Synthesis of a Zn(II)-2-aminoimidazole Framework as an Efficient Carbonic Anhydrase Mimic

Carbonic anhydrase (CA) plays a crucial role in the CO2 capture processes by catalyzing the hydration of CO2. In this study, we synthesized a bioinspired carbonic anhydrase Zn-MOF (metal-organic framework) incorporating 2-aminoimidazole and Zn2+ as initial constituents. The synthesized Zn-MOF exhibited promising potential for efficiently catalyzing the CO2 hydration. Structural analyses such as SEM, XRD, and BET confirmed that the Zn-MOF crystal consisted of stacked grains with an average size of approximately 36 nm, forming a micron-sized spherical structure. Functionally, Zn-MOF exhibited effective catalytic activity toward both CO2 hydration and ester hydrolysis. The introduction of amino groups significantly enhanced the esterase activity of Zn-MOF to 0.28 U/mg at ambient temperature, which was twice that of ZIF-8. Furthermore, the introduction of amino groups resulted in remarkable hydrothermal stability, with the esterase activity reaching 0.72 U/mg after undergoing hydrothermal treatment at 80 °C for 12 h. Additionally, Zn-MOF exhibited enhanced capability in CO2 hydration at a pH value exceeding 8.5. After six repeated uses, ZIF-8 and Zn-MOF retained approximately 68 and 65% of their initial enzyme activity, respectively, underscoring the potential practical applicability of Zn-MOF in industrial CO2 capture processes. This work showcases the development of a novel Zn-MOF crystal as an efficient CA mimic, effectively emulating the active sites of natural CA using 2-aminoimidazole as a coordinating ligand for Zn2+ coordination. These findings not only advance the field of innovative enzyme mimics but also pave the way for further exploration of industrial CO2 capture catalysts.

Highly Selective Recovery of Gold by In Situ Magnetic Field-Assisted Fe/Co-MOF@PDA/NdFeB Double Network Gel

There are enormous economic benefits to conveniently increasing the selective recovery capacity of gold. Fe/Co-MOF@PDA/NdFeB double-network organogel (Fe/Co-MOF@PDA NH) is synthesized by aggregation assembly strategy. The package of PDA provides a large number of nitrogen-containing functional groups that can serve as adsorption sites for gold ions, resulting in a 21.8% increase in the ability of the material to recover gold. Fe/Co-MOF@PDA NH possesses high gold recovery capacity (1478.87 mg g-1) and excellent gold selectivity (Kd = 5.71 mL g-1). With the assistance of an in situ magnetic field, the gold recovery capacity of Fe/Co-MOF@PDA NH is increased from 1217.93 to 1478.87 mg g-1, and the recovery rate increased by 24.7%. The above excellent performance is attributed to the efficient reduction of gold by FDC/FC+, Co2+/Co3+ double reducing couple, and the optimization of the reduction reaction by the magnetic field. After the samples are calcined, high-purity gold (95.6%, 22K gold) is recovered by magnetic separation. This study proposes a forward-looking in situ energy field-assisted strategy to enhance precious metal recovery, which has a guiding role in the development of low-carbon industries.

Improvement of optical and structural properties of ZIF-8 by producing multifunctional Zn/Co bimetallic ZIFs for wastewater treatment from copper ions and dye

In the paper, high specific surface area (SSA) mono and bimetallic zeolitic imidazolate frameworks (ZIFs) based on zinc and cobalt metals are successfully synthesized at room temperature using different ratios of Zn to Co salts as precursors and ammonium as a solvent to tailor the properties of the produced ZIF and optimize the efficiency of the particles in water treatment from dye and copper ions, simultaneously. The results declare that monometallic and bimetallic ZIF microparticles are formed using ammonium and the tuning of pore sizes and also increasing the SSA by inserting the Co ions in Zn-ZIF particles is accessible. It leads to a significant increase in the thermal stability of bimetallic Zn/Co-ZIF and the appearance of an absorption band in the visible region due to the existence of Co in the bimetallic structures. The bandgap energies of bimetallic ZIFs are close to that of the monometallic Co-ZIF-8, indicating controlling the bandgap by Co ZIF. Furthermore, the ZIFs samples are applied for water treatment from copper ions (10 and 184 ppm) and methylene blue (10 ppm) under visible irradiation and the optimized multifunctional bimetallic Zn/Co ZIF is introduced as an admirable candidate for water treatment even in acidic conditions.

