Mechanical Synthesis of COF Nanosheet Cluster and Its Mixed MatrixMembrane for Efficient CO2 RemovalChangchang Zou,† Qianqian Li,† Yinying Hua, Bihang Zhou, Jingui Duan,* and Wanqin Jin*

State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemical Engineering, Jiangsu National SynergeticInnovation Centre for Advanced Materials, Nanjing Tech University, Nanjing 210009, China

*S Supporting Information

ABSTRACT: Covalent organic framework (COF) membranes used for selective removal of CO2 were believed as an efficientand low-cost solution to energy and environmental sustainability. In this study, the amide modified COF nanosheet cluster with a2D structure was facilely prepared through solid reaction, exhibiting good adsorption-based CO2 selectivity (223 at 273 K and 90at 298 K) toward N2. Remarkably, the mixed matrix membrane (MMM) that consists of a lesser amount of COF filler (1 wt %)shows promising CO2/N2 gas selectivity (∼64). In addition, the competitive adsorption prompts the selectivity to ∼72 under anequimolar CO2/N2 mixture, which surpasses the values of all reported COF membranes. It is worth to note that the binary gasseparation is stable during 120 h.

KEYWORDS: solid reaction, covalent organic framework, morphology transformation, mixed matrix membrane,CO2/N2 gas separation

■ INTRODUCTION

As the primary anthropogenic greenhouse gas, CO2 is changingthe global climate. The development of efficient selective car-bon capture and storage (CCS), is, therefore, a scientific chal-lenge of the highest order.1,2 Currently, a variety of methods,such as chemisorption with amide solvent, physical adsorp-tion with porous adsorbents, and membrane technology, havebeen proposed for CO2 capture.

3,4 However, due to the groupof benefits in lower energy consumption, ease of opera-tion, environmental friendliness, and mechanical simplicity, themembrane-based process was believed as one of the mostpromising technologies in CCS.5−11

Due to its low cost, good mechanical simplicity, highscalability, and water resistance, an organic polymer (celluloseacetate) membrane was first reported for gas separation in2001.12 Since then, various organic membranes have begun todraw widespread attention for feasible usage in gas separa-tion.13−16 However, polymeric membranes are often limitedby a permeability and selectivity trade-off. In parallel to thedevelopment of polymeric membrane, inorganic membraneswith good separation performance are expensive, brittle, anddifficult to upscale.17 Due to the integrated advantages of size/

shape selectivity of functional fillers and the processability/mechanical stability of polymers, MMMs that consist of func-tional inorganic fillers, such as carbon tubes, mesoporoussilicon, zeolites, metal organic frameworks, and porous metaloxides, were developed as an alternative solution to overcomethese limitations.7,14,18,19 Despite those, the majority of MMMsusually suffer the poor compatibility between constituents,leading to decreased separation behavior, as the gas moleculesbypass the particles.18 Thus, the problems we now face arebecoming practical, i.e., how to address the issue of filleragglomeration and precipitation during membrane preparation,and further boosting CO2 separation by MMMs.14

The stability of a matrix solution during the fabricating pro-cess is important. Thus, some techniques, such as adding non-solvents into the dope formulation, performing the spinning athigh temperature, and optimizing the shear and elongationalforce, were developed to prepare homogeneous dispersions ofinorganic porous fillers within a polymer solution.19−21 Further,

Received: June 5, 2017Accepted: August 9, 2017Published: August 9, 2017

Research Article

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© 2017 American Chemical Society 29093 DOI: 10.1021/acsami.7b08032ACS Appl. Mater. Interfaces 2017, 9, 29093−29100

controlling the surface properties of fillers, according to the ruleof similarity and intermiscibility, was believed as one of themost attractive ways. For examples, the controlling of metalorganic frameworks (MOFs)/polymer compatibility is a littleeasier than that of the zeolite/polymer, as the organic ligands inMOFs are more similar to polymer chains, but zeolites are not.22

In contrast with well-designed porous MOFs, COFs areanother new kind of crystalline porous materials, which areassembled by the linkage of organic moieties only in periodicnetworks through strong covalent bonds with light ele-ments.23,24 Due to the diversity of organic building units andchemical reactions, more and more COF materials with tunablepore chemistry, robust stability, as well as good COF/polymercompatibility offer significant opportunity for advanced mem-brane preparation and application.25,26 Whereas, unlike popular3D MOF structures, most of the reported COFs show 2Dlamellar structures that derived from the packing of organicnanosheet by weak interactions. In other words, once the weakinteraction was overcome, it is possible to prepare multilayeredor even single layered COF nanosheets from bulk lamellarCOFs. Therefore, the shorter transmission routes and func-tional pore properties will make 2D COF nanosheets extremelyattractive for membrane-based separation purposes.27−30

