N2 Separation through Two

Subscriber access provided by United Arab Emirates University | Libraries Deanship

Article 2

2

Molecular Dynamics Simulations of CO/N Separation through Two-Dimensional Graphene Oxide Membranes Wen Li, Xin Zheng, Zihan Dong, Chuanyong Li, Wensen Wang, Youguo Yan, and Jun Zhang J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.6b06940 • Publication Date (Web): 31 Oct 2016 Downloaded from http://pubs.acs.org on November 3, 2016

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 free 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 accessible to all readers and 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.

The Journal of Physical Chemistry C 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 20

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

The Journal of Physical Chemistry

Molecular Dynamics Simulations of CO2/N2 Separation through Two-Dimensional Graphene Oxide Membranes Wen Li,†,‡,§ Xin Zheng,†,‡,§ Zihan Dong,†,‡ Chuanyong Li,†,‡ Wensen Wang†,‡ Youguo Yan,†,‡,* and Jun Zhang,†,‡,*

† College of Science, China University of Petroleum, 266580 Qingdao, Shandong, People’s Republic of China ‡ Key Laboratory of New Energy Physics & Materials Science in Universities of Shandong, China University of Petroleum, 266580 Qingdao, Shandong, People’s Republic of China

1 ACS Paragon Plus Environment


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 20

Abstract: Graphene oxide (GO), as an ultrathin, high-flux and energy-efficient separation membrane, has shown great potential for CO2 capture. In this study, using molecular dynamics simulations, the separation of CO2 and N2 through the interlayer gallery of GO membranes was studied. The preferential adsorption of CO2 in the GO channel derived from their strong interaction is responsible for the selectivity of CO2 over N2. Furthermore, the influences of interlayer spacing, oxidization degree and channel length on the separation of CO2/N2 were investigated. Our studies unveil the underlying mechanism of CO2/N2 separation in the interlayer GO channel, and the results might be helpful in guiding rational design of GO membranes for gas separation.


Page 3 of 20

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


Introduction In the past decades, the increasing emission of CO2 arouses serious environmental problems,1-3 especially the greenhouse effect.4-5 Meanwhile, the CO2 also has widespread applications in many industrial fields, such as enhanced oil recovery,6 microelectronics cleaning7 and industrial extraction.8 Capturing CO2 from N2, on one hand could reduce the amount of CO2 in the atmosphere, on the other hand could realize the recycle of CO2. Therefore, many efforts have been devoted to developing various strategies to separate CO2/N2.9-12 Recent investigations have shown that membrane separation is a high-efficient approach for gas separation due to its low energy cost.13-15 The separation membranes could be divided into organic (polymers) membranes, inorganic (carbon, glass, metal, ceramics) membranes and the hybrid (inorganic polymeric or organic-inorganic) membranes. For all types of membranes, abundant researches have demonstrated that there is a trade-off between selectivity and permeability, and the permeability of a membrane is inversely proportional to its thickness. Moreover, the aging and plasticization of these membrane materials is another obstacle to maintain the long-lived gas separation performance. To remedy the shortages of these traditional membrane materials, nanoporous graphene, a single atomic layer membrane, has been used for gas separation and obtained great success.16-20 It presents high selectivity and large permeability simultaneously. But its separation performance is largely dependent on the pore sizes in the graphene. Although using elaborate oxidative etching or electron/ion bombardment could drill holes in graphene, a precise, large-area and high-density perforation remains a technical challenge.21-23 In contrast to graphene, its oxidized form, graphene oxide (GO) membrane with a laminar structure 3 ACS Paragon Plus Environment