ZIF-8 Vibrational Spectra: Peak Assignments and Defect Signals

Zeolitic imidazolate framework (ZIF-8) is a promising material for gas separation applications. It also serves as a prototype for numerous ZIFs, including amorphous ones, with a broader range of possible applications, including sensors, catalysis, and lithography. It consists of zinc coordinated with 2-methylimidazolate (2mIm) and has been synthesized with methods ranging from liquid-phase to solvent-free synthesis, which aim to control its crystal size and shape, film thickness and microstructure, and incorporation into nanocomposites. Depending on the synthesis method and postsynthesis treatments, ZIF-8 materials may deviate from the nominal defect-free ZIF-8 crystal structure due to defects like missing 2mIm, missing zinc, and physically adsorbed 2mIm trapped in the ZIF-8 pores, which may alter its performance and stability. Infrared (IR) spectroscopy has been used to assess the presence of defects in ZIF-8 and related materials. However, conflicting interpretations by various authors persist in the literature. Here, we systematically investigate ZIF-8 vibrational spectra by combining experimental IR spectroscopy and first-principles molecular dynamics simulations, focusing on assigning peaks and elucidating the spectroscopic signals of putative defects present in the ZIF-8 material. We attempt to resolve conflicting assignments from the literature and to provide a comprehensive understanding of the vibrational spectra of ZIF-8 and its defect-induced variations, aiming toward more precise quality control and design of ZIF-8-based materials for emerging applications.

Enhanced adsorption and removal of Cd(II) from aqueous solution by amino-functionalized ZIF-8

Zeolite imidazolate framework-8 (ZIF-8), which is a special subgroup of metal-organic frameworks (MOFs), was synthesized and modified by ethylenediamine (ZIF-8-EDA) to prepare an efficient adsorbent for the high sorption of Cd2+ ions from solution. The synthesized and modified ZIF-8 (ZIF-8-EDA) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. The optimum conditions for dosage of adsorbent, initial ion concentration, pH, and contact time were 0.05 g/l, 50 mg/l, 6, and 60 min, respectively, for cadmium ion sorption from aqueous solutions with a removal efficiency of 89.7% for ZIF-8 and 93.5% for ZIF-8-EDA. Adsorption kinetics and equilibrium data were analyzed using the Langmuir and Freundlich equations. The Langmuir model fitted the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for the cadmium ions was 294.11(mg/g). The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was feasible, spontaneous, and endothermic at 20-50 °C. Based on the results, the amino functionalized ZIF-8 had improved adsorption performance due to the replacing of the starting linker with organic ligands that had effective functional groups, leading to chemical coordination due to the interaction of metal ions with the non-bonding pair of electrons on the N atoms of the amino functional group. The selectivity toward metal ion adsorption by ZIF-8-EDA was Cd2+ > Pb2+ > Ni2+‏.

Enzymatic hydrolysates of κ-carrageenan by κ-carrageenase-CLEA immobilized on amine-modified ZIF-8 confer hypolipidemic activity in HepG2 cells

κ-Carrageenase can degrade κ-carrageenan to produce bioactive κ-carrageenan oligosaccharides (KCOs) that have potential applications in pharmaceutical, food, agricultural, and cosmetics industries. Immobilized enzymes gain their popularity due to their good reusability, enhanced stability, and tunability. In this study, the previously characterized catalytic domain of Pseudoalteromonas purpurea κ-carrageenase was covalently immobilized on the synthesized amine-modified zeolitic imidazolate framework-8 nanoparticles with the formation of cross-linked enzyme aggregates, and the immobilized κ-carrageenase was further characterized. The immobilized κ-carrageenase demonstrated excellent pH stability and good reusability, and exhibited higher optimal reaction temperature, better thermostability, and extended storage stability compared with the free enzyme. The KCOs produced by the immobilized κ-carrageenase could significantly decrease the TC, TG, and LDL-C levels in HepG2 cells, increase the HDL-C level in HepG2 cells, and reduce the free fatty acids level in Caco-2 cells. Biochemical assays showed that the KCOs could activate AMPK activity, increase the ratios of p-AMPK/AMPK and p-ACC/ACC, and downregulate the expression of the lipid metabolism related proteins including SREBP1 and HMGCR in the hyperlipidemic HepG2 cells. This study provides a novel and effective method for immobilization of κ-carrageenase, and the KCOs produced by the immobilized enzyme could be a potential therapeutic agent to prevent hyperlipidemia.

