Acid-catalyzed Sol-gel Process Research Articles

Partial fluorinated silica incorporated with tuneable alkyl cross-linker based multi-cationic alkaline membrane for vanadium redox flow battery

Herein, we report partial fluorinated polymer (poly(vinylidene fluoride-co-hexafluoropropylene); PVDF-co-HFP)-based multi-cationic (quaternary ammonium, and imidazolium groups) cross-linked (tuneable carbon chain cross-linker) anion exchange membrane (AEM) incorporated with functionalized silica to avoid any structural deformations under harassed environment. Prepared membranes are cross-linked using different cross-linking agents, to study the effect of cross-linker chain length on the membrane performance. Incorporation of functionalized silica by acid-catalyzed sol-gel process improves membrane properties and stabilities. Reported PVIm-C10-APS AEM shows high conductivity (7.20 × 10−2 S/cm), and ion exchange capacity (1.48 meq/g). Well optimized positively charged PVIm-C10-APS AEM exhibits extremely low permeability of vanadium cations because of “Donnan exclusion” (9.80 × 10−7 cm2/s). During VRFB operation, PVIm-C10-APS AEM exhibits 98.10% coulombic efficiency (CE) and 77.60% voltage efficiency at 100 mA/cm2 without any significant deterioration up to 300 charge-discharge cycles. Further, PVIm-C10-APS membrane also shows >1.50 V OCV and 345 mW/cm2 peak power density at 400 mA/cm2. Reported AEM has been bench-marked with other membranes reported in the literature, and assessed as a promising material for VRFB or membrane separator for energy devices.

Enhancing photo voltaic solar panel efficiency by using a combination of silica based and phase change material coating

This study attempts to enhance the overall efficiency of a photo voltaic solar panel by employing a dual-coating approach. The initial coating consists of a Silica-based anti-reflective material synthesized through an acid-catalyzed sol–gel process, utilizing cetyltrimethylammonium bromide as a template. Subsequently, the second coating was formulated using a phase change material, such as expanded graphite infused with paraffin jelly. The coating materials were characterized using Ultraviolet-Visual ray spectroscopy, Fourier Transform-Infrared Ray spectroscopy, Field Emission-Scanning Electron Microscopy, x-ray Diffraction sepctroscopy, and Thermogravimetry analysis. The panels’ performance had been investigated under three conditions: uncoated, single-coated, and double-coated. These panels were subjected to both indoor and outdoor experiments. Indoor tests were conducted in a laboratory with induced irradiance levels of 350, 600, and 850 W/m2. The corresponding variations in maximum power output, maximum surface temperature and peak current were recorded. For the outdoor experiments, two sets of panels were installed on a rooftop. One set underwent daily surface cleaning, while the other was left untouched, allowing dust accumulation. Over a 45-day period, outdoor experiments were carried out (daily cleaned and unclean panels) to examine the impact of dust accumulation on power loss, current, voltage, surface temperature, energy generation and panel efficiency. Upon comparing the performance of uncoated, single-coated, and double-coated solar panels, it was observed that photovoltaic solar panels coated with both silica-based anti-reflective coating and paraffin jelly-infused expanded graphite coating exhibited superior performance when compared to other coating options.

Synthesis of nanosize zinc oxide through aqueous sol–gel route in polyol medium

BackgroundThis study is aimed to synthesize nanosize zinc oxide by acid catalyzed sol–gel process using zinc nitrate hexahydrate as precursor, aqueous isopropanol as solvent and glycerin for making polyol system. The polyol mediated procedure was employed in combination with calcination induced synthesis of nanoparticles of numerous sizes obtained with the variation in calcination temperature from 500 to 900 ℃. The crystal structure of the prepared samples was characterized by X-ray diffraction analysis (XRD). Infrared spectroscopy (IR) was used to identify the surface hydroxyl groups. Thermal stability was confirmed by differential scanning calorimetry-thermogravimetric analysis (DSC-TGA) whereas field emission scanning electron microscopy (FESEM) was used to study the surface morphology of nanoparticles.ResultsResults revealed the formation of hexagonal wurtzite structure of irregular shaped nanoparticles having size ranging from 50–100 nm. However, the particles combined to form agglomerates of 200–400 nm with the rise in calcination temperature.ConclusionsThese results indicate that nanosize zinc oxide can be synthesized successfully by a simple process comprising of glycerin as a low-cost, non-toxic and eco-friendly polyol followed by calcination at ambient temperatures.