We are interested in porous material and membrane designfor feasible applications.31−37 In the present study, the 2D COFstructure with rich amide groups was selected as membranefiller, because of its facile synthesis and also the preferredchannel for CO2 transport (Scheme 1). Through solid reac-tion, the well prepared honeycomb-like COF nanosheet clus-ter (named as TpPa-1-nc) showed good adsorption-basedCO2 selectivity (223 at 273 K and 90 at 298 K) toward N2.Remarkably, a single gas permeation experiment showedthat the TpPa-1-nc incorporated MMM exhibited a highCO2/N2 ideal selectivity (∼64), which was further improved to∼72 under an equimolar CO2/N2 mixture, as the preferred

Scheme 1. COF Structure with Rich Amide Groupa

aSynthesized by Schiff base aldehyde−amine condensation (a); structure of PEBA (b); SEM image of cross-section of TpPa-1-nc/PEBA compositemembrane (c).

Figure 1. IR (a) and PXRD (b) of synthesized TpPa-1 during processof solid reaction.

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competitive adsorption. In addition, long-term test showed thatmixture gas separation is stable in 120 h.

■ EXPERIMENTAL MATERIALSAll the reagents were commercially available and used as received. Driedphloroglucinol, trifluoroacetic acid, hexamethylenetetraamine, and p-phen-ylenediamine were purchased from J&K Chemicals. Polyether-block-amide (PEBA) was purchased from Arkema, France. Methanol and

dichloromethane were purchased from Sinopharm Chemical ReagentCo., Ltd. FTIR spectra were recorded in the range of 4000−400 cm−1

on a Nicolet ID5 ATR spectrometer. Powder X-ray diffraction (PXRD)patterns were collected using a Bruker AXS D8 Discover powderdiffractometer equipped with a Cu Ka X-ray source at 40 kV, 40 mA.1H and 13C NMR spectra were recorded on a Bruker 500 FT-NMRspectrometer. Solid 13C CP-MAS NMR spectra were measured on aBruker AVANCE III 400 MHz spectrometer. The morphologies ofCOF materials during solid reaction were examined by field emission

Figure 2. SEM images of TpPa-1 during solid reaction (after washing): 5 min (a, b), 15 min (c, d), 25 min (e, f), 35 min (g, h), 45 min (i, j), and55 min (k, l).

Figure 3. TEM images of nanosheet from TpPa-1-nc (a, b). Pore size analysis (c, d).

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scanning electron microscope (SEM, S4800, Hitachi) and transmissionelectron microscopy (TEM, JEOL JEM-2010 UHR). A thermo-gravimetric analyzer (TGA, STA 209 F1, NETZSCH) was used todetermine the thermal stability of the MMMs with a heating rate of10 °C·min−1 in a N2 atmosphere. Differential scanning calorimetry(DSC, Q2000, TA Instruments, USA) measurements were performedfrom −80 to −20 °C in a N2 atmosphere to study the glass transitiontemperature (Tg) of the membranes. The gas adsorption isotherms ofTpPa-1-nc were collected by BELSORP-mini II, Bel Inc., Japan.Synthesis of TpPa-1-nc. COF material was synthesized through

solid reaction by Schiff base aldehyde−amine condensation accordingto a previous report.24 1,3,5-Triformylphloroglucinol and p-phenyl-enediamine were placed in a mortar and ground using a pestle at roomtemperature. As time passed, the color of materials changed from lightyellow, yellow, orange, and then to dark red finally, indicating theformation of conjugated units (Figure S1). After 35 min, the reactionmixture was collected and washed for getting pure TpPa-1-nc.Preparation of MMMs. PEBA polymer was selected to disperse

TpPa-1-nc. A poly(vinylidene fluoride) (PVDF) ultrafiltration membranewas used as support (average pore size: 450 nm). A certain amount ofTpPa-1-nc was dispersed in ethanol and water with a mass ratio of (7:3),followed by stirring of 10 min. Then, PEBA was added and heatedwith stirring and refluxing under 80 °C for 2 h. The mass ratio ofPEBA to solvent is 5:95, while the contents of TpPa-1-nc in thepolymer matrix varied from 0 to 2 wt %. The membrane was preparedby spin-coating the mixed solution on PVDF supports, which wasprepared by being immersed in water for 24 h to infiltrate fully. TheMMMs were then dried at room temperature for 24 h, then curing inthe oven at 70 °C for another 12 h. A pristine PEBA membrane wasalso prepared using a similar process for comparison. TpPa-1-ncloading in MMMs was calculated using the following formula:

= ×Wmm

100%COFCOF

PEBA (1)

COF Characterization. Solid reactions with a number ofadvantages ripple throughout many industries. Generally, during theinitial process of grinding, the particles of starting material assembledtogether and then reacted with each other. Then, the continuousgrinding will break the formed product particle into smaller sizes.Taking this in consideration, the grinding of solid reaction can notonly offer the energy for reaction but also overcome the weak inter-action of the layers during 2D COF formation.In order to confirm our idea, small amount samples were collected

at different reaction times (5, 15, 25, 35, 45, and 55 min). IR andPXRD were used to monitor the reaction process during 55 min(Figure 1). The new IR peaks around (1605, 1579, and 1286 cm−1)and their gradual increased intensity showed the formation of C−N,CC, and CO bonds, respectively (Figure 1a). Meanwhile, thecrystallinity of obtained TpPa-1 at different times was evaluated by thepowder X-ray diffraction (PXRD). As shown in Figure 1b, the newlyemerged and gradually enhanced diffraction peaks at 8° (2θ) matchedwith the reported data, demonstrating the successful preparation ofTpPa-1.24 It should be noted that the PXRD peaks at high angleindicate the existence of partial unreacted starting materials.After washing with methanol and dichloromethane (for starting

material removal), the structure and morphology of TpPa-1 particleswere investigated by PXRD and scanning electron microscopy (SEM),respectively. As shown in Figure S2, the absence of peaks around highangle reveal the complete removal of starting materials and phasepurity of TpPa-1. The similar IR spectra between as-synthesized andwashed COF prove the maintenance of the in-phase structure andbond connection. Additionally, 13C cross-polarization magic-anglespinning (CP-MAS) solid-state NMR spectra confirmed the successfulCOF synthesis (Figure S3). The morphology and size of TpPa-1particles (after washing) were studied by SEM during solid reaction(Figure 2). At the early stage (5 min), the products consist solely of anamorphous solid with a relatively broad average size distribution(Figure 2a,b). Then, some small species can be found on the surface ofthe amorphous solid after 15 min grinding (Figure 2c,d). As expected,plenty of nanosheets with about 13 nm average thickness, confirmed

by atomic force microscope (AFM) study (Figure S6), were foundafter grinding the sample for another 20 min. The nanosheetsassembled together and formed honeycomb-like clusters (TpPa-1-nc)(Figure 2g,h). However, over time (55 min), the honeycomb-likeTpPa-1-nc gradually lost visible pores and became an amorphousblock with a size of 5−10 μm (Figure 2k,l). This first and directobservation of COF synthesis reveals a unique transformation: theamorphous solid could transform to a honeycomb-like cluster with ahigh aspect ratio nanosheet. Additionally, the flat nanosheet fromTpPa-1-nc was also studied by TEM, shown in Figure 3. Furtheranalysis showed that the average micropore with 4.4−5.0 Å distributedevenly on those flat sheets (Figure 3c,d). Thus, as building block, theintegrated features of light elements, regular microporosity, andnanosheet morphology could greatly increase the compatibility andstability of TpPa-1-nc within a polymeric matrix, leading to promisingmembrane structure and performance.

CO2 and N2 gas isotherms were collected to evaluate the permanentporosity of TpPa-1-nc. As shown in Figure 4a, CO2 adsorption of

TpPa-1-nc exhibits a type-I adsorption isotherm, characteristic ofmicroporous material. On the basis of the CO2 adsorption isotherm,the Brunauer−Emmett−Teller (BET) and Langmuir surface areas are

Figure 4. CO2 and N2 adsorption of TpPa-1-nc at 195 K (a), 273 and298 K (b). Isosteric heats of adsorption for CO2 in TpPa-1-nc (c).

