Self-Sacrificial Template Strategy Coupled with Smart in Situ Seeding

Communication pubs.acs.org/cm

Self-Sacrificial Template Strategy Coupled with Smart in Situ Seeding for Highly Oriented Metal−Organic Framework Layers: From Films to Membranes Sheng Zhou, Yanying Wei,* Jiamin Hou, Liang-Xin Ding, and Haihui Wang* School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, China S Supporting Information *

R

ecent decades have witnessed the rapid development of metal−organic frameworks (MOFs).1−3 As a class of crystalline porous materials, MOFs are assembled from organic links and metal-based connectors.4 By varying the building elements, MOF structures can be rationally designed for various applications, e.g., chemical sensors,5 catalysts,2,6,7 gas adsorbents,8−10 optical devices11,12 and gas separation membranes.13−18 To integrate their functions and maximize their potential, processing porous MOFs into large-scale films on different substrates is essential.19,20 In particular, precise control over the specific orientation within the framework architecture is highly desirable for certain specific applications.21 However, obtaining oriented MOF layers using a facile and straightforward method remains challenging.22 Recently, several advances have addressed the fabrication of MOF layers in a preferred orientation.23 Typically, solutionbased layer-by-layer growth is coupled with Langmuir− Blodgett methods (LB-LbL),24,25 and a liquid-phase epitaxybased step-by-step approach, wherein the oriented MOF crystals grow on organically functionalized surfaces,26−28 has been widely adopted for constructing oriented MOF films on dense flat substrates. However, these methods exhibit some limitations. First, controlling the building units at each step of stepwise methods such as “layer-by-layer” deposition, is difficult; thus, this method is not suitable for large-scale production in industry. Second, maintaining the orientation of the MOF layer on noncontinuous substrates, e.g., porous substrates, is also difficult; such substrates are necessary for applications in membrane separation. For example, Shekhah et al. achieved highly oriented ZIF-8 films on an −OH − functionalized Au substrate using the liquid-phase epitaxy method,29 but no preferred orientation was observed when using porous alumina supports.30 To resolve the first limitation, Falcaro et al. reported a one-step approach to fabricate oriented Cu2(BDC)2 films via the conversion of a crystalline copper hydroxide surface, but these results have not been replicated for porous substrates.31 To resolve the second limitation, secondary growth with preseeding using a solvothermal method is commonly used.32,33 However, this strategy requires nanosized MOF seeds for pretreatment, which complicates the procedure. Thus, new strategies for facile one-pot syntheses of oriented MOF layers that are suitable for growth on both dense and porous substrates are urgently needed. Herein, we propose a self-sacrificial template strategy coupled with a smart “in situ seeding” process for a one-pot synthesis of highly oriented MOF layers on both dense and porous substrates. As shown in Figure 1, one-dimensional ZnO © 2017 American Chemical Society

Figure 1. Schematic illustration of the fabrication of oriented MOF layers on (a) dense and (b) porous substrates.

nanorod arrays are electrodeposited onto the substrate surface to guide the subsequent oriented growth of Zn-ZIF-8 and CoZIF-67 films (with the same ligand, 2-methylimidazolate, 2MIM) which are designed as self-sacrificial templates, thus enabling the controlled in situ growth of oriented MOF layers in a one-pot synthesis. In Figure 1b, when a porous stainless steel net (SSN) is used as the substrate instead of a dense Ti sheet (Figure 1a), the homologous synthesis of oriented ZnZIF-8 membranes is difficult because the ZnO nanorods are vertical to the tangent plane of each cylindrical SSN fiber with a radial distribution. However, nonhomologous Co-ZIF-67 membranes with the preferred orientation can be obtained using a smart “in situ seeding” process, wherein the “in situ seeds” of Zn-ZIF-8 generated from the sacrificed ZnO nanorods supply highly concentrated nucleation sites for CoZIF-67 crystals that greatly contribute to the oriented growth. First, oriented Zn-ZIF-8 and Co-ZIF-67 films were prepared on a dense substrate of Ti sheet using the self-sacrificial template strategy, as shown in Figure 1a. The microstructures of the electrodeposited ZnO nanorod arrays on the Ti sheet, as characterized by scanning electron microscopy (SEM), are shown in Figure 2a. Clearly, the nanorods align almost vertically on the flat Ti sheet, and the purity of the ZnO Received: July 30, 2017 Revised: August 18, 2017 Published: August 25, 2017 7103

