Zeolitic Imidazolate Framework Membranes Research Articles

Oriented growth of large-area metal-organic framework ZIF-8 membrane for hydrogen separation

Optimal orientation is the key factor to optimize the gas separation performance of metal-organic framework (MOF) membranes. However, it is still greatly challenging to prepare large-area oriented MOF membranes for industrial applications. Herein, we prepared compact and (100) oriented zeolitic-imidazolate framework-8 (ZIF-8) membranes with membrane area up to 500 cm2 on the graphite substrate via support-induced strategy within 2 h. With membrane thickness of only 620 nm, the (100) oriented ZIF-8 membranes exhibit high gas separation performances due to the reduction of inter-crystalline defects and permeation resistance. At 100 °C and 1 bar, the separation factors of H2/CO2, H2/CH4 and H2/C3H8 are 18.5, 58.2 and 101.6, respectively, with H2 permeance of about 160 x 10−9 mol m−2 s−1·Pa−1. The different positions of the 500 cm2 ZIF-8 membrane show complete consistency in orientation and separation performance, recommending this membrane suitable for future industrial applications. Further, also oriented ZIF-67 and MOF-303 membranes can be consistently prepared by this strategy, confirming its versatility for the preparation of large-area MOF membranes.

Unexpectedly High Propylene/Propane Separation Performance of Asymmetric Mixed-Matrix Membranes through Additive-Assisted In Situ ZIF-8 Filler Formation: Experimental and Computational Studies.

Zeolitic-imidazolate framework-8 (ZIF-8), composed of a zinc center tetrahedrally coordinated with 2-methylimidazolate linkers, has garnered extensive attention as a selective filler for propylene-selective mixed-matrix membranes (MMMs). Recently, we reported an innovative and scalable MMM fabrication approach, termed "phase-inversion in sync with in situ MOF formation" (PIMOF), aimed at addressing the prevailing challenges in MMM processing. In this study, we intend to investigate the effect of additives, specifically sodium formate and 1,4-butanediol, on the modification of ZIF-8 filler formation within the polymer matrix in order to further improve the separation performance of the asymmetric MMMs prepared by the PIMOF. Remarkably, MMMs prepared with sodium formate as an additive in the coagulation bath exhibited an unprecedented C3H6/C3H8 separation factor of 222.5 ± 1.8 with a C3H6 permeance of 10.1 ± 0.3 GPU, surpassing that of MMMs prepared without additives (a C3 separation factor of 57.7 ± 11.2 with a C3 permeance of 22.5 ± 4.5 GPU). Our computational work complements the experimental investigation by studying the effect of ZIF-8 nanoparticle size on the specific surface interaction energy and apertures of ZIF-8. Calculations indicate that by having smaller ZIF-8 nanoparticles, stronger interactions are present with the polymer affecting the aperture of ZIF-8 nanoparticles. This reduction in aperture size is expected to improve selectivity toward propylene by reducing the permeability of propylene. These results represent a significant advancement, surpassing the performance of all previously reported propylene-selective MMMs and most high-quality polycrystalline ZIF-8 membranes. The notably enhanced separation performance primarily arises from the formation of exceedingly small ZIF-8-like particles with an amorphous or poorly crystalline structure, corroborated by our computational work.

Linker-exchanged zeolitic imidazolate framework membranes for efficient CO2 separation

Metal organic framework (MOF) membranes have exhibited great potential for efficient gas separation owing to their excellent chemical and structural tunability. To realize CO2 separation from flue gas, linker modification or exchange is generally required to functionalize MOF membranes. However, the reported linker-exchanged polycrystalline MOF membranes have not yet achieved attractive CO2 separation performance due to the sacrificed permeance of the overly reduced pore apertures when employing bulky linkers. Herein, we report a 3-amino-1,2,4-triazole (Atz)-exchanged polycrystalline ZIF-8 membrane (Atz-ZIF-8) with Atz molar ratios ranging from 3% to 29% which shows an excellent CO2/N2 separation performance that significantly surpasses that of other linker-exchanged ZIF-8 membranes. The as-synthesized Atz-ZIF-8 membranes possess additional uncoordinated amines for CO2-preferential adsorption, resulting in an excellent CO2/N2 selectivity of 29. What's more, the size and configuration of Atz is similar to 2-methylimidazole (2-mIm), so the window size of Atz-ZIF-8 membranes is not significantly reduced, and thus high CO2 permeance (690 GPU) is achieved. Considering the superior performance and accessible manufacturing process, we conclude that our work could provide guidelines on designing advanced linker-exchanged ZIF-8 based polycrystalline membranes towards post-combustion carbon capture.