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around 255 and 436 m2·g−1, respectively. CO2 uptake of TpPa-1-ncreached to 100.6 cm3·g−1 at 195 K/1 bar, while a trace amount of N2

(4.2 cm3·g−1) uptake was observed. Interestingly, similar adsorptiontrends were also found at 273 and 298 K (Figure 4b). In light of theseobvious adsorption gaps, gas selectivity of TpPa-1-nc was calculated bydetermining the Henrys law constants (Table S1). As expected, theCO2/N2 gas selectivity is as high as 223 at 273 (90 at 298 K), whichcan be explained by high CO2 adsorption heat toward TpPa-1-nc(35 kJ·mol−1) (Figure 4c). In addition, the calculated pore sizedistribution from the CO2 isotherm (273 K) matches well with theTEM result (Figure S10).Membrane Characterization. The thermogravimetric results

showed that all MMMs started to decompose around 380 °C,indicating high thermal stability (Figure S11). PXRD of a series ofMMMs (peak around 11°) confirmed the integrity of the TpPa-1skeletal structure after membrane fabrication (Figure S12). To furtherunveil the uniform distribution of TpPa-1-nc within membranes, SEMimages of the surface and cross-section of MMMs were collected(Figure 5). The continuous membrane surfaces showed graduallyincreased granular protuberances without interfacial voids or pinholes,following the increased ratio of TpPa-1-nc in the PEBA matrix. The thick-nesses of the MMMs are around 2.6−2.8 μm on the support, while theTpPa-1-nc can be found clearly inside the membrane (Figure 5d, inset).

Gas Permeation Tests. Before measurements, the as-preparedMMMs were activated to remove guest molecules at 60 °C undervacuum for 24 h. In addition, to guarantee the reliability of results, themeasurements were repeated at least three times for each point. Unlikethe defined ideal selectivity above (from single gas adsorption iso-therms), the selectivity defined from membrane-based technology isthe ratio of permeabilities, S(A/B) = PA/PB. Permeabilities (P) weredetermined using a CO2/N2 gas pair at 25 °C, 3 bar. As displayed inFigure 6, the MMMs exhibited gradually improved permeability ofboth CO2 and N2 accompanying the increase of TpPa-1-nc loading.This is because CO2 and N2 can diffuse freely through the TpPa-1-ncchannel. In addition, differential scanning calorimetry measure-ments showed that the glass transition temperature (Tg) increasedfrom −47.5 °C for pristine PEBA to −45.2 °C for 1 wt % MMM(Figure S13). This means TpPa-1-nc could disrupt the inherent orga-nization of the polymer chains, and enhance the accessible free volumein the matrix for gas molecule transmission.38−40 Among these fiveMMMs, the ideal gas selectivity increases with TpPa-1-nc loading, andreaches to 64 at the loading of 1 wt %, which is a 56% improvementthan that of the pure PEBA membrane. This is because the increasedpermeability of CO2 is more rapid than that of N2 when the TpPa-1-ncloading is lower than 1 wt %. Principally, the nature properties of highpolarizability and quadrupole moment lead CO2 molecules themselves

Figure 5. SEM micrographs of surface (a, c, e, g) and cross-section (b, d, f, h) of MMMs with varied loading of TpPa-1-nc.

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to aggregate and permeate into the membrane; then, the generatedCO2 concentration gradient was manifested by amide modifiedTpPa-1-nc, and thus resulted in facilitated CO2 transport within theMMM.41 With the loading above 1 wt %, increased permeability ofCO2 became slower than that of N2, and thus leads to decreasedselectivity. This is because more nonselective interface defects (spacebetween nanosheets in a cluster) were generated when a larger amountof TpPa-1-nc was added into the matrix.42 Despite the uniformdistribution of TpPa-1-nc in polymer solution, such kinds of interfacedefects cannot be fully filled by polymer chains.Generally, the permeation selectivity result from mixture gas test is

higher than that of single gas test, as the competitive adsorptionand diffusion will occur inside the functional membrane. Thus, in lightof high CO2/N2 separation factor from a single gas test, we then per-formed CO2/N2 mixture (1:1) separation on the MMM with 1 wt %COF filler at room temperature. As shown in Figure 7, the average

separation factor increased to ∼72, 12.5% higher than the calculatedideal separation factor (∼64). More importantly, such mixture gasseparation is stable in 120 h. To the best of our knowledge, the separa-tion factor of the CO2/N2 mixture by TpPa-1-nc MMM (1 wt %)surpasses the value of all COF-based membranes.27,43−45 In contrastwith other PEBA supported MMMs, TpPa-1-nc MMM (1 wt %) has acompetitive advantage in CO2/N2 separation, even though it is hard tomake a direct quantitative comparison due to different sample loadingand operation conditions (Table 1).Additionally, binary gas separation experiments by TpPa-1-nc

MMM (1 wt %) were also explored at different temperatures (from20 to 60 °C). As shown in Figure 8, high temperature leads toincreased gas permeance, because higher temperature promotes themotion of polymer and weakens the interaction between a permeatingmolecule and a polymer molecule, and then results in the reduced

transfer resistance for faster diffusion. However, due to the higher ratioof increased N2 permeability, the reduced selectivity was observed athigh temperature. Despite those, the gas selectivity remains as high as45 at 40 °C, revealing the high possibility for selective CO2 removalunder feasible condition.

