanced CO2 capacity and selectivity. Chemical Engineering Journal 2017, 321, 600-607. 45. Liu, J.; Wang, Y.; Benin, A. I.; Jakubczak, P.; Willis, R. R.; LeVan, M. D., CO2/H2O Adsorption Equilibrium and Rates on Metal-Organic Frameworks: HKUST-1 and Ni/DOBDC. Langmuir : the ACS journal of surfaces and colloids 2010, 26, (17), 14301-14307. 46. Yazaydın, A. Ö.; Snurr, R. Q.; Park, T.-H.; Koh, K.; Liu, J.; LeVan, M. D.; Benin, A. I.; Jakubczak, P.; Lanuza, M.; Galloway, D. B.; Low, J. J.; Willis, R. R., Screening of Metal−Organic Frameworks for Carbon Dioxide Capture from Flue Gas Using a Combined Experimental and Modeling Approach. Journal of the American Chemical Society 2009, 131, (51), 18198-18199. 47. He, Y.; Xiang, S.; Zhang, Z.; Xiong, S.; Wu, C.; Zhou, W.; Yildirim, T.; Krishna, R.; Chen, B., A microporous metal– organic framework assembled from an aromatic tetracarboxylate for H2 purification. Journal of Materials Chemistry A 2013, 1, (7), 2543. 48. An, J.; Geib, S. J.; Rosi, N. L., High and Selective CO2 Uptake in a Cobalt Adeninate Metal−Organic Framework Exhibiting Pyrimidine- and Amino-Decorated Pores. Journal of the American Chemical Society 2010, 132, (1), 38-39. 20


Page 20 of 37

Page 21 of 37 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


21



TOC 154x90mm (600 x 600 DPI)


Page 22 of 37

Page 23 of 37 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 1 (a) 84x63mm (300 x 300 DPI)



Figure 1 (b) 84x67mm (300 x 300 DPI)


Page 24 of 37

Page 25 of 37 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 2 (a) 84x65mm (300 x 300 DPI)



Figure 2 (b) 84x60mm (300 x 300 DPI)


Page 26 of 37

Page 27 of 37 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 3(a) 84x67mm (300 x 300 DPI)



Figure 3(b) 84x67mm (300 x 300 DPI)


Page 28 of 37

Page 29 of 37 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 30 of 37

Page 31 of 37 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 4(c) 84x65mm (300 x 300 DPI)



Figure 4 (d) 84x71mm (300 x 300 DPI)


Page 32 of 37

Page 33 of 37 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 5 100x30mm (300 x 300 DPI)





Page 34 of 37

Page 35 of 37 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 7 84x66mm (300 x 300 DPI)


Page 36 of 37

Page 37 of 37 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 8 84x68mm (300 x 300 DPI)


Postsynthetic Strategy To Prepare ACN@Cu-BTCs with Enhanced

Recommend Documents