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

shows great potential for molecular separation.20,

24-28

Page 4 of 20

Unlike the nanoporous graphene, the GO

membrane does not need to drill hole for gas separation, and the interlayer spaces of the laminar GO membrane could act as the main channels for molecular separation. Through controlling humidity, inserting nanoparticles between adjacent layers or modifying chemical groups with different chain length, different interlayer spaces could be achieved and used to separate various chemical species. This might open an avenue for gas separation using low-cost GO membrane.29 Recently, Jin et al. found that the molecular-sieving interlayer spaces and straight diffusion pathways of GO laminates yielded fast and selective CO2 permeation over N2,30 which was attractive for CO2 capture. However, there are still many questions remaining to be clarified. First, the nature of the GO interlayer channel exhibiting the selectivity of CO2 over N2 is unclear. Second, how the CO2 molecules pass across the interlayer spaces of GO membranes needs to be elucidated. To unravel these questions, a molecular-level study is urgently needed. But conducting measurement and observation at molecular-level is still an experimental challenge. In the past decades, molecular dynamics (MD) simulations have been developed to investigate microscopic interactions, which can provide detailed information about dynamical, energetic and structural information of complex systems at the molecular level.31-37 Using MD simulations, the adsorption and diffusion of water, gas and ion in the interlayer spaces of GO laminates have been investigated.37-39 These studies have proved that the MD simulation is an efficient method to investigate the transport behavior of gas in GO membrane. Therefore, in this paper, we performed molecular dynamics simulations to investigate the separation mechanism of CO2/N2 in GO membrane. Furthermore, the influences of the oxidation degree，interlayer spacing and channel length of the GO membrane on its 4 ACS Paragon Plus Environment

Page 5 of 20

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


separation performance were also studied.

Models and Methods According to the experimental evidences40 and Lerf-Klinowski model,41 the GO flake mainly includes oxygenic functional groups of hydroxyl, epoxy and carboxyl. The hydroxyl and epoxy primarily locate on the basic plane, while the carboxyl mostly distributes on the edges. In this work, the gas molecules mainly pass through the membrane along the interlayer spaces, and the modified groups on the edges have negligible effect on the gas transport performance. Correspondingly, for simplicity, the constructed GO sheet only contains the randomly distributed hydroxyl and epoxy groups on the two basal planes, as shown in Figure 1a. The oxidization degree is denoted as RO/C = NO/NC with typical ranges of 0%-60%. Here, the NO and NC represent the number of oxygen atoms and carbon atoms, respectively. Figure 1b shows the molecular structures of CO2 and N2. Figure 1c displays the initial model with dimensions of 29.52 Å × 42.61 Å × 300.00 Å. As shown, two GO sheets were placed onto two sides of a slit to construct a horizontal channel. The interlayer spacing is defined as the vertical distance between upper and lower basal planes of GO sheets. Two graphene slabs were placed on the leftmost and rightmost. In simulation, the channel was fixed apart from the modified hydroxyl and epoxy groups. The rightmost graphene lab was fixed, and the leftmost graphene will be applied a force to push gases passing across the channel. Finally, 80 CO2 and 80 N2 were put inside the left chamber.



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 6 of 20

Figure 1. (a) The structure of GO with modified groups of hydroxyl and epoxy; (b) Atomic structures of CO2 and N2; (c) Model of the built box. Here the white, blue, cyan, and red balls denote the hydrogen, nitrogen, carbon, oxygen, respectively.

In this study, the systems were simulated with the LAMMPS software.42 A constant velocity (1.5 Å/ns) was applied onto the leftmost graphene slab to push the gas passing across the channel. During the simulation, all-atom optimized potential OPLS-AA was used for GO.43 The 12-6 Lennard-Jones potential 4εc-o[(σc-o/r)12 − (σc-o/r)6] was used to calculate the van der Waals interactions between gas and GO with parameters listed in Table S1.37, 44 Here, r presents the distance between two atoms. The cutoff distance of the van der Waals interactions was set as 12 Å. In this study, the electrostatic interactions were specially considered. The preferable three-site model with three partial charges was adopted for CO2,45 while the well-known Lennard-Jones potential was adopted to model the neutral N2.46 The detailed partial charges on gas molecules and GO were also shown in Table S1. The long-range Coulomb interactions were computed by using the particle-particle particle-mesh (PPPM) algorithm. Periodic boundary conditions were applied in all directions. All the simulations were conducted in canonical ensemble (NVT) at 298 K controlled by the Nose-Hoover thermostat method. The time step was set as 1 fs, and total of 10 ns simulation was conducted for each model. The data were collected 6 ACS Paragon Plus Environment

Page 7 of 20

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


every 2 ps and full-precision trajectory was recorded.