3D N-doped carbon derived from zeolitic imidazole framework as heterogeneous catalysts for decomposition of pulp and paper mill effluent: Optimization and kinetics study

Three specific catalysts, namely ZIF-67 (zeolitic imidazolate framework-67), Co@NCF (Co@Nitrogen-Doped Carbon Framework), and 3D NCF (Three-Dimensional Nitrogen-Doped Carbon Framework), were prepared and studied for pulp and paper mill effluent degradation using heterogeneous activation of peroxymonosulfate (PMS). Numerous characterizations, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and N2 adsorption, were used to characterize the properties of three different catalysts. 3D NCF is remarkably effective at heterogeneous activation of PMS to generate sulfate radicals to degrade pulp and paper mill effluent (PPME) compared to the other as-prepared catalysts. The catalytic activity reveals a sequence of 3D NCF > Co@NCF > ZIF-67.3D NCF could degrade organic pollutants in 30 min at an initial COD concentration of 1146 mg/L of PPME, 0.2 g/L catalysts, 2 g/L PMS, and 50 °C. Consequently, it was observed that the degradation of PPME using 3D NCF followed first-order kinetics, with an activation energy of 40.54 kJ mol-1. Overall, 3D NCF/PMS system reveals promising performance for PPME removal.

Pervaporation Polyvinyl Alcohol Membranes Modified with Zr-Based Metal Organic Frameworks for Isopropanol Dehydration

Metal-organic frameworks (MOFs) are perceptive modifiers for the creation of mixed matrix membranes to improve the pervaporation performance of polymeric membranes. In this study, novel membranes based on polyvinyl alcohol (PVA) modified with Zr-MOFs (MIL-140A, MIL-140A-AcOH, and MIL-140A-AcOH-EDTA) particles were developed for enhanced pervaporation dehydration of isopropanol. Two membrane types (substrateless-freestanding; and formed on polyacrylonitrile support-composite) were prepared. The additional cross-linking of membranes with glutaraldehyde was carried out to circumvent membrane stability in pervaporation dehydration of diluted solutions. The synthesized Zr-MOFs were characterized by scanning electron microscopy, X-ray powder diffraction analysis, and specific surface area measurement. The structure and physicochemical properties of the developed membranes were investigated by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, thermogravimetric analysis, swelling experiments, and contact angle measurements. The PVA and PVA/Zr-MOFs membranes were evaluated in pervaporation dehydration of isopropanol in a wide concentration range. It was found that the composite cross-linked PVA membrane with 10 wt% MIL-140A had optimal pervaporation performance in the isopropanol dehydration (12-100 wt% water) at 22 °C: 0.15-1.33 kg/(m²h) permeation flux, 99.9 wt% water in the permeate, and is promising for the use in the industrial dehydration of alcohols.