■ CONCLUSIONSIn summary, the unique morphology change from amorphousCOF particle to honeycomb-like COF nanosheet cluster wasfirst observed during solid reaction. The functional amide groupand uniform micropore make such a COF cluster achievinggood surface area and CO2/N2 adsorption selectivity. Moreimportantly, the PEBA-based MMM with 1 wt % COF nano-sheet cluster showed the highest separation factor (∼72) foran equimolar CO2/N2 mixture in all COF-based membranes.Gas separation is stable during 120 h. Thus, the excellentperformance of energy saved MMMs along with easily preparedCOF filler holds great promise for scale up selective CO2removal from N2.

■ ASSOCIATED CONTENT*S Supporting InformationThe Supporting Information is available free of charge on theACS Publications website at DOI: 10.1021/acsami.7b08032.

Detailed experimental procedures and materials, COFsynthesis, PXRD, calculated Henrys constants, TG, SEM,TEM, and dual-site Langmuir−Freundlich fit of adsorp-tion isotherms (PDF)

■ AUTHOR INFORMATIONCorresponding Authors*E-mail: duanjingui@njtech.edu.cn (J.D.).*E-mail: wqjin@njtech.edu.cn (W.J.).

Table 1. Separation Performance of CO2/N2 by PEBASupported MMMs with Varied Fillers

fillers polymerloading(wt %)

PCO2

(GPU) SCO2/N2refs

MWNT PEBA 2 21.9a 78.6 46ZIF-8 PEBA 15 9.6a 30.3 474A Zeolite PEBA 10 1.0a 54 40SWNT PEBA 5 1.1a 73 48TpPa-1-nc PEBA 1 7.5 72 this work

aThe value was calculated according to the reported CO2 permeanceand membrane thickness.

Figure 8. Effect of temperature on separation performance of MMM-1.0.

Figure 6. Gas permeability and CO2/N2 separation factor of MMMswith varied TpPa-1-nc loadings at 298 K.

Figure 7. Long-term test of equimolar CO2/N2 mixture separation onTpPa-1-nc MMM (1 wt %) at room temperature.

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ORCIDJingui Duan: 0000-0002-8218-1487Wanqin Jin: 0000-0001-6940-5047Author Contributions†These authors contributed equally.

NotesThe authors declare no competing financial interest.

■ ACKNOWLEDGMENTS

We thank the National Science Foundation of China(21671102), the National Science Foundation of JiangsuProvince (BK20161538), and Innovative Research TeamProgram by the Ministry of Education of China (IRT17R54),Six Talent Peaks Project in Jiangsu Province (JY-030), PriorityAcademic Program Development of Jiangsu Higher EducationInstitutions, and the State Key Laboratory of Materials-Oriented Chemical Engineering (ZK201406) for the financialsupport.

