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Aging in polymers of intrinsic microporosity has slowed exploitation due to a decay in performance over time since densification makes them unsuitable for industrial applications. This work aimed to study the impact of the operation and storage temperature on the gas separation properties and aging rates of PIM-1 self-standing films. The permeability, diffusivity, and solubility of the tested membranes were monitored through permeation tests for pure carbon dioxide and nitrogen at a maximum upstream pressure of 1.3 bar for temperatures ranging from -20 °C to 25 °C. This study found significant benefits in the operation of glassy polymeric membranes at low temperatures, resulting in a favourable trade-off in separation performance and a reduction in the aging rate by three orders of magnitude. This brings new opportunities for the industrial application of PIMs in innovative carbon capture processes.

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Ionic diodes provide ionic current rectification (ICR), which is useful for micro-/nanofluidic devices for ionic current-mediated applications. However, the modulation of ICR is not fully developed, and current challenges include limited active control and localized modulation for further multiplexing of micro-/nanofluidic ionic diodes. Herein, a microfluidic device integrated with particle-assembly-based ionic diodes (PAIDs) and a gas-flow channel above them is presented. Exploiting in-situ gas permeation through a polymeric film, precise control over the physiochemical conditions of the nanopores within the PAIDs, leading to the modulation of ICR is demonstrated. The investigation not only characterizes the rectification properties of the PAIDs but also unveils their capacitor-like behavior and the ability to actively modulate ICR using various gas flows. Furthermore, the reversible modulation of ICR through dynamic switching of gas-dissolved solutions, enabling ion-signal amplification is showcased. This pioneering approach of in situ gas-permeation offers programmable manipulation of ion transport along PAIDs, thereby positioning ionic diodes as versatile nanofluidic components. Looking ahead, the development of multiplexed PAIDs in an addressable manner on a chip holds promise for practical applications across diverse fields, including ion signaling, ion-based logic, chemical reactors, and (bio)chemical sensing.

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Although thin-film composite membranes have achieved great success in CO2 separation, further improvements in the CO2 permeance are required to reduce the size and cost of the CO2 separation process. Herein, we report the fabrication of composite membranes with high CO2 permeability using a laser-patterned porous membrane as the support membrane. High-aspect-ratio micropatterns with well-defined micropores on their surface were carved on microporous polymer supports by a direct laser writing process using a short-pulsed laser. By using a Galvano scanner and optimizing the laser conditions and target materials, in-plane micropatterns, such as microhole arrays, microline grating, microlattices, and out-of-plane hierarchical micropatterns, were created on porous membranes. An aqueous suspension of hydrogel microparticles doped with an amine-based mobile carrier was sprayed onto the patterned surface to form a defect-free thin separation layer. The surface area of the separation layer on the patterned support is up to 80% larger than that of flat pristine membranes, resulting in a 52% higher CO2 permeance (1106 GPU) with a CO2/N2 selectivity of 172. The laser-patterned porous membranes allow the development of inexpensive and high-performance functional membranes not only for CO2 separation but also for other applications, such as water treatment, cell culture, micro-TAS, and membrane reactors.

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To research the effect of hydrogen permeation on the friction characteristics of the seal materials on the hydrogen equipment, the molecular models of 10% PEEK/PTFE composites and its frictional models were established, respectively, and molecular dynamics (MDs) and giant canonical Monte Carlo (GCMC) methods were used to simulate the diffusion coefficient, dissolution coefficient and permeability coefficient of the hydrogen in PEEK/PTFE composites. The effect of a different amount of hydrogen on the friction and wear of PEEK/PTFE composites was also studied. The results showed that few permeations of the hydrogen gas mainly demonstrated having a positive effect on the surface of the PEEK/PTFE composites, and the wear rate of the PEEK/PTFE composites showed a slight decreasing trend. The wear rate of the PEEK/PTFE composites gradually decreased when more hydrogen molecules penetrated the matrix. With the further penetration of the hydrogen molecules, the wear rate and friction coefficient of the PEEK/PTFE composites rapidly increased, showing a negative effect. With the further penetration of the hydrogen molecule, the friction coefficient of the composite displayed a small fluctuation and then a rapid decreasing trend. Meanwhile, effective improvement measures were proposed, and the introduction of the graphene was verified to be effective to reduce the negative effect of the hydrogen permeation, thereby improving the friction performance of the PEEK/PTFE composites.