Zeolitic Imidazolate Framework‑8 (ZIF-8) modified titanium alloy for controlled release of drugs for osteoporosis

The aim of this work was to prepare a biocompatible implant material that enables the release of drug for osteoporosis—risedronate. To achieve this goal, a titanium implant coated with a biocompatible Zeolitic Imidazolate Framework 8 (ZIF-8) layer was prepared that promotes osseointegration at the bone-implant interface. The modifications of the titanium alloy as well as sorption and desorption processes were confirmed using a variety of methods: SEM, EDS XPS, and FT-IR imaging (to determine surface modification, drug distribution, and risedronate sorption), and UV–Vis spectroscopy (to determine drug sorption and release profile). Both the ZIF-8 layer and the drug are evenly distributed on the surface of the titanium alloy. The obtained ZIF-8 layer did not contain impurities and zinc ions were strongly bounded by ZIF-8 layer. The ZIF-8 layer was stable during drug sorption. The drug was released in small doses for 16 h, which may help patients recover immediately after surgery. This is the first case of using ZIF-8 on the surface of the titanium alloy as carrier that releases the drug under the influence of body fluids directly at the site of the disease. It is an ideal material for implants designed for people suffering from osteoporosis.

Novel easily separable core–shell Fe3O4/PVP/ZIF-8 nanostructure adsorbent: optimization of phosphorus removal from Fosfomycin pharmaceutical wastewater

The synthesis of an easily separable novel core–shell Fe3O4/PVP/ZIF-8 nanostructure adsorbent and its usage for Fosfomycin pharmaceutical wastewater treatment.

Facile and single-step entrapment of chloramphenicol in ZIF-8 and evaluation of its performance in killing infectious bacteria with high loading content and controlled release of the drug

CLN@ZIF-8 was prepared by trapping chloramphenicol during ZIF-8 synthesis with high DLC and DLE. It showed H2O2-sensitive controlled release with higher drug release under the simulated infectious conditions and short-time antibacterial activity.

Novel Cellulose Triacetate (CTA)/Cellulose Diacetate (CDA) Blend Membranes Enhanced by Amine Functionalized ZIF-8 for CO2 Separation

Currently, cellulose acetate (CA) membranes dominate membrane-based CO₂ separation for natural gas purification due to their economical and green nature. However, their lower CO₂ permeability and ease of plasticization are the drawbacks. To overcome these weaknesses, we have developed high-performance mixed matrix membranes (MMMs) consisting of cellulose triacetate (CTA), cellulose diacetate (CDA), and amine functionalized zeolitic imidazolate frameworks (NH₂-ZIF-8) for CO₂ separation. The NH₂-ZIF-8 was chosen as a filler because (1) its pore size is between the kinetic diameters of CO₂ and CH₄ and (2) the NH₂ groups attached on the surface of NH₂-ZIF-8 have good affinity with CO₂ molecules. The incorporation of NH₂-ZIF-8 in the CTA/CDA blend matrix improved both the gas separation performance and plasticization resistance. The optimized membrane containing 15 wt.% of NH₂-ZIF-8 had a CO₂ permeability of 11.33 Barrer at 35 °C under the trans-membrane pressure of 5 bar. This is 2-fold higher than the pristine membrane, while showing a superior CO₂/CH₄ selectivity of 33. In addition, the former had 106% higher CO₂ plasticization resistance of up to about 21 bar and an impressive mixed gas CO₂/CH₄ selectivity of about 40. Therefore, the newly fabricated MMMs based on the CTA/CDA blend may have great potential for CO₂ separation in the natural gas industry.

Ultrathin porous amine-based solid adsorbent incorporated zeolitic imidazolate framework-8 membrane for gas separation