■ REFERENCES(1) Nugent, P.; Belmabkhout, Y.; Burd, S. D.; Cairns, A. J.; Luebke,R.; Forrest, K.; Pham, T.; Ma, S. Q.; Space, B.; Wojtas, L.; Eddaoudi,M.; Zaworotko, M. J. Porous materials with optimal adsorptionthermodynamics and kinetics for CO2 separation. Nature 2013, 495,80−84.(2) McDonald, T. M.; Mason, J. A.; Kong, X.; Bloch, E. D.; Gygi, D.;Dani, A.; Crocella, V.; Giordanino, F.; Odoh, S. O.; Drisdell, W. S.;Vlaisavljevich, B.; Dzubak, A. L.; Poloni, R.; Schnell, S. K.; Planas, N.;Lee, K.; Pascal, T.; Wan, L. F.; Prendergast, D.; Neaton, J. B.; Smit, B.;Kortright, J. B.; Gagliardi, L.; Bordiga, S.; Reimer, J. A.; Long, J. R.Cooperative insertion of CO2 in diamine-appended metal-organicframeworks. Nature 2015, 519, 303−308.(3) Peng, Y.; Li, Y.; Ban, Y.; Jin, H.; Jiao, W.; Liu, X.; Yang, W. Metal-organic framework nanosheets as building blocks for molecular sievingmembranes. Science 2014, 346, 1356−1359.(4) Peng, Y.; Li, Y. S.; Ban, Y. J.; Jin, H.; Jiao, W. M.; Liu, X. L.; Yang,W. S. Metal-organic framework nanosheets as building blocks formolecular sieving membranes. Science 2014, 346, 1356−1359.(5) Liu, G. P.; Jin, W. Q.; Xu, N. P. Graphene-based membranes.Chem. Soc. Rev. 2015, 44, 5016−5030.(6) Rangnekar, N.; Mittal, N.; Elyassi, B.; Caro, J.; Tsapatsis, M.Zeolite membranes - a review and comparison with MOFs. Chem. Soc.Rev. 2015, 44, 7128−7154.(7) Seoane, B.; Coronas, J.; Gascon, I.; Benavides, M. E.; Karvan, O.;Caro, J.; Kapteijn, F.; Gascon, J. Metal-organic framework based mixedmatrix membranes: a solution for highly efficient CO2 capture? Chem.Soc. Rev. 2015, 44, 2421−2454.(8) Xiao, Y. C.; Low, B. T.; Hosseini, S. S.; Chung, T. S.; Paul, D. R.The strategies of molecular architecture and modification ofpolyimide-based membranes for CO2 removal from natural gas-Areview. Prog. Polym. Sci. 2009, 34, 561−580.(9) David, O. C.; Gorri, D.; Nijmeijer, K.; Ortiz, I.; Urtiaga, A.Hydrogen separation from multicomponent gas mixtures containingCO, N-2 and CO2 using Matrimid (R) asymmetric hollow fibermembranes. J. Membr. Sci. 2012, 419, 49−56.(10) Reijerkerk, S. R.; Nijmeijer, K.; Ribeiro, C. P.; Freeman, B. D.;Wessling, M. On the effects of plasticization in CO2/light gasseparation using polymeric solubility selective membranes. J. Membr.Sci. 2011, 367, 33−44.(11) Friess, K.; Hynek, V.; Sipek, M.; Kujawski, W. M.; Vopicka, O.;Zgazar, M.; Kujawski, M. W. Permeation and sorption properties ofpoly(ether-block-amide) membranes filled by two types of zeolites.Sep. Purif. Technol. 2011, 80, 418−427.(12) Baker, R. W. Future Directions of Membrane Gas SeparationTechnology. Ind. Eng. Chem. Res. 2002, 41, 1393−1411.