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Carbon dioxide (CO2), which results from fossil fuel combustion and industrial processes, accounts for a substantial part of the total anthropogenic greenhouse gases (GHGs). As a result, several carbon capture, utilization and storage (CCUS) technologies have been developed during the last decade. Chemical absorption, adsorption, cryogenic separation and membrane separation are the most widely used post-combustion CO2 capture technologies. This study reviews post-combustion CO2 capture technologies and the latest progress in membrane processes for CO2 separation. More specifically, the objective of the present work is to present the state of the art of membrane-based technologies for CO2 capture from flue gases and focuses mainly on recent advancements in commonly employed membrane materials. These materials are utilized for the fabrication and application of novel composite membranes or mixed-matrix membranes (MMMs), which present improved intrinsic and surface characteristics and, thus, can achieve high selectivity and permeability. Recent progress is described regarding the utilization of metal-organic frameworks (MOFs), carbon molecular sieves (CMSs), nanocomposite membranes, ionic liquid (IL)-based membranes and facilitated transport membranes (FTMs), which comprise MMMs. The most significant challenges and future prospects of implementing membrane technologies for CO2 capture are also presented.

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In this study, high-performance FAU (NaY type) zeolite membranes were successfully synthesized using small-sized seeds of 50 nm, and their gas separation performance was systematically evaluated. Employing nano-sized NaY seeds and an ultra-dilute reaction solution with a molar composition of 80 Na2O: 1Al2O3: 19 SiO2: 5000H2O, the effects of synthesis temperature, crystallization time, and porous support (α-Al2O3 or mullite) on the formation of FAU membranes were investigated. The results illustrated that further extending the crystallization time or increasing the synthesis temperature led to the formation of a NaP impurity phase on the FAU membrane layer. The most promising FAU membrane with a thickness of 2.7 µm was synthesized on an α-Al2O3 support at 368 K for 8 h and had good reproducibility. The H2 permeance of the membrane was as high as 5.34 × 10-7 mol/(m2 s Pa), and the H2/C3H8 and H2/i-C4H10 selectivities were 183 and 315, respectively. The C3H6/C3H8 selectivity of the membrane was as high as 46, with a remarkably high C3H6 permeance of 1.35 × 10-7 mol/(m2 s Pa). The excellent separation performance of the membrane is mainly attributed to the thin, defect-free membrane layer and the relatively wide pore size (0.74 nm).

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Membrane technology is a promising method for gas separation. Due to its low energy consumption, environmental safety, and ease of operation, membrane separation has a distinct advantage over the cryogenic distillation conventionally used to capture light inert gases. For efficient gas recovery and purification, membrane materials should be highly selective, highly permeable, thermally stable, and low-cost. Currently, many studies are focused on the development of high-tech materials with specific properties using industrial waste. One of the promising waste products that can be recycled into membrane materials with improved microstructure is cenospheres-hollow aluminosilicate spherical particles that are formed in fly ash from coal combustion during power generation. For this purpose, based on narrow fractions of fly ash cenospheres containing single-ring and network structure globules, silicate glass/mullite composites were prepared, characterized, and tested for helium-neon mixture separation. The results indicate that the fragmented structure of the cenosphere shells with areas enriched in SiO2 without modifier oxides, formed due to the crystallization of defective phases of mullite, quartz, cristobalite, and anorthite, significantly facilitates the gas transport process. The permeability coefficients He and Ne exceed similar values for silicate glasses; the selectivity corresponds to a high level even at a high temperature: αHe/Ne-22 and 174 at 280 °C.