A novel gas separation approach is proposed in this work by combining an amine-based solid adsorbent with a zeolitic imidazolate framework-8 (ZIF-8) membrane. This was achieved by incorporating the amine-based solid adsorbent during the fabrication of the ZIF-8 membrane on a macroporous substrate. An amine-based solid adsorbent was prepared using porous ZIF-8-3-isocyanatopropyltrimethoxysilane (IPTMS) and N-[(3-trimethoxysilyl)propyl]diethylenetriamine (3N-APS) amine compounds. The as-prepared porous amine-based solid adsorbent (denoted as ZIF-8-IPTMS-3N-APS) possessed excellent adsorptive CO₂/N₂ and CO₂/CH₄ separation performances. As the adsorbent needs to be regenerated, this could indicate that the CO₂ adsorption separation process cannot be continuously operated. In this work, an amine-based solid adsorbent was applied during the preparation of the ZIF-8 membranes owing to the following reasons: (i) gas separation by the membrane can be operated continuously; (ii) the amino group provides a heterogeneous nucleation site for ZIF-8 to grow; and (iii) the reparation of surface defects on the macroporous substrate can be performed prior to the growth of the ZIF-8 membrane. Herein, the ZIF-8 membrane was successfully fabricated, and it possessed excellent CO₂/CH₄, CO₂/N₂, and H₂/CH₄ separation performances. The 0.6 μm ultrathin ZIF-8 membrane demonstrated a high CO₂ permeance of 4.75 × 10^-6 mol m^-2 s^-1 Pa^-1 at 35 °C and 0.1 MPa, and ideal CO₂/N₂ and CO₂/CH₄ selectivities of 4.67 and 6.02, respectively. Furthermore, at 35 °C and 0.1 MPa, the ideal H₂/CH₄ selectivity of the ZIF-8 membrane reached 31.2, and a significantly high H₂ permeance of 2.45 × 10^-5 mol m^-2 s^-1 Pa^-1.

[EMIM][Tf2N]-Modified Silica as Filler in Mixed Matrix Membrane for Carbon Dioxide Separation

This study focuses on the effect of modified silica fillers by [EMIN][Tf₂N] via physical adsorption on the CO₂ separation performance of a mixed matrix membrane (MMM). The IL-modified silica was successfully synthesized as the presence of fluorine element was observed in both Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectrometer (XPS) analyses. The prepared MMMs with different loadings of the IL-modified silica were then compared with an unmodified silica counterpart and neat membrane. The morphology of IL-modified MMMs was observed to have insignificant changes, while polymer chains of were found to be slightly more flexible compared to their counterpart. At 2 bar of operating pressure, a significant increase in performance was observed with the incorporation of 3 wt% Sil-IL fillers compared to that of pure polycarbonate (PC). The permeability increased from 353 to 1151 Barrer while the CO₂/CH₄ selectivity increased from 20 to 76. The aforementioned increment also exceeded the Robeson upper bound. This indicates that the incorporation of fillers surface-modified with ionic liquid in an organic membrane is worth exploring for CO₂ separation.

Cobalt metal-organic framework-based ZIF-67 for the trace determination of herbicide molinate by ion mobility spectrometry: investigation of different morphologies

Co-MOF-based zeolitic imidazolate frameworks (ZIF-67) with various morphologies were prepared via an innovative way under distinct reaction conditions. By changing the reaction conditions, including the cobalt source, solvent, time, temperature, and linking agent to the cobalt ions, the morphological evolution of Co-MOF-based ZIF-67 was investigated. The Co-MOF-based ZIF-67 was applied as an adsorbent fiber in the solid-phase microextraction (SPME) technique for extracting a herbicide, namely molinate (as a test compound), in aqueous samples. For recognizing the molinate molecules, drift tube ion mobility spectrometry (IMS) was employed as a sensitive, rapid, and simple detection technique. Two essential parameters, namely extraction temperature and extraction time, influenced the extraction efficiency, and these parameters were also analyzed and optimized. The linear dynamic range (LDR) and the determination coefficient were found to be 0.5-20.0 μg L-1 and 0.9990, respectively. In this regard, the limit of quantification (LOQ) and the detection limit (LOD) were calculated and found to be 0.5 μg L-1 and 0.15 μg L-1, respectively. Finally, the effect of the adsorbent with different morphologies on the extraction efficiency was compared.

CO2 capture using membrane contactors: a systematic literature review

With fossil fuel being the major source of energy, CO2 emission levels need to be reduced to a minimal amount namely from anthropogenic sources. Energy consumption is expected to rise by 48% in the next 30 years, and global warming is becoming an alarming issue which needs to be addressed on a thorough technical basis. Nonetheless, exploring CO2 capture using membrane contactor technology has shown great potential to be applied and utilised by industry to deal with post- and pre-combustion of CO2. A systematic review of the literature has been conducted to analyse and assess CO2 removal using membrane contactors for capturing techniques in industrial processes. The review began with a total of 2650 papers, which were obtained from three major databases, and then were excluded down to a final number of 525 papers following a defined set of criteria. The results showed that the use of hollow fibre membranes have demonstrated popularity, as well as the use of amine solvents for CO2 removal. This current systematic review in CO2 removal and capture is an important milestone in the synthesis of up to date research with the potential to serve as a benchmark databank for further research in similar areas of work. This study provides the first systematic enquiry in the evidence to research further sustainable methods to capture and separate CO2.