Results and Discussion The separation performance. Generally, the typical GO multilayer membranes have interlayer spacing of 7.3 Å and oxidation degree ranging from 30% to 60% determined by the experimental conditions. Therefore, we first performed simulations for systems with interlayer spacing of 7.3 Å and oxidization degree of 30%. To present the separation performance of this system, time evolution of the number of gases in the three regions in Figure 1c was recorded in Figure 2a. Figure 2a gives the results: (1) the N2 almost cannot pass through the channel; (2) the CO2 first fills the channel, and then, when the channel is saturated, the CO2 starts entering into the right chamber. These results indicate that the interlayer channel of GO multilayer could efficiently separate the CO2 and N2. In addition, a quantitative characterization of gas distribution at 10 ns is represented in Figure 2b, which further confirms the gas transport behavior.

Figure 2. (a) Time evolution of the number of gas in the three regions as labeled in Figure 1c. (b) The number density distributions of CO2 and N2 along Z direction.

The separation mechanism. Figure 2a indicates the GO channel was preferentially occupied by the CO2. To understand the different affinity between CO2 and N2 with the GO channel, we calculated the 7 ACS Paragon Plus Environment


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 8 of 20

interaction energy between the GO and CO2 (N2) as displayed in Figure 3. It shows that the attraction intensity between the GO and CO2 are far larger than that between GO and N2. Therefore, the CO2 could preferentially adsorb onto the GO channel, and then the CO2 saturated channel allows the subsequent CO2 passage while suppresses the passage of N2. To prove it, pure N2 was adopted in this system. Figure S1 clearly demonstrates that the N2 could enter into and pass across the channel. Above discussions confirm that the competitive adsorption between CO2 and N2 accounts for the separation of the CO2/N2.

Figure 3. The time evolution of interaction energy between GO and CO2 (N2).

Furthermore, the microscopic transport process was studied. In the GO channel, there are three types of regions with different interlayer spaces due to the existence of modified groups. As shown in Figure 4a, they are described as oxidized region (d1=3.38 Å), half oxidized region (d2=5.34 Å) and pristine graphene region (d3=7.3 Å), respectively. In order to study the transport behavior in these three regions, we built three channels analogous to these three regions as shown in Figure 4(b-d).


Page 9 of 20

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. (a) A schematic of GO channels with three kinds of spacing. (b-d) Three built channels (oxidized, half oxidized, and pristine) resemble of the different regions as shown in (a), respectively.

Figure 5 gives the number of gas molecules passed the channel along with the simulation time. In the oxidized channel (Figure 4b), there is no gas molecules passed across the channel. This result could be ascribed to the limited channel size of 3.38 Å, which is comparable to the sizes of CO2 (3.30 Å) and N2 (3.64 Å). In the half oxidized channel, both the CO2 and the N2 exhibit enough large permeability, but the selectivity is low. In the pristine channel, the CO2 and N2 could equally pass across the channel without any selectivity. The transport behavior in these three regions indicates the half oxidized and pristine region could offer quick transport channel for either CO2 or N2, hence only the oxidized region could endow the GO channel with high selectivity. However, the CO2 could not transport through the oxidized channel derived of the limited size. Based on these analyses, we propose the selectivity mechanism as follow. Generally, in the synthesized GO membrane, the distribution of the three regions is random. So when the passing gases meet the oxidized region, they will bypass it and go ahead through the half oxidized region or pristine region. This point can be confirmed by the transport pathway displayed in Figure S2. As a result, the existence of oxidized region will decrease the permeability of the channel. Meanwhile, due to the strong affinity between the modified groups and the CO2, the existence of modified group will strengthen the preferential adsorption of CO2 and yield an enhanced selectivity. 9 ACS Paragon Plus Environment


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 20

In summary, the pristine and half oxidized regions endow the channel with permeability, and the oxidized region grants the channel selectivity.

Figure 5. The time evolutions of the number of permeated CO2 and N2 for (a) Oxidized channel, (b) Half oxidized channel, and (c) Pristine channel.