Partially Reduced TiO2 Aerogel as a Catalyst of Oxygen Reduction Reaction in Alkaline Solution

A resorcinol-formaldehyde/titanium oxide (RF/TiO2) aerogel was synthesized via an acid-catalyzed sol-gel process followed by CO2 supercritical drying. After the thermal treatment of the RF/TiO2 aerogel, the partially reduced TiO2 aerogel (PRTA) was prepared as a catalyst for oxygen reduction reaction (ORR). Magnéli phase (Ti4O7) and anatase with oxygen vacancies were formed in PRTA. The specific surface area and the pore volume of PRTA were 637 m2 g−1 and 1.72 cm3 g−1, respectively. RF-derived carbon, TiO2(a)/TiO2(r), and TiO2(a) were also prepared to estimate the origin of ORR activity. The Eonset, E1/2, and Jlimit were 0.75 V, 0.65 V, and 3.33 mA cm−2, respectively. Its stability outperformed Pt/C. This preparation method is inspiring for preparing the Magnéli phase with a better pore structure.

Sol–gel hybrid films based on organosilanes with long alkyl chains

In this paper, we report the synthesis of different silica materials via the acid-catalyzed sol–gel process at room temperature (25°C), using silane precursors with various alkyl chains (dimethyl, octyl and/or hexadecyl), in order to obtain thin films with anti-reflective and hydrophobic properties. Chemical, optical and structural properties of obtained silica materials were thoroughly characterized with various techniques such as FTIR and UV–Vis spectroscopy, AFM analysis, ellipsometric measurements, ESEM and TEM microscopy. Wettability of thin films was evaluated by water contact angle measurements. FTIR spectra of silica materials revealed that the intensity of the Si–O–Si characteristic bands varies depending on the precursor type. From AFM results, we found that the obtained films present a different microstructure as a function of the silica sol formulations. The hydrophobic character of the thin films increases with increasing the length of the hydrophobic chains following the order: dimethyl < octyl < hexadecyl. UV–Vis analysis of the coatings covered with silica materials presents a low reflectance (15.5%). The proposed method in this work has the potential to be a low-cost processing path of nanostructured anti-reflection transparent substrates.

Facile synthesis of robust hybrid xerogels by an emulsion assistant method

In this study, we report a convenient one-pot synthesis of silsesquioxane hybrid xerogels with excellent mechanical flexibility by using copolymer emulsion as templates. During the acid-catalyzed sol-gel process of the precursors, the random copolymers of n-butyl methacrylate (n-BMA) and hydroxyethyl methacrylate (HEMA), not only suppressed macroscopic phase separation but also were incorporated in the skeleton of polysilsesquioxane by synergistic physical and chemical interactions. The resultant gels could be directly dried via ambient-pressure drying (APD) to gain xerogels without visible volume shrinkage. This unique preparation process is economical and environment-friendly without involving any organic solvents. The morphology and physicochemical performance of the monolithic hybrid xerogels can be readily tailored by changing the compositions and the concentrations of silsesquioxanes and copolymers in the reaction solutions. Xerogels fabricated from methyltrimethoxysilane showed excellent thermal insulation property, inherently superhydrophobicity, and outstanding mechanical strength against compression up to 50 MPa. Besides, the compressed specimen could recover its original shape by immersing in solvents and subsequently drying.

Room-Temperature In Situ Synthesis of a Highly Efficient CsPbBr3/SiO2 Sol Entirely in Ethanol Solvent by Constructing Amine-Functionalized Silica Micelles.

Cesium lead halide perovskite nanocrystals (CLHP NCs) have drawn considerable attention because of their promising optoelectrical properties. However, owing to the extreme vulnerability of CLHP NCs to water and polar alcohols, until now most synthesis approaches inevitably adopted ecounfriendly solvents. It is still a challenge to employ green polar alcohol (ethanol) as a solvent to synthesize CLHP NCs. In this work, we realized the room-temperature in situ synthesis of CsPbBr3/SiO2 sol entirely in ethanol by innovatively constructing amine-functionalized silica micelles, which originated from the synergistic effect of 3-aminopropyltriethoxysilane and tetraethylorthosilicate (TEOS) during an acid-catalyzed sol-gel process. The sol exhibited high stability and an absolute photoluminescence quantum yield of 61.9% in ethanol without a further modification process. The light-emitting intensity of the sol preserved for 34 days merely declined to 62.1%. This work sheds light on the less common strategy of directly synthesizing CsPbBr3 NCs and long-term stable preservation in a strongly polar solvent.