DOI: 10.1021/acs.chemmater.7b03211 Chem. Mater. 2017, 29, 7103−7107

Communication

Chemistry of Materials

Zn-ZIF-8 crystals tend to grow along the direction in which Zn2+ is sequentially released, i.e., exactly along the ZnO nanorods that are vertical to the substrate, leading to oriented growth. Moreover, the self-sacrificial strategy is also efficient for fabricating various oriented MOF layers with different central metals on a dense substrate. For example, the nonhomologous synthesis of oriented Co-ZIF-67 layers using ZnO nanorods as a self-sacrificial template is also achieved, as illustrated in Figure 1a. Top-view and cross-sectional SEM images are shown in Figure 2e,f and are analogous to the features of the oriented ZnZIF-8 layers (they are distinguished by Fourier transform infrared spectra, FTIR, Figure S3). The preferred orientation of {001} is further confirmed by the XRD pattern (Figure 2b), in which the (002) reflection becomes dominant with the calculated CPO(002)/(011) of 111. Compared with conventional methods, the self-sacrificial template strategy not only is versatile but also simplifies the synthesis process, exhibiting high potential for future applications. As mentioned, constructing oriented MOF layers on porous substrates using traditional liquid-phase epitaxy is difficult. However, highly oriented MOF membranes easily grew on porous SSN substrates using a self-sacrificial template strategy coupled with the smart “in situ seeding” process (schematically shown in Figure 1b). The SSN substrate is premodified with ZnO nanorod arrays via electrodeposition. Unlike those grown on dense Ti sheets, the ZnO nanorods align in different directions because the SSN fibers are cylindrical, as shown in Figure 3a, and the XRD pattern of ZnO in Figure S1 shows no specific orientation. After the one-pot solvothermal synthesis, a

Figure 2. (a) SEM images of electrodeposited ZnO nanorods on a Ti sheet. (b) XRD patterns of oriented Zn-ZIF-8 and Co-ZIF-67 films grown using self-sacrificial template strategy on the Ti sheet. (c, d) Top-view and cross-sectional view SEM images of oriented Zn-ZIF-8 on Ti sheet, respectively. (e, f) Top-view and cross-sectional SEM images of oriented Co-ZIF-67 film on the Ti sheet, respectively.

phase is confirmed by the X-ray diffraction (XRD) pattern shown in Figure S1. Moreover, the relative intensity of the (002) reflection of the ZnO nanorods supported on the Ti sheet is much stronger than that in the standard PDF card, indicating the vertical orientation of the one-dimensional ZnO nanorods. After one-pot solvothermal growth using the ZnO nanorods as a self-sacrificial template, a continuous oriented Zn-ZIF-8 film is obtained (Figure 2c, 2d). As a polyhedron with a rhombic dodecahedral shape, the Zn-ZIF-8 crystals exhibit six corners pointing along ⟨001⟩ (4-fold rotation axis, Figure S2),33 and these corners can be observed when viewed along the ⟨001⟩ direction. The top-view SEM image of the as-synthesized Zn-ZIF-8 film clearly shows that most corners lay on a 4-fold rotation axis (Figure 2c), which actually indicates that the top view is in accordance with the ⟨001⟩ direction. The corresponding cross-sectional SEM image shown in Figure 2d exhibits a column-like film wall perpendicular to the substrate. The preferred orientation is further confirmed by XRD, as shown in Figure 2b. The (002) reflection is significantly enhanced, and the dominant peak has varied from the (011) reflection of the simulated crystals to the (002) reflection of the as-prepared MOF film. The crystallographic preferred orientation (CPO) index of the (002) reflection in relation to the (011) reflection (CPO(002)/(011)) is calculated to be 188, indicating a pronounced crystal orientation of {001} planes parallel to the substrate. It is noted that as a kind of amphoteric oxide, ZnO can directly take part in the crystalline of Zn-ZIF-8 to fabricate different structures.34−36 Herein, when the vertically aligned ZnO nanorod templates gradually dissolve and release Zn2+ during solvothermal growth, the ligands coordinate immediately. Therefore, in the following crystallization process,