The effects of interlayer spacing and oxidation degree. From above discussions, the interlayer configuration is the crucial factor determining the transport behavior of gas molecules. Here, two configurational parameters, the interlayer spacing and oxidation degree, were considered to investigate the transport behavior of gas molecules. Three interlayer spacing of 6.3 Å, 7.3 Å and 8.3 Å and a series of oxidation degrees of 0%, 10%, 20%, 30%, 40%, 50% and 60% were adopted. The permeability and selectivity of these GO membranes were summarized in Table 1. The selectivity was defined by following equation:47

⁄

⁄ ⁄

(1)

Where x is the molar fraction of the gas component in the left chamber at the initial simulation, y is the molar fraction of the gas component in the right chamber after the simulation. The permeability could be characterized by follow equation:

μ

(2)

where n is the amount of substance of gas molecules passed across the channel, A is the cross section area of channel, P is the applied pressure, and t is the corresponding simulation time. 10 ACS Paragon Plus Environment

Page 11 of 20

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. The permeability and selectivity of channels with different interlayer spacings and oxidation degrees. GPU (gas permeation unit), 1 GPU = 3.35×10-10 mol· m-2 ·s-1 ·Pa-1. Oxidization degree

Interlayer spacing

0%

10%

20%

30%

40%

50%

60%

µCO (106 GPU)

1.83

1.76

1.41

0

0

0

0

µ N (106 GPU)

1.62

0.28

0.07

0

0

0

0

1.13

6.25

20

－

－

－

－

1.52

1.46

1.28

1.28

1.46

0

0

1.52

1.28

0.24

0.06

0.06

0

0

1

1.14

5.25

21

24

－

－

1.44

1.39

1.39

1.18

1.12

1.28

1.28

1.34

1.39

1.07

0.96

0.96

0.43

0.11

1.08

1

1.30

1.22

1.17

3

12

2

6.3 Å

2

SCO

2/N2 6

µCO (10 GPU) 2

7.3 Å

6

µ N (10 GPU) 2

SCO

2/N2 6

µCO (10 GPU) 2

8.3 Å

6

µ N (10 GPU) 2

SCO

2/N2

Table 1 presents that, on one side, with the increase of oxidization degree, the overall permeability decreases, while the selectivity increases. This result could be ascribed to the fact that the increased oxidization degree reduces the transport space and reinforces the affinity of the channel to CO2, which leads to a high selectivity. This point could be readily understood by the schematic in Figure 6. On the other side, when a narrower channel (6.3 Å) was adopted, the transport space is compressed. Correspondingly, the gas molecules could only pass through these channels with low oxidization degree, and the maximum selectivity is limited to a value of 20, which is smaller than the maximum value of 24 in channel with interlayer spacing of 7.3 Å. When a wider channel (8.3 Å) was adopted, the gas molecules have large permeability in every channel, and high oxidization degree endows the channel with high selectivity. But, the selectivity is also largely smaller than that obtained in channel with interlayer spacing of 7.3 Å.



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 12 of 20

Figure 6. The schematic of the channels with the increase of oxidation levels (from a to c) of GO. The black solid lines denote graphene. The red balls and white hollow circles represent the oxygen and hydrogen atoms of oxidative functional groups.

It is worthy noted that the oxidization degree of the channel has insignificant influence on the permeability of CO2 when the channel is permeable. So, the selectivity becomes the point that should be focused on in industrial application. Table 1 indicates the optimal selectivity of channels with different interlayer spacing emerges at different oxidization degrees. The larger of the distance is, the higher of oxidization degree is needed. This result could be reasonably understood by the changes of the permeability of N2, which is affected by the adsorption quantity of CO2 determined by the oxidization degree. The influence of channel length. The influence of the channel length on the gas transport behavior was further studied. As demonstrated in Figure 7, with the increase of channel length, the permeability decreases and the selectivity enhances. The results could be explained by the fact that the prolonged channel increases the transporting distance of gas molecules, resulting in a lower permeability; meanwhile, the extended channel provides a long selectivity region and yields a higher selectivity.


Page 13 of 20

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. The number of permeated CO2 and N2 under three different channel lengths (8.75 Å, 17.5 Å and 35 Å).