Investigation of the Effects of Acid Content and Annealing on the Properties of Nanostructured TiO2 Sol

Titanium dioxide (TiO2) sol was prepared using tetrabutyl titanate as a precursor via an acid catalyzed sol-gel process. Investigation of the effects of acid content and annealing on the properties of nanostructured TiO2 materials. The influence of acid content on the sol density, viscosity, stability and particle size were studied and based on the kinematic viscosity data, Gibbs energies of activation for viscous flow (ΔG*) were also calculated. Furthermore, the prepared samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and ultraviolet-visible (UV-Vis) spectrophotometer. The results showed that the increase of acid content nearly had no obvious influence on the chemical structure of TiO2 sol. With the increase of annealing temperature, titanium dioxide changes from amorphous phase to crystalline phase, anatase coexists with rutile at 600 °C, sample absorbance increases, and the edge of UV-Vis spectra shows red shift. Ti-O-Ti bond is the main structure of TiO2 sol, and the formed TiO2 molecule has linear structure.

Room-Temperature in Situ Synthesis of Highly Efficient CsPbBr3/SiO2 Sol in Entirely Ethanol Solvent by Constructing Amine-Functionalized Silica Micelles.

Cesium lead halide perovskite nanocrystals (CLHP NCs) have drawn considerable attention because of their promising optoelectrical properties. However, owing to extreme vulnerability of CLHP NCs to water and polar alcohols, up to date, most of the synthesis approaches have inevitably adopted eco-unfriendly solvents. It is still a big challenge to employ green polar alcohol (ethanol) as a solvent to synthesize CLHP NCs. In this work, we realized a room-temperature in situ synthesis of CsPbBr3/SiO2 sol entirely in ethanol by innovatively constructing amine-functionalized silica micelles, which is originated from the synergistic effect of 3-aminopropyltriethoxysilane and tetraethyl orthosilicate (TEOS) during an acid-catalyzed sol-gel process. The sol exhibited high stability and an absolute photoluminescence quantum yield of 61.9% in ethanol without a further modification process. The light emitting intensity of the sol preserved for 34 days merely declined to 62.1%. This work sheds light on the less common strategy of directly synthesizing CsPbBr3 NCs and long-term stable preservation in a strong polar solvent.

Polyfluoroalkyl-silica porous coatings with high antireflection properties and low surface free energy for glass in solar energy application

Polyfluoroalkyl-silica porous coating stacks with durable antireflection (AR) properties have been obtained for photovoltaic (PV) application. An acid-catalyzed sol-gel process combined with evaporation induced self-assembly and the presence of a non-hydrolyzable polyfluoroalkyl group linked to the central atom of the silicon alkoxide was conducted. The aim was to obtain a low surface energy coating, devised to mitigate soiling adherence, without losing the AR properties of a baseline coating. In particular, the influence of polyfluoroalkyl chain length on the thickness, the water contact angle and optical transmission properties was first analyzed. The optimized polyfluoroalkyl-silica porous coating presented low surface energy < 20 mJ/m2, even with the desired low roughness values required for obtaining a negligible scattering of the incoming solar radiation. This coating was studied as an AR mono-layer and as an external coating in an AR bi-layer stack, with the presence of an inner dense-structured silica layer, that contributed to both the optical performance and durability, acting as an alkali diffusion preventing layer. The AR bi-layer stack deposited on two sides of glass provided a transmittance gain of 7.1%. Those optical properties were inalterable after accelerated aging tests, which sustains the reliability of the materials for solar energy applications.