Figure 3. (a) SEM images of electrodeposited ZnO nanorods on SSN. (b) XRD patterns of Zn-ZIF-8 and Co-ZIF-67 membranes grown using the self-sacrificial template strategy on SSN. (c, d) Top-view and cross-sectional SEM images of Zn-ZIF-8 membrane on SSN, respectively. (e, f) Top-view and cross-sectional SEM images of oriented Co-ZIF-67 membrane on SSN, respectively. 7104


Communication


subsequent growth of the Co-ZIF-67 membrane. With the formation of “in situ seeds” of Zn-ZIF-8, the heterogeneous nucleation of Co-ZIF-67 crystals gradually appears on the surface of the primitive Zn-ZIF-8 crystal seeds. Jeong et al. reported a Zn-ZIF-8@Co-ZIF-67 core−shell structure, and several small Co-ZIF-67 crystals were observed on the facets of a single Zn-ZIF-8 crystal.38 Similarly, many Co-ZIF-67 crystal nuclei are expected to form on the surface of each “in situ seed” of Zn-ZIF-8. As a result, the density and concentration of the heterogeneous nucleation sites for Co-ZIF-67 are greatly improved, and the evolution selection model proposed by van der Drift39 is favored. During the ensuing growth process, Co-ZIF-67 crystals meet laterally neighboring crystals and eventually overgrow their neighbors along the fastest growth direction of ⟨001⟩ to form top layers with the preferred orientation. The primitive heterogeneous seeds of Zn-ZIF-8 are generated in situ from the sacrificial template of ZnO nanorods during one-pot Co-ZIF-67 membrane growth, also called an “in situ seeding” process. Moreover, the proposed mechanisms of oriented growth in different cases are summarized in Figure S5. To further verify the proposed “in situ seeding” process, the gradual growth of the oriented Co-ZIF-67 membrane is tracked over time. SEM images and an energy dispersion spectrum (EDS) elemental analysis of the gradually formed oriented CoZIF-67 layers are recorded every 2 h during the in situ growth process, as shown in Figures 4b, S6 and S7. After the first 2 h of growth, the Zn atomic percentage on the top surface of the crystal layer is determined to be 1.35% (Figure 4b), and the XRD pattern (Figure 4c) presents no diffraction peaks related to ZnO except for the ZIF phase structure, demonstrating the sacrificed ZnO nanorods and the “in situ seed” formation of ZnZIF-8 crystals. The FTIR spectra results of the 2-h Co-ZIF-67 layer are compared with those of the pure Zn-ZIF-8 and CoZIF-67 crystals in Figure S8, wherein a slight blue shift in the metal−nitrogen stretching frequency falls between that of Co− N bonds and Zn−N bonds, indicating the coexistence of ZnZIF-8 and Co-ZIF-67 during this time. After longer growth times, the Zn percentage decreases to 0.48% due to the increased amount of Co-ZIF-67 crystals and continues to decrease to 0.27% after 6 h of growth (Figure 4b). After 12 h, the Zn content declines to 0.12% on the top view of the asprepared Co-ZIF-67 membrane. Furthermore, in the cross section of the membrane shown in Figure 4d, the line-scanning result of the Zn distribution along the membrane wall demonstrates that Zn is located only at the bottom in a root layer of Zn-ZIF-8 layer that connects to the upper Co-ZIF-67 membrane and the SSN substrate below, which is transformed from the self-sacrificial templates of the ZnO nanorods. In contrast, the amount of Co is relatively lower at the bottom of the membrane layer, which is enriched with Zn. The XRD patterns in Figure 4c show that the intensity of the (002) diffraction of the membrane increases with synthesis time and exhibits a perfectly oriented Co-ZIF-67 membrane layer with a CPO(002)/(011) of 143, which is in good agreement with our assumptions for membrane growth with smart “in situ seeding” (Figure 4a). In fact, both the orientative self-sacrificial template and “in situ seeding” are indispensable for the preparation of oriented MOF membranes on a porous substrate. As a counterexample, when the porous substrates modified by nonorientative spherical ZnO particles are used as the sacrificed template to grow Co-ZIF-67 membranes (Figure S9), no orientation is observed (Figure S10), indicating the importance of the