Conclusions In this study, MD simulations were conducted to investigate the permeability and selectivity of CO2/N2 passing through an interlayer channel of GO membrane. The preferential adsorption of CO2 because of the modified groups was found to be responsible for the high selectivity and large permeability of CO2 over N2. The effects of oxidization degree and interlayer spacing were also investigated, and the high oxidization degree endows the channel with high selectivity and low permeability, meanwhile the large interlayer spacing enables the channel having large permeability and low selectivity. Furthermore, the channel length was found to be another factor influencing the gas transport performance, and the elongated channel decreases the permeability and enhances the selectivity. This work is expected to trigger further studies on the design of GO membrane structure to improve its separation performance in multiple applications.

Associated Contents Supporting Information



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 20

The force field parameters used in this work; the migration trajectory of CO2 molecule in channel; the final configuration of N2 molecules alone used as separated gas source; these materials are available free of charge via the Internet at http://pubs.acs.org.

Author Information Corresponding Authors Jun Zhang* E-mail: [email protected] Tel: 86-0532-86983366 Youguo Yan* E-mail: [email protected] Tel: 86-0532-86983415 Notes The authors declare no competing financial interests. §These authors contribute equally to this work.

Acknowledgements This work is financially supported by National Basic Research Program of China (2015CB250904), National Natural Science Foundation of China (51302321), Shandong Provincial Natural Science Foundation, China (2014ZRE28048), and Fundamental Research Funds for the Central Universities (14CX0222A, 15CX05049A, 15CX06073A).

Reference (1) Rochelle, G. T., Amine Scrubbing for CO2 Capture. Science 2009, 325, 1652-1654. (2) Olajire, A. A., CO2 Capture and Separation Technologies for End-of-Pipe Applications-A Review. Energy 2010, 35, 2610-2628. (3) Team, C. W.; Pachauri, R.; Reisinger, A., Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. IPCC, Geneva, Switzerland 2007. 14 ACS Paragon Plus Environment

Page 15 of 20

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


(4) Karl, T. R.; Trenberth, K. E., Modern Global Climate Change. Science 2003, 302, 1719-1723. (5) Halmann, M. M.; Steinberg, M., Greenhouse Gas Carbon Dioxide Mitigation: Science and Technology; CRC press, 1998. (6) Forte, E.; Galindo, A.; Trusler, J. P. M., Experimental and Molecular Modeling Study of the Three-Phase Behavior of (n-Decane + Carbon Dioxide + Water) at Reservoir Conditions. J. Phys. Chem. B 2011, 115, 14591-14609. (7) Purtell, R.; Rothman, L.; Eldridge, B.; Chess, C., Precision Parts Cleaning Using Supercritical Fluids. J. Vac. Sci. Technol., A 1993, 11, 1696-1701. (8) Kamali, H.; Golmakani, E.; Golshan, A.; Mohammadi, A.; Sani, T. A., Optimization of Ethanol Modified Supercritical Carbon Dioxide on the Extract Yield and Antioxidant Activity from Biebersteinia Multifida DC. J. Supercrit. Fluids 2014, 91, 46-52. (9) Yang, Q.; Ma, L.; Zhong, C.; An, X.; Liu, D., Enhancement of CO2/N2 Mixture Separation Using the Thermodynamic Stepped Behavior of Adsorption in Metal−Organic Frameworks. J. Phys. Chem. C 2011, 115, 2790-2797. (10) Bae, Y.-S.; Farha, O. K.; Hupp, J. T.; Snurr, R. Q., Enhancement of CO2/N2 Selectivity in A Metal-Organic Framework by Cavity Modification. J. Mater. Chem. 2009, 19, 2131-2134. (11) Williams, J. J.; Wiersum, A. D.; Seaton, N. A.; Düren, T., Effect of Surface Group Functionalization on the CO2/N2 Separation Properties of MCM-41: A Grand-Canonical Monte Carlo Simulation Study. J. Phys. Chem. C 2010, 114, 18538-18547. (12) Powell, C. E.; Qiao, G. G., Polymeric CO2/N2 Gas Separation Membranes for the Capture of Carbon Dioxide from Power Plant Flue Gases. J. Membr. Sci. 2006, 279, 1-49. 15 ACS Paragon Plus Environment