Fabrication of Polycrystalline Zeolitic Imidazolate Framework Membranes by a Vapor-Phase Seeding Method.

The reliable fabrication of polycrystalline zeolitic imidazolate framework (ZIF) membranes continues to pose challenges for their industrial applications. Here, we present a vapor-phase seeding approach that integrates atomic layer deposition (ALD) with ligand vapor treatment to synthesize ZIF membranes with high propylene/propane separation performance. This method began with depositing a ZnO coating onto the support surface via ALD. The support underwent treatment with 2-methylimidazole vapor to transform ZnO to ZIF-8, forming the seed layer. Subsequent secondary growth was employed at near-room temperature, allowing the seeds to grow into a continuous membrane. ZIF-8 membranes made on macroporous ceramic support by this method consistently demonstrated propylene permeances above 1 × 10-8 mol Pa-1 m-2 s-1 and a propylene/propane separation factor exceeding 50. Moreover, we demonstrated the effectiveness of the vapor-phase seeding method in producing the ZIF-67 membrane.

Fabrication of ZIF-8 membranes by direct assembly of nanosheets from bottom-up synthesis growth solution

Metal-organic frameworks (MOFs) host intrinsically porous structure and rich structural and chemical features. Several MOFs with pore aperture comparable to the size of gas molecules have attracted interest to form the selective layer of membranes. Synthesis of MOFs in nanosheet morphology is highly attractive for this because one can use highly-scalable filter coating to make MOF membranes. However, conventional nanosheet based processing route require several processing steps including centrifugation to prepare a coating dispersion. Herein, we report facile preparation of zeolitic imidazolate frameworks (ZIF) membranes by a straightforward assembly of nanosheets. ZIF-8 nanosheets were obtained by a direct bottom-up synthesis route where crystallization was optimized to obtain large, well-faceted 40-nm-thick nanosheets. Membranes, preferentially oriented along the c-out-of-plane direction, were fabricated by directly filtering the growth solution over a porous polymeric support without any further purification of nanosheets. This also ensures that only a small amount of precursor solution is used minimizing waste. The obtained membranes were compact and free of pinhole defects and yielded H2/C3H8 ideal selectivity over 3000 at 25 °C. We anticipate that this approach can be applied to several MOFs which can be synthesized in nanosheet morphology, advancing the scalability prospects of MOF membranes.

Adsorptive zeolitic imidazolate framework-8 membrane on ceramic support for the removal of lead(II) ions

Lead has long been recognised as a highly toxic material that can inflict a fatal effect on humans and other living organisms. To prevent consumption through drinking, an appropriate strategy must be utilised to remove lead(II) ions from water. This article presents the lead(II) removal efficacy through the use of an adsorptive membrane made of the Zeolitic Imidazolate Framework-8 (ZIF-8) developed on an alumina support. X-ray diffraction, scanning electron microscope, atomic force microscopy, Fourier transform infrared, atomic absorption, and X-ray photoelectron spectroscopies were first employed to appraise the physicochemical properties of the membranes. A batch adsorption approach was then used to determine the adsorption efficiency of the ZIF-8 membrane. The SC48 sample, which was synthesised for 48 h, demonstrated the best lead(II) adsorption capability, with an adsorption capacity of 115.38 mg/g. Cross-flow filtration test conducted under ideal conditions revealed that the average lead(II) removal rate was 92.13% with a water permeation of 288.41 Lm−2h−1bar−1. Additionally, the regeneration study exhibited the reusability potential of the ZIF-8 membrane. It was found that the membrane adsorption mechanism is by chemisorption as determined through the isotherms and kinetic study.

Construction of a thermally stable ZIF-8 membrane embedded inside a porous support for H2/CO2 separation: Close interlocking between membrane grains and porous support grains