continuous Zn-ZIF-8 membrane can be observed on the SSN, as shown in Figure 3c,d. However, the XRD pattern in Figure 3b shows no clear preferred orientation of the Zn-ZIF-8 membrane with a CPO(002)/(011) of only 7.5 (the value should be higher than 50 for a strongly oriented crystalline layer37). Moreover, the cross-sectional SEM image shows the fan-shaped structure of the Zn-ZIF-8 membranes, in contrast with the column-like cross section of Zn-ZIF-8 films grown on the Ti sheet shown. This difference can be explained by the nonorientation of the templates, on which ZnO nanorods are deposited perpendicular to the surface of each SSN fiber rather than along the horizontal plane. Therefore, under the guidance of the radially distributed ZnO nanorods, the resulting Zn-ZIF8 membrane exhibits analogous fan-shaped cross-sectional structures without a preferred orientation. In contrast, nonhomologous Co-ZIF-67 membranes exhibit remarkable orientation when grown on ZnO nanorod-modified SSN substrates, as shown in Figure 3e,f (Co-ZIF-67 are also distinguished from Zn-ZIF-8 by FTIR spectra, Figure S4). As revealed by the XRD patterns in Figure 3b, the (002) reflection is the major peak, with a CPO(002)/(011) of 143, indicating the preferred orientation of the {001} plane. This interesting result can be explained by the “in situ seeding” process for the special nonhomologous growth of CoZIF-67 on the self-sacrificial ZnO nanorod template, which benefits from the fact that Co-ZIF-67 has the same topology (SOD) and ligand (2-MIM) as Zn-ZIF-8. As schematically shown in Figure 4a, once the ZnO nanorods are exposed to the precursor solution containing Co2+ and 2-MIM under solvothermal conditions, they begin to sacrifice themselves and capture 2-MIM to instantly form primitive Zn-ZIF-8 anchored on SSNs, which serves as the “in situ seeds” for the

Figure 4. (a) Schematic illustration of the “in situ seeding” process. (b) Atomic percentages of Zn and Co on Co-ZIF-67 membrane surface as a function of growth time. (c) XRD patterns of Co-ZIF-67 membranes grown for different times. (d) Line-scanning analysis of different elements across cross section of oriented Co-ZIF-67 membranes. 7105


Communication


orientation, even when the template is randomly oriented. We also demonstrated the possibility of preparing oriented MOF layers on both dense substrates as a film and porous substrates as a gas separation membrane. This facile, effective strategy is a breakthrough for other methodological limitations of substrates and may also be promising for the fabrication of other MOF layers with a crystalline orientation.

orientative self-sacrificial template. Moreover, the indispensable “in situ seeding process” is based on the template effect and acts as an “amplifier” when the template contribution is limited. A schematic video of the different growth processes of the homologous Zn-ZIF-8 and nonhomologous Co-ZIF-67 membranes on ZnO nanorod-modified SSN can be found in the Supporting Information. Furthermore, the highly oriented Co-ZIF-67 membranes grown on porous SSN are tested for single-gas permeation using the Wicke−Kallenbach technique (Figure S11) at room temperature. A clear-cutoff between H2 and other gases is observed in Figure 5a. The ideal selectivity of H2/CO2, H2/N2,

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.chemmater.7b03211. Materials synthesis, experimental details, data analysis procedures (PDF) Schematic video of different growth processes of homologous Zn-ZIF-8 and nonhomologous Co-ZIF-67 membranes on ZnO nanorod-modified SSN (AVI)

■

AUTHOR INFORMATION

Corresponding Authors

*Y. Wei. Email: [email protected]. *H. Wang. Email: [email protected]. ORCID

Haihui Wang: 0000-0002-2917-4739 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We gratefully acknowledge the funding from the Natural Science Foundation of China (21536005, 51621001 and 21606086), Natural Science Foundation of the Guangdong Province (2014A030312007), Guangdong Natural Science Funds for Distinguished Young Scholar and the Guangzhou Technology Project (no. 201707010317).