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The effect of the stereoregularity of poly(1-trimethylsilyl-1-propyne) [PTMSP] (cis-content from 50 to 90%) on physical aging was investigated by measurement of the gas permeability. Films from pure PTMSP as well as those with the addition of the antioxidant Irganox 1076 were exposed to the air. The permeability of pure PTMSP films increases with an increase in cis-stereoregularity and correlates with an increase in interchain distances (according to X-ray analysis). For pure PTMSP films, the most significant aging (up to 50% of permeability drop) was observed for polymers with mixed microstructure, and the slowest aging (10-30% of permeability drop) was observed for polymers with cis-regular structure. For PTMSP films with added Irganox 1076, some decrease in permeability with time is also observed. The addition of Irganox 1076 to PTMSP in mixed as well as cis-enriched configurations visibly slows down aging. In the case of cis-regular PTMSP with a slow aging rate, the introduction of an antioxidant does not provide any advantages. The high stability of cis-regular PTMSP demonstrates the possibility of obtaining more stable membrane materials with the highest equilibrium state of the polymer selective layer prepared by casting solution.

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The potential of nanocomposite membranes (NCMs) prepared by the sodium alginate polymer and embedded with synthesized zeolitic imidazole framework-8 (ZIF-8) as fillers having microporous structure in the application of separation of gaseous mixture generated by the process of methane reforming was assessed. ZIF-8 crystals were created through hydrothermal synthesis, with sizes varying from 50 to 70 nm. NCMs were prepared with a 15% filler loading, i.e., synthesized ZIF-8. NCMs (ZIF-8) having H2 permeability of 28 Barrer and H2/CH4 selectivity of 125 outperformed neat polymer membranes in terms of separation performance at ambient temperature and 4 kg/cm2 pressure. The purity of H2 increased to as high as 95% among the measured values. The NCMs did not, however, outperform a neat polymer membrane in terms of their ability to separate mixtures of gases. Moreover, the combination of ZIF-8 as a filler with sodium alginate was new and had not been reported previously. As a result, it is worthwhile to investigate.

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An experimental setup for the evaluation of permeation of gaseous species with the possibility of simultaneously collecting electrochemical impedance spectroscopy data in disk-shaped ceramic membranes was designed and assembled. It consists of an alumina sample holder with thermocouple tips and platinum electrodes located close to both sides of the sample. Water-cooled inlet and outlet gas connections allowed for the insertion of the sample chamber into a programmable split tubular furnace. Gas permeation through a ceramic membrane can be monitored with mass flow controllers, a mass spectrometer, and an electrochemical impedance analyzer. For testing and data validation, ceramic composite membranes were prepared with the infiltration of molten eutectic compositions of alkali salts (lithium, sodium, and potassium carbonates) into porous gadolinia-doped ceria. Values of the alkali salt melting points and the permeation rates of carbon dioxide, in agreement with reported data, were successfully collected.

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Developing blend membrane material is one feasible and effective route for improving the gas separation efficiency and commercial attractiveness of membrane technologies. Here, free-standing membranes were prepared by casting method using Pebax-1074 as continuous polymer matrix and poly(ethylene glycol) (PEG) as dispersive organic fillers. The morphology, surface functional groups, microstructure and thermal stability of the membranes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry, respectively. The effects of preparation variables including average molecular weight and dosage of PEG on the microstructure, morphology and properties of the blend membranes were investigated. In addition, the effects of operation conditions including permeation temperature and permeation pressure on the gas separation performance of the blend membranes were also examined. The results showed that the addition of PEG can obviously modify the structure-properties and significantly improve the separation performance of resultant membranes. Under the conditions of 30°C and 0.25 MPa, the optimal CO2 permeability and CO2/N2 selectivity respectively reached to 124.3Barrer and 115.8 for the blend membranes made by PEG600 with a content of 20% in Pebax-1074 matrix. In brief, the as-prepared blend membranes are proved to be promising for CO2/N2 separation application.