Zeolitic imidazolate framework-8 (ZIF-8) membranes have emerged as promising wall candidates for use in membrane reactors. These membranes can improve the water gas shift (WGS) reaction performance because of their exceptional thermal stability and marked H2/CO2 sieving ability. Here, we propose a modified counter diffusion scheme to form an unprecedented, thermally stable ZIF-8 membrane: Pre-deposition of a zinc precursor (zinc acetate dihydrate) and subsequent solvothermal reaction with a methanolic solution of the ligand (2-methylimidazole). It appears that the pre-deposition and drying of the Zn precursor on and inside a porous support were key to retarding the diffusion of the Zn source, thus leading to the primary contact between the Zn source and ligand molecules within the porous support. As a result, it is likely that a continuous ZIF-8 layer was formed on the top surface and, more preferentially, at the interface with the grains of the porous support, reaching an infiltration depth of approximately 80 μm. Accordingly, this allowed for the effective blocking of the support pores by ZIF-8 grains, as well as their high dispersion. Notably, the resulting ZIF-8 membrane exhibited a maximum H2/CO2 separation factor of ca. 8.7 at a WGS reaction temperature of 300 °C. Unlike the conventional membrane architecture, ZIF-8 grains were densely embedded inside the porous support, thus reducing the risk of mechanical damage. Furthermore, the unique membrane structure was desirable for securing superior thermal stability for reliable and sustainable H2/CO2 separation at 300 °C for up to 72 h.

Influence of Humidity and Heating Rate on the Continuous ZIF Coating during Hydrothermal Growth.

Zeolitic imidazolate frameworks (ZIFs) have potential for various gas and ion separations due to their well-defined pore structure and relatively easy fabrication process compared to other metal-organic frameworks and zeolites. As a result, many reports have focused on preparing polycrystalline and continuous ZIF layers on porous supports with good separation performance in various target gases, such as hydrogen extraction and propane/propylene separation. To utilize the separation properties in industry, membrane is required to be prepared in large scale with high reproducibility. In this study, we investigated how humidity and chamber temperature influence the structure of a ZIF-8 layer prepared by the hydrothermal method. Many synthesis conditions can affect the morphology of polycrystalline ZIF membranes, and previous studies have mainly focused on reaction solutions, such as precursor molar ratio, concentration, temperature, and growth time. On the other hand, we found that the humidity of the chamber and the heating rate of the solution also lead to dramatic changes in the morphology of ZIF membranes. To analyze the trend between humidity and chamber temperature, we set up the chamber temperature (ranging from 50 °C to 70 °C) and relative humidity (ranging from 20% to 100%) using a thermo-hygrostat chamber. We found that as the chamber temperature increased, ZIF-8 preferentially grew into particles rather than forming a continuous polycrystalline layer. By measuring the temperature of the reacting solution based on chamber humidity, we discovered that the heating rate of the reacting solution varied with humidity, even at the same chamber temperature. At a higher humidity, the thermal energy transfer was accelerated as the water vapor delivered more energy to the reacting solution. Therefore, a continuous ZIF-8 layer could be formed more easily at low humidity ranges (ranging from 20% to 40%), while micron ZIF-8 particles were synthesized at a high heating rate. Similarly, under higher temperatures (above 50 °C), the thermal energy transfer was increased, leading to sporadic crystal growth. The observed results were obtained with a controlled molar ratio, in which zinc nitrate hexahydrate and 2-MIM were dissolved in DI water at a molar ratio of 1:45. While the results are limited to these specific growth conditions, our study suggests that controlling the heating rate of the reaction solution is critical for preparing a continuous and large-area ZIF-8 layer, particularly for the future scale-up of ZIF-8 membranes. Additionally, humidity is an important factor in forming the ZIF-8 layer, as the heating rate of the reaction solution can vary even at the same chamber temperature. Further research related to humidity will be necessary for the development of large-area ZIF-8 membranes.

Enhancing the C3 separation performances of polycrystalline ZIF-8 membranes by additive-assisted secondary growth

Polycrystalline zeolitic-imidazolate framework-8 (ZIF-8) membranes have shown very promising for propylene/propane (C3) separation. Though high-performance ZIF-8 membranes have been prepared by various synthesis methods, secondary growth method offers unique advantages due to its decoupling of a seeding step and a growth step, leading to membranes with better microstructures, thereby not only better separation performances but also higher reproducibility. However, there are only a few reports on ZIF-8 membranes with ultra-high C3 separation factors (i.e., >200) that are made by secondary growth method. Here, we report polycrystalline ZIF-8 membranes by a secondary growth method modified with an addition of 1,4-butanediol (Bdiol). The membranes showed significantly improved C3 separation factors up to ∼283 as compared to those prepared without modification. It was found that adding Bdiol in the secondary growth solution improved the microstructures of the ZIF-8 membranes, thereby enhancing their C3 separation performances. Furthermore, the presence of Bdiol in the growth solution enabled formation of well-intergrown ZIF-8 membranes even with a low linker-to-metal ratio (∼16), otherwise not possible to form ZIF-8 membranes. Interestingly, the resulting membranes showed a plate-like morphology with the highest separation factor of ∼283 among those prepared. All membranes in this work exhibited enhanced C3 separation performances as compared to those synthesized without modification.