■

REFERENCES

(1) Eddaoudi, M.; Kim, J.; Rosi, N.; Vodak, D.; Wachter, J.; O’Keeffe, M.; Yaghi, O. M. Systematic design of pore size and functionality in isoreticular MOFs and their application in methane storage. Science 2002, 295, 469−472. (2) Lee, J.; Farha, O. K.; Roberts, J.; Scheidt, K. A.; Nguyen, S. T.; Hupp, J. T. Metal−organic framework materials as catalysts. Chem. Soc. Rev. 2009, 38, 1450−1459. (3) Xu, X.; Lu, Y.; Yang, Y.; Nosheen, F.; Wang, X. Tuning the growth of metal-organic framework nanocrystals by using polyoxometalates as coordination modulators. Sci. China. Mater. 2015, 58, 370−377. (4) Furukawa, H.; Cordova, K. E.; O’Keeffe, M.; Yaghi, O. M. The chemistry and applications of metal-organic frameworks. Science 2013, 341, 1230444. (5) Kreno, L. E.; Leong, K.; Farha, O. K.; Allendorf, M.; Van Duyne, R. P.; Hupp, J. T. Metal−organic framework materials as chemical sensors. Chem. Rev. 2012, 112, 1105−1125. (6) Seo, J. S.; Whang, D.; Lee, H.; Jun, S. I.; Oh, J.; Jeon, Y. J.; Kim, K. A homochiral metal-organic porous material for enantioselective separation and catalysis. Nature 2000, 404, 982−986. (7) Gustafsson, M.; Bartoszewicz, A.; Martín-Matute, B. n.; Sun, J.; Grins, J.; Zhao, T.; Li, Z.; Zhu, G.; Zou, X. A family of highly stable lanthanide metal− organic frameworks: structural evolution and catalytic activity. Chem. Mater. 2010, 22, 3316−3322. (8) Millward, A. R.; Yaghi, O. M. Metal− organic frameworks with exceptionally high capacity for storage of carbon dioxide at room temperature. J. Am. Chem. Soc. 2005, 127, 17998−17999.

Figure 5. (a) Single-gas permeance of different gases through the oriented Co-ZIF-67 membrane at 25 °C and 1 bar as a function of the kinetic diameter. The inset shows the gas selectivity. (b) Long-term operation performance for separating H2/CO2 at 150 °C and 1 bar.

H2/CH4, H2/C2H6 and H2/C3H8 are shown in the inset of Figure 5a, which greatly exceeds the corresponding Knudsen diffusion selectivity and indicates the membrane is intact and free of defects. Moreover, the H2 permeance through the membrane increases with temperature and reaches ∼0.6 × 10−6 mol m−2 s−1 Pa−1 at 150 °C with a selectivity of 9 for the H2/ CO2 mixture (Figure S12). In particular, the gas separation performance is maintained for approximately 1000 h at 150 °C, indicating good stability of the membrane (Figure 5b). In summary, we developed a self-sacrificial template strategy coupled with smart “in situ seeding” for the preparation of highly oriented MOF layers. The template of electrodeposited one-dimensional vertical ZnO nanorods plays an important role in the oriented growth of the MOF layer, which guides the growth direction and controls the crystalline orientation. In addition, another concept of “in situ seeding” was proposed as a complement to the template function to assist the nonhomologous synthesis of MOF layers with preferred crystalline 7106