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A clean and sustainable energy source, biogas is widely accessible worldwide. The caloric value of biogas is related to its methane content, and therefore removal of other gases is essential for reaping the benefits of this cleaner resource. In contrast to other classical techniques, membrane technology is relatively new yet extremely promising for methane enrichment. The methane enrichment performance of polymeric membranes is constrained, hence newer material combinations have been investigated to enhance membrane performance. In this study, blend membranes comprised of polyetherimide (PEI) and polyvinyl acetate (PVAc) in varying proportions were prepared by adopting the wet-phase inversion technique. The generated pure, and blend membranes were characterized for the morphological, thermal, and structural study. The interactions of PEI and PVAc in blend samples were verified by FTIR analysis. On the other hand, SEM investigation indicated that the membranes have an anisotropic porous structure with a dense skin layer at the top. Subsequently, a single glass transition temperature (Tg), as validated by DSC analysis, indicates that the blended polymers are miscible. Furthermore, membranes' performance for gas separation was assessed regarding selectivity and permeance at feed pressures ranging from 2 to 6 bar. The permeation results showed that the CO2 permeance has increased by 40.47% with the addition of 4 wt % PVAc at 2 bar pressure. Furthermore, ideal selectivity improves as the blend ratio increases; nonetheless, the highest value for CO2/CH4 ideal selectivity was attained with a 2 wt % PVAc addition and at 2 bar pressure, which is approximately 26% greater than the pure PEI membrane. At 4 bar pressure, optimum CO2/N2 selectivity value of 22.50 was achieved. The findings indicate that PVAc is an excellent option for expanding the separation performance of blended polymeric membranes for biogas enrichment.

Asunto(s)

RESUMEN

The poly(vinyl alcohol) (PVA) and starch-based polymeric films with a ratio of 2:8 were prepared using solution casting followed by a solvent evaporation method. Four types of membranes with varied concentrations of grapefruit seed extract (GSE) i.e., 2.5-10 wt% was incorporated in the films. The prepared membranes were assessed for transparency test, mechanical properties, surface morphology, permeability test for O2, and antimicrobial properties. The PVA/starch-10% GSE loaded film showed excellent mechanical properties showing highest 1344 ± 0.7% elongation at break but poor optical transparency with 53.8% to 68.61%. The Scanning Electron Microscopic study reveals the good compatibility between the PVA, Starch, and GSE. The gas permeability test reveals that the prepared films have shown good resistance to the O2 permeability 0.0326-0.316 Barrer at 20 kg/cm2 feed pressure for the prepared membranes showing excellent performance. By adding the little amount of GSE into the PVA/starch blend membranes showed promising antimicrobial efficacy against MNV-1. For 4 h. incubation, PVA/starch blend membranes containing 2.5%, 5%, and 10% GSE caused MNV-1 reductions of 0.92, 1.89, and 2.27 log PFU/ml, respectively. Similarly, after 24 h, the 5% and 10% GSE membranes reduced MNV-1 titers by 1.90 and 3.26 log PFU/ml, respectively. Antimicrobial tests have shown excellent performance to resist microorganisms. The water uptake capacity of the membrane is found 72% for the PVA/starch pristine membrane and is reduced to 32% for the 10% GSE embedded membrane. Since the current pandemic situation due to COVID-19 occurred by SARSCOV2, the prepared GSE incorporated polymeric blend films are the rays of hope in the packaging of food stuff.

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Extracorporeal membrane oxygenation is a technique that provides short-term supports to the heart and lungs. It removes CO2 from the blood and provides enough oxygen, which is a huge help in the fight against COVID-19. As the key component, the artificial lung membranes have evolved in three generations including silicon, polypropylene and poly (4-methyl-1-pentene). Herein, we for the first time design and fabricate a novel poly (4-methyl-1-pentene)/polypropylene (PMP/PP) thin film composite (TFC) membrane with the anticoagulant coating composed of poly (sodium 4-styrenesulfonate) and cross-linked poly (vinyl alcohol). Poly (sodium 4-styrenesulfonate) provides sulfonic acid groups to inhibit the coagulant factors (FVIII and FXII), and cross-linked poly (vinyl alcohol) increase the stability of the anticoagulant coating and further improve the hydrophilicity via abundant hydroxyl groups to depress the protein adsorption. Long-term anticoagulant property was demonstrated by whole human blood for 28 days. Blood compatibility was evaluated by hemolysis rate, anticoagulation activity (APTT, TT and PT), complement activation, platelet activation and contact activation. Pure CO2, O2 and N2 permeation rates were determined to evaluate the mass transfer properties of PMP/PP TFC membranes. Gas permeation results revealed that gas permeation flux increased in the TFC membranes because of the decrease of crystallinity. Overall, the so prepared PMP/PP membrane shows good CO2/O2 selectivity and blood compatibility as novel TFC artificial lung membrane.