Amylases immobilization by sol–gel entrapment: application for starch hydrolysis

α-amylase from Bacillus subtilis, α-amylase from Aspergillus oryzae, and β-amylase from barley were encapsulated within silica-based matrix by acid-catalyzed sol–gel process. The resulting systems were characterized by Fourier transform infrared spectroscopy (FT-IR) in the attenuated total reflection (ATR) mode, nitrogen adsorption (BET and BJH methods), scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). The products from enzymatic hydrolysis of starch were analyzed by the DNS method (reducing sugars) and high-performance liquid chromatography (HPLC). The biocatalytic activity of the immobilized systems (reducing sugars in the range of 0–30.5 μmol/mL) was compared with that of the free systems (reducing sugars in the range of 11.7–33.7 μmol/mL). The porosity analysis showed that xerogels with a high surface area (above 300 m2/g) were obtained. The morphological analyses carried out by microscopy demonstrated the existence of predominantly granular (relatively spherical particles) structures. HPLC results show large differences in the musts obtained from the free enzymes and the corresponding immobilized systems. The encapsulated systems demonstrated high activity and differentiated form of saccharifying the starch.

Effect of water content on the performance and structure of nanosized TiO2 sol

Titanium dioxide (TiO2) sol was prepared using tetrabutyl titanate as a precursor via an acid catalyzed sol–gel process. The influence of water content on the sol density, viscosity, stability and particle size were studied and based on the kinematic viscosity data, Gibbs energies (ΔG*) of activation of the viscous flow was also calculated. Furthermore, the obtained TiO2 materials were characterized by infrared spectroscopy (IR) and X-ray diffraction (XRD) analysis. The results showed that, with the increase of water content, the sol viscosity and zeta potential were increased and the particle size distribution was narrow. When the molar ratio of H2O/Ti reached 4, the prepared sol was transparent, uniform and stable, and the sol average particle size gets the minimum. Ti–O–Ti bond was the primary structure of TiO2 sol and the formed titanium molecules possessed the line-typed structure. The increase of water content nearly had no obvious influence on the chemical structure of sol. The TiO2 gel material was the amorphous state and it turned into anatase type after calcination at 350°C.

Hydrophobic and spectrally broadband antireflective methyl-silylated silica coatings with high performance stability for concentrated solar applications

An efficient and environment-friendly process, consisting of acid-catalyzed sol-gel process combined with evaporation induced self-assembly, was conducted to build antireflective (AR) layer stacks for concentrated solar applications. Considering the external factors that may alter the optical properties of the system when operating outdoors, such as soiling, harsh climate conditions and alkali ions diffusion from glass, several stack configurations were proposed. Particularly, the effect of a methyl-silylating post-treatment, the presence of the inner layer and the optimization of sintering temperature have been devised in order to minimize soiling adherence and alkali diffusion from the glass substrate and to assure the required robustness to comply with the durability requirements. The assessment consisted of (i) an analysis of the optical transmittance, reflectance and refractive index and (ii) hydrophobicity and effect of water absorption on the external porous coatings in relation to the results of accelerated aging tests following photovoltaics standards. The main goal was to achieve the most rational design, based on a proper trade-off between cost efficiency, processability, optical properties and reliability during real life operation.

Antireflective mesoporous silica coatings by optimization of water content in acid-catalyzed sol-gel method for application in glass covers of concentrated photovoltaic modules

Porous silica layers with outstanding antireflective properties have been prepared by acid-catalyzed sol-gel process in presence of organic phases as structure directing agents (SDA) and excess water, with the aim of offering a cost-competitive, easy up-scaling and high efficiency process that contributes to reduce current levelized cost of energy (LCOE) of concentrating photovoltaics (CPV). The process has been optimized by controlling the water/alkoxide ratio, which is an important structure-regulating tool, having a strong influence in the structural properties of sol-gel synthesized materials. Hydrolysis of the inorganic precursor has been accomplished in high water/alkoxide conditions and in the presence of SDAs. Evaporation induced self-assembly (EISA) during coating deposition and the scanning of four types of SDAs have permitted to select the coating that fulfilled specific thickness and refractive index values with, in parallel, excellent results on sol stability. The final optimization has produced mesoporous coatings with ∼9 nm mean pore size, leading to an enhancement in transmittance up to 7.4% over bare glass in the 300–1500 nm wavelength range. The transmittance spectra have been used as inputs for the theoretical calculation of the short-circuit current density of a commercially available multijunction solar cell for CPV applications.