Caesium adsorption on a zeolitic imidazolate framework (ZIF-8) functionalized by ferrocyanide

¹³⁷Cs is one of the most hazardous radionuclides in nuclear waste owing to its toxicity. Developing an adsorbent for Cs⁺ with a high capacity and selectivity is a challenging task. A metal-organic framework (MOF) is a material with a high surface area that has been widely applied in wastewater treatment. Exploiting the affinity between ferrocyanide (FC) and Cs⁺, zeolitic imidazolate framework-8 (ZIF-8) was chemically functionalized with FC, ZIF-8-FC to selectively capture Cs⁺. After functionalization, ZIF-8-FC has a hollow morphology and small FC related crystals, which might result in better migration of Cs⁺ inside ZIF-8-FC. This synergistic effect was proven by the Q_max of ZIF-8-FC, 422.42 mg g^-1, which is 15.9 times higher than that of ZIF-8. Additionally, ZIF-8-FC retained its good adsorption performance within a pH range of 3-11 and an excellent Cs⁺ selectivity even in artificial seawater conditions. The structure of ZIF-8-FC after adsorption proves its stability. Furthermore, the thermodynamic adsorption implied that higher temperatures are more favorable for Cs⁺ uptake. This work demonstrates the remarkable adsorption and selectivity of ZIF-8-FC, which make it a promising candidate for remediation of radioactive Cs⁺.

Use of metal-organic framework to remove chromium (VI) from aqueous solutions

Chromium is one of the heavy metals found in industrial wastewaters, which have highly toxic to human beings and the environment. Exposure with it may cause some hazard diseases including stomach ulcers, liver, vomiting, kidney and nerve tissue damage, cancer in the lungs, and eventually death. The main objective of this study was to evaluate the efficiency of Uio-66 and ZIF-8 in removing chromium from aqueous solutions. For the synthesis of Uio-66 and ZIF-8, hydrothermal and sol-gel methods were used, respectively. The prepared Uio-66 and ZIF-8 were identified by FTIR, XRD, FE-SEM, EDX, and BET. All experiments were done in batch conditions. Uio-66 and ZIF-8 efficiency for chromium adsorption from aqueous solutions were investigated by variables like initial concentration (10-200 mg/l), pH (3 to 11), Uio-66 and ZIF-8 dosage (0.2 to 1 g/l) and contact time (45 min). The FE-SEM image showed that the sizes of Uio-66 crystals were between 140 and 280 nm. The specific surface area and total pore volume of the prepared Uio-66 and ZIF-8 were 800 m2/g, 0.45 m3/g, 1050 m2/g, and 0.57 m3/g, respectively. The results show chromium adsorption has increased in acid conditions. Equilibrium dosage for Uio-66 and ZIF-8 was 0.4 g/l and 0.6 g/l, respectively. Adsorption equilibrium was performed after 60 min and after this time, chromium adsorption did not significantly change. The study results showed that the experimental data obtained fitted with kinetic model pseudo-order- reaction and isotherm model of Langmuir.

Electrospun Nylon 6,6/ZIF-8 Nanofiber Membrane for Produced Water Filtration

This study develops electrospun nylon 6,6 nanofiber membrane (NFM), incorporating zeolitic imidazolate framework-8 (ZIF-8) as the additive for produced water (PW) filtration. Electrospun NFM is suitable to be used as a filter, especially for water treatment, since it has a huge surface area to volume ratio, high porosity, and great permeability compared to the conventional membranes. These properties also enhance its competitiveness to be used as reverse osmosis pre-treatment, as the final stage of PW treatment water reuse purpose. However, the fouling issue and low mechanical strength of NFM reduces hydraulic performance over time. Therefore, this study employs ZIF-8 as an additive to improve nylon 6,6 NFM properties to reduce fouling and increase membrane tensile strength. Results show that the optimum loading of ZIF-8 was at 0.2%. This loading gives the highest oil rejection (89%), highest steady-state pure water permeability (1967 L/(m2·h·bar)), 2× higher than untreated nylon 6,6 NFM with tensile strength 5× greater (3743 MPa), and a steady-state permeability of 1667 L/(m2·h·bar) for filtration of real produced water.