RESUMEN

Graphene oxide (GO) oligo-layered laminates were self-assembled on porous ceramic substrates via their simple dip-coating into aqueous GO dispersions. To augment the stability of the developed composite GO/ceramic membranes and control the morphology and stacking quality of the formed laminate, short-((3-glycidoxypropyl)trimethoxy silane-GLYMO, (3-aminopropyl)triethoxy silane-APTES), and long-chain (polydopamine-PDA) molecules were involved and examined as interfacial linkers. A comparative study was performed regarding the linker's capacity to enhance the interfacial adhesion between the ceramic surface and the GO deposit and affect the orientation and assemblage characteristics of the adjacent GO nanosheets that composed the formed oligo-layered laminates. Subsequently, by post-filtrating a GO/H2O suspension through the oligo-layered laminate membranes, the respective multi-layered ones have been developed, whereas ethylenediamine (EDA) was used in the suspension as an efficient molecular linker that strongly bonds and interlocks the GO nanosheets. The definition of the best linker and approach was conducted on macroporous α-alumina disks, due to the use of inexpensive raw materials and the ability to fabricate them in the lab with high reproducibility. To validate the concept at a larger scale, while investigating the effect of the porous substrate as regards its micrometer-scale roughness and surface chemistry, specific chemical modifications that yielded membranes with the best gas permeability/selectivity performance were replicated on a commercial single-channel monolith with a ZrO2 microfiltration layer. XRD, Raman, ATR, FESEM, and XPS analyses were conducted to study the structural, physicochemical, surface, and morphological properties of the GO/ceramic composite membranes, whereas permeance results of several gases at various temperatures and trans-membrane pressures were interpreted to shed light on the pore structural features. Concerning the short-chain linkers, the obtained results ascertain that GLYMO causes denser and more uniform assembly of GO nanosheets within the oligo-layered laminate. PDA had the same beneficial effect, as it is a macromolecule. Overall, this study shows that the development of gas-separating membranes, by just dipping the linker-modified substrate into the GO suspension, is not straightforward. The application of post-filtration contributed significantly to this target and the quality of the superficially deposited, thick GO laminate depended on this of the chemically attached oligo-layered one.

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Gas permeation and pervaporation are technologies that emerged several decades ago. Even though they have discovered increasing popularity for industrial separation processes, they are not represented equally within process simulation tools except for commercial systems. The availability of such a numerical solution shall be extended due to the design of a membrane model with Visual Basic based on the solution-diffusion model. Although this works approach is presented for a specific process simulator application, the algorithm can generally be transferred to any other programming language and process simulation solver, which allows custom implementations or modeling. Furthermore, the modular design of the model enables its further development by operators through the integration of physical effects. A comparison with experimental data of gas permeation and pervaporation applications as well as other published simulation data delivers either good accordance with the results or negligible deviations of less than 1% from other data.

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Aquivion® E87-12S Perfluorosulfonated acid ionomer material (PFSA) has been studied as a membrane technology for natural gas sweetening from CO2, H2S due to its interesting chemical and mechanical stability and good separation performance for polar compounds in humid environments. In the present work, permeation of the H2S/CO2/CH4 ternary mixture in this short-side PFSA chain was investigated at pressures up to 10 bar, temperatures up to 50 °C, and in a range of relative humidity (RH) from 20% to 90%. The results obtained confirm the strong dependence of Aquivion® on water activity and temperature, and its ability to separate gases based on their water solubility without substantial differences between pure and mixed gas experiments. Indeed, even when tested in ternary mixture, the permeation behavior remains similar to that observed for pure components and binary mixtures. In particular, the permeability of H2S is higher than that of CO2 and methane CH4, reaching values of 500 Barrer at 50 °C and 80% RH, against 450 and 23 Barrer for the other two gases respectively. Additionally, when tested at higher pressures of up to 10 bar under humid conditions, the membrane properties remained largely unchanged, thus confirming the overall stability and durability of Aquivion® E87-12S in acid environments.