NMR Diffusion Study of Ionic Liquids and Ionogels for Use in Lithium Ion Batteries

Solid-state electrolytes have been explored increasingly for use in Li+ batteries on account of their ability to address the safety issues, packaging constraints, and volumetric design concerns associated with liquid electrolytes. Recently, ionogels, pseudo-solid-state electrolytes consisting of an ionic liquid electrolyte confined in a mesoporous inorganic matrix, have attracted interest because of their high ionic conductivity, stability, and solution processability. Due to the complexity of the trapped liquid, the nature of the ion interaction and movement is not well established. Understanding how the ions behave inside the matrix is paramount for increasing the ionic conductivity and Li+ transference number. The literature for these characteristics is lacking in several key areas including, but not limited to, variations in the electrolyte’s Li+ concentration, the choice of silica precursors, and diffusion under different conditions. The ionogel matrix was synthesized using a non-aqueous organic acid catalyzed sol-gel process to form a nanoporous silica matrix around an ionic liquid, BMIM TFSI with variable amounts of LiTFSI added, thus confining the electrolyte. The choice of silica precursors and use of an organic acid allows for a crack free monolith to form under rapid gelation conditions. The silica component maintains a highly porous network with surface areas up to 1300 m2/g and an average pore size of 20nm as measured through N2 adsorption. The ionic liquid (IL) electrolyte component constitutes 75 vol% of the ionogel. Thermal gravimetric analysis shows that the ionogel is thermally stable to 400 oC. Due to the interconnected porosity and large percentage of liquid, conductivities of ̴10-3 S/cm were measured at room temperature for the prepared monoliths using electrochemical impedance spectroscopy (EIS). The degree to which each ion contributes to the total conductivity can be determined by combining the conductivity measurements with self-diffusion measurements obtained by pulsed field gradient nuclear magnetic resonance (PFG NMR) methods. Furthermore the presence of ion pairing or aggregation can be ascertained by direct comparison between the NMR-predicted and EIS-measured conductivity. In this work, the PFG NMR stimulated echo sequence was used to measure the self-diffusion coefficients of the IL cation, Li+, and anion via 1H, 7Li and 19F, respectively, in the IL and ionogel with a concentration of 1M LiTFSI, at variable temperature covering the 0o – 100oC range. Two main confinement effects of all mobile ions in the ionogel are observed (i) a reduction in self-diffusion values of all ions compared to the pure IL; (ii) the presence of a relatively immobile fraction of the ions. Interestingly the effective Li transference numbers defined as D(Li)/[D(Li) + D(BMIM) + D(TFSI)] in the liquid electrolyte and the and ionogel are comparable, with a value of approximately 0.20.

In-situ monitoring of silica shell growth on PS-b-P4VP micelles as templates using DLS

Polystyrene-block-poly(4-vinylpyrdine) (PS-b-P4VP) block copolymer (BCP) was used as a template for the preparation of PS-b-P4VP@SiO2 core-shell particles using an acid catalyzed sol-gel process. The process of silica shell formation and development of shell morphology were studied using a combination of in-situ dynamic light scattering (DLS) and transmission electron microscopy (TEM). The results obtained reveal that shell formation and growth principally involve the following stages: (I) sol assembly around BCP micelles; (II) hydrolysis-condensation reaction accelerated by the protonated P4VP corona of BCP micelles; (III) shell densification; and (IV) shell growth. Present work provides insight into the sol-gel process which takes place in systems containing “reactive” templates, such as protonated PS-b-P4VP micelles, and discloses the mechanism and pathways of silica shell formation. We demonstrate that the whole process can be effectively monitored in-situ using conventional DLS. The results are of significant importance for fabrication of targeted core-shell nanostructures.

Kinetics of Coloration in Photochromic Tungsten(VI) Oxide/Silicon Oxycarbide/Silica Hybrid Xerogel: Insight into Cation Self-diffusion Mechanisms