ZnO nanofiber skeleton induced robust zeolitic imidazolate framework membranes for gas separation

Rationally designing compact metal-organic framework (MOF) membrane is highly desired but challenging. Herein, we proposed a ZnO nanofiber skeleton induced zeolitic imidazolate framework (ZIF) membrane inspired by the reinforced concrete structure. In this process, the ZnO nanofiber skeleton was employed as active anchor sites to assist the heteroepitaxial growth of continuous membranes, like the reinforcing steel in structure. The formed ZIFs particles were tightly embedded in the skeleton like the concrete. With this approach, highly compact Co-based ZIF-9 membrane and Zn-based ZIF-8 membrane were successfully achieved and exhibit effective H2 separation performance. For ZIF-9 membrane, the H2 permeance and the ideal selectivity of H2/CO2 are 2.19 × 10−7 mol m−2 s−1 Pa−1 and 15.3, respectively. For ZIF-8 membrane, the H2 permeance and the ideal selectivity of H2/CH4 are 2.26 × 10−6 mol m−2 s−1 Pa−1 and 9.7, respectively. More importantly, benefiting from the novel structure, the membrane showed a highly robust architecture under different pressures, good durability against rubbing, and separation stability of 100 h. This strategy provides a new approach toward other compact and robust MOF membrane.

Defect engineering on zeolitic imidazolate framework membrane via thermal annealing for organic solvent nanofiltration

Zeolitic imidazolate frameworks (ZIFs) have been attracting intensive attention in membrane separation fields because of their ultrahigh specific surface areas, well-defined apertures, and variable topological characteristics. However, the aperture sizes of ZIFs are smaller than the kinetic diameters of most organic solvent molecules, which impedes their applications in organic solvent separation. Herein, we develop a thermal annealing-derived methodology for defect engineering on the ZIF-67 membrane. This post-synthetic modification not only expanded the aperture size of ZIF-67 but also repaired intercrystalline cracks in the polycrystalline ZIF-67 layer. By controlling the thermal annealing conditions, the permeability of the polycrystalline ZIF-67 membrane toward organic solvent nanofiltration was enhanced by two times. Moreover, the annealed ZIF-67 membrane showed a high rejection of more than 99.6% for dyes (Evans blue) and pharmaceutical molecules (tetracycline, vitamin B12). This work provides an avenue for the controllable modification of ZIFs membranes to broaden their applications.

Robust ZIF-8 and its derivative composite membrane for antibiotic desalination with high performance

Zeolitic imidazolate framework (ZIF) membranes have great potential applications in nanofiltration. However, preparing continuous and intact ZIF membranes on the surface of a substrate remains challenging. In this study, we assembled ZIF-8 nanoparticles in situ in the pores of a porous alumina substrate via a freezing-assisted counter-diffusion method. Although a continuous ZIF-8 membrane was not formed on the surface of the substrate, the obtained nano-confined composite membrane was dense enough to separate antibiotics and salt. The rejection rate of tetracycline was above 99 %, while that of sodium chloride was below 20 %, demonstrating good antibiotic desalination performance. The permeance of the ZIF-8 membrane reached 23.5 LMH/bar. Due to the nano-confined structure, the obtained ZIF-8 composite membrane was robust. Besides, polishing the surface layer did not reduce the separation performance. Moreover, sulfurizing the ZIF-8 membrane improved its stability in water. It also improved the permeance to 31.3 LMH/bar, which remained stable for 100 h. Therefore, the obtained robust ZIF-8 membrane and its derivative composite membrane fabricated via freezing-assisted counter-diffusion have great potential in antibiotic desalination.

Graphene Nanoribbon Hybridization of Zeolitic Imidazolate Framework Membranes for Intrinsic Molecular Separation.