(13) Seoane, B.; Coronas, J.; Gascon, I.; Benavides, M. E.; Karvan,O.; Caro, J.; Kapteijn, F.; Gascon, J. Metal-organic framework basedmixed matrix membranes: a solution for highly efficient CO2 capture?Chem. Soc. Rev. 2015, 44, 2421−2454.(14) Bachman, J. E.; Long, J. R. Plasticization-resistant Ni-2(dobdc)/polyimide composite membranes for the removal of CO2 from naturalgas. Energy Environ. Sci. 2016, 9, 2031−2036.(15) Cui, Z.; Drioli, E.; Lee, Y. M. Recent progress in fluoropolymersfor membranes. Prog. Polym. Sci. 2014, 39, 164−198.(16) Pera-Titus, M. Porous Inorganic Membranes for CO2 Capture:Present and Prospects. Chem. Rev. 2014, 114, 1413−1492.(17) Caro, J. Hierarchy in inorganic membranes. Chem. Soc. Rev.2016, 45, 3468−3478.(18) Song, Q. L.; Nataraj, S. K.; Roussenova, M. V.; Tan, J. C.;Hughes, D. J.; Li, W.; Bourgoin, P.; Alam, M. A.; Cheetham, A. K.; Al-Muhtaseb, S. A.; Sivaniah, E. Zeolitic imidazolate framework (ZIF-8)based polymer nanocomposite membranes for gas separation. EnergyEnviron. Sci. 2012, 5, 8359−8369.(19) Keskin, S.; Sholl, D. S. Selecting metal organic frameworks asenabling materials in mixed matrix membranes for high efficiencynatural gas purification. Energy Environ. Sci. 2010, 3, 343−351.(20) Denny, M. S., Jr.; Cohen, S. M. In Situ Modification of Metal-Organic Frameworks in Mixed-Matrix Membranes. Angew. Chem., Int.Ed. 2015, 54, 9029−9032.(21) Das, M. C.; Xiang, S. C.; Zhang, Z. J.; Chen, B. L. FunctionalMixed Metal-Organic Frameworks with Metalloligands. Angew. Chem.,Int. Ed. 2011, 50, 10510−10520.(22) Denny, M. S., Jr; Moreton, J. C.; Benz, L.; Cohen, S. M. Metal−organic frameworks for membrane-based separations. Nat. Rev. Mater.2016, 1, 16078.(23) El-Kaderi, H. M.; Hunt, J. R.; Mendoza-Cortes, J. L.; Cote, A. P.;Taylor, R. E.; O’Keeffe, M.; Yaghi, O. M. Designed synthesis of 3Dcovalent organic frameworks. Science 2007, 316, 268−272.(24) Biswal, B. P.; Chandra, S.; Kandambeth, S.; Lukose, B.; Heine,T.; Banerjee, R. Mechanochemical synthesis of chemically stableisoreticular covalent organic frameworks. J. Am. Chem. Soc. 2013, 135,5328−5331.(25) Kang, Z. X.; Peng, Y. W.; Qian, Y. H.; Yuan, D. Q.; Addicoat, M.A.; Heine, T.; Hu, Z. G.; Tee, L.; Guo, Z. G.; Zhao, D. Mixed MatrixMembranes (MMMs) Comprising Exfoliated 2D Covalent OrganicFrameworks (COFs) for Efficient CO2 Separation. Chem. Mater.2016, 28, 1277−1285.(26) Lu, H.; Wang, C.; Chen, J.; Ge, R.; Leng, W.; Dong, B.; Huang,J.; Gao, Y. A novel 3D covalent organic framework membrane grownon a porous alpha-Al2O3 substrate under solvothermal conditions.Chem. Commun. 2015, 51, 15562−15567.(27) Ying, Y. P.; Liu, D. H.; Ma, J.; Tong, M. M.; Zhang, W. X.;Huang, H. L.; Yang, Q. Y.; Zhong, C. L. A GO-assisted method for thepreparation of ultrathin covalent organic framework membranes forgas separation. J. Mater. Chem. A 2016, 4, 13444−13449.(28) Shan, M.; Seoane, B.; Rozhko, E.; Dikhtiarenko, A.; Clet, G.;Kapteijn, F.; Gascon, J. Azine-Linked Covalent Organic Framework(COF)-Based Mixed-Matrix Membranes for CO2/CH4 Separation.Chem.-Eur. J. 2016, 22, 14467−14470.(29) Lin, L. C.; Choi, J. W.; Grossman, J. C. Two-dimensionalcovalent triazine framework as an ultrathin-film nanoporousmembrane for desalination. Chem. Commun. 2015, 51, 14921−14924.(30) Wang, Y.; Li, J. P.; Yang, Q. Y.; Zhong, C. L. Two-DimensionalCovalent Triazine Framework Membrane for Helium Separation andHydrogen Purification. ACS Appl. Mater. Interfaces 2016, 8, 8694−8701.(31) Duan, J.; Higuchi, M.; Zheng, J.; Noro, S. I.; Chang, I. Y.;Hyeon-Deuk, K.; Mathew, S.; Kusaka, S.; Sivaniah, E.; Matsuda, R.;Sakaki, S.; Kitagawa, S. Density Gradation of Open Metal Sites in theMesospace of Porous Coordination Polymers. J. Am. Chem. Soc. 2017,DOI: 10.1021/jacs.7b05702.(32) Duan, J. G.; Jin, W. Q.; Kitagawa, S. Water-resistant porouscoordination polymers for gas separation. Coord. Chem. Rev. 2017, 332,48−74.

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DOI: 10.1021/acsami.7b08032ACS Appl. Mater. Interfaces 2017, 9, 29093−29100