Silicon oxycarbide/silica composites with well-dispersed tungsten(VI) oxide (WO3) nanoparticles were obtained as transparent hybrid xerogels via an acid-catalyzed sol-gel process (hydrolysis/condensation polymerization) of 3-(triethoxysilyl)propyl methacrylate (TESPMA) and tetraethoxysilane (TEOS). The self-diffusion mechanism of alkali-metal cations and the kinetics of the photochromic coloration process in the WO3/TESPMA/TEOS hybrid xerogel systems have been systematically investigated. Under continuous UV illumination, a gradual color change (colorless → blue) corresponding to the reduction of W(6+) into W(5+) states in WO3 nanoparticles can be confirmed from the WO3/TESPMA/TEOS hybrid xerogels containing alkali-metal sulfates, although no coloration of the hybrid xerogel without alkali-metal sulfate was observed. The coloration behavior depended exclusively on a variety of alkali-metal cations present in the hybrid xerogel system. Furthermore, a detailed analysis of the self-diffusion mechanism confirmed that the alkali-metal cations electrostatically interact with a layer of unreacted silanol groups on the TESPMA/TEOS matrix surface, and subsequently pass through the interconnected pore network of the hybrid xerogel. More interestingly, in the context of an Arrhenius analysis, we found a good coincidence between the activation energies for alkali-metal cation self-diffusion and UV-induced coloration in the WO3/TESPMA/TEOS hybrid xerogel system containing the corresponding alkali-metal sulfate. It is experimentally obvious that the photochromic properties are dominated by the diffusion process of alkali-metal cations in the WO3/TESPMA/TEOS hybrid xerogel system. Such hybrid materials with cation-controlled photochromic properties will show promising prospects in applications demanding energy-efficient "smart windows" and "smart glasses".

Morphology control of silica/poly(methyl methacrylate-co-styrene) hybrid nanoparticles via multiple-miniemulsion approach

AbstractAn appropriate approach has been used for the preparation of silica/P(MMA-co-St) hybrid nanoparticles through converting previously prepared inverse miniemulsions into a direct miniemulsion and consequently, using the droplet nucleation polymerization technique. In the early stage of the procedure, silica particles were synthesized from TEOS in the presence of NH4OH or HCl as a catalyst through a base or acid-catalyzed sol-gel process. TEOS, ethanol and tirmethoxyvinylsilan were mixed in MMA:St (50:50) to create the inverse miniemulsion I, similarly CTAB, NH4OH/HCl and distilled water were dispersed into MMA:St (50:50) and called inverse miniemulsion II. Then, the two mentioned inverse miniemulsions were emulsified in water to achieve direct miniemulsion. The nature of the catalyst and TEOS concentration varied, for the aims of investigation, their effect on the morphology and size of hybrid nanoparticles. This route provided a unique process for silica/polymer hybrid nanoparticles production, avoiding organic solvents. Transmission electron microscopy micrographs revealed that, the morphology of the hybrid nanoparticles can be controlled by the nature of the catalyst.

Characterization of Biocompatible Nanocomposite based on Silica, Dextran and Lidocaine

A silica/dextran/lidocaine nanocomposite (SiO/DEX/LID) was synthesized using acid-catalyzed sol-gel process. The resulting material was characterised using diffuse reflectance infrared Fourier transform spectroscopic analysis, diffusive reflectance spectroscopy in UV–Vis range, X-ray photoelectron spectroscopy and nitrogen adsorption method. LID was found to interact with the silica/dextran nanocomposite (SiO/DEX) via hydrogen bond formation between the carbonyl group of LID and SiO/DEX network. Analysis of nanocomposite with help of the series of complementary techniques ruled out the possibility of interaction between LID and the silica modified surface through the nitrogen atoms of the drug molecule. The findings reveal the potential of SiO/DEX/LID nanocomposite for being used in the preparation of medical patches for wounds and burns healing.

Structure–property tuning in hydrothermally stable sol–gel-processed hybrid organosilica molecular sieving membranes

Supported microporous organosilica membranes made from bridged silsesquioxane precursors by an acid-catalyzed sol–gel process have demonstrated a remarkable hydrothermal stability in pervaporation and gas separation processes, making them the first generation of ceramic molecular sieving membranes with sufficient performance under industrially relevant conditions. The commercial availability of various α,ω-bis(trialkoxysilyl)alkane and 1,4-bis(trialkoxysilyl)benzene precursors facilitates the tailoring of membrane properties like pore size and surface chemistry via the choice of precursor(s) and process variables. Here, we describe the engineering of sols for making supported microporous thin films, discuss the thermal and hydrothermal stability of microporous organosilicas and give a short overview of the developments and applications of these membranes in liquid and gas separation processes since their first report in 2008.