Zeolitic imidazolate frameworks (ZIFs) are promising for gas separation membrane, but their molecular cut-off differs from that expected from its intrinsic aperture structure because of their flexibility. Herein, we introduced graphene nanoribbons (GNRs) to rigidify the ZIF framework. Because the sp2 edge of the GNRs induces strong anchoring effects, the modified layer can be rigidified. Particularly, when the GNRs were embedded and distributed in the ZIF-8 layer, an intrinsic aperture size of 3.4 Å was observed, resulting in high H2 /CO2 separation (H2 permeance: 5.2×10-6 mol/m2 Pa s, ideal selectivity: 142). The performance surpasses the upper bound of polycrystalline MOF membrane performance. In addition, the membrane can be applied to blue H2 production, as demonstrated with a simulated steam reformed gas containing H2 /CO2 /CH4 . The separation performance was retained in the presence of water. The fundamentals of the molecular transport through the rigid ZIF-8 framework were revealed using molecular dynamics simulations.

Graphene Nanoribbon Hybridization of Zeolitic Imidazolate Framework Membranes for Intrinsic Molecular Separation

AbstractZeolitic imidazolate frameworks (ZIFs) are promising for gas separation membrane, but their molecular cut‐off differs from that expected from its intrinsic aperture structure because of their flexibility. Herein, we introduced graphene nanoribbons (GNRs) to rigidify the ZIF framework. Because the sp2 edge of the GNRs induces strong anchoring effects, the modified layer can be rigidified. Particularly, when the GNRs were embedded and distributed in the ZIF‐8 layer, an intrinsic aperture size of 3.4 Å was observed, resulting in high H2/CO2 separation (H2 permeance: 5.2×10−6 mol/m2 Pa s, ideal selectivity: 142). The performance surpasses the upper bound of polycrystalline MOF membrane performance. In addition, the membrane can be applied to blue H2 production, as demonstrated with a simulated steam reformed gas containing H2/CO2/CH4. The separation performance was retained in the presence of water. The fundamentals of the molecular transport through the rigid ZIF‐8 framework were revealed using molecular dynamics simulations.

A Facile Method to Prepare Defect‐Sealed Zeolitic Imidazolate Framework Membrane on Cu Net for Gas Separation

AbstractA direct method is reported for the preparation of zeolitic imidazolate framework (ZIF) membrane on Cu net without any surface modification technologies. The synthetic mechanism can be attributed to the in situ formed Cu‐N interlayer serving as the nucleation sites, which promote the growth of ZIF membrane. The dense polycrystaline membrane shows moderate H2/CH4 separation performance comparable to previous reports. To further eliminate membrane defects, polymer/MOF suspension instead of pure polymer can be used to accurately seal the valley among crystalline grains. As a result, the as‐prepared composite membrane with highly exposed crystal surface shows enhanced H2/CH4 selectivity of 71.0 with little loss in H2 permeance.

Modeling of deposit formation in mesoporous substrates via atomic layer deposition: Insights from pore‐scale simulation

AbstractAtomic layer deposition (ALD) has been a promising technique in fabricating membranes and tuning their properties with a precision at the atomic level. Fabrication of zeolitic imidazolate framework (ZIF) membranes using the ligand‐induced permselectivation (LIPS) method starts with the formation of an oxide in a mesoporous substrate by ALD and is followed by the transformation of this oxide to ZIF using imidazolate vapor treatment. The objective of the ALD step is to block the mesopores with a thin deposit, that is, one with small penetration depth and small thickness on the top surface of the substrate. Unlike typical ALD on nonporous substrates, where all available sites react per ALD cycle, thin deposit formation in a mesoporous substrate requires that only a small fraction of the available deposition sites (i.e., close to the substrate surface) is subjected to ALD. Consequently, reactant dosing and duration of pulses are important process variables which, together with diffusion and reaction kinetics determine the deposit structure. Quantitative understanding of the interplay of these variables and phenomena can enable the rational design of ALD within mesoporous substrates. Here, we extend our earlier modeling effort considering the coexistence of ALD both inside the pores and on the external surface of the substrate. Finite‐volume based models were developed and validated to simulate the two distinct modes of deposition cycle by cycle. The total mass uptake of the substrate with ALD cycles can be predicted using the combined surface deposition and pore reaction–diffusion models as affirmed by in situ quartz crystal microbalance experimental data. The ALD reactor model combined with the deposition model can accurately capture the number of ALD cycles needed to block the pores of the substrate. Based on the model, we designed a modified ALD process and examined the performance of the corresponding LIPS membranes. The present modeling work provides a new understanding of the deposit formation via ALD within mesoporous substrates for a variety of membrane applications.