CO2-Philic [EMIM][Tf2N] Modified Silica in Mixed Matrix Membrane for High Performance CO2/CH4 Separation

Separation of carbon dioxide (CO2) from methane (CH4) using polymeric membranes is limited by trade-off between permeability and selectivity as depicted in Robeson curve. To overcome this challenge, this study develops membranes by incorporating silica particles (Si) modified with [EMIM][Tf2N] ionic liquid (IL) at different IL:Si ratio to achieve desirable membrane properties and gas separation performance. Results show that the IL:Si particle has been successfully prepared, indicated by the presence of fluorine and nitrogen elements, as observed via Fourier-Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectrometer (XPS). Incorporation of the modified particles into membrane has given prominent effects on morphology and polymer chain flexibility. The mixed matrix membrane (MMM) cross-section morphology turns rougher in the presence of IL:Si during fracture due to higher loadings of silica particles and IL. Furthermore, the MMM becomes more flexible with IL presence due to IL-induced plasticization, independent of IL:Si ratio. The MMM with low IL content possesses CO2 permeance of 34.60 ± 0.26 GPU with CO2/CH4 selectivity of 85.10, which is far superior to a pure polycarbonate (PC) and PC-Sil membranes at 2 bar, which surpasses the Robeson Upper Bound. This higher CO2 selectivity is due to the presences of CO2-philic IL within the MMM system.

Advanced Porous Materials in Mixed Matrix Membranes

Membrane technology has gained great interest in industrial separation processing over the past few decades owing to its high energy efficiency, small capital investment, environmentally benign characteristics, and the continuous operation process. Among various types of membranes, mixed matrix membranes (MMMs) combining the merits of the polymer matrix and inorganic/organic fillers have been extensively investigated. With the rapid development of chemistry and materials science, recent studies have shifted toward the design and application of advanced porous materials as promising fillers to boost the separation performance of MMMs. Here, first a comprehensive overview is provided on the choices of advanced porous materials recently adopted in MMMs, including metal-organic frameworks, porous organic frameworks, and porous molecular compounds. Novel trends in MMMs induced by these advanced porous fillers are discussed in detail, followed by a summary of applying these MMMs for gas and liquid separations. Finally, a concise conclusion and current challenges toward the industrial implementation of MMMs are outlined, hoping to provide guidance for the design of high-performance membranes to meet the urgent needs of clean energy and environmental sustainability.

Hierarchical ZIF-8 toward Immobilizing Burkholderia cepacia Lipase for Application in Biodiesel Preparation

A hierarchical mesoporous zeolitic imidazolate framework (ZIF-8) was processed based on cetyltrimethylammonium bromide (CTAB) as a morphological regulating agent and amino acid (l-histidine) as assisting template agent. Burkholderia cepacia lipase (BCL) was successfully immobilized by ZIF-8 as the carrier via an adsorption method (BCL-ZIF-8). The immobilized lipase (BCL) showed utmost activity recovery up to 1279%, a 12-fold boost in its free counterpart. BCL-ZIF-8 was used as a biocatalyst in the transesterification reaction for the production of biodiesel with 93.4% yield. There was no significant lowering of conversion yield relative to original activity for BCL-ZIF-8 when continuously reused for eight cycles. This work provides a new outlook for biotechnological importance by immobilizing lipase on the hybrid catalyst (ZIF-8) and opens the door for its uses in the industrial field.

An investigation of blended polymeric membranes and their gas separation performance

Novel blend glassy/rubbery polymeric membranes were produced, and, by adding 20% PVA_c to PES, good selectivity results were obtained.