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(33) Duan, J. G.; Higuchi, M.; Kitagawa, S. Predesign and SystematicSynthesis of 11 Highly Porous Coordination Polymers withUnprecedented Topology. Inorg. Chem. 2015, 54 (4), 1645−1649.(34) Liu, G. P.; Jin, W. Q.; Xu, N. P. Two-Dimensional-MaterialMembranes: A New Family of High-Performance SeparationMembranes. Angew. Chem., Int. Ed. 2016, 55, 13384−13397.(35) Duan, J.; Jin, W.; Krishna, R. Natural gas purification using aporous coordination polymer with water and chemical stability. Inorg.Chem. 2015, 54, 4279−4284.(36) Duan, J.; Higuchi, M.; Krishna, R.; Kiyonaga, T.; Tsutsumi, Y.;Sato, Y.; Kubota, Y.; Takata, M.; Kitagawa, S. High CO2/N2/O2/COseparation in a chemically robust porous coordination polymer withlow binding energy. Chem. Sci. 2014, 5, 660−666.(37) Duan, J. G.; Higuchi, M.; Horike, S.; Foo, M. L.; Rao, K. P.;Inubushi, Y.; Fukushima, T.; Kitagawa, S. High CO2/CH4 and C-2Hydrocarbons/CH4 Selectivity in a Chemically Robust PorousCoordination Polymer. Adv. Funct. Mater. 2013, 23, 3525−3530.(38) Jomekian, A.; Behbahani, R. M.; Mohammadi, T.; Kargari, A.High speed spin coating in fabrication of Pebax 1657 based mixedmatrix membrane filled with ultra-porous ZIF-8 particles for CO2/CH4 separation. Korean J. Chem. Eng. 2017, 34, 440−453.(39) Liu, S. N.; Liu, G. P.; Zhao, X. H.; Jin, W. Q. Hydrophobic-ZIF-71 filled PEBA mixed matrix membranes for recovery of biobutanol viapervaporation. J. Membr. Sci. 2013, 446, 181−188.(40) Surya Murali, R.; Ismail, A. F.; Rahman, M. A.; Sridhar, S. Mixedmatrix membranes of Pebax-1657 loaded with 4A zeolite for gaseousseparations. Sep. Purif. Technol. 2014, 129, 1−8.(41) Zhao, D.; Ren, J. Z.; Wang, Y.; Qiu, Y. T.; Li, H.; Hua, K. S.; Li,X. X.; Ji, J. M.; Deng, M. C. High CO2 separation performance ofPebax (R)/CNTs/GTA mixed matrix membranes. J. Membr. Sci. 2017,521, 104−113.(42) Shen, J.; Liu, G. P.; Huang, K.; Li, Q. Q.; Guan, K. C.; Li, Y. K.;Jin, W. Q. UiO-66-polyether block amide mixed matrix membranes forCO2 separation. J. Membr. Sci. 2016, 513, 155−165.(43) Lu, H.; Wang, C.; Chen, J. J.; Ge, R. L.; Leng, W. G.; Dong, B.;Huang, J.; Gao, Y. N. A novel 3D covalent organic frameworkmembrane grown on a porous alpha-Al2O3 substrate undersolvothermal conditions. Chem. Commun. 2015, 51, 15562−15565.(44) Tong, M. M.; Yang, Q. Y.; Ma, Q. T.; Liu, D. H.; Zhong, C. L.Few-layered ultrathin covalent organic framework membranes for gasseparation: a computational study. J. Mater. Chem. A 2016, 4, 124−131.(45) Wu, X. Y.; Tian, Z. Z.; Wang, S. F.; Peng, D. D.; Yang, L. X.;Wu, Y. Z.; Xin, Q. P.; Wu, H.; Jiang, Z. Y. Mixed matrix membranescomprising polymers of intrinsic microporosity and covalent organicframework for gas separation. J. Membr. Sci. 2017, 528, 273−283.(46) Murali, R. S.; Sridhar, S.; Sankarshana, T.; Ravikumar, Y. V. LGas Permeation Behavior of Pebax-1657 Nanocomposite MembraneIncorporated with Multiwalled Carbon Nanotubes. Ind. Eng. Chem.Res. 2010, 49, 6530−6538.(47) Nafisi, V.; Hagg, M. B. Development of dual layer of ZIF-8/PEBAX-2533 mixed matrix membrane for CO2 capture. J. Membr. Sci.2014, 459, 244−255.(48) Yu, B.; Cong, H. L.; Li, Z. J.; Tang, J. G.; Zhao, X. S. Pebax-1657nanocomposite membranes incorporated with nanoparticles colloidscarbon nanotubes for CO2/N2 and CO2/H2 separation. J. Appl.Polym. Sci. 2013, 130, 2867−2876.

■ NOTE ADDED AFTER ASAP PUBLICATIONDue to a production error, this paper was published on theWeb on August 21, 2017, before all of the text corrections wereimplemented. The corrected version was reposted on August30, 2017.

ACS Applied Materials & Interfaces Research Article

DOI: 10.1021/acsami.7b08032ACS Appl. Mater. Interfaces 2017, 9, 29093−29100

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