Removal of carbon dioxide using zeolitic imidazolate frameworks: Adsorption and conversion via catalysis

AbstractCarbon dioxide (CO2) is one of the culprit causes of global climatic changes. Furthermore, the efficient separation of CO2 from other gaseous mixtures using zeolitic imidazolate framework (ZIF)‐based materials is vital for several processes such as flue gas separation, gas sweetening, and natural gas processing. ZIF‐based materials are emerging adsorbents and catalysts for CO2 gas removal via adsorption and conversion into valuable chemicals. ZIF‐based adsorbents with high‐adsorption/conversion efficiencies and tunable properties can be achieved by judicious synthesis and fabrication methods. We reviewed ZIF‐based materials for CO2 removal via adsorption and catalysis (e.g., cycloaddition, carboxylation, hydrogenation, N‐formylation, electrocatalysis, and photocatalysis). In addition, recent development methods such as membrane technologies and ways to improve the gas separation performance of ZIF membranes were highlighted. The prospective point of view to promote industrial applications and commercialization of ZIF‐based materials was briefly discussed. Once challenges such as low performance and reproducibility for ZIF‐based materials are solved, scalability and cost‐effectiveness should not become issues.

In Situ Tracking of Nonthermal Plasma Etching of ZIF-8 Films.

Surface characterization is critical for understanding the processes used for preparing catalysts, sorbents, and membranes. Nonthermal plasma (NTP) is a process that achieves high reactivity at low temperatures and is used to tailor the surface properties of materials. In this work, we combine the capabilities of infrared reflection absorption spectroscopy (IRRAS) with NTP for the in situ interrogation of zeolitic imidazolate framework-8 (ZIF-8) thin films to probe modifications in the material induced by oxygen and nitrogen plasmas. The IRRAS measurements in oxygen plasma reveal etching of organic ligands with sequential removal of the methyl group and imidazole ring and with the formation of carbonyl moieties (C═O). In contrast, nitrogen plasma induces mild etching and grafting of nitrile groups (-C≡N). Scanning electron microscopy imaging shows that oxygen plasma, at prolonged times, significantly degrades the ZIF-8 film at the grain boundaries. Treatment of ZIF-8 membranes using mild plasma conditions yields a fivefold enhancement for H2/N2 and CO2/CH4 ideal selectivities and an eightfold enhancement for CO2/N2 ideal selectivity. Additionally, the new tools described here can be used for spectroscopic in situ tracking of plasma-induced chemistry on thin films in general.

Interfacial nanoarchitectonics for ZIF-8 membranes with enhanced gas separation.

Metal-organic framework (MOF) membranes are potentially useful in gas separation applications. Conventional methods of MOF membrane preparation require multiple steps and high-pressure conditions. In this study, a reliable one-step interfacial synthesis method under atmospheric pressure has been developed to prepare zeolitic imidazolate framework-8 (ZIF-8) membranes supported on porous α-Al2O3 disks. To obtain optimal ZIF-8 membranes, three reaction parameters were investigated, namely, reaction temperature, reaction time, and concentration of the organic linker (i.e., 2-methylimidazole). The growth of ZIF-8 membranes under various parameters was evaluated by field-emission scanning electron microscopy, and the optimal synthesis conditions were determined (i.e., 80 °C for 12 h in 50 mM of 2-methylimidazole). The as-synthesized ZIF-8 membranes were then applied to CO2/N2 gas separation, which exhibited a maximum separation factor of 5.49 and CO2 gas permeance of 0.47 × 10−7 mol·m−2·s−1·Pa−1.

Carbon nanotube supported oriented metal organic framework membrane for effective ethylene/ethane separation.

Zeolitic imidazolate framework 8 (ZIF-8) is effective for C3H6/C3H8 separation because of the “sieving effect” of a six-membered (6-M) window. Here, we demonstrate that ZIF-8 is a versatile material that could effectively separate C2H4 from C2H6 via its 4-M window along the <100> direction. We established a facile and environmentally friendly carbon nanotube (CNT)–induced oriented membrane (CNT-OM) approach to fabricate a {100}-oriented ZIF-8 membrane (100-M). In this approach, 2-methyimidazole was anchored onto the CNT surface followed by 3-hour in situ growth in aqueous solution at room temperature. The obtained 100-M, whose 4-M window is aligned along the transport pathway, showed ~3 times higher C2H4/C2H6 selectivity than a randomly oriented membrane. Thus, this work demonstrates that the membrane orientation plays an important role in tuning selectivity toward different gas pairs. Furthermore, 100-M exhibited excellent mechanical stability that could sustain the separation performance after bending at a curvature of ~109 m−1.