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 16 of 20

(13) Ritter, J. A.; Ebner, A. D., State‐of‐the‐Art Adsorption and Membrane Separation Processes for Hydrogen Production in the Chemical and Petrochemical Industries. Sep. Sci. Technol. 2007, 42, 1123-1193. (14) Freemantle, M., Membranes for Gas Separation. Chem. Eng. News 2005, 83, 3. (15) Bernardo, P.; Drioli, E.; Golemme, G., Membrane Gas Separation: A Review/State of the Art. Ind. Eng. Chem. Res. 2009, 48, 4638-4663. (16) Celebi, K.; Buchheim, J.; Wyss, R. M.; Droudian, A.; Gasser, P.; Shorubalko, I.; Kye, J.-I.; Lee, C.; Park, H. G., Ultimate Permeation Across Atomically Thin Porous Graphene. Science 2014, 344, 289-292. (17) Li, D.; Hu, W.; Zhang, J.; Shi, H.; Chen, Q.; Sun, T.; Liang, L.; Wang, Q., Separation of Hydrogen Gas from Coal Gas by Graphene Nanopores. J. Phys. Chem. C 2015, 119, 25559-25565. (18) Tao, Y.; Xue, Q.; Liu, Z.; Shan, M.; Ling, C.; Wu, T.; Li, X., Tunable Hydrogen Separation in Porous Graphene Membrane: First-Principle and Molecular Dynamic Simulation. ACS Appl. Mater. Interfaces 2014, 6, 8048-8058. (19) Blankenburg, S.; Bieri, M.; Fasel, R.; Müllen, K.; Pignedoli, C. A.; Passerone, D., Porous Graphene as An Atmospheric Nanofilter. Small 2010, 6, 2266-2271. (20)Huang, L.; Zhang, M.; Li, C.; Shi, G., Graphene-Based Membranes for Molecular Separation. J. Phys. Chem. Lett. 2015, 6, 2806-2815. (21) O’Hern, S. C.; Boutilier, M. S. H.; Idrobo, J.-C.; Song, Y.; Kong, J.; Laoui, T.; Atieh, M.; Karnik, R., Selective Ionic Transport through Tunable Subnanometer Pores in Single-Layer Graphene Membranes. Nano Lett. 2014, 14, 1234-1241. (22) Surwade, S. P.; Smirnov, S. N.; Vlassiouk, I. V.; Unocic, R. R.; Veith, G. M.; Dai, S.; Mahurin, S. M., 16 ACS Paragon Plus Environment

Page 17 of 20

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


Water Desalination Using Nanoporous Single-Layer Graphene. Nat. Nanotechnol. 2015, 10, 459-464. (23) Perreault, F.; Fonseca de Faria, A.; Elimelech, M., Environmental Applications of Graphene-based Nanomaterials. Chem. Soc. Rev. 2015, 44, 5861-5896. (24) Liu, G.; Jin, W.; Xu, N., Graphene-based Membranes. Chem. Soc. Rev. 2015, 44, 5016-5030. (25) Gadipelli, S.; Guo, Z. X., Graphene-based Materials: Synthesis and Gas Sorption, Storage and Separation. Prog. Mater. Sci. 2015, 69, 1-60. (26) Joshi, R. K.; Alwarappan, S.; Yoshimura, M.; Sahajwalla, V.; Nishina, Y., Graphene Oxide: the New Membrane Material. Appl. Mater. Today 2015, 1, 1-12. (27) Smith, Z. P.; Freeman, B. D., Graphene Oxide: A New Platform for High-Performance Gas- and Liquid-Separation Membranes. Angew. Chem., Int. Ed. 2014, 53, 10286-10288. (28) Huang, H.; Ying, Y.; Peng, X., Graphene Oxide Nanosheet: An Emerging Star Material for Novel Separation Membranes. J. Mater. Chem. A 2014, 2, 13772-13782. (29) Kim, H. W., et al., Selective Gas Transport Through Few-Layered Graphene and Graphene Oxide Membranes. Science 2013, 342, 91-95. (30) Shen, J.; Liu, G.; Huang, K.; Jin, W.; Lee, K.-R.; Xu, N., Membranes with Fast and Selective Gas-Transport Channels of Laminar Graphene Oxide for Efficient CO2 Capture. Angew. Chem. 2015, 127, 588-592. (31) Sun, C.; Boutilier, M. S. H.; Au, H.; Poesio, P.; Bai, B.; Karnik, R.; Hadjiconstantinou, N. G., Mechanisms of Molecular Permeation through Nanoporous Graphene Membranes. Langmuir 2014, 30, 675-682. (32) Cohen-Tanugi, D.; Grossman, J. C., Water Desalination across Nanoporous Graphene. Nano Lett. 17 ACS Paragon Plus Environment