Communication

Chemistry of Materials (9) Farha, O. K.; Yazaydın, A. Ö .; Eryazici, I.; Malliakas, C. D.; Hauser, B. G.; Kanatzidis, M. G.; Nguyen, S. T.; Snurr, R. Q.; Hupp, J. T. De novo synthesis of a metal−organic framework material featuring ultrahigh surface area and gas storage capacities. Nat. Chem. 2010, 2, 944−948. (10) Cadiau, A.; Adil, K.; Bhatt, P. M.; Belmabkhout, Y.; Eddaoudi, M. A metal-organic framework−based splitter for separating propylene from propane. Science 2016, 353, 137−140. (11) Wang, C.; Zhang, T.; Lin, W. Rational synthesis of noncentrosymmetric metal−organic frameworks for second-order nonlinear optics. Chem. Rev. 2012, 112, 1084−1104. (12) Ranft, A.; Niekiel, F.; Pavlichenko, I.; Stock, N.; Lotsch, B. V. Tandem MOF-based photonic crystals for enhanced analyte-specific optical detection. Chem. Mater. 2015, 27, 1961−1970. (13) Brown, A. J.; Brunelli, N. A.; Eum, K.; Rashidi, F.; Johnson, J.; Koros, W. J.; Jones, C. W.; Nair, S. Interfacial microfluidic processing of metal-organic framework hollow fiber membranes. Science 2014, 345, 72−75. (14) Peng, Y.; Li, Y.; Ban, Y.; Jin, H.; Jiao, W.; Liu, X.; Yang, W. Metal-organic framework nanosheets as building blocks for molecular sieving membranes. Science 2014, 346, 1356−1359. (15) Bux, H.; Liang, F.; Li, Y.; Cravillon, J.; Wiebcke, M.; Caro, J. Zeolitic imidazolate framework membrane with molecular sieving properties by microwave-assisted solvothermal synthesis. J. Am. Chem. Soc. 2009, 131, 16000−16001. (16) Hess, S. C.; Grass, R. N.; Stark, W. J. MOF Channels within Porous Polymer Film: Flexible, Self-Supporting ZIF-8 Poly (ether sulfone) Composite Membrane. Chem. Mater. 2016, 28, 7638−7644. (17) Barankova, E.; Tan, X.; Villalobos, L. F.; Litwiller, E.; Peinemann, K. V. A Metal Chelating Porous Polymeric Support: The Missing Link for a Defect-Free Metal-Organic Framework Composite Membrane. Angew. Chem., Int. Ed. 2017, 56, 2965−2968. (18) Wang, Z.; Knebel, A.; Grosjean, S.; Wagner, D.; Bräse, S.; Wöll, C.; Caro, J.; Heinke, L. Tunable molecular separation by nanoporous membranes. Nat. Commun. 2016, 7, 13872. (19) Talin, A. A.; Centrone, A.; Ford, A. C.; Foster, M. E.; Stavila, V.; Haney, P.; Kinney, R. A.; Szalai, V.; El Gabaly, F.; Yoon, H. P.; Léonard, F.; Allendorf, M. D. Tunable electrical conductivity in metalorganic framework thin-film devices. Science 2014, 343, 66−69. (20) Shekhah, O.; Liu, J.; Fischer, R.; Wöll, C. MOF thin films: existing and future applications. Chem. Soc. Rev. 2011, 40, 1081−1106. (21) So, M. C.; Jin, S.; Son, H.-J.; Wiederrecht, G. P.; Farha, O. K.; Hupp, J. T. Layer-by-layer fabrication of oriented porous thin films based on porphyrin-containing metal−organic frameworks. J. Am. Chem. Soc. 2013, 135, 15698−15701. (22) Yao, J.; Wang, H. Zeolitic imidazolate framework composite membranes and thin films: synthesis and applications. Chem. Soc. Rev. 2014, 43, 4470−4493. (23) Otsubo, K.; Haraguchi, T.; Sakata, O.; Fujiwara, A.; Kitagawa, H. Step-by-step fabrication of a highly oriented crystalline threedimensional pillared-layer-type metal−organic framework thin film confirmed by synchrotron x-ray diffraction. J. Am. Chem. Soc. 2012, 134, 9605−9608. (24) Makiura, R.; Motoyama, S.; Umemura, Y.; Yamanaka, H.; Sakata, O.; Kitagawa, H. Surface nano-architecture of a metal−organic framework. Nat. Mater. 2010, 9, 565−571. (25) Motoyama, S.; Makiura, R.; Sakata, O.; Kitagawa, H. Highly Crystalline Nanofilm by Layering of Porphyrin Metal− Organic Framework Sheets. J. Am. Chem. Soc. 2011, 133, 5640−5643. (26) Liu, B.; Shekhah, O.; Arslan, H. K.; Liu, J.; Wöll, C.; Fischer, R. A. Enantiopure metal−organic framework thin films: oriented SURMOF growth and enantioselective adsorption. Angew. Chem., Int. Ed. 2012, 51, 807−810. (27) Shekhah, O.; Wang, H.; Paradinas, M.; Ocal, C.; Schüpbach, B.; Terfort, A.; Zacher, D.; Fischer, R. A.; Wö ll, C. Controlling interpenetration in metal−organic frameworks by liquid-phase epitaxy. Nat. Mater. 2009, 8, 481−484. (28) Arslan, H. K.; Shekhah, O.; Wieland, D. F.; Paulus, M.; Sternemann, C.; Schroer, M. A.; Tiemeyer, S.; Tolan, M.; Fischer, R.