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A series of pendant-type alkoxysilane structures with various carbon numbers (C1-C8) were used to fabricate sol-gel derived organosilica membranes to evaluate the effects of the C/Si ratio and fluorine doping. Initially, this investigation was focused on the effect that carbon-linking (pendant-type) units exert on a microporous structure and how this affects the gas-permeation properties of pendant-type organosilica membranes. Gas permeation results were compared with those of bridged-type organosilica membranes (C1-C8). Network pore size evaluation was conducted based on the selectivity of H2/N2 and the activation energy (Ep) of H2 permeation. Consequently, Ep (H2) was increased as the C/Si ratio increased from C1 to C8, which could have been due to the aggregation of pendant side chains that occupied the available micropore channel space and resulted in the reduced pore size. By comparison, these permeation results indicate that pendant-type organosilica membranes showed a somewhat loose network structure in comparison with bridged-type organosilica membranes by following the lower values of activation energies (Ep). Subsequently, we also evaluated the effect that fluorine doping (NH4F) exerts on pendant-type [methytriethoxysilane (MTES), propyltrimethoxysilane (PTMS)] and bridged-type [1,2-bis(triethoxysilyl)methane (BTESM) bis(triethoxysilyl)propane (BTESP)] organosilica structures with similar carbon numbers (C1 and C3). The gas-permeation properties of F-doped pendant network structures revealed values for pore size, H2/N2 selectivity, and Ep (H2) that were comparable to those of pristine organosilica membranes. This could be ascribed to the pendant side chains, which might have hindered the effectiveness of fluorine in pendant-type organosilica structures. The F-doped bridged-type organosilica (BTESM and BTESP) membranes, on the other hand, exhibited a looser network formation as the fluorine concentration increased.

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Selective, nanometer-thin organosilica layers created by plasma-enhanced chemical vapor deposition (PECVD) exhibit selective gas permeation behavior. Despite their promising pure gas performance, published data with regard to mixed gas behavior are still severely lacking. This study endeavors to close this gap by investigating the pure and mixed gas behavior depending on temperatures from 0 °C to 60 °C for four gases (helium, methane, carbon dioxide, and nitrogen) and water vapor. For the two permanent gases, helium and methane, the studied organosilica membrane shows a substantial increase in selectivity from αHe/CH4 = 9 at 0 °C to αHe/CH4 = 40 at 60 °C for pure as well as mixed gases with helium permeance of up to 300 GPU. In contrast, a condensable gas such as CO2 leads to a decrease in selectivity and an increase in permeance compared to its pure gas performance. When water vapor is present in the feed gas, the organosilica membrane shows even stronger deviations from pure gas behavior with a permeance loss of about 60 % accompanied by an increase in ideal selectivity αHe/CO2 from 8 to 13. All in all, the studied organosilica membrane shows very promising results for mixed gases. Especially for elevated temperatures, there is a high potential for separation by size exclusion.

RESUMEN

In this study, nickel-doped aminosilica membranes containing pendant groups were prepared with 3-aminopropyltriethoxysilane (APTES), trimethoxy[3-(methylamino)propyl]silane (MAPTS), 3 N,N-dimethyl aminopropyltrimethoxysilane (DAPTMS), N-[3-(trimethoxysilylpropyl]ethylene diamine (TMSPED), and 1-[3-(trimethoxysilyl)propyl] urea (TMSPU). Differences in the structures of terminal amine ligands significantly contributed to the formation of a coordinated structural assembly. Ultraviolet-visible spectroscopy (UV-vis), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and N2 adsorption isotherms revealed that short and rigid pendant amino groups successfully coordinated with nickel to produce subnanopores in the membranes, while an ion-exchange interaction was suggested for longer and sterically hindered aminosilica precursors. Moreover, the basicity of amine precursors affected the affinity of ligands for the development of a coordinated network. A pristine aminosilica membrane showed low levels of H2 permeance that range from 0.1 to 0.5 × 10-6 mol m-2 s-1 Pa-1 with a H2/N2 permeance ratio that ranges from 15 to 100. On the contrary, nickel coordination increased the H2 permeance to 0.1-3.0 × 10-6 mol m-2 s-1 Pa-1 with H2/N2 permeance ratios that range from 10 to 68, which indicates the formation of a microporous structure and enlargement of pore sizes. The strong level of coordination affinity between nickel ions and amine groups induced rearrangement of the flexible pendant chain into a more rigid structure.