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 18 of 20

2012, 12, 3602-3608. (33) Jiang, D.-e.; Cooper, V. R.; Dai, S., Porous Graphene as the Ultimate Membrane for Gas Separation. Nano Lett. 2009, 9, 4019-4024. (34) Ban, S.; Xie, J.; Wang, Y.; Jing, B.; Liu, B.; Zhou, H., Insight into the Nanoscale Mechanism of Rapid H2O Transport within a Graphene Oxide Membrane: Impact of Oxygen Functional Group Clustering. ACS Appl. Mater. Interfaces 2016, 8, 321-332. (35) Wei, N.; Peng, X.; Xu, Z., Understanding Water Permeation in Graphene Oxide Membranes. ACS Appl. Mater. Interfaces 2014, 6, 5877-5883. (36) Wu, H.; Chen, J.; Liu, H., Molecular Dynamics Simulations about Adsorption and Displacement of Methane in Carbon Nanochannels. J. Phys. Chem. C 2015, 119, 13652-13657. (37) Jiao, S.; Xu, Z., Selective Gas Diffusion in Graphene Oxides Membranes: A Molecular Dynamics Simulations Study. ACS Appl. Mater. Interfaces 2015, 7, 9052-9059. (38) Medhekar, N. V.; Ramasubramaniam, A.; Ruoff, R. S.; Shenoy, V. B., Hydrogen Bond Networks in Graphene Oxide Composite Paper: Structure and Mechanical Properties. ACS Nano 2010, 4, 2300-2306. (39) Kim, D.; Kim, D. W.; Lim, H.-K.; Jeon, J.; Kim, H.; Jung, H.-T.; Lee, H., Intercalation of Gas Molecules in Graphene Oxide Interlayer: the Role of Water. J. Phys. Chem. C 2014, 118, 11142-11148. (40) Gao, W.; Alemany, L. B.; Ci, L.; Ajayan, P. M., New Insights into the Structure and Reduction of Graphite Oxide. Nat. Chem. 2009, 1, 403-408. (41) Lerf, A.; He, H.; Forster, M.; Klinowski, J., Structure of Graphite Oxide Revisited. J. Phys. Chem. B 1998, 102, 4477-4482. (42) Plimpton, S., Fast Parallel Algorithms for Short-Range Molecular Dynamics. J. Comput. Phys. 1995, 18 ACS Paragon Plus Environment

Page 19 of 20

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


117, 1-19. (43) Shih, C.-J.; Lin, S.; Sharma, R.; Strano, M. S.; Blankschtein, D., Understanding the pH-Dependent Behavior of Graphene Oxide Aqueous Solutions: A Comparative Experimental and Molecular Dynamics Simulation Study. Langmuir 2012, 28, 235-241. (44) Jorgensen, W. L.; Maxwell, D. S.; Tirado-Rives, J., Development and Testing of the OPLS All-Atom Force Field on Conformational Energetics and Properties of Organic Liquids. J. Am. Chem. Soc. 1996, 118, 11225-11236. (45) Potoff, J. J.; Siepmann, J. I., Vapor–Liquid Equilibria of Mixtures Containing Alkanes, Carbon Dioxide, and Nitrogen. AIChE J. 2001, 47, 1676-1682. (46) Chae, K.; Violi, A., Mutual Diffusion Coefficients of Heptane Isomers in Nitrogen: A Molecular Dynamics Study. J. Chem. Phys. 2011, 134, 044537. (47) Wall, Y.; Braun, G.; Kaltenborn, N.; Voigt, I.; Brunner, G., Separation of CO2/N2 by Means of a Carbon Membrane. Chem. Eng. Technol. 2012, 35, 508-512.



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 of Content


Page 20 of 20

N2 Separation through Two

Recommend Documents