A.; Wöll, C. Intercalation in layered metal−organic frameworks: reversible inclusion of an extended π-system. J. Am. Chem. Soc. 2011, 133, 8158−8161. (29) Shekhah, O.; Eddaoudi, M. The liquid phase epitaxy method for the construction of oriented ZIF-8 thin films with controlled growth on functionalized surfaces. Chem. Commun. 2013, 49, 10079−10081. (30) Shekhah, O.; Swaidan, R.; Belmabkhout, Y.; Du Plessis, M.; Jacobs, T.; Barbour, L. J.; Pinnau, I.; Eddaoudi, M. The liquid phase epitaxy approach for the successful construction of ultra-thin and defect-free ZIF-8 membranes: pure and mixed gas transport study. Chem. Commun. 2014, 50, 2089−2092. (31) Falcaro, P.; Okada, K.; Hara, T.; Ikigaki, K.; Tokudome, Y.; Thornton, A. W.; Hill, A. J.; Williams, T.; Doonan, C.; Takahashi, M. Centimetre-scale micropore alignment in oriented polycrystalline metal-organic framework films via heteroepitaxial growth. Nat. Mater. 2017, 16, 342−348. (32) Liu, Y.; Zeng, G.; Pan, Y.; Lai, Z. Synthesis of highly c-oriented ZIF-69 membranes by secondary growth and their gas permeation properties. J. Membr. Sci. 2011, 379, 46−51. (33) Bux, H.; Feldhoff, A.; Cravillon, J.; Wiebcke, M.; Li, Y.-S.; Caro, J. Oriented zeolitic imidazolate framework-8 membrane with sharp H2/C3H8 molecular sieve separation. Chem. Mater. 2011, 23, 2262− 2269. (34) Zhan, W.-w.; Kuang, Q.; Zhou, J.-z.; Kong, X.-j.; Xie, Z.-x.; Zheng, L.-s. Semiconductor@ metal−organic framework core−shell heterostructures: A case of ZnO@ ZIF-8 nanorods with selective photoelectrochemical response. J. Am. Chem. Soc. 2013, 135, 1926− 1933. (35) Li, S.; Zhang, W.; Zhu, Y.; Zhao, Q.; Huo, F. Synthesis of MOFs and their composite structures through sacrificial-template strategy. Cryst. Growth Des. 2015, 15, 1017−1021. (36) Zhou, S.; Wei, Y.; Zhuang, L.; Ding, L.-X.; Wang, H. Introduction of metal precursors by electrodeposition for the in situ growth of metal−organic framework membranes on porous metal substrates. J. Mater. Chem. A 2017, 5, 1948−1951. (37) Jeong, H.-K.; Krohn, J.; Sujaoti, K.; Tsapatsis, M. Oriented molecular sieve membranes by heteroepitaxial growth. J. Am. Chem. Soc. 2002, 124, 12966−12968. (38) Kwon, H. T.; Jeong, H.-K.; Lee, A. S.; An, H. S.; Lee, J. S. Heteroepitaxially grown zeolitic imidazolate framework membranes with unprecedented propylene/propane separation performances. J. Am. Chem. Soc. 2015, 137, 12304−12311. (39) Van der Drift, A. Evolutionary selection, a principle governing growth orientation in vapour-deposited layers. Philips Res. Rep 1967, 22, 267−288.

7107


Self-Sacrificial Template Strategy Coupled with Smart in Situ Seeding

